rabaul caldera papua new guinea volcanic hazards surveillance and eruption contingency planning abstract planning for volcanic contingencies at the rabaul caldera complex is a difficult task requiring urgent attention in view of the results of volcano surveillance and historical eruption frequency historical eruption periodicities have ranged from about 2 to 59 years the most recent eruptions were in 1937 1943 and caused more than 500 fatalities in may 1937 surveillance since 1971 has revealed uplift of part of the caldera floor and increasing seismicity in a ring structure believed to define the caldera bounding fault or faults these phenomena are interpreted as the prelude to a possible eruption potential eruption sites are all close to rabaul town and outlying residential areas and include the volcanoes of sulphur creek last active about 1850 vulcan and tavurvur 1937 1943 and rabalanakaia but new sites should also be considered in relation to the results of volcano surveillance a wide range of volcanic hazards accompanying different scales of eruption must be considered for the rabaul area the most likely types of eruption may be similar to the relatively small events that have been witnessed over the last century whose hazards included air fall tephra pumice rafts pyroclastic flows and surges volcanic earthquakes volcanic gas discharges tsunamis lightning strikes and the fall of mud rain torrential run off and mudflows as a result of accompanying rain storms other potential eruption types of much larger scale could involve cauldron subsidence which could cause destructive tsunamis and could be accompanied by explosive activity of major proportions air fall tephra is considered to be one of the main hazards from a future eruption and its effects in and around rabaul are primary influences in the choice of evacuation routes and points of refuge hence theoretical tephra dispersal patterns have been considered in some detail air fall tephra deposition from rabaul eruption clouds at heights of less than about 4 km is determined by a biannual change in wind direction from southeast in may to october november trade winds to northwest during the monsoon from december to march april in contrast clouds that rise higher than about 4 km are blown by east winds all year round another principal hazard is pyroclastic flows and surges which took place during the 1937 vulcan eruption but have until recently been overlooked although flows or surges or both are clearly distinguishable on eruption photographs the lack of suitable evacuation routes and problems in choosing safe and reasonably accessible refuge points compound the difficulties in preparing a practicable contingency plan however in small moderate eruptions the safest areas around rabaul are considered to be at the duke york islands about 30 km to the east and at cape gazelle about 25 km to the southeast seaborne evacuation to main ports in central new britain or on the neighbouring islands of new ireland and bougainville or overland evacuation using a southwards expanded road system would be necessary in the event of forewarning of a major eruption

the quaternary evolution of the gulf of corinth central greece coupling between surface processes and flow in the lower continental crust abstract the gulf of corinth in central greece is an active normal fault zone with particularly clear evidence of isostatic footwall uplift constrained by quaternary marine terraces and hanging wall subsidence and sedimentation it is bounded to the south by a pliocene to early pleistocene sedimentary basin which is now eroding into the gulf previous work has suggested that the relief across this region has increased dramatically since the early pleistocene due to the isostatic response to increased rates of footwall erosion and hanging wall sedimentation it is indeed assumed here that incision accompanying the draw down of global sea level at 0 9 ma during the first major pleistocene glaciation initiated the erosion of the basin south of the gulf of corinth and so abruptly increased the sedimentation rate in the gulf the resulting transient thermal and isostatic response to these changes is modelled with the subsiding depocentre and eroding sediment source coupled by flow in the lower continental crust the subsequent enhancement of relief involving an increase in bathymetry from near zero to 900 m and 500 m of uplift of the eroding land surface in the sediment source is shown to be a direct consequence of this change the model is sensitive to the effective viscosity of the lower crust and can thus resolve this parameter by matching observations a value of 6 1019 pa s is indicated suggesting a viscosity at the moho no greater than 1018 pa s similar transient topographic effects caused by increased rates of sedimentation and erosion are likely to be widespread within the geological record suggesting that this coupling process involving flow in the weak lower crust may be of major geological and geomorphological importance

alkyldibenzofurans in terrestrial rocks influence of organic facies and maturation abstract dibenzofuran dbf dibenzothiophene dbt and phenanthrene phe have been determined along with their methyl derivatives mdbfs mdbts mps in coals carbonaceous shales and mudstones of lower cretaceous to upper carboniferous ages from the elmworth gas field canada and from the sakoa madagascar and ruhr coal germany basins the samples contained mainly terrestrial organic matter with thermal maturities in the 0 7 1 9 mean vitrinite reflectance rr range the pronounced predominance of mdbfs over mdbts in the sakoa samples is typical of plant debris deposited in lacustrine swamp environments onset of intense mdbf generation occurs at fairly low rank 0 77 rr as indicated by elevated concentrations of 50 120 g mdbfs g total organic carbon toc influences of lithology organic matter type and maturity on distributions of the target compounds were extracted from the molecular concentration data by multivariate statistical methods such as principal components analysis pca and fuzzy c means cluster analysis with nonlinear mapping nlm a specific source effect on 1 mdbt concentrations suggests that lichens contributed to the senescent coal forming forest in the sakoa coal basin alkyldibenzofurans hence are potential lichen biomarkers mdbfs can be used as maturity indicators only beyond 1 0 rr where ruhr coals displayed a distinct increase in the 1 4 mdbf ratio

rise and fall of the southern santa cruz mountains california from fission tracks geomorphology and geodesy the santa cruz mountains are closely associated with a left bend along the right lateral san andreas fault the loma prieta area on the northeast side of the san andreas consists of fault bounded blocks that rise along active deeply rooted reverse and oblique slip faults six samples from a transect across this area yield concordant apatite fission track ages averaging 4 6 0 5 ma these ages date the time of cooling below 110 c and suggest that about 3 km of unroofing has occurred over the last 4 6 m y allowing for current elevations of about 1 km this suggests an average uplift rate of the order of 0 8 mm yr over the last 4 6 m y to further define the extent and distribution of this young uplift we used morphometric analyses of the youthful topography of the area steep drainage slopes and high local relief indicate that the area northeast of the san andreas forms a well defined zone of high uplift in contrast the region on the southwest side of the san andreas is characterized by broad upwarping and folding more subdued topography old fission track ages and mean quaternary uplift rates of 0 1 0 4 mm yr geodetic data 1906 san francisco earthquake and subsequent strain transients 20 years of interseismic deformation 1989 loma prieta earthquake and 2 years of post loma prieta earthquake strain show that the southern santa cruz mountains repeatedly rise and subside through a complex sequence of bay area deformation events an additional deformation element that involves reverse slip averaging 2 3 mm yr along the foothills thrust system must occur to explain the longer term uplift pattern in the loma prieta area since the late pliocene the asymmetry in deformation on opposite sides of the san andreas probably reflects the contrasting rock types on opposite sides of the fault the influence of preexisting structures and the interaction with neighboring faults of the san andreas system

uplift of the sierra nevada of california gravity and most seismic interpretations agree that the sierra nevada is at present isostatically compensated by a crustal root the most reasonable timing for emplacement of the root was during mesozoic batholithic intrusions this is difficult to reconcile with the evidence that major uplift of the mountains occurred in the past 10 m y a simple quantitative model for flexural isostasy of an elastic plate before and after breaking resolves this problem and explains the tilt of the sierra nevada block and variations in topography along the range we postulate that cooling and elastic strengthening of the mesozoic magmatic arc prevented its reaching local isostatic equilibrium during erosion in the cenozoic thus an overcompensated residual mountain range was held down elastically until basin and range extension broke the elastic plate along the owens valley and allowed rapid uplift the moho density contrast that best models the amplitude of both late cenozoic uplift and prior topography is slightly larger than seismic and gravity models suggest this implies that up to 20 of the uplift may be driven by density contrasts in the upper mantle the idea of overcompensated erosional remnants and their release upon lithospheric faulting has a more general application to anorogenic uplift of mountain blocks

stress sensitivity of fault seismicity a comparison between limited offset oblique and major strike slip faults we present a new three dimensional inventory of the southern san francisco bay area faults and use it to calculate stress applied principally by the 1989 m 7 1 loma prieta earthquake and to compare fault seismicity rates before and after 1989 the major high angle right lateral faults exhibit a different response to the stress change than do minor oblique right lateral thrust faults seismicity on oblique slip faults in the southern santa clara valley thrust belt increased where the faults were unclamped the strong dependence of seismicity change on normal stress change implies a high coefficient of static friction in contrast we observe that faults with significant offset 50 100 km behave differently microseismicity on the hayward fault diminished where right lateral shear stress was reduced and where it was unclamped by the loma prieta earthquake we observe a similar response on the san andreas fault zone in southern california after the landers earthquake sequence additionally the offshore san gregorio fault shows a seismicity rate increase where right lateral oblique shear stress was increased by the loma prieta earthquake despite also being clamped by it these responses are consistent with either a low coefficient of static friction or high pore fluid pressures within the fault zones we can explain the different behavior of the two styles of faults if those with large cumulative offset become impermeable through gouge buildup coseismically pressurized pore fluids could be trapped and negate imposed normal stress changes whereas in more limited offset faults fluids could rapidly escape the difference in behavior between minor and major faults may explain why frictional failure criteria that apply intermediate coefficients of static friction can be effective in describing the broad distributions of aftershocks that follow large earthquakes since many of these events occur both inside and outside major fault zones

pore network characteristics of lacustrine shales in the dongpu depression bohai bay basin china with implications for oil retention abstract pore development and the location of retained hydrocarbons are key topics to understand the shale oil system in an attempt to investigate pore network characteristics and oil retention in lacustrine shales 24 samples from the es3 shales in the dongpu depression bohai bay basin were subjected to mineralogical petrological geochemistry and pore structure investigations using x ray diffraction xrd thin section field emission scanning electronic microscope fe sem n2 adsorption desorption after removing retained oil by solvent extraction 12 selected samples were again analyzed by rock eval pyrolysis and n2 adsorption desorption experiment according to the mineral compositions and petrological characteristics six types of lithofacies are identified in the es3 shales in the dongpu depression laminated calcareous shales lenticular calcareous shales laminated argillaceous shales massive argillaceous shales laminated siliceous shales and massive siliceous shales geochemical characteristics of these shales are quite different as calcareous laminated shales have higher toc contents than massive argillaceous and siliceous shales interparticle pores intraparticle pores organic matter pores and fracture pores are observed in the studied samples while bitumens were found retaining in well connected pore network the n2 adsorption desorption experiments on samples before and after solvent extraction reveal the different pore structure characteristics in six lithofacies and the occurrence of oil in lacustrine shales in general pore volumes within pore diameter range of 1 7 10nm and 10 200nm of samples show increase after solvent extraction indicating that large and small pores in shales both play important roles in oil retention oil retained in shales can be divided as free and heavy fractions as from the pyrolysis results in lacustrine shales larger pores are main storage space for hydrocarbon larger pores in different lithologies have similar capacity for free oil retention while those in calcareous and argillaceous shales are more efficient for heavy oil retention for both free and heavy oil small pores in argillaceous shales are efficient for their storage

chronology of neogene and quaternary uplift and magmatism in the caucasus constraints from k ar dating of volcanism in armenia abstract the greater caucasus is one of earth s highest actively uplifting mountain ranges the adjoining caspian sea basin contains a substantial proportion of its hydrocarbon reserves like other parts of the former soviet union the neogene and quaternary chronology of these important regions has not previously been well defined it has thus been impossible to obtain reliable estimates for rates of processes such as uplift of the caucasus and sedimentation in the caspian sea previous studies have established the relative timings of events in the region using correlation schemes between volcanism glaciations and the stratigraphy of the caspian basin however a range of absolute chronologies has previously been proposed for these sediments and igneous rocks based mainly on different interpretations of their magnetostratigraphic records by k ar dating we determine the ages of volcanism at three localities in armenia as 1 1 0 8 and 0 8 ma using these data and other evidence we propose a revision to the chronology of this region in which a distinctive brief interval of normal magnetic polarity in the local sedimentary and volcanic magnetostratigraphic records is matched to the cobb mountain event in the global record rather than the olduvai event or an earlier subchron as had previously been thought we thus interpret a 1 5 ma timing for the start of volcanism in the lesser caucasus and also suggest a 1 2 ma timing for the late akchagyl transgression of the caspian sea a key event in the regional stratigraphy when this water body reached its greatest extent we tentatively correlate this transgression with the melting event following glaciation during stage 36 of the oxygen isotope timescale which was thus the first time during the pleistocene when eastern europe was covered by a lowland ice sheet time averaged since 1 ma the flanks of the eastern greater caucasus mountains are shown to have uplifted at 0 6 mm a 1 and the lesser caucasus at 0 3 mm a 1 we show that the rate and spatial scale of this uplift are too great to be the result of plate convergence and suggest instead that this uplift is caused by crustal thickening due to inward lower crustal flow to beneath these mountain ranges at the start of magmatism in both the greater and lesser caucasus the estimated crustal thickness was 45 km we thus suggest that this magmatism has been caused by heating of the mantle lithosphere due to earlier crustal thickening the temperature rise required to initiate magmatism being the same in both cases

paleoseismic investigations in the santa cruz mountains california implications for recurrence of large magnitude earthquakes on the san andreas fault trenching microgeomorphic mapping and tree ring analysis provide information on timing of paleoearthquakes and behavior of the san andreas fault in the santa cruz mountains at the grizzly flat site alluvial units dated at 1640 1659 a d 1679 1894 a d 1668 1893 a d and the present ground surface are displaced by a single event this was the 1906 surface rupture combined trench dates and tree ring analysis suggest that the penultimate event occurred in the mid 1600 s possibly in an interval as narrow as 1632 1659 a d there is no direct evidence in the trenches for the 1838 or 1865 earthquakes which have been proposed as occurring on this part of the fault zone in a minimum time of about 340 years only one large surface faulting event 1906 occurred at grizzly flat in contrast to previous recurrence estimates of 95 110 years for the santa cruz mountains segment comparison with dates of the penultimate san andreas earthquake at sites north of san francisco suggests that the san andreas fault between point arena and the santa cruz mountains may have failed either as a sequence of closely timed earthquakes on adjacent segments or as a single long rupture similar in length to the 1906 rupture around the mid 1600 s the 1906 coseismic geodetic slip and the late holocene geologic slip rate on the san francisco peninsula and southward are about 50 70 and 70 of their values north of san francisco respectively the slip gradient along the 1906 rupture section of the san andreas reflects partitioning of plate boundary slip onto the san gregorio sargent and other faults south of the golden gate if a mid 1600 s event ruptured the same section of the fault that failed in 1906 it supports the concept that long strike slip faults can contain master rupture segments that repeat in both length and slip distribution recognition of a persistent slip rate gradient along the northern san andreas fault and the concept of a master segment remove the requirement that lower slip sections of large events such as 1906 must fill in on a periodic basis with smaller and more frequent earthquakes

seismic activity on neighbouring faults as a long term precursor to large earthquakes in the san francisco bay area activity in moderate size earthquakes accelerated in the several decades before the large california earthquakes of 1989 1906 and 1868 this type of precursor seems to require the presence of several major faults in close enough proximity to one another that moderate size shocks are selectively triggered on surrounding faults during the latter stages of the cycle of strain buildup to large earthquakes it may be possible to use quantitative aspects of similar seismic precursors to make predictions of large earthquakes on timescales of a few years to one decade

seismic activity of the san francisco bay region moment magnitude m with objective confidence level uncertainties are estimated for felt san francisco bay region earthquakes using bakun and went worth s 1997 analysis strategy for seismic intensity observations the frequency magnitude distribution is well described for m 5 5 events since 1850 by a gutenberg richter relation with a b value of 0 90 the seismic moment rate m yr since 1836 is 2 68 1018 n m yr 95 confidence range 1 29 1018 n m yr to 4 07 1018 n m yr the seismic moment rate since 1850 is nearly the same m yr in the 56 years before 1906 is about 10 times that in the 70 years after 1906 in contrast m yr since 1977 is about equal that in the 56 years before 1906 80 1 14 of the plate motion moment accumulation rate is available for release in earthquakes the historical m yr and the portion of the plate motion moment accumulation rate available for release in earthquakes are used in a seismic cycle model to estimate the rate of seismic activity in the twenty first century high and low rates of future seismic activity are both permissible given the range of possible seismic cycle recurrence times t and the uncertainties in the historical m and in the percentage of plate motion available for release in earthquakes if the historical seismic moment rate is not greater than the estimated 2 68 1018 n m yr and the percentage of the plate motion moment accumulation available for release in earthquakes is not less than the estimated 80 then for all t the rate of seismic moment release from now until the next 1906 sized shock will be comparable to the rate from 1836 to 1905 when m 6 1 2 shocks occurred every 15 to 20 years

absence of earthquake correlation with earth tides an indication of high preseismic fault stress rate because the rate of stress change from the earth tides exceeds that from tectonic stress accumulation tidal triggering of earthquakes would be expected if the final hours of loading of the fault were at the tectonic rate and if rupture began soon after the achievement of a critical stress level we analyze the tidal stresses and stress rates on the fault planes and at the times of 13 042 earthquakes which are so close to the san andreas and calaveras faults in california that we may take the fault plane to be known we find that the stresses and stress rates from earth tides at the times of earthquakes are distributed in the same way as tidal stresses and stress rates at random times while the rate of earthquakes when the tidal stress promotes failure is 2 higher than when the stress does not this difference in rate is not statistically significant this lack of tidal triggering implies that preseismic stress rates in the nucleation zones of earthquakes are at least 0 15 bar h just preceding seismic failure much above the long term tectonic stress rate of 10 4 bar h

paleoseismic studies of the san francisco peninsula segment of the san andreas fault zone near woodside california a late holocene slip rate is proposed for the san francisco peninsula segment of the san andreas fault zone at the filoli center located between the town of woodside and upper crystal springs reservoir california at this site the primary trace of the san andreas fault zone traverses n35 w across the head of a large alluvial fan offsetting buried stream channel deposits one deposit with a minimum calibrated accelerator mass spectrometry ams radiocarbon age of 2070 120 years b p is offset 30 2 m yielding an average geologic slip rate of 17 4 mm yr 1 for the late holocene a stratigraphically lower channel sequence with a minimum calibrated ams radiocarbon age of 330 200 years b p is offset 4 1 0 5 m we interpret that this older sequence records both the penultimate earthquake on the peninsula segment accompanied by 1 6 0 7 m of dextral slip and the 2 5 m of slip that occurred in 1906 on the basis of radiocarbon analyses and historical descriptions we propose that the pre 1906 earthquake occurred in june 1838 our interpretations suggest that the san francisco peninsula segment of the san andreas fault zone may rupture in earthquakes of at least two magnitudes 1 a large magnitude mw 8 event with a recurrence of 250 320 years that involves the north coast san francisco peninsula and santa cruz mountains segments as occurred in 1906 and 2 a mw 7 0 7 4 1838 type event that ruptures only the san francisco peninsula segment the apparent difference in slip rate of 7 7 mm yr 1 between the north coast segment 24 3 mm yr 1 and the peninsula segment 17 4 mm yr 1 suggests a possible slip rate gradient on the northern california section of the san andreas fault

water rock interactions in fault gouge measurements were made of the amounts of d 18o and h2o in fault gouge collected over a depth of 400 m in the san andreas fault of california the amounts and isotopic compositions of the pore fluids also analyzed suggest that formation waters from adjacent franciscan rocks have migrated into the gouge and mixed with local meteoric water thus the gouge is an open system permeable to fluid flow this permeability has important implications concerning heat flow along the fault zone

mineralogical analyses and in vitro screening tests for the rapid evaluation of the health hazard of volcanic ash at rabaul volcano papua new guinea the continuous ash and gas emissions from the tavurvur cone in rabaul caldera papua new guinea during 2007 08 raised concerns regarding how exposure would affect the respiratory health of nearby populations and impact on the environment as part of a formal evaluation of the effects of volcanic emissions on public health we investigated the potential health hazard of the ash using a suite of selected mineralogical analyses and in vitro toxicity screening tests the trachy andesitic ash comprised 2 1 6 7 vol respirable sub 4 m diameter particles the crystalline silica content was 1 9 5 0 wt cristobalite in the bulk sample with trace amounts of quartz and or tridymite scanning electron microscopy showed that the ash particles were angular with sparse fibre like particles 3 60 m max diameter observed in some samples which we confirmed to be caso4 gypsum at 6 wt in the bulk samples and not asbestiform fibres the ash specific surface area was low 0 1 2 7 m2 g 1 the leached solution from one of the ash samples was slightly acidic ph 5 6 but did not contain high levels of toxic metals such as f cu zn mn as ni and cd when compared to previously tested volcanic ash leachates ash samples generated potentially harmful hydroxyl radicals through an iron mediated catalytic reaction in the range of 0 15 2 47 mol m 2 after 30 min of reaction however measurement of particle oxidative capacity potential oxidative stress reaction using ascorbic acid and silica like injury to red blood cells erythrolysis assay i e measurement of cell death nevertheless revealed low biological reactivity the findings suggest that acute exposure to the ash would have a limited potential to exacerbate pre existing conditions such as asthma or chronic bronchitis and the potential for chronic exposure leading to silicosis was low

investigation of coupling between surface processes and induced flow in the lower continental crust as a cause of intraplate seismicity many studies have highlighted the role of coupling between surface processes and flow in the lower continental crust in deforming the crust and creating topographic relief over quaternary timescales on the basis of the rheological knowledge gained it is suggested that intraplate seismicity can also be caused by coupling between surface processes and flow in the lower continental crust this view is shown to be a natural consequence of the modern idea that isostatic equilibrium is maintained by flow in the weak lower crust in response to erosion and sedimentation it is supported by a general correlation between the vigour of surface processes and rates of intraplate seismicity and by instances of seasonal seismicity that correlates with seasonal climate human interference in the environment can affect surface loading for instance deforestation for agriculture or urban development can cause increased erosion rates global warming is expected to cause increased storminess and thus increased erosion rates and or global sea level rise the possibility of increased rates of seismicity resulting from these processes should thus be considered in future hazard assessment copyright 2006 john wiley sons ltd

cenozoic structural deformation and dynamic processes of the bohai bay basin province china abstract cenozoic structures in the bohai bay basin province can be subdivided into eleven extensional systems and three strike slip systems the extensional systems consist of normal faults and transfer faults the normal faults predominantly trend nne and ne and their attitudes vary in different tectonic settings paleogene rifting sub basins were developed in the hanging walls of the normal faults that were most likely growth faults neogene quaternary sequences were deposited in both the rifting sub basins and horsts to form a unified basin province the extensional systems were overprinted by three nne trending right lateral strike slip systems fault zones although the principal displacement zones pdz of the strike slip fault zones are developed only in the basement and lower basin sequences in some cross sections the structural deformation characteristics of the upper basin sequences also indicate that they are basement involved right lateral strike slip fault zones according to the relationships between faults and sedimentary sequences the extensional systems were mainly developed from the middle paleocene to the late oligocene whereas the strike slip systems were mainly developed from the oligocene to the miocene strike slip deformation was intensified as extensional deformation was weakened extensional deformation was derived from horizontal tension induced by upwelling of hot mantle material whereas strike slip deformation was probably related to a regional stress field induced by plate movement

deformation around stepovers in strike slip fault zones abstract this stuck addresses the kinematics of stepovers in strike slip fault zones where left lateral faults step rightward or right lateral faults step leftward a stepover is regarded as containing an internal strike slip fault whose ends link to transform faults surrounded by uniformly distributed deformation the kinematics are governed by k the ratio of slip rates on the internal fault and transform faults and gq the angle between these taults the convergence direction across the deformation at angle to the internal fault is an azimuth along which vectors do not rotate around vertical axes the lebanon stopover on the dead sea fault zone and the big bend stepover on the san andreas fault zone provide case studies in lebanon the time averaged deformation since 15 ma involves k 0 06 32 and 34 it accounts for 30 of anticlockwise rotation of cretaceous magnetization vectors in the lebanon mountains and 50 rotation of jurassic vectors the present phase of deformation around the big bend which began at 5 7 ma and imolves k 0 89 20 and 98 has instead only caused small rotations both clockwise and anticlockwise much of this region s structure including the dramatic up to 80 clockwise rotation of magnetization vectors in the transverse ranges is shown to relate instead to an earlier deformation phase with much lower k

sulfur and carbon isotopic compositions of the permian to triassic tsr and non tsr altered solid bitumen and its parent source rock in ne sichuan basin abstract reservoir solid bitumens from the permian to triassic and potential source rocks in the northeastern sichuan basin were measured for elemental and stable carbon 13c and sulfur 34s isotopic compositions to determine the chemical and isotopic composition of non tsr and tsr altered solid bitumen and to develop proxies to reflect the extent of bitumen alteration by tsr non tsr altered reservoir bitumen samples showed s c atomic ratios 0 03 and had 13c values closer to longtan formation p3l kerogen than to the lower silurian and cambrian kerogens and 34s values slightly more enriched than p3l kerogens the tsr altered solid bitumens have incorporated significant amounts of tsr derived h2s resulting in s c atomic ratios 0 047 0 074 and 34s values 13 4 24 0 being significantly higher than those of the solid bitumen not altered by tsr s c 0 013 0 030 34s 5 8 9 6 and the potential source rock kerogen the incorporation has produced a decrease in n c ratio and negative shift of 2 7 in 13c values that resulted from increasing tsr h2s back reactions with 12c rich n alkanes from the gas phase soluble solid bitumen or paleo oil to generate organic sulfur compounds such as ethanethiol that were incorporated into the solid bitumens which is followed by further aromatization and polymerization the solid bitumens show positive relationships of s c ratios and 34s values to the associated gas h2s h2s c1 6 or tsr extents and thus the s c ratios and 34s values can be used as proxies to reflect tsr extents

geology and eruptive history of the rabaul caldera area papua new guinea abstract rabaul caldera is the most recently active 1937 1943 of four adjoining volcanic centres aligned north south through the northern extremity of eastern new britain geological mapping after the 1983 1985 rabaul seismic and deformation crisis has partially revealed a long and complex eruption history dominated by numerous explosive eruptions the largest accompanied by caldera collapse the oldest exposed eruptives are the basaltic pre caldera cone tovanumbatir lavas k ar dated at 0 5 ma the dacitic rabaul quarry lavas exposed in the caldera wall and k ar dated at 0 19 ma are overlain by a sequence of dacitic and andesitic pyroclastic flow and fall deposits uplifted coral reef limestones interbedded within the pyroclastic sequence on the northeast coast suggest that explosive eruptions in the rabaul area had commenced prior to the 0 125 ma last interglacial high sea level stand the pyroclastic sequence includes the large boroi ignimbrites and malaguna pyroclastics both 40 ar 39 ar dated at about 0 1 ma and the barge tunnel ignimbrite 40 ar 39 ar dated at around 0 04 ma few reliable ages exist for the many younger eruptives these include holocene ignimbrites of the latest caldera forming eruptions the raluan pyroclastics variously dated 14c at either about 3500 or 7000 yr b p and the ca 1400 yr b p rabaul pyroclastics at least eight intracaldera eruptions have occurred since the 1400 yr b p collapse building small pyroclastic and lava cones within the caldera a major erosional episode is evident as a widespread unconformity in the upper pyroclastic stratigraphy at rabaul lacking relevant radiometric ages this episode is assumed to have occurred during last glaciation low sea levels and is here arbitarily dated at ca 20 ka at least five possibly nine significant ignimbrite eruptions have occurred at rabaul during the last 20 ka the new eruptive history differs considerably from that previously published which considered ignimbrite eruption and caldera collapse to have first occurred at 3500 yr b p rabaul volcanism has been dominated by two main types a basaltic and basaltic andesite cone building eruptions and b dacitic and rarely andesitic or rhyolitic plinian ignimbrite eruptions of both high and low aspect ratio types the 1400 yr b p rabaul ignimbrite is a type example of a low aspect ratio high energy and potentially very damaging eruption fine vitric ash deposits common in the rabaul pyroclastic sequence demonstrate the frequent modification of eruptions by external water probably related to early caldera lakes or bays interbedding of these fine ashes with plinian pumice lapilli beds suggests that many early eruptions occurred from multiple vents located in both wet and dry areas

acid alteration in the fumarolic environment of usu volcano hokkaido japan abstract the last eruptive activity of usu volcano in 1977 78 involved the development of high temperature 550 710 c fumaroles the gases emitted were h2o rich 95 99 mol with cl s 0 05 0 9 f cl 0 3 0 2 and with rh 2 5 close to the rock buffer feo feo1 5 cooling and oxidation of the high temperature gases resulted in the formation of acidic condensates ph 1 6 that interacted with the wall rock complete leaching of the cations ca na mg al and fe from the primary minerals and matrix glass occurred leaving in place only silica these mobilized cations precipitated as secondary minerals from acidic fluids that circulated in microcracks sem study shows mineral associations reflecting increasing fluid oxidation a al fluorides such as ralstonite namgalf6 h2o pyrite and anhydrite gypsum b an al hydroxide hematite gypsum and amorphous silica or cristobalite c al sulfates such as hydronium alunite h3o al3 so4 2 oh 6 alunite kal3 so4 2 oh 6 amorphous silica cristobalite hematite and anhydrite gypsum d al sulfates al fluorides amorphous silica cristobalite pyrite and anhydrite gypsum a ti oxide a fe mg sulfate and barite are present in minor amounts clay minerals are absent from the observed assemblages primary phenocrysts and matrix glass undergo a complete transformation to silica enriched in fluorine 1 7 wt this fluorine enrichment in the silicified parts of silicates and in silica incrustations suggests that f may play a role in silica mobilization modeling of the cooling of the high temperature gases was performed with the program gasworks the calculations suggest that 66 of the total sulfur from the gases may be lost by deposition as native sulfur at temperatures below 160 c thermochemical modeling of condensate rock interaction using chiller indicates that the cooling of gases was the source of the altering solutions oxidation by atmospheric o2 of the sulfur reduced species in the volcanic gas condensates resulted in their extreme acidification condensate rock interactions produce supersaturation with respect to the following mineral assemblages at 95 c 1 pyrite native sulfur cristobalite barite anhydrite diaspore log m h 2 s aq 2 32 2 cristobalite anhydrite hematite alunite diaspore log m h 2 s aq gypsum replaces anhydrite at t 25 c the calculated mineral assemblages are in agreement with those observed in the field

holocene slip rate and earthquake recurrence of the northern calaveras fault at leyden creek northern california the northern calaveras fault traverses a heavily populated area in the eastern san francisco bay region and has not had a large earthquake in more than 130 years to obtain data on the number timing and recurrence of large paleoearthquakes we conducted paleoseismologic investigations at leyden creek which crosses the fault in the rugged southern east bay hills the site is characterized by a prominent west facing scarp and fivc fluvial terraces on the western upstream side of the fault on the eastern downstream side of the fault the creek flows through a narrow bedrock canyon that constricts the modern valley and has constrained the location of a late pleistocene palcovalley the margin of a buried bedrock valley west of the fault trends nearly perpendicular to the fault and is offset 54 18 14 m in a right lateral sense from the narrow bedrock canyon based on radiocarbon ages for alluvial sediments predating and postdating this paleovalley margin we estimate an age of 11 5 3 1 ka for the valley margin and a holocene slip rate of 5 2 mm yr for the fault at leyden creek slickensides exposed in multiple trenches across the fault show that the most recent movement was predominantly lateral with a minor component of down to the west slip multiple displaced scarp derived colluvial deposits are interpreted as results of five or six surface ruptures within the past 2500 years twenty one radiocarbon samples from scarp derived colluvium and interfingered alluvial deposits suggest an average interval between surface rupture carthquakes of 250 to 850 years

patterns of seismic activity preceding large earthquakes we analyze the patterns of seismic activity which precede large events in a mechanical model of a fault the model generates a statistical distribution of events similar to that observed for a single fault with a scaling region consistent with the gutenberg richter law at small and moderate magnitudes and an excess of events at large magnitudes we find only slight variation in the scaling behavior during a loading cycle however we do observe systematic variations in space and time of the overall rate of activity in the model the activity accelerates dramatically preceding a large event and is usually a maximum hi the neighborhood of the future epicenter these results are compared to california seismicity data where we find that activity patterns vary regionally looking at patterns of activity in the san francisco bay area since 1948 we find an increase of activity on the calaveras fault near san jose beginning in the 1980s which if our model is relevant would forecast a large earthquake in that region the 1989 loma prieta earthquake occurred on the san andreas fault within 30 km of the section of the calaveras fault showing increased activity

assessment of leachable elements in volcanic ashfall a review and evaluation of a standardized protocol for ash hazard characterization abstract volcanic ash presents a widespread and common hazard during and after eruptions complex interactions between solid ash surfaces and volcanic gases lead to the formation of soluble salts that may be mobilized in aqueous environments a variety of stakeholders may be concerned about the effects of ash on human and animal health drinking water supplies crops soils and surface runoff as part of the immediate emergency response rapid dissemination of information regarding potentially hazardous concentrations of soluble species is critical however substantial variability in the methods used to characterize leachable elements makes it challenging to compare datasets and eruption impacts to address these challenges the international volcanic health hazard network www ivhhn org organized a two day workshop to define appropriate methods for hazard assessment the outcome of this workshop was a consensus protocol for analysis of volcanic ash samples for rapid assessment of hazards from leachable elements which was subsequently ratified by leading volcanological organizations the purpose of this protocol is to recommend clear standard and reliable methods applicable to a range of purposes during eruption response such as assessing impacts on drinking water supplies and ingestion hazards to livestock and also applicable to research purposes where possible it is intended that the methods make use of commonly available equipment and require little training to evaluate method transferability an interlaboratory comparison exercise was organized among six laboratories worldwide each laboratory received a split of pristine ash and independently analyzed it according to the protocol for a wide range of elements collated results indicate good repeatability and reproducibility for most elements thus indicating that the development of this protocol is a useful step towards providing standardized and reliable methods for ash hazard characterization in this article we review recent ash leachate studies report the outcomes of the comparison exercise and present a revised and updated protocol based on the experiences and recommendations of the exercise participants the adoption of standardized methods will improve and facilitate the comparability of results among studies and enable the ongoing development of a global database of leachate information relevant for informing volcanic health hazards assessment

the november 2017 mw 5 5 pohang earthquake a possible case of induced seismicity in south korea the moment magnitude mw 5 5 earthquake that struck south korea in november 2017 was one of the largest and most damaging events in that country over the past century its proximity to an enhanced geothermal system site where high pressure hydraulic injection had been performed during the previous 2 years raises the possibility that this earthquake was anthropogenic we have combined seismological and geodetic analyses to characterize the mainshock and its largest aftershocks constrain the geometry of this seismic sequence and shed light on its causal factors according to our analysis it seems plausible that the occurrence of this earthquake was influenced by the aforementioned industrial activities finally we found that the earthquake transferred static stress to larger nearby faults potentially increasing the seismic hazard in the area

application of sulfur and carbon isotopes to oil source rock correlation a case study from the tazhong area tarim basin china abstract up until now it has been assumed that oil in the palaeozoic reservoirs of the tazhong uplift was derived from upper ordovician source rocks oils recently produced from the middle and lower cambrian in wells zs1 and zs5 provide clues concerning the source rocks of the oils in the tazhong uplift tarim basin china for this study molecular composition bulk and individual n alkane 13 c and individual alkyl dibenzothiophene 34 s values were determined for the potential source rocks and for oils from cambrian and ordovician reservoirs to determine the sources of the oils and to address whether 13 c and 34 s values can be used effectively for oil source rock correlation purposes the zs1 and zs5 cambrian oils and six other oils from ordovician reservoirs were not significantly altered by tsr the zs1 oils and most of the other oils have a v shape in the distribution of c 27 c 29 steranes bulk and individual n alkane 13 c values predominantly between 31 to 35 vpdb and bulk and individual alkyldibenzothiophene 34 s values between 15 to 23 vcdt these characteristics are similar to those for some cambrian source rocks with kerogen 13 c values between 34 1 and 35 3 and 34 s values between 10 4 and 21 6 the oil produced from the lower ordovician in well ym2 has similar features to the zs1 cambrian oils these new lines of evidence indicate that most of the oils in the tazhong uplift contrary to previous interpretations were probably derived from the cambrian source rocks and not from the upper ordovician conversely the 13 c and 34 s values of zs1c cambrian oils have been shown to shift to more positive values due to thermochemical sulfate reduction tsr thus 13 c and 34 s values can be used as effective tools to demonstrate oil source rock correlation but only because there has been little or no tsr in this part of the section

geodetic measurement of horizontal deformation in the northern san francisco bay region california analysis of geodolite observations in the coast ranges of northern california indicates that relative plate motion is spread over a wide zone little or no deformation occurs to the southwest of the san andreas fault itself to the northeast of the san andreas fault a region transected by the parallel rodgers creek and maacama faults 25 6 mm yr of right lateral slip is distributed over about 60 km there is a peak shear strain of 0 6 0 1 rad yr near the san andreas fault elsewhere in the deforming zone shear strain rates are 0 3 0 04 rad yr at the northeastern boundary of the study area the strain rate is less than 0 2 rad yr except for the high strain rate near the san andreas fault there is no evidence of any localization of deformation to the surface traces of the faults nor is there any evidence of creep or aseismic slip on any of the faults in the area the data indicate that the relative motion between the pacific and north american plate occurs primarily to the northeast of the san andreas fault the observations are inconsistent with models that include slip at depth on only the san andreas fault the data can be fit equally well by models with slip at depth on all three of the major faults or with motion distributed across the entire zone from the san andreas fault to the napa valley fault preliminary analysis of observations to the farallon islands about 40 km southwest of the san andreas fault suggests that little or no additional relative motion is accommodated on that side of the san andreas fault in particular it is unlikely that the 20 mm yr difference between the plate motion rate about 55 mm yr and the san andreas fault system rate about 35 mm yr can be explained by deformation between the san andreas fault and the farallon islands

geology geochemistry and genesis of the cretaceous and paleocene sandstone and conglomerate hosted uragen zn pb deposit xinjiang china a review abstract the uragen zn pb deposit in wuqia county xinjiang china is hosted in sandstones and conglomerates of the lower cretaceous kezilesu group and argillaceous dolomite of the paleocene aertashi formation in the kashi sag northwestern tarim basin the deposit is characterized mainly by low grade zn pb 3 wt and large tonnage 3 mt metals in the southern ore zone potentially 10 mt metals for the whole deposit with an average zn pb ratio of about 5 8 the orebodies are tabular and stratiform mainly distributed in a syncline the ores are characterized by disseminated sulfides with minor massive veinlet patchy structures and fine grained locally colloform and framboidal textures the main primary metallic minerals are sphalerite galena pyrite and marcasite and minor supergene minerals include smithsonite hydrozincite anglesite calamine jarosite and limonite the ore minerals mainly occur as replacement of cements matrix and framework grains of the host rocks and as open space filling to a lesser extent based on the fact that orebodies straddle across a hiatus between the lower cretaceous and paleocene host rocks and on the replacement and open space filling textures and structures the mineralization is interpreted to be epigenetic the tightly clustered pb isotopic values of the main stage ore minerals 206 pb 204 pb ranging from 18 608 to 18 663 207 pb 204 pb from 15 619 to 15 669 208 pb 204 pb from 38 677 to 38 839 suggest that a single source supplied the metals whereas the wide range of s isotopes 34 s from 27 9 to 14 6 vcdt indicates multiple sources of reduced sulfur including those from thermal sulfate reduction tsr and bacterial sulfate reduction bsr the organic matter in the ores is characterized by relatively low concentrations of saturated hydrocarbons high concentrations of aromatic hydrocarbons asphaltenes and non hydrocarbons and low maturity compared to that in the host rocks and equivalent strata away from mineralization both hydrocarbons in the ores and host rocks show little biodegradation these characteristics of organic matter suggest that the site of mineralization was buried to significant depths and heated to above 80 c before the charging of hydrocarbons thus non development of biodegradation that some of the hydrocarbons were consumed in mineralization thus decreased maturity probably used as reducing agents for sulfate reduction in situ and that bacteria derived sulfur in the ores was not generated in situ mineralization probably resulted from mixing of a metal rich fluid with multiple fluids carrying reduced sulfur from different sources including some reduced sulfur from in situ tsr however it remains unclear whether the metal carrying fluid was derived from a near surface groundwater system and flowed downward to the site of mineralization at burial conditions or was derived from deeper parts of the basin and flowed up to the site of mineralization as part of a hydrothermal system the distinction of the two models requires a better understanding of the thermal profile across the deposit

evolving towards a critical point a review of accelerating seismic moment energy release prior to large and great earthquakes there is growing evidence that some proportion of large and great earthquakes are preceded by a period of accelerating seismic activity of moderate sized earthquakes these moderate earthquakes occur during the years to decades prior to the occurrence of the large or great event and over a region larger than its rupture zone the size of the region in which these moderate earthquakes occur scales with the size of the ensuing mainshock at least in continental regions a number of numerical simulation studies of faults and fault systems also exhibit similar behavior the combined observational and simulation evidence suggests that the period of increased moment release in moderate earthquakes signals the establishment of long wavelength correlations in the regional stress field the central hypothesis in the critical point model for regional seismicity is that it is only during these time periods that a region of the earth s crust is truly in or near a self organized critical soc state such that small earthquakes are capable of cascading into much larger events the occurrence of a large or great earthquake appears to dissipate a sufficient proportion of the accumulated regional strain to destroy these long wavelength stress correlations and bring the region out of a soc state continued tectonic strain accumulation and stress transfer during smaller earthquakes eventually re establishes the long wavelength stress correlations that allow for the occurrence of larger events these increases in activity occur over longer periods and larger regions than quiescence which is usually observed within the rupture zone of a coming large event the two phenomena appear to have different physical bases and are not incompatible with one another

lower limit of hydrocarbon generation in source rocks a case study from the dongpu depression bohai bay basin east china abstract with the increasing demand for hydrocarbons exploration tends to be deeper and unconventional resources however whether there are the lower limits for exploration depth or thermal maturity ro appears to be particularly essential it is of considerable significance to determine the lower limit of hydrocarbon generation llhg since this limit can provide guidelines for hydrocarbon potential estimation according to the mechanisms of hydrocarbon generation and expulsion five methods are combined to determine and verify the llhg whose values can be expressed by llhg ro and llhg h source rock samples from the paleogene shahejie formation es in the dongpu depression were taken as an example to determine the llhg and then controlling factors of the llhg were discussed llhg ro values for es range from 3 23 to 3 97 average 3 71 and llhg h values range from 5244 m to 5525 m average 5433 m regionally llhg values display obvious differences between the northern and southern of depression llhg values in the north are roughly larger than those in the south in the northern depression the llhg ro values are ranging from 3 61 to 3 97 average 3 81 and llhg h values are ranging from 5415 m to 5545 m average 5488 m however in the southern part the llhg ro values range from 3 20 to 3 74 average 3 48 and the llhg h values range from 5265 m to 5375 m average 5278 m the main controlling factors for llhg diversity between the north and the south of depression are organic matter om type and abundance formation temperature and pressure

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

dependence of active normal fault dips on lower crustal flow regimes two key questions are raised by the presence in the basin and range province of subhorizontal normal faults which were active in and around the miocene first how did they develop when their existence seems to be precluded by elementary rock mechanics arguments second if they did slip in the recent geological past why do normal faults now active in the brittle upper crust have steeper dips both in the western usa and elsewhere one may now answer both questions by considering the stress field in regions where the isostatic response during extension involves horizontal flow in the plastic lower crust this stress tensor will have inclined principal axes making it possible for normal faults to form with either very steep or subhorizontal dips depending on the sense of flow this can be controlled by environmental conditions which influence rates of hanging wall sedimentation and footwall erosion and thus determine lateral variations in lithostatic pressure in the lower crust regional scale lateral variations in the geothermal gradient caused by subduction can also influence lower crustal flow regimes in adjacent zones of continental extension enabling extension to occur on low angle normal faults dipping away from the active continental margin

lunar solar periodicities of large earthquakes in southern california large earthquakes in southern california with epicentres between 33 and 36 n have statistically significant 12 hourly lunar fortnightly and 18 6 yr periodicities smaller earthquakes in the same region do not display these periodicities a search for tidal effects associated with these periodicities shows that large earthquakes have significant correlations with the times and orientations of daily semi daily tidal stresses while the lunar fornightly term is associated with the ocean tides along the southern californian coast

iron induced hydroxyl radical generation from basaltic volcanic ash abstract iron induced hydroxyl radical generation from the surface of volcanic ash particles is a possible mechanism of respiratory toxicity in addition to crystalline silica induced pathogenicity here we show that volcanic ash generates hydroxyl radicals with greater reactivity in iron rich silica poor samples such as basaltic ash basaltic particles expose at the surface high levels of poorly coordinated iron ions in both fe ii and fe iii oxidation states which are likely to be the cause of such reactivity hitherto basaltic ash has been disregarded as a hazard due to the lack of crystalline silica particulate but future hazard assessment should consider its toxic potential

the 1759 earthquake in the bekaa valley implications for earthquake hazard assessment in the eastern mediterranean region analysis of macroseismic data based on primary sources for large though infrequent historical earthquakes ms 6 5 that occurred along an approximately 350 km long segment of the northern part of the dead sea fault system primarily in lebanon and syria for the period 1100 1988 reveals the following 1 ten events occurred in three relatively short periods tens of years with repeat times of 200 350 years 2 the events most probably broke this north segment of the dead sea fault system possibly including the westernmost segment of the east anatolian fault system near the border between syria and turkey 3 the lack of such large events during the past 100 years should not be interpreted to minimize potential earthquake hazard in this region and 4 the ms 7 plus earthquake on november 25 1759 almost certainly produced surface faulting probably along the yammouneh fault in the bekaa valley and caused heavy destruction with great loss of life in numerous villages and towns including safad damascus beirut and baalbek this main event was preceded by a ms 6 plus foreshock on october 30 1759 in the southern part of the epicentral area of the main shock near the towns of safad and qunaitra which were almost totally destroyed with considerable loss of life

four thousand years of seismicity along the dead sea rift a study of major earthquake occurrence along the dead sea transform 35 5 36 5 e 27 2 37 5 n during the past four millenia has been attempted geological archaeological biblical historical and seismological evidence were integrated in an effort to quantify the space time distribution of seismicity in the said province the overall earthquake activity in the conterminous near east indicates a stable pattern and appeared to have been stationary over the examined time window about 110 earthquakes in the magnitude range 6 7 ml 8 3 affected the area during the past 2500 years of these 42 originated along the dead sea fault system itself while 68 were imported from the helenic cyprian arcs and the anatolian elburz zagros fault systems these events were responsible for the repeated destruction of many cultural centers in the dead sea region proper the major seismic activity since 2100 b c e before christian era has been confined to the vicinity of its eastern shore with extremal seismicity at its southern tip near the prehistorical site of bab a dara a 31 15 n 35 32 e this may constitute the first solid evidence that the biblical cities of the plain sodom gommorah etc were located there recent studies of earthquake deformations in the lisan deposits near bab a dara a agree with our findings at the present time a magnitude 6 earthquake is pending at the northern edge of the levant rift with its average recurrence interval 83 years exceeded by one standard deviation 32 years

long term uplift of the santa cruz coastline in response to repeated earthquakes along the san andreas fault abstract the 18 october 1989 loma prieta earthquake m s 7 1 provides unprecedented insights into geomorphological processes of the santa cruz mountains region of central california in particular it inspires a simple explanation for the uplift that the area has been experiencing through its recent geological past predicted tectonic uplift from 442 oblique slip earthquakes on the loma prieta fault plane reproduces the variable elevations of 36 positions along the lowest santa cruz marine terrace within observational uncertainties an inferred formation height of 8 9 3 m ties the cutting of this terrace with the global sea level highstand at 125 kyr b p since then uplift rates between 0 13 and 0 35 mm yr have been maintained along the coast about one third as fast as previously proposed loma prieta type earthquakes recur every three to six centuries and account for less than half of the strike slip plate motion on this segment of the san andreas repetition of these characteristic events over much longer periods likely explains the deformation of the older terraces and motivates the configuration of this portion of the coastal range

geodetic estimate of coseismic slip during the 1989 loma prieta california earthquake offsets in the relative positions of geodetic stations resulting from the loma prieta earthquake can be explained with a dislocation model that includes buried oblique slip on a rupture surface extending 37 km along the strike of the san andreas fault dipping 70 degree to the sw and extending from a depth of about 5 to 17 5 km assuming uniform slip on a rectangular surface the mean values for a range of reasonable fault geometries are 1 6 plus minus 0 3 m right lateral strike slip and 1 2 plus minus 0 3 m reverse slip slip on an adjacent extension of the rupture to the southeast recorded in the aftershock sequence is not well constrained by the geodetic data the geodetic data clearly preclude rupture extending near the surface

the late cenozoic evolution of the tuolumne river central sierra nevada california erosional remnants of volcanic rock deposited in a 10 m y old channel of the tuolumne river permit its partial reconstruction projection of the reconstructed channel west to the central valley and east to the range crest together with several assumptions about the position of the hinge line and changes in channel gradient allows estimates of the amount of uplift at the range crest during the past 10 m y at tioga pass this amounts to as much as 1 830 m as compared to the 2 150 m estimated in an earlier study for deadman pass at the san joaquin river 30 km to the south comparison of the geometry of these river systems leads to the conclusion that 10 m y ago an ancestral range of hills occupied the present site of the sierran crest and although of relatively moderate relief it was a barrier to westward drainage even before late cenozoic uplift at that time the san joaquin river was apparently the only river flowing westward across the range from well south of mount whitney north to sonora pass the tuolumne river evidently never extended east of this range comparison of the ancient channel with the modern channel of the tuolumne river permits analysis of the later evolution of the river system and the development of hetch hetchy valley and the grand canyon of the tuolumne at rancheria mountain where the volcanic dam in the ancient channel was highest the river was forced to shift laterally southward around the dam and adjacent to the volcanic infilling and start its new channel in granitic bedrock near rancheria mountain as much as 1 525 m of new channel incision has taken place in the past 10 m y and the modern channel is about 915 m lower than the abandoned channel an undetermined amount of this downcutting was from glacial erosion the tuolumne river system provides no direct evidence for timing the onset of uplift but the shape of the 10 m y old channel at rancheria mountain suggests that uplift had been underway for some time before the volcanic infilling this timing is compatible with evidence from the upper san joaquin river hetch hetchy valley on the tuolumne is a much fresher glaciated valley than is yosemite valley hetch hetchy was filled to the brim with glacial ice as recently as 15 000 20 000 yr ago tioga glaciation whereas yosemite valley probably has not been filled for 750 000 yr or more sherwin glaciation thus the upper reaches of yosemite valley cliffs have been shaped by spalling rather than by glacial scour and are much more irregular than those in hetch hetchy

large earthquake occurrence affected by small stress changes abstract many observations suggest that relatively small changes in stress may trigger or inhibit earthquakes this result is surprising because the perturbing stress is only a small fraction of the stress drop from the affected earthquake we investigate this phenomenon by simulating the earthquake fault with a numerical model that is physically realistic a fault is not homogeneous and therefore the failure criteria will vary over the surface of the fault we model fault heterogeneity as simple coulomb failure on smaller but mostly uniform areas that comprise the fault as a result of multiple and repeated failures over these small areas the fault can have a very uneven stored stress we show that it is possible for small changes in confining stress of a few tenths of a bar to advance or retard the occurrence of large earthquakes by decades because such stress changes can be generated by nearby earthquakes and over much longer time scales by postseismic strain diffusion from large distant earthquakes estimates of the probabilities of earthquake occurrence must take into account these stress perturbations in order to be reliable

re evaluation of the 1836 hayward fault and the 1838 san andreas fault earthquakes abstract current seismic hazard models include two major earthquakes m 7 in the san francisco bay area that are close in space and time an 1836 event on the northern hayward fault and an 1838 event on the peninsula section of the san andreas fault analysis and interpretation of the available historical accounts indicate that the 1836 event occurred east of monterey bay far from the hayward fault and was of m 6 also the 1838 event was not confined to the 60 km peninsula san andreas as current models indicate instead faulting probably extended from san francisco to san juan bautista 140 km indicating a significantly larger earthquake m 7 than previously thought damaging effects of the 1836 earthquake were reported only from santa clara to carmel and no contemporary effects were reported to the north of santa clara or near the hayward fault the illusion of an 1836 hayward earthquake evolved from a newspaper reminiscence published following the 1868 hayward earthquake stating that the 1868 effects in the east bay were similar to those of an 1836 event the article describes various strong effects in the east bay that differ completely from the effects recorded for the 1836 earthquake but are very similar to those documented for the major 1838 san andreas earthquake that caused extensive damage on both sides of san francisco bay based on this and other evidence we conclude that the reminiscence describes the destructive june 1838 effects but it erroneously indicates the date as june 1836 there is no evidence for any major historical earthquakes in the san francisco bay area before the 1838 earthquake back to the founding of mission san francisco dolores in 1776 during the 1838 san andreas fault earthquake the shaking intensity in monterey was as strong as or stronger than during the great 1906 san andreas fault earthquake this suggests that the 1838 san andreas fault rupture may have extended to san juan bautista as it did in 1906 numerous probable aftershocks were felt in the area south of san juan bautista these damaged carmel and santa cruz in 1840 and alisal 16 km west of the san andreas fault in 1841 the northern end of the 1838 faulting was previously assumed to be 25 km south of san francisco however mission san francisco dolores was damaged in 1838 but not in 1906 suggesting that the 1838 faulting extended to san francisco also the 1838 aftershocks were felt in oakland as frequently and violently as those following the major 1868 hayward earthquake suggesting that the 1838 faulting on the san andreas extended to the latitude of oakland the 1838 fault segment ruptured again 68 years later as part of the overlapping 1906 san andreas fault rupture this and similar evidence from southern california indicates that m 7 san andreas fault earthquakes can recur at intervals of 68 years or less when they are followed by m 8 earthquakes on overlapping segments of the fault

re evaluation of extension across the pearl river mouth basin south china sea implications for continental lithosphere deformation mechanisms abstract the tertiary pearl river mouth basin in the south china sea is one of relatively few localities where independent estimates of extension from upper crustal normal faulting crustal thinning and subsidence have been compared previous work indicates that these methods all support extension factor 1 8 for this basin however the estimate from faulting used the controversial rigid domino method whereas summing normal fault heaves gives only 1 3 instead this study pursues the possibility that the true value for this basin is 1 3 and the published estimates of extension from subsidence and crustal thinning are exaggerated because they do not take account of outflow of lower crustal material from beneath this basin such outward channel flow will occur when the lithostatic pressure at the base of the brittle upper crust is greater beneath a basin than beneath its surroundings in response to such a pressure gradient material lost from beneath this basin has probably flowed to beneath the adjacent chinese landmass where it isostatically compensates the erosion that has supplied much of the basin s sediment

the respiratory health hazard of tephra from the 2010 centennial eruption of merapi with implications for occupational mining of deposits ashfall into heavily populated areas during the october november 2010 eruption of merapi volcano indonesia created anxiety regarding the growing impacts to health as the eruption escalated and the hazard zone widened we made a preliminary assessment of the respiratory hazards to human health of the tephra deposits ashfall lahar and pdc surge from the eruption using a laboratory protocol specifically developed to study the toxic potential of volcanic ash particles twenty samples collected from a range of locations were analysed for health pertinent mineralogical parameters grain size crystalline silica content morphology surface area bulk chemistry and leachable elements and bio reactivity hydroxyl radical generation haemolytic potential oxidative capacity pro inflammatory response the grain size pertinent to respiratory health was variable ranging from 1 4 15 6 vol sub 4 m and 3 0 28 9 vol sub 10 m diameter material no fibre like particles were observed cristobalite was present in all samples ranging from 1 9 9 5 wt but surface reactivity and in vitro toxicity assays showed low reactivity for all samples tested the risk of direct exposure to ash from fallout was in any case low due to seasonal rains limiting its re suspension and the immediate and effective clean up of communities by local people who supplied the ash to the indonesian construction industry for use as aggregate however mining of the lahar and thick pdc deposits in the valleys draining the volcano is performed on a vast industrial scale which could result in high occupational exposure to thousands of sand miners at merapi during the dry seasons further study of the health hazard of the mined merapi deposits is warranted

coseismic deformation during the 1989 loma prieta earthquake and range front thrusting along the southwestern margin of the santa clara valley california damage patterns caused by the 1989 loma prieta earthquake along the southwestern margin of the santa clara valley california form three zones that coincide with mapped and inferred traces of range front thrust faults northeast of the san andreas fault damage in these zones was largely contractional consistent with past displacement associated with these faults the damage zones coincide with gravity and aeromagnetic anomalies modeling of the anomalies defines a southwest dipping thrust fault that places the franciscan complex over cenozoic sedimentary rocks to minimum depths of 2 km diffuse loma prieta earthquake aftershocks encompass the downward projection of this modeled thrust to depths of 9 km our results indicate that in this region the potential for concentrated damage arising from either primary deformation along the thrust faults themselves or by sympathetic motion triggered by earthquakes on the san andreas fault may be higher than previously recognized

the immediate environmental effects of tephra emission the earth s history is punctuated by large explosive eruptions that eject large quantities of magma and silicate rock fragments into the atmosphere these tephra particles can sometimes be dispersed across millions of square kilometres or even entire continents the interaction of tephra with or in receiving environments may induce an array of physical chemical and biological effects the consequences for affected systems and any dependent communities may be chronic and localised in the event of frequent small eruptions while larger and rarer events may have acute regional scale impacts it is therefore necessary to document the range of possible impacts that tephra may induce in receiving environments and any resulting effects in interconnected systems we collate results from many studies to offer a detailed multidisciplinary and interdisciplinary review of the immediate post eruptive effects of tephra emission into the atmosphere onto vegetation soil or ice snow surfaces and in aquatic systems we further consider the repercussions that may be induced in the weeks to years afterwards in the atmosphere tephra can influence cloud properties and air chemistry by acting as ice nuclei in or by offering sites for heterogeneous reactions respectively tephra on vegetation causes physical damage and sustained coverage may elicit longer term physiological responses tephra deposits on soils may alter their capacity to exchange gas water and heat with the atmosphere or may have a specific chemical effect such as nutrient input or acidification on sensitive soils tephra deposition onto snow or ice may affect ablation rates rivers and lakes may experience turbidity increases and changes in their morphology as a result of fallout and prolonged months or years erosion from the tephra covered catchment in the first weeks after deposition tephra leaching may affect river chemistry the abundance and speciation of phytoplankton populations in lakes may be altered by tephra induced changes in water chemistry or sediment water nutrient cycling in the oceans tephra deposition may fertilise fe limited waters with potential impacts on the global carbon cycle embracing the full complexity of environmental effects caused by tephra fall demands a renewed investigative effort drawing on interdisciplinary field and laboratory studies combined with consideration of the interconnectivity of induced impacts within and between different receiving environments

seasonal seismicity of northern california before the great 1906 earthquake during the late nineteenth century coastal parts of northern california experienced seismicity which was more intense than at any other time in its historical record and was concentrated in spring the seasonal character of this anomalous seismicity was statistically significant from the 1880s if not earlier until the time of the great 1906 earthquake it can be explained as a result of seasonal stress transients caused by the large seasonal sediment loads which accumulated in coastal bays that overlie active strike slip faults as a result of hydraulic mining of gold in inland areas such localised loading will increase the absolute vertical stress and reduce the absolute horizontal stress thus facilitating shear failure by unclamping vertical fault planes however rather than simply influencing the timing of earthquakes which would otherwise have occurred anyway sometime later this process appears to have affected the character of the region s seismicity causing a sequence of magnitude 5 6 earthquakes which propagated outward from these coastal depocentres these results have three important implications first the proposed physical mechanism is only feasible provided the deepest continental crust in this region has a viscosity no greater than 1017 pa s giving it a maxwell time of the order of weeks these observations of seasonal seismicity thus suggest that such low viscosities are reasonable a conclusion which has been difficult to establish using other evidence they indicate that future calculations of the stress field in this region for instance for investigating the role of earthquake triggering should incorporate this response by lower crustal flow not just the immediate elastic effect second the conclusion that seasonal stress transients caused by seasonal changes in surface processes can affect seismicity has important implications for hazard assessment it raises the possibility that surface processes may influence the seasonal timing and character of seismicity in other regions also finally it indicates that the decades of intense seismicity widely interpreted as precursory activity to the 1906 earthquake were atypical of the longer term record analogous sequences of moderate sized events cannot necessarily be expected to provide advance warning of future large earthquakes in this region

volcanic ash leachates a review and recommendations for sampling methods tephra in plumes can scavenge and thereby rapidly deposit volatiles including sulphur halogen and metal species these may then be leached e g by rainfall potentially releasing heavy loadings to soils and water bodies several eruptions have resulted in contamination of pasture sometimes with serious impacts on livestock water quality has also been an issue in some areas affected by tephra fall this work synthesises the literature on volcanic ash leachates and considers the controls on volatile adsorption general trends emerge for basaltic intermediate and silicic tephra as well as for variable particle size and transport distance the applications of ash leachate data to plume gas geochemistry calculation of volatile budgets and environmental impact assessment are evaluated comparisons for different eruptions are hampered by disparities in leachate analysis techniques a standardised methodology is therefore proposed to facilitate future health impact assessment and volcanological interpretation of results from different sites

cristobalite in a rhyolitic lava dome evolution of ash hazard prolonged and heavy exposure to particles of respirable crystalline silica rich volcanic ash could potentially cause chronic fibrotic disease such as silicosis in individuals living in areas of frequent ash fall here we show that the rhyolitic ash erupted from chaiten volcano chile in its dome forming phase contains increased levels of the silica polymorph cristobalite compared to its initial plinian eruption ash erupted during the initial explosive phase 2 5 may 2008 contained approximately 2 wt cristobalite whereas ash generated after dome growth began from 21 may 2008 contains 13 19 wt the work suggests that active obsidian domes crystallise substantial quantities of cristobalite on time scales of days to months probably through vapour phase crystallisation on the walls of degassing pathways rather than through spherulitic growth in glassy obsidian the ash is fine grained 9 7 17 7 vol 4 m in diameter the respirable range and the particles are mostly angular sparse fibre like particles were confirmed to be feldspar or glass

time intervals between characteristic earthquakes and correlations with smaller events an analysis based on a mechanical model of a fault certain correlations between characteristic events and smaller events are studied in the context of a spatially homogeneous mechanical model for a fault the model satisfies a one dimensional quasi linear wave equation in which the key nonlinearity is associated with the slipstick friction force at the interface between tectonic plates we find that the model gives rise to slipping events of all sizes the smaller events are consistent with the gutenberg richter statistical law whereas the characteristic events have a separate statistical distribution the crossover from smaller events to characteristic events coincides with a correlation length which sets the scale for clustering of smaller events before the characteristic rupture numerical results and scaling arguments relate the features of the distribution of characteristic events to the corresponding features of the distribution of smaller events as well as the length of the fault the distribution of time intervals between characteristic events has the distinguishing features of asymmetry and a finite upper cutoff the mean t and standard deviation of the time interval distribution are found to be related to features of the magnitude versus frequency distribution of smaller events and the coefficient of variation t is independent of the driving rate because this analysis relates properties of characteristic earthquakes to statistical features of smaller more numerous events as well as geometric features of the fault it may ultimately be useful for long term earthquake prediction

geochemical characteristics and significance of heteroatom compounds in lacustrine oils of the dongpu depression bohai bay basin china by negative ion fourier transform ion cyclotron resonance mass spectrometry abstract saline and freshwater lacustrine oils from the dongpu depression bohai bay basin were characterized by negative ion electrospray ionization esi fourier transform ion cyclotron resonance mass spectrometry ft icr ms esi ft icr ms detected a large range of nitrogen and oxygen compounds in the oils mostly comprising n1 o1 o2 and n1o1 species the low mature oils are dominated by o1 species with double bond equivalent of 4 dbe 4 mainly alkylphenols o2 species with dbe 5 6 i e hopanoid secohopanoic and steroid acids and dbe 1 i e fatty acids indicating a genetic relationship between oxygen compounds and their precursors the nitrogen and oxygen compounds were significantly influenced by maturity with the lower maturity oils analyzed enriched in o2 species particularly fatty acids and 4 5 ring naphthenes with biologically sourced hydrocarbon skeletons ratios of o2 n1 0 7 c20 30 c15 45 dbe1 o2 0 4 and dbe5 6 dbe12 22 o2 6 0 may be useful indicators of low maturity with increasing maturity the condensation degree of the compounds increased and the carbon number decreased the relative abundances of n1 and o1 species with the following specific dbe carbon number ranges were particularly sensitive to maturity dbe9 12 dbe15 18 n1 c20 28 c29 40 dbe12 n1 c20 30 c31 50 dbe15 n1 dbe9 12 dbe4 20 o1 and c20 30 c31 50 dbe8 o1 in some instances the ft icr ms proxies provided a more reliable indication of high maturity levels than traditional sterane based maturity parameters however several of these species were also responsive to other influences namely c20 28 c29 40 dbe12 n1 and c20 30 c31 50 dbe15 n1 ratios reflected an organofacies control and dbe9 12 dbe4 20 o1 and c20 30 c31 50 dbe8 o1 ratios changed with thermochemical sulfate reduction tsr confirmed by 34s variances of oscs in light of the multiple controls on the nitrogen and oxygen compounds dbe9 12 dbe15 18 n1 ratio seems unaffected by organofacies or tsr and was considered the most reliable maturity proxy displaying a similar or better maturity relationship than ts ts tm aside from secondary alteration effects the freshwater samples showed several compositional differences to the saline samples albeit from a limited data set including generally higher o2 and n1 particularly low mw product abundances lower abundances and quite different distribution of o1 products these distinctions suggest esi ft icr ms analysis has potential for distinguishing these sample types

suppression of large earthquakes by stress shadows a comparison of coulomb and rate and state failure stress shadows generated by california s two most recent great earthquakes 1857 fort tejon and 1906 san francisco substantially modified 19th and 20th century earthquake history in the los angeles basin and in the san francisco bay area simple coulomb failure calculations which assume that earthquakes can be modeled as static dislocations in an elastic half space have done quite well at approximating how long the stress shadows or relaxing effects should last and at predicting where subsequent large earthquakes will not occur there has however been at least one apparent exception to the predictions of such simple models the 1911 m 6 0 earthquake near morgan hill california occurred at a relaxed site on the calaveras fault we examine how the more complex rate and state friction formalism based on laboratory experiments might have allowed the 1911 earthquake rate and state time to failure calculations are consistent with the occurrence of the 1911 event just 5 years after 1906 if the calaveras fault was already close to failure before the effects of 1906 we also examine the likelihood that the entire 78 years of relative quiet only four m 6 earthquakes in the bay area after 1906 is consistent with rate and state assumptions given that the previous 7 decades produced 18 m 6 earthquakes combinations of rate and state variables can be found that are consistent with this pattern of large bay area earthquakes assuming that the rate of earthquakes in the 7 decades before 1906 would have continued had 1906 not occurred these results demonstrate that rate and state offers a consistent explanation for the 78 year quiescence and the 1911 anomaly although they do not rule out several alternate explanations

petrology of the rabaul caldera area papua new guinea abstract the volcanic rocks erupted in the rabaul area mostly belong to a calc alkaline association here designated the main series they range from high alumina basalt minimum sio2 48 4 through medium k basaltic andesite to high k andesite dacite and rhyodacite maximum sio2 69 3 rare sodic rhyolites sio2 73 75 are mineralogically and geochemically distinct from the main series volcanics the rhyolites contain quartz and hornblende whereas the main series volcanics have a quartzfree anhydrous mineralogy even in the most siliceous rhyodacites amphibole and biotite which occur rarely in dacite are deuteric major and trace elements in the main series rocks show coherent continuous variation trends against sio2 rhyolite analyses consistently depart from these trends particularly for the incompatible elements k rb ba zr y and ree leastsquares mass balance calculations for major elements and rayleigh fractionation computations for trace elements show that the main series magma compositions can be modelled stepwise as products of a pure crystal fractionation process rhyolite cannot be derived from main series magma by crystal fractionation geochemical scatter in the main series may be caused by co genetic magma mixing as seen in the malaguna pyroclastics and latlat pyroclastics units hybrid mixing between main series magma and rhyolite is rare but may account for some anomalous medium k dacites such as the kulau ignimbrite derivation of parental high alumina basalt by partial melting in the mantle wedge is assumed while rhyolite which has an inappropriate geochemistry for a partial melt from subducted lithosphere is thought to be a product of partial melting of high alumina basalt underplating the crust volcanic hazard is related to magma composition with dacite sio2 65 and rhyolite capable of producing ignimbrite being the most dangerous changes in the style of rabaul volcanicity throughout the life of the caldera are not well documented but progressive weakening of the faulted substructure may now be allowing more primitive basalts and less fractionated intermediate magmas to reach the surface more freely

characterization of respirable volcanic ash from the soufriere hills volcano montserrat with implications for human health hazards volcanic ash generated in the long lived eruption of the soufriere hills volcano montserrat is shown to contain respirable sub 4 m particles and cristobalite a crystalline silica polymorph respirable particles of cristobalite can cause silicosis raising the possibility that volcanic ash is a respiratory health hazard this study considers some of the main factors which affect human exposure to respirable volcanic ash namely the composition and proportions of respirable ash and the composition and concentrations of airborne suspended particulates the composition size distribution and proportion by weight of respirable particles in representative samples of the soufriere hills tephra dome collapse ash fall deposits dome collapse pyroclastic flow matrix vulcanian explosion ash and mixed ash have been characterized dome collapse ash fall deposits are significantly richer in respirable particles 12 wt than the other tephra samples in particular the matrices of dome collapse pyroclastic flow deposits 3 wt within the respirable fraction dome collapse ash contains the highest proportion of crystalline silica particles 20 27 number of which 97 wt is cristobalite compared with other primary tephra types 0 4 5 6 number this enrichment of crystalline silica in the dome collapse ash is most pronounced in the very fine particle fraction sub 2 m the results are explained as being due to significant size fractionation during fragmentation of pyroclastic flows resulting in a fines depleted dome collapse matrix and a fines rich dome collapse ash deposit for all sample types the sub 4 m fraction comprises 45 55 wt of the sub 10 m fraction aeolian deposit lahar deposit and airborne samples of suspended ash collected on filters were characterized these samples show enrichment of crystalline silica in the respirable fraction 10 18 number the results are consistent with ash in the environment having a mixed origin but originating predominantly from dome collapse eruptions the reworked ash however contains low proportions of respirable ash 3 wt compared to primary ash samples the concentration of ash particles re suspended by road vehicles on montserrat is found to decrease exponentially with height above the ground indicating higher exposure for children compared with adults pm4 concentration at 0 9 m height of two year old child is 3 times that at 1 8 m adult height the composition of the re suspended road particles is similar to that re suspended by the wind

geochemistry of ash leachates from the 1993 lascar eruption northern chile implication for recycling of ancient evaporites abstract volcanic formations in the central andes overlie extensive amounts of ancient evaporites of cenozoic age recycling of buried salts in present closed basins through the hydrological cycle is a well known process another salt recycling process through volcanic activity has been detected in a recent eruption of the lascar volcano in northern chile about 10 9 metric tons of air fall tephra was deposited over the surrounding closed basins leaching experiments were carried out on ashes deposited near the summit and in a lower neighbouring valley summit ash leachates are almost pure caso 4 solutions whereas the valley ashes leachates are enriched in minor components leachates of the summit ash are near neutral whereas those of the valley ash have ph as high as 10 5 sulfur isotope composition of the leached sulfate is consistent with the volcanic recycling of tertiary gypsum present in the sedimentary section beneath the volcanic cordillera as a rough estimate about 700 000 tons of easily soluble caso 4 were added in only three days to the surrounding closed basins the high ph of the valley ash leachates is due to the hydration of alkali and alkaline earth metal oxides formed during pyrolysis of vegetation by hot ash efflorescent salts encrusted on plants and dissolution of volcanic glass provided some of the minor components the almost pure caso 4 composition of the leach waters is compositionally distinct from any present inflow waters in the central andes addition of caso 4 may explain some of the differences between the observed brine compositions and those predicted by simulating the evaporation of regular inflows the recycling of sedimentary gypsum is probably not restricted to lascar volcano the recycling of ancient salts and possibly also the pyrolysis of vegetation may have been crucial processes in the salt balance of closed basins during the intense volcanic activity of the tertiary

shale oil occurring between salt intervals in the dongpu depression bohai bay basin china abstract the saline mudstone sequence of the paleogene shahejie formation in the dongpu depression of bohai bay basin is a major source rock for conventional hydrocarbons however shale oil having a density of 0 9 g cm 3 and a viscosity of 21 mpa s has also been discovered and is being produced from these mudstones to better understand the occurrence of such shale oil geochemical petrological and mineralogical investigations were carried out on a suite of saline mudstone samples by using rock eval x ray diffraction and sem the shahejie formation samples analyzed in the current study are characterized by type ii kerogen with lesser amounts of types i and iii such that petroleum generation ranges from fair to excellent in general terms with the exception of es1 uppermost member which is immature to marginally mature for oil generation the sequence studied ranges from mature for oil generation to mature for wet gas generation on the basis of vitrinite reflectance data the most prospective depths for shale oil condensate generation are between 2300 and 4000 m depth in area studied the saline mudstones comprise mainly clay minerals followed by carbonates quartz and feldspar based solely on the brittle mineral index the amounts of carbonate and quartz in many of the samples lead to a similar or greater suitability for hydraulic fracturing than for many haynesville woodford and upper bakken shales sem studies show that abundant micro fractures commonly occur in the mudstones and these include tectonic fractures bedding plane fractures shrinkage fractures and over pressured fractures for the es3 m middle third member unit shale oil prospectivity is likely to be enhanced around the towns of wl wenliu lt liutun and hbz hubuzhai due to the increased frequency of tectonic fractures which would contribute to oil storage and flow mineral interparticle mineral intraparticle and organic matter pores are well developed in the rocks studied mineral dissolution has created secondary pores in some areas such that reservoir capacity is increased the increased concentration of organic acids between 2800 and 3500 m is likely to lead to enhanced shale oil prospectivity the micro fractures and dissolution pores are probably the main reservoirs for shale oil accumulation the association of these features with saline facies potentially offers an exploration tool for further shale oil occurrences in the studied area as well as in other areas containing similar lithologies

the mechanical feasibility of low angle normal faulting abstract low angle normal faulting is precluded by elementary rock mechanics arguments however the existence of many low angle normal faults in regions such as western north america has long suggested that this familiar theory is incomplete initiation of a low angle normal fault requires the stress tensor within the brittle upper crust to have inclined principal axes which necessitates a substantial shear stress within the vertical plane nonetheless no one has previously identified any specific extensional stress field which is suitably oriented to allow shear failure of previously unfractured rock at a low angle dip of 30 in preference to the steeper dip of 50 60 predicted by standard theory despite previous claims to the contrary this study shows for the first time that appropriately oriented stress fields can exist however they require the shear stress to locally reach 100 mpa near the base of a 10 km thick brittle layer this is only possible under extreme conditions as it requires dramatic lateral variations in the state of stress across the extending region it is suggested that a shear stress of this order can develop due to the combined effects of lower crustal flow which imparts a horizontal shear traction at the base of the brittle layer and loading which imparts shear traction in the vertical plane associated with the isostatic response to changes in heat flow caused by changes to the geometry of subducting slabs beneath an extending region regional patterns of low angle normal faulting in western north america are thus interpreted in terms of changes to the geometry of subduction of the farallon plate

natural controls of fluvial denudation rates in major world drainage basins we present a new compilation of estimates of modern rates of mechanical and chemical denudation for externally drained basins exceeding 5 105 km2 in area these estimates are based on sediment and solute load data selected in order to represent natural rates as far as possible chemical denudation rates have been calculated by deducting the nondenudational component of solute load mechanical denudation rates range from 1 mm kyr 1 for the st lawrence and dnepr basins to 670 mm kyr 1 for the brahmaputra basin chemical denudation rates vary from 1 mm kyr 1 kolyma niger nile and rio grande basins to 27 mm kyr 1 chiang jiang basin the kolyma basin has the lowest 4 mm kyr 1 and the brahmaputra basin the highest overall rate of denudation 688 mm kyr 1 relationships between denudation rates and a range of morphometric hydrologic and climatic variables are investigated through correlation and regression analysis morphometric variables such as mean local relief are accurately calculated for large basins for the first time by using the national geophysical data center 10 minute topographic database variables expressing basin relief characteristics and runoff are found to be most strongly associated with both mechanical and chemical denudation rates with more than 60 of the variance in total denudation being accounted for by basin relief ratio and runoff basin area runoff variability and mean temperature however are only weakly associated with rates of denudation although direct comparisons cannot be made it appears that rates of basin denudation derived from present day mass flux estimates are not overall significantly different from estimates of long term rates based on sediment volume and thermochronologic data it therefore appears that the key factors identified as controlling denudation rates here are also applicable to the geological time spans relevant to the interaction between tectonic and denudational processes

geochemical characteristics of the zhaolanzhuang sour gas accumulation and thermochemical sulfate reduction in the jixian sag of bohai bay basin abstract natural gas from the zhaolanzhuang field of the jizhong superdepression bohai bay basin contains the highest proportions of h 2 s 40 92 among the sour gases encountered in china the gas payzones include the eocene oligocene kongdian formation ek and the es4 member of the shahejie formation the sedimentary sequence consists of halite anhydrite carbonate sandstone and shale interbeds deposited in the evaporative brackish water lacustrine salt lake setting in the deepest part of the jinxian sag the total thickness of evaporites is more than 1000 m of which halite accounts for over 40 various organic rich mudstones intercalated with the evaporites are currently within the conventional hydrocarbon window with a depth of 2500 3500 m and likely the source for the oil and sour gas in the zhaolanzhuang field the temperatures of the gas reservoirs range from 75 to 100 c too low for significant thermochemical sulfate reduction the co occurrence of abundant elemental sulfur with the sour gas and the 34 s values of the various sulfur containing compounds indicate that the h 2 s gases were most likely derived from much deeper source kitchens where significant thermochemical sulfate reduction has occurred

compound specific sulfur isotopes of saline lacustrine oils from the dongpu depression bohai bay basin ne china abstract lacustrine oils from type i ii kerogen from the dongpu depression of bohai bay basin have been characterised by compound specific sulfur isotope and hydrocarbon biomarker analyses the sample suite included sixteen saline lacustrine oils from the northern part of the dongpu depression most of which i e all but two interbedded samples could be separated into four tectonically aligned oil families of1 4 on the basis of differences in their hydrocarbon composition e g high mw n alkanes isoprenoids polycyclic terpenoids the other two oils studied were freshwater lacustrine oils from the south of the dongpu depression the hydrocarbon composition of which indicated a fifth oil family of5 the 34s values of organic sulfur compounds 34soscs in the oils showed several general differences consistent with the five hydrocarbon biomarker defined oil families including the relative magnitude of their 34s values ave 34soscs values of1 19 relatively depleted 34s of2 28 enriched 34s of3 24 intermediate 34s of4 25 intermediate 34s and of5 18 depleted 34s and the respective 34soscs profiles of the oils e g the intermediate 34s values of the lt oils of3 showed little variance with alkylation

formation of cristobalite nanofibers during explosive volcanic eruptions high resolution transmission electron microscopy hrtem observations of unaltered volcanic air fall deposits from the ongoing lava dome explosive eruption at chaiten volcano chilean patagonia revealed the presence of highly crystalline silica nanofibers in the respirable fraction of the volcanic ash 240 c beta form of cristobalite with average lengths of hundreds of nanometers and widths on the order of tens of nanometers we propose that the beta cristobalite nanofibers are formed during explosive eruptions by the reduction of amorphous silica by carbon monoxide to its reactive suboxide sio which is later oxidized to form one dimensional crystalline silica nanostructures nucleation and growth of the nanofibers are enhanced by the high surface area of the micrometer to nanometer sized fragments of silica glass in the volcanic column the formation of nanocrystalline cristobalite fibers during explosive lava dome eruptions poses new challenges for the assessment of the short and long term health hazards associated with the respirable nanofibrous components of volcanic ash

predictive modeling of the seismic cycle of the greater san francisco bay region the seismic cycle for the san francisco bay region is synthesized by a model combining the pre and post 1906 seismic histories the long term acceleration of seismic release seismic moment benioff strain release or event count in the seismic cycle and the shorter term accelerations preceding the larger earthquakes within that cycle are modeled using an empirical predictive technique called time to failure analysis in which rate of seismic release is proportional to an inverse power of the remaining time to failure the exponent of time to failure in the accelerating sequences appears to be scale invariant and the length of the full cycle is estimated at 269 50 years the 1989 loma prieta earthquake which is the culmination of the first subcycle in the present long term seismic cycle should have been predictable with an uncertainty of 2 years in time and 0 5 in magnitude although the specific location at loma prieta was not predictable by this technique if our model is correct and if the loma prieta earthquake is the culmination of a subcycle the san francisco bay region should be entering a relatively long 20 50 years period of seismic quiescence above magnitude 6 a great earthquake such as the 1906 san francisco event would appear to be more than a century in the future

evolution of moderate seismicity in the san francisco bay region 1850 to 1993 seismicity changes related to the occurrence of large and great earthquakes the rate of seismic activity of moderate size m 5 5 earthquakes in the san francisco bay sfb region has varied considerably during the past 150 years as measured by the rate of seismic moment release seismic activity in the sfb region is observed to accelerate prior to m 7 0 earthquakes in 1868 1906 and 1989 and then to decelerate following them we examine these seismicity changes in the context of the evolution of the stress field in the sfb region as a result of strain accumulation and release using a model of dislocations in an elastic halfspace we use a coulomb failure function cff to take into account changes in both shear and normal stresses on potential failure planes of varying strike and dip in the sfb region we find that the occurrence of a large or great earthquake creates a stress shadow a region where the stress driving earthquake deformation is decreased interseismic strain accumulation acts to reverse this process gradually bringing faults in the sfb region out of the stress shadow of a previous large or great earthquake and back into a state where earthquake failure is possible as the stress shadow generated by a large or great earthquake disappears it migrates inward toward the fault associated with that large or great event the observed changes in the rate of occurrence of moderate earthquakes in the sfb region are broadly consistent with this model in detail the decrease in seismicity throughout most of the sfb region and a localized increase in the monterey bay region following the great 1906 earthquake is consistent with our predicted stress changes the timing and location of moderate size earthquakes when the rate of seismicity increases again in the 1950s is consistent with areas in which the 1906 stress shadow had been eliminated by strain accumulation in the sfb region those earthquakes that are most inconsistent with our stress evolution model including the 1911 earthquake southeast of san jose are found to occur in regions where dip slip faulting is common in addition to strike slip the 1906 earthquake brought that zone of dip slip faulting closer to failure suggesting that the 1911 event may have been a reverse faulting earthquake rather than a strike slip one similar to the 1984 morgan hill earthquake the occurrence of activity on faults very close to the san andreas such as the lake elsman earthquakes of 1988 and 1989 appear to be associated with the last disappearence of the stress shadow on the loma prieta segment of the san andreas fault thus events of that type may represent an intermediate term precursor to a large earthquake such as the 1989 loma prieta event much of the moderate size earthquake activity in the sfb region appears to be modulated in time by the buildup and release of stress in large and great earthquakes a tensorial approach to earthquake prediction i e taking into account changes in the components of the stress tensor has several advantages over examining scalar changes such as those in seismic activity and moment release rates this tensorial approach allows for both activation and quiescence but in different subregions prior to as well as after large earthquakes

a constitutive law for rate of earthquake production and its application to earthquake clustering seismicity is modeled as a sequence of earthquake nucleation events in which the distribution of initial conditions over the population of nucleation sources and stress ing history control the timing of earthquakes the model is implemented using solutions for nucleation of unstable fault slip on faults with experimentally derived rate and state dependent fault properties this yields a general state variable constitutive formulation for rate of earthquake production resulting from an applied stressing history to illustrate and test the model some characteristics of seismicity following a stress step have been explored it is proposed that various features of earthquake clustering arise from sensi tivity of nucleation times to the stress changes induced by prior earthquakes the model gives the characteristic omori aftershock decay law and interprets aftershock parameters in terms of stress change and stressing rate earthquake data appear to support a model prediction that aftershock duration defined as the time for rates to return to the back ground seismicity rate is proportional to mainshock recurrence time observed spatial and temporal clustering of earthquake pairs arises as a consequence of the spatial depen dence of stress changes of the first event of the pair and stress sensitive time dependent nucleation applications of the constitutive formulation are not restricted to the simple stress step models investigated here it may be applied to stressing histories of arbitrary complexity the apparent success at modeling clustering phenomena suggests the possibil ity of using the formulation to estimate short to intermediate term earthquake probabil ities following occurrence of other earthquakes and for inversion of temporal variations of earthquake rates for changes in driving stress

the respiratory health hazards of volcanic ash a review for volcanic risk mitigation studies of the respiratory health effects of different types of volcanic ash have been undertaken only in the last 40 years and mostly since the eruption of mt st helens in 1980 this review of all published clinical epidemiological and toxicological studies and other work known to the authors up to and including 2005 highlights the sparseness of studies on acute health effects after eruptions and the complexity of evaluating the long term health risk silicosis non specific pneumoconiosis and chronic obstructive pulmonary disease in populations from prolonged exposure to ash due to persistent eruptive activity the acute and chronic health effects of volcanic ash depend upon particle size particularly the proportion of respirable sized material mineralogical composition including the crystalline silica content and the physico chemical properties of the surfaces of the ash particles all of which vary between volcanoes and even eruptions of the same volcano but adequate information on these key characteristics is not reported for most eruptions the incidence of acute respiratory symptoms e g asthma bronchitis varies greatly after ashfalls from very few if any reported cases to population outbreaks of asthma the studies are inadequate for excluding increases in acute respiratory mortality after eruptions individuals with pre existing lung disease including asthma can be at increased risk of their symptoms being exacerbated after falls of fine ash a comprehensive risk assessment including toxicological studies to determine the long term risk of silicosis from chronic exposure to volcanic ash has been undertaken only in the eruptions of mt st helens 1980 usa and soufriere hills montserrat 1995 onwards in the soufriere hills eruption a long term silicosis hazard has been identified and sufficient exposure and toxicological information obtained to make a probabilistic risk assessment for the development of silicosis in outdoor workers and the general population a more systematic approach to multi disciplinary studies in future eruptions is recommended including establishing an archive of ash samples and a website containing health advice for the public together with scientific and medical study guidelines for volcanologists and health care workers

the iugs systematics of igneous rocks in order to create a sustainable classification of igneous rocks which all geologists might use an international body was set up by the iugs the iugs subcommission on the systematics of igneous rocks in the course of creating the classification the subcommission has established ten principles for its construction and for defining an appropriate nomenclature the principles are 1 use descriptive attributes 2 use actual properties 3 ensure suitability for all geologists 4 use current terminology 5 define boundaries of rock species 6 keep it simple to apply 7 follow natural relations 8 use modal mineralogy 9 if mode not feasible use chemistry 10 follow terminology of other iugs advisory bodies these principles and their rationale have not previously been enunciated the classification separates and individually classifies the pyroclastic carbonatitic melititic lamprophyric and charnockitic rocks before entering the main qapf classification for plutonic and volcanic rocks which is based on the modal mineral proportions of quartz q alkali feldspar a and plagioclase p or of alkali feldspar a plagioclase p and feldspathoids f rocks with mafic content 90 have their own classification if the mineral mode cannot be determined as is often the case for volcanic rocks then a chemical classification of total alkalis versus silica tas is used the nomenclature for these classifications necessitates only 297 rock names out of the c 1500 that exist

structural deformation and sedimentation in an active caldera rabaul papua new guinea abstract recent seismic and tectonic activity in rabaul caldera papua new guinea suggests that magma is accumulating at a shallow depth beneath this partially submerged structure and that a new volcano may be developing changes in onshore elevation since 1971 as much as 2 m on south matupit island indicate that rapid and large scale uplifts have occurred on the seafloor near the center of the caldera the frequency of seismic events within the caldera has also increased during this period earthquake locations define an elliptical ring surrounding the center of this uplift within the caldera a marine geophysical survey in 1982 by the u s geological survey s r v s p lee in rabaul caldera shows the development of a bulge in the seafloor near the center of the caldera high resolution seismic reflection profiles show that this bulge consists of two domal uplifts bounded and separated by two major north south trending fault zones deformed sediments overlie these zones a prominent slump flanks the area of the bulge five major acoustic units were identified in the seismic reflection profiles an acoustic basement and four sedimentary units consisting of irregularly layered cross layered contorted and well layered sequences the acoustic basement is probably composed of crystalline volcanic rocks and the layered acoustic units are probably sediments primarily ash deposited in different environments the cross layered irregularly layered and contorted units appear to have been deposited in a dynamic environment subjected to strong currents seismicity and or mass wasting while the well layered units were deposited in a low energy environment locally well layered sequences interfinger with the other sedimentary units indicating a transitional environment that alternated between high energy and low energy depositional processes a submarine channel cuts most of the acoustic units and appears to be the conduit for sediment transport out of the caldera it occupies an older buried channel north of the caldera that is presently being exhumed in the south active erosion of well layered sediments is taking place what are believed to be several young volcanic cones also disrupt the depositional layers we conclude that the bulge in the seafloor and the associated fault zones are a result of emplacement of magma at a shallow depth contorted sediment and slumps adjacent to the bulge are probably the result of uplift and seismic activity the pattern of seismicity appears to reflect increased magma pressure at depth beneath the caldera floor this activity may eventually lead to an eruption

leachability of uranium and other elements from freshly erupted volcanic ash abstract a study of leaching of freshly erupted basaltic and dacitic air fall ash and bomb fragment samples unaffected by rain shows that glass dissolution is the dominant process by which uranium is initially mobilized from air fall volcanic ash si li and v are also preferentially mobilized by glass dissolution gaseous transfer followed by fixation of soluble uranium species on volcanic ash particles is not an important process affecting uranium mobility gaseous transfer however may be important in forming water soluble phases adsorbed to ash surfaces enriched in the economically and environmentally important elements zn cu cd pb b f and ba quick removal of these adsorbed elements by the first exposure of freshly erupted ash to rain and surface water may pose short term hazards to certain forms of aquatic and terrestrial life such rapid release of material may also represent the first step in transportation of economically important elements to environments favorable for precipitation into deposits of commercial interest ash samples collected from the active guatemalan volcanoes fuego and pacaya high al basalts and santiaguito hornblende hypersthene dacite bomb fragments from augustine volcano andesite dacite alaska and heimaey basalt vestmann islands iceland and fragments of rhyolitic pumice from various historic eruptions were subjected to three successive leaches with a constant water to ash weight ratio of 4 1 the volcanic material was successively leached by 1 distilled deionized water ph 5 0 5 5 at room temperature for 24 h which removes water soluble gases and salts adsorbed on ash surfaces during eruption 2 dilute hcl solution ph 3 5 4 0 at room temperature for 24 h which continues the attack initiated by the water and also attacks acid soluble sulfides and oxides 3 a solution 0 05 m in both na co and nahco ph 9 9 at 80 c for one week which preferentially dissolves volcanic glass the first two leaches mimic interaction of ash with rain produced in the vicinity of an active eruption the third leach accelerates the effect of prolonged contact of volcanic ash with alkaline ground water present during ash diagenesis

sakurajima volcano a physico chemical study of the health consequences of long term exposure to volcanic ash regular eruptions from sakurajima volcano japan repeatedly cover local urban areas with volcanic ash the frequency of exposure of local populations to the ash led to substantial concerns about possible respiratory health hazards resulting in many epidemiological and toxicological studies being carried out in the 1980s however very few mineralogical data were available for determination of whether the ash was sufficiently fine to present a respiratory hazard in this study we review the existing studies and carry out mineralogical geochemical and toxicological analyses to address whether the ash from sakurajima has the potential to cause respiratory health problems the results show that the amount of respirable 4 m material produced by the volcano is highly variable in different eruptions 1 1 18 8 vol the finest samples derive from historical plinian eruptions but considerable amounts of respirable material were also produced from the most recent vulcanian eruptive phase since 1955 the amount of cristobalite a crystalline silica polymorph which has the potential to cause chronic respiratory diseases is 3 5 wt in the bulk ash scanning electron microscope and transmission electron microscope imaging showed no fibrous particles similar to asbestos particles surface reactivity tests showed that the ash did not produce significant amounts of highly reactive hydroxyl radicals 0 09 1 35 mol m 2 at 30 min in comparison to other volcanic ash types a basic toxicology assay to assess the ability of ash to rupture the membrane of red blood cells showed low propensity for haemolysis the findings suggest that the potential health hazard of the ash is low but exposure and respiratory conditions should still be monitored given the high frequency and durations of exposure

building damage in rabaul papua new guinea 1994 damage information on 173 buildings was collected in the immediate aftermath of the september 1994 eruption which destroyed large sections of rabaul town papua new guinea the extent of damage is presented on a five point scale and related to construction characteristics and tephra load total roof loads in rabaul town ranged from 2 to 16 kn m 2 about 100 to 950 mm tephra thickness most buildings which collapsed completely experienced loads 7 5 kn m 2 but many buildings sustained half this load with little more than cosmetic damage timber framed buildings suffered more than buildings with at least some concrete block walls however some old steel framed buildings experienced severe damage with tephra loads as low as 2 kn m 2 comparisons with tephra loads and building damage elsewhere are limited but suggest that rabaul buildings experiencing roof loads of 2 5 kn m 2 generally survived reasonably well however the comparisons are unsatisfactory because of inadequate data on tephra unit weights roof design building ages the quality of workmanship and the natural variability of construction materials particularly timber the rabaul data suggest that concrete block walls increase building resistance to tephra loads but it is doubtful that conventional residential buildings can be designed to sustain tephra loads exceeding 7 kn m 2 the rabaul experience also indicates that building codes for volcanic areas need to consider mudfills and post eruption corrosion of sheet metal roofs and wall cladding most importantly had the majority of buildings in rabaul survived the september 1994 tephra falls wet season mudflows a few months later would still have made most of the town unsafe and uninhabitable

holocene slip rate of the hayward fault at union city california measured offsets of well dated alluvial fan deposits near the masonic home in union city constrain holocene slip rate of the hayward fault between 7 and 9 mm yr our best minimum geologic slip rate over the past 8 27 0 08 kyr i e 8270 years is 8 0 0 7 mm yr a steep stream its channel cut into bedrock flows southwest out of the east bay hills crosses the fault and deposits its load on an alluvial fan we cut two 5 m deep fault parallel trenches 20 30 m southwest of the main fault through the crest of the fan walls of the trenches reveal a series of nested distributary channel fills these channels had cut into old surfaces that are indicated by paleosols developed on flood silts we distinguished many channel fills by their shape clast size flow direction elevation and relation to paleosols enabling us to correlate them between both trenches two distinct episodes of fan deposition occurred during the holocene reconstructing the apex positions of these fan units indicates that about 42 6 m and 66 6 m of fault slip has occurred since their inceptions at about 4 58 0 05 ka and 8 27 0 05 ka respectively we lowered the age and age uncertainty of the younger unit from earlier reports based on new multiple radiocarbon dates the 4 58 ka slip rate of 9 2 1 3 mm yr is not significantly different at 95 confidence from the 8 27 ka slip rate of 8 0 0 7 mm yr because current regional strain rates are fully consistent with neogene plate tectonic rates lisowski et al 1991 and the historic surface rate of creep in union city is only 4 7 0 1 mm yr galehouse 1994 the larger 8 mm yr holocene slip rate implies that strain is now accumulating on a locked zone at depth the 8 mm yr rate is probably minimal because earlier trenching evidence nearby implies that some unknown additional amount of fault deformation occurs outside of the narrow fault zone assumed in measuring slip lienkaemper et al 1991 suggest that the fast creep rate of 9 mm yr measured near the southern end of the hayward fault may underestimate the deep slip rate because 1868 surface slip occurred there in addition to the continuing fast creep if the historic deep slip rate equals the long term rate then the 9 mm yr creep rate reflects the minimum seismic loading rate of the hayward fault better than the 8 mm yr holocene rates do