late pleistocene glaciation of the kosciuszko massif snowy mountains australia abstract late pleistocene glaciation of the australian mainland was restricted to a small area of the southeastern highlands geomorphic mapping of the area and exposure dating using the in situ produced cosmogenic isotope 10be provides evidence for at least two distinct glaciations the early kosciuszko glaciation consisted of a single glacier advance before 59 300 5400 years ago snowy river advance the late kosciuszko glaciation comprised three glacier advances 32 000 2500 headley tarn advance 19 100 1600 blue lake advance and 16 800 1400 years ago mt twynam advance the early kosciuszko glaciation was the most extensive and the late kosciuszko advances were progressively less extensive these periods of glaciation in the highlands correspond to episodes of periglacial activity and peaks in lake levels and river discharge at lower elevations in southeastern australia glacier advances on the kosciuszko massif correlate with advances in tasmania south america and new zealand and are broadly representative of hemispheric climate changes during the last glacial cycle

erosional and climatic effects on long term chemical weathering rates in granitic landscapes spanning diverse climate regimes abstract we used cosmogenic nuclide and geochemical mass balance methods to measure long term rates of chemical weathering and total denudation in granitic landscapes in diverse climatic regimes our 42 study sites encompass widely varying climatic and erosional regimes with mean annual temperatures ranging from 2 to 25 c average precipitation ranging from 22 to 420 cm year 1 and denudation rates ranging from 23 to 755 t km 2 year 1 long term chemical weathering rates range from 0 to 173 t km 2 year 1 in several cases exceeding the highest granitic weathering rates on record from previous work chemical weathering rates are highest at the sites with rapid denudation rates consistent with strong coupling between rates of chemical weathering and mineral supply from breakdown of rock a simple empirical relationship based on temperature precipitation and long term denudation rates explains 89 95 of the variation in long term weathering rates across our network of sites our analysis shows that for a given precipitation and temperature chemical weathering rates increase proportionally with fresh material supply rates we refer to this as supply limited weathering in which fresh material is chemically depleted to roughly the same degree regardless of its rate of supply from breakdown of rock the temperature sensitivity of chemical weathering rates is two to four times smaller than what one would expect from laboratory measurements of activation energies for feldspar weathering and previous inter comparisons of catchment mass balance data from the field our results suggest that climate change feedbacks between temperature and silicate weathering rates may be weaker than previously thought at least in actively eroding unglaciated terrain similar to our study sites to the extent that chemical weathering rates are supply limited in mountainous landscapes factors that regulate rates of mineral supply from erosion such as tectonic uplift may lead to significant fluctuations in global climate over the long term

holocene tsunamis in the southwestern bering sea russian far east and their tectonic implications the bering sea coast of kamchatka overlies a boundary between the proposed okhotsk and bering blocks or micro plates of the north american plate in the russian far east a history of tsunamis along this coast for the past 4000 yr indicates that the zone north of the kuril kamchatka subduction zone produces tsunamigenic earthquakes every few centuries such a record is consistent with convergence of the proposed okhotsk and bering blocks along the bering sea coast of kamchatka a tsunami deposit from the 1969 m w 7 7 ozernoi earthquake helps us interpret older tsunami deposits newly studied tephra layers from shiveluch volcano as well as previously established marker tephra layers in northern kamchatka provide age control for historic and prehistoric tsunami deposits based on 50 measured sections along 14 shoreline profiles tsunami deposit frequencies in the southwestern bering sea are about five per thousand years for tsunamis generated north of the kuril kamchatka trench

direct correlation of terrestrial and marine paleoclimatic records from four glacial interglacial cycles dsdp site 594 southwest pacific abstract over the last 350 ka changes in the composition of vegetation on new zealand inferred from pollen analysis of the upper 40 m of dsdp site 594 at 2 4 ka sample intervals reflect regional climatic variations which appear synchronous with implied variations in glacier fluctuation and in global climatostratigraphy described from sedimentary and oxygen isotope records from the same samples nelson et al 1985 pollen assemblages from isotope stages 1 5e 7a 7b and 9 are distinguished by conifer and broadleaf forest taxa which vary in composition between the last four interglacials suggesting significant differences in precipitation temperature and or migration rates glacial pollen assemblages which imply the expansion of herbland and decline in forest components show less variation and generally indicate comparatively cool conditions on the east coast of south island interstadial vegetation is composed of a mosaic of shrubland herbland vegetation the close correspondence between variations in the amplitude and timing of these continuous records of forest development in the changing vegetation of south island new zealand and oxygen isotope climatostratigraphy supports previous suggestions that late quaternary southern and northern hemisphere climatic fluctuations were essentially synchronous

a field study of the chemical weathering of ancient sedimentary organic matter weathering profiles developed on organic carbon rich black shales were studied to examine the loss and degradation of organic matter om during weathering and its role in the geochemical carbon cycle analysis of weathered shales reveals between 60 and nearly 100 total organic carbon toc loss in highly weathered samples relative to initial unweathered toc content pyrite loss coincides with or precedes organic carbon loss elemental analysis and flash pyrolysis gas chromatography py gc of kerogen concentrates indicate that there is little or no selective enrichment or depletion of norg containing sorg containing alkylaromatic branched alkyl or long chain n alkyl moieties in most profiles during weathering kerogen o c ratios consistently increase with toc and pyrite loss infrared spectroscopy ir reveals an increase in the relative abundance of c c and c o bonds relative to alkyl c h bonds in progressively weathered samples these results suggest a two component model for kerogen weathering largely non selective oxidation and hydration followed by cleavage dissolution of oxidized kerogen fragments the extent of weathering in a given outcrop is likely limited by a combination of the rate of physical erosion and exposure of the rock to oxidizing surface waters with om type composition playing a lesser role

effect of variable bathymetry on the amplitude of teleseismic tsunamis a ray tracing experiment we apply surface wave ray tracing techniques to tsunami propagation in an ocean of variable depth because tsunami velocities are proportional to the square root of the depth of the water column the juxtaposition of oceanic plateaux and basins generates strong lateral velocity gradients and bathymetric features can act as lenses focusing or defocusing the tsunami waves we present a reconstruction of the tsunami wave field from the great chilean earthquake of 1960 an order of magnitude computation based on the concept of ray density provides qualitative agreement with observations at several sites in the pacific ocean we also demonstrate the possibility of using reciprocal maps to identify tsunamigenic zones that present particular danger for a given receiving shore

340 000 year centennial scale marine record of southern hemisphere climatic oscillation in order to investigate rapid climatic changes at mid southern latitudes we have developed centennial scale paleoceanographic records from the southwest pacific that enable detailed comparison with antarctic ice core records these records suggest close coupling of mid southern latitudes with antarctic climate during deglacial and interglacial periods glacial sections display higher variability than is seen in antarctic ice cores which implies climatic decoupling between mid and high southern latitudes due to enhanced circum antarctic circulation structural and temporal similarity with the greenland ice core record is evident in glacial sections and suggests a degree of interhemispheric synchroneity not predicted from bipolar ice core correlations

a seismological reassessment of the source of the 1946 aleutian tsunami earthquake summary we present a re evaluation of the seismological properties of the aleutian tsunami earthquake of 1946 april 1 characterized by a deceptively low conventional magnitude 7 4 in view of its catastrophic tsunami both in the near and far fields relocation of 40 aftershocks show that the fault zone extends a minimum of 181 km along the aleutian trench in a geometry requiring a bilateral rupture from the original nucleation at the epicentre their spatial and temporal distribution are typical of the aftershock patterns of a large earthquake and rule out the model of a landslide source exclusive of a dislocation the analysis of the spectra of mantle waves favours the model of a large seismic source with a static moment of 8 5 10 28 dyn cm making the event one of the ten largest earthquakes ever recorded hence the destructive tsunami in the far field and of a slow bilateral rupture at an average velocity of only 1 12 km s 1 hence the destructive interference in all azimuths for all but the longest mantle waves the exceptionally slow character of the earthquake is confirmed by a deficiency in radiated seismic energy expressed by the lowest value measured to date of the energy tomoment ratio the earthquake appears as an end member in the family of tsunami earthquakes resulting from the combination of anomalous but not unprecedented parameters such as low stress drop and rupture velocity

nitrogen in rock occurrences and biogeochemical implications 1 there is a growing interest in the role of bedrock in global nitrogen cycling and potential for increased ecosystem sensitivity to human impacts in terrains with elevated background nitrogen concentrations nitrogen bearing rocks are globally distributed and comprise a potentially large pool of nitrogen in nutrient cycling that is frequently neglected because of a lack of routine analytical methods for quantification nitrogen in rock originates as organically bound nitrogen associated with sediment or in thermal waters representing a mixture of sedimentary mantle and meteoric sources of nitrogen rock nitrogen concentrations range from trace levels 200 mg n kg 1 in granites to ecologically significant concentrations exceeding 1000 mg n kg 1 in some sedimentary and metasedimentary rocks nitrate deposits accumulated in arid and semi arid regions are also a large potential pool nitrogen in rock has a potentially significant impact on localized nitrogen cycles elevated nitrogen concentrations in water and soil have been attributed to weathering of bedrock nitrogen in some environments nitrogen released from bedrock may contribute to nitrogen saturation of terrestrial ecosystems more nitrogen available than required by biota nitrogen saturation results in leaching of nitrate to surface and groundwaters and where soils are formed from ammonium rich bedrock the oxidation of ammonium to nitrate may result in soil acidification inhibiting revegetation in certain ecosystems collectively studies presented in this article reveal that geologic nitrogen may be a large and reactive pool with potential for amplification of human impacts on nitrogen cycling in terrestrial and aquatic ecosystems

the tsunami earthquake of 13 april 1923 in northern kamchatka seismological and hydrodynamic investigations we present a seismological and hydrodynamic investigation of the earthquake of 13 april 1923 at ust kamchatsk northern kamchatka which generated a more powerful and damaging tsunami than the larger event of 03 february 1923 thus qualifying as a so called tsunami earthquake on the basis of modern relocations we suggest that it took place outside the fault area of the mainshock across the oblique pacific north america plate boundary a model confirmed by a limited dataset of mantle waves which also confirms the slow nature of the source characteristic of tsunami earthquakes however numerical simulations for a number of legitimate seismic models fail to reproduce the sharply peaked distribution of tsunami wave amplitudes reported in the literature by contrast we can reproduce the distribution of reported wave amplitudes using an underwater landslide as a source of the tsunami itself triggered by the earthquake inside the kamchatskiy bight

geomorphic controls on andean denudation rates abstract to predict erosion rates throughout the andes we conducted a multiple regression analysis of the sediment discharge from 47 drainage basins in the bolivian andes and various topographic climatologic and geologic parameters these mountainous basins are typically large 17 81 000 km2 documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes 10 9 7 6 begin document landscape mathrm mean 11 000 end document km2 often have decades of measurement data on daily water and sediment discharge and display an extraordinary range of denudation 0 01 6 9 mm yr

spectral analysis of tsunami waves separation of source and topography effects a new approach is proposed to separate the influence of source and topography in observed tsunami spectra and to reconstruct the initial source spectrum the method assumes a linear tide gauge response to external forcing and is based on comparative analysis of tsunami and background spectra evaluation of the ratio of tsunami to background spectra gives functional characteristics that are invariant of station location and dependent only on the source parameters three events the urup tsunami of december 22 1991 northwest pacific the hokkaido southwest okushiri tsunami of july 12 1993 sea of japan and the shikotan tsunami of october 4 1994 northwest pacific are used as examples of the proposed approach the source spectra reconstructed from the analysis of different tide gauges were found to be in good agreement with each other and with the seismological geodetic and field survey data

a theoretical model coupling chemical weathering rates with denudation rates uplift of the himalayas has been proposed to have locally accelerated chemical weathering thus leading to enhanced co2 sequestration and global cooling this hypothesis assumes that rapid erosion exposes fresh highly reactive minerals at earth s surface empirical studies quantifying the relationship between erosion and weathering have produced apparently conflicting results where the nature of the relationship is dependent on the weathering regime of the sampled landscapes we derive a quantitative model that defines this relationship across the range of weathering regimes from supply limited to kinetically limited conditions the model matches trends in field data collected by others and reconciles apparently conflicting results the model also demonstrates that as erosion rates increase potential increases in weathering rate from the exposure of fresher materials are offset by the decrease in the total volume of minerals exposed due to thinner regolith we conclude that the relationship between weathering and erosion is one of diminishing returns in which increases in erosion rate lead to progressively smaller increases in weathering rate indeed at the highest erosion rates weathering rates may decline the ability therefore of accelerated uplift and erosion to stimulate greater co2 sequestration may be significant in landscapes eroding at rates of 10 102 t km 2 yr 1 however where erosion rates are greater than 102 t km 2 yr 1 increases in denudation may not be matched by increases in chemical weathering finally our results suggest that watersheds with regolith thicknesses of 0 5 m will yield the greatest solute fluxes

intraplate seismicity of the pacific basin 1913 1988 we establish here a comprehensive database of intraplate seismicity in the pacific basin relocation and analysis of 894 earthquakes yield 403 reliable intraplate earthquakes during 1913 1988 these numbers do not include earthquake swarms which account for another 838 events most of the remainder 304 events are actually plate boundary earthquakes that have been erroneously located in intraplate regions a significant number occur in recent years when location capabilities should have guarded against this situation relocations involve a careful linear inversion of p and s arrivals accompanied by a monte carlo statistical analysis we have also attentively removed the high number of clerical errors and nuclear tests that exist in epicenter bulletins

nitrogen in future biosphere studies this article suggests a theme for future nitrogen studies involving the functioning and evolution of the biosphere together with certain aspects of human biology it is hoped that this theme could be developed into a multi authored book at some point in the future although numerous new case studies may be required the biosphere can be considered to be a single interactive system comprised of numerous component parts including the atmosphere rain rivers lakes oceans continental ecosystems marine ecosystems soils and sediments in order to study the internal complexity of each of the components and the relationships that exist between them one can choose a common theme the author believes that nitrogen is a good prospect because of its ubiquitous nature and complex chemistry the burial of sedimentary volatiles in the continental crust has contributed to the long term chemical evolution of the exterior environments of the earth the most marked effects notably the accumulation of atmospheric oxygen have been due to the burial of reduced carbon an understanding of the passage of sedimentary volatiles through the crust will provide important constraints on the evolution of the biosphere and may lead to a more meaningful comparative planetology carbon is difficult to trace through crustal processes because its high temperature form graphite is incompatible with the crystal structures of silicate minerals however the high temperature form of sedimentary nitrogen ammonium readily enters into potassic minerals and it can be easily traced through crustal processes herein the fate of sedimentary nitrogen is traced from wet sediments through metamorphic rocks into granites and other crustal melts without the trapping of nitrogen in the crust and the liberation of oxygen that is a consequence of biological nitrogen fixation the n2 o2 of the atmosphere may have been about 82 9 to 16 3 and the total atmospheric pressure about 1 2 atm most of the changes in the oxygen content is due to dilution by nitrogen with only about 5 of the present atmospheric oxygen being a consequence of nitrogen fixation the ancient continental surfaces would have been volcanic deserts containing little 1 ppm or no nitrogen today nitrogen rich soils support continental ecosystems one can use nitrogen as a window to speculate on the colonisation of the continents by land plants herein nitrogen fixation by legumes is considered in detail and by drawing analogies with the present day the author speculates on the colonisation of the continents by land plants having speculated on the co evolution of the atmosphere soils and continental ecosystems one can place a human being in the centre of a tropical forest and begin to examine how they relate to the modern biosphere the chosen example is the metabolism of plant protein and the roles of glutamate dehydrogenase gdh vitamin b2 and flavin mononucleotide fmn the realisation of this theme would imply numerous new case studies notably those concerning the continental crust where nitrogen studies were linked to mineralogy petrology and other geochemical tracers including sr o al and k and where the short range order of 15n were taken into consideration

the rukwa earthquake of 13 december 1910 in east africa we reappraised the rukwa earthquake of 1910 in the east african rift system with a magnitude of 7 4 no earthquake in east africa is known to be larger and it is rivalled only by the recent earthquake in southern sudan on 20 may 1990 more than 80 per cent of the moment release in the rift during the last 110 years is due to the rukwa earthquake and its aftershocks that occurred between the tanganyka and nyasa systems in spite of its large magnitude the rukwa earthquake caused very little damage to local types of dwellings and no loss of life with increasing development of urban areas with modern types of houses there is now increasing risk in east africa from major earthquakes

a terrestrial palynological record for the last two glacial cycles from southwestern new zealand abstract a pollen profile from okarito pakihi bog in south westland new zealand extending from near present back to marine isotope stage mis 6 provides a continuous record of vegetation and climate change for the past two glacial cycles independent chronological control was obtained by ams radiocarbon dating of organic sediments in the upper part of the sequence and osl dating of inorganic silts in the lower part with a unique tie point provided by the ca 26 5 cal ka kawakawa tephra as was probably a common occurrence in this region the basin developed as a moraine dammed proglacial lake and remained lacustrine until the early holocene when a peat bog developed survival of the depositional site through subsequent multiple ice advances unusual in a glaciated landscape was probably assisted by lateral displacement of the basin relative to its source area across the alpine fault there is good correspondence between inferred periods of substantial treeline depression in the pollen profile and the record for ice advance in this region more cooling events are evident in the pollen record however presumably due to the fragmentary nature of glacial geomorphology the pollen record also shows broad consistency with the mis record and hence with the milankovitch orbital forcing model but with some departures including an early onset to the last glacial maximum lgm several sub milankovitch scale events are also evident including a mid lgm warming and lateglacial reversals during both the last and the penultimate deglaciation

restraining bend tectonics in the santa cruz mountains california imaged using 10be concentrations in river sands reverse faults frequently generate large and destructive earthquakes yet their seismic hazard remains diffi cult to assess with traditional paleoseismic tools because their surface expressions are often complex and subtle this contribution assesses the utility of millennial scale denudation rates derived from in situ cosmogenic 10be for revealing the spatial patterns and magnitudes of rock uplift produced by slip along reverse faults we present seventeen basin averaged denudation rates from rivers draining the santa cruz mountains along the san andreas fault california usa which closely reproduce known uplift rate patterns associated with a restraining bend along the fault an additional component of vertical deformation appears to be superposed on the uplift due to the restraining bend this may result from regional transpression further irregularities in the fault trace or interactions with neighboring faults our results indicate that 10be derived denudation rates can reveal patterns of rock uplift adjacent to reverse faults over length scales relevant for characterizing their seismic hazard potential

the persistence of memory the fate of ancient sedimentary organic carbon in a modern sedimentary system the cycle of organic carbon burial and exhumation moderates atmospheric chemistry and global climate over geologic timescales the burial of organic carbon occurs predominantly at sea in association with clay sized particles derived from the erosion of uplifted continental rocks it follows that the history of the fine grained particles on land may bear on the nature of the organic carbon buried in this study the evolution of clay associated organic matter was followed from bedrock source to the seabed in the eel river sedimentary system of northern california using natural abundance 13c and 14c tracers approximately half of the fine grained organic carbon delivered to the shelf is derived from ancient sedimentary organic carbon found in the uplifted mesozoic tertiary franciscan complex of the watershed the short residence time of friable soils on steep hill slopes coupled with rapid sediment accumulation rates on the shelf slope act to preserve the ancient organic carbon a comparable quantity of modern organic carbon is added to particles in the watershed and on the shelf and slope the bimodal mixture of ancient and modern c in soils and sediments may be characteristic of many short mountainous rivers if the eel river chemistry is typical of such rivers more than 40 tg of ancient organic c may be delivered to the world s oceans each year a flux of that magnitude would have a significant influence on marine and global c cycles

strong climate and tectonic control on plagioclase weathering in granitic terrain abstract investigations to understand linkages among climate erosion and weathering are central to quantifying landscape evolution we approach these linkages through synthesis of regolith data for granitic terrain compiled with respect to climate geochemistry and denudation rates for low sloping upland profiles focusing on na as a proxy for plagioclase weathering we quantified regolith na depletion na mass loss and the relative partitioning of denudation to physical and chemical contributions the depth and magnitude of regolith na depletion increased continuously with increasing water availability except for locations with mean annual temperature

an indian ocean tsunami triggered remotely by an onshore earthquake in balochistan pakistan this paper describes and documents instrumentally recorded tsunami waves that are interpreted as secondary effects of a 7 7 magnitude earthquake in southern pakistan on 24 september 2013 the tsunami waves were almost unnoticed because the wave heights were low and the tsunami occurred at low tide the historical record of tsunami events within the arabian sea northern indian ocean is fragmentary large tsunamigenic earthquakes are known to be generated in the makran subduction zone the area that forms the boundary of the arabian and eurasian plates submarine sliding is reported along the owen fracture zone which marks the boundary between the arabian and indian plates hence the tsunami hazard potential within the arabian sea is enigmatic our analysis is based on sea level oscillations recorded at various tide gauge stations along the coastlines of oman pakistan and iran as well as eyewitness accounts of the event in oman our results indicate that the waves were in the range of 1 m or less in height they were first recorded along the eastern coast of oman and propagated toward the west we suggest that the waves must have been triggered by a submarine slide on the makran margin cascading effects resulting in large submarine slope failures within the arabian sea are more frequent than postulated the hazard potential is underestimated as such secondary effects of distant ruptures onshore were previously not taken into account

geologic nitrogen and climate change in the geochemical budget of karkevagge swedish lapland abstract while nitrogen is an essential nutrient for plant growth in the terrestrial environment and generally fixed by biological processes in soils in arctic and alpine environments n is a severely limited nutrient because of both climatic and soil constraints it is widely believed that geologic nitrogen is such a small component of the nitrogen cycle that this source is generally not viewed as being a significant component however it has been estimated that in fact as much as 20 of the total nitrogen budget may be stored in geological materials and where n is severely limited such as in arctic and alpine environments geologic n may in fact be a dominant source of n for biological processes nitrogen saturation may therefore have substantial impacts on geochemical cycles involving both soil and water chemistry in order to determine the potential for the rocks and soils of karkevagge to be significant sources of n samples of the principal rock units of the valley along with soil developed on a variety of rock types were sampled ammonia ammonium contents were determined using ion chromatography ammonia ammonium contents of the sampled rock materials display a wide range of abundances with marble containing a mean nh4 abundance of 4300 mg n kg quartz schist 1600 mg n kg biotite schist 4300 mg n kg and garnet mica schist 4500 mg n kg soil ammonia ammonium abundances were found to be 1600 mg n kg n pool abundances range from 2 5 kg m3 for marble to 8 7 for garnet mica schist soil n pools were found to be 3 0 kg m3 the inorganic n present as ammonia ammonium measured in bedrock represents substantial n input into the geochemical budget the n in bedrock originates from organically bound nitrogen associated with sediment or geothermal waters representing a mixture of sedimentary mantle and meteoric sources nitrogen in the soil originates from the weathering of n rich rocks the presence of unweathered nitrate minerals or fluid inclusions released to the soil and ultimately to plants by assimilation by biota or nitrification geologic nitrogen in karkevagge rocks and soils may represent a large and reactive pool with the potential for considerable impact on the geochemical system to investigate the potential responses of nitrogen release as well as other nutrients to increasing co2 concentration scenarios flow through leaching experiments were conducted on crushed rock samples and soils from the study area leaching experiments revealed two to three fold increases in both n and k release with a tripling of carbon dioxide concentrations ammonium shows more rapid release than potassium which suggests substantial changes in nitrogen cycling with increasing co2 enrichment of the atmosphere

tsunamigenic earthquakes past and present milestones we review a number of events which taken individually have significantly affected our understanding of the generation of tsunamis by earthquake sources and our efforts at mitigating their hazards notably through the development of warning algorithms starting with the 1700 cascadia earthquake we examine how significant tsunamis have changed our views in fields as diverse as seismotectonics the diversity of earthquake cycles the development of warning algorithms the response of communities at risk to warnings and their education the latter being either formal or rooted in ancestral heritage we discuss in detail lessons from the 2004 sumatra disasters and review the performance of warning centers and the response of affected populations during the nine significant tsunamis which have taken place since 2004

mineralization of organogenic ammonium in the monterey formation santa maria and san joaquin basins california usa abstract inorganic fixed ammonium nh4 contents as high as 0 28 wt were measured in organicrich quartz grade siliceous rocks of the miocene monterey formation from the santa maria and san joaquin basins california the greatest amount of fixed nh4 was found in rocks associated with hydrocarbons in the point arguello and lost hills oil fields where the nh 4 nh 4 k molar ratio of bulk samples ranges from 0 17 0 35 the formation of nh4 illite is suggested by the parallel increase in the percent of illite in the mixed layered illite smectite i s and in the nh 4 nh 4 k molar ratio of the clay sized fraction with increasing burial depth mineralization of nh4 appears to be promoted by the coincident timing of the smectite to illite clay mineral transformation and the release of nh4 during catagenesis nh4 feldspar may form at shallow burial depths in rocks from the point arguello field that contain a greater amount of detrital k feldspar and in which the i s contains only 10 20 illite quartzgrade siliceous monterey rocks from coastal outcrops in the lions head area lack significant amounts of hydrocarbons and have nh 4 nh 4 k molar ratios of 0 14 0 21 rocks from the lions head area show a strong positive correlation between diagenetic illite and fixed nh4 contents with nh4 constituting 18 21 mol of the fixed interlayer cations in the i s low grade opal a and opal ct siliceous miocene rocks from coastal outcrops in the pt pedemales area have low fixed nh4 contents 0 01 wt because these rocks contain minor amounts of diagenetic k bearing minerals i s contains 10 illite and they lack significant amounts of generated or migrated hydrocarbons the increase in the organic c n ratio with burial depth most likely reflects the preferential release of n compared to c and suggests that nh4 release is greatest during shallow burial bacterial degradation and deep burial catagenesis oil generation the results of this study support the suggestion of williams et al 1989 that high fixed nh4 contents may provide a long term geologic record of low temperature

the 1956 earthquake and tsunami in amorgos greece summary we conduct a comprehensive study of the amorgos greece earthquake and tsunami of 1956 july 09 the largest such event in the aegean sea in the 20th century systematic relocation of the main shock and 34 associated events defines a rupture area measuring 75 40 km the use of the preliminary determination of focal mechanism algorithm resolves the longstanding controversy about the focal geometry of the event yielding a normal faulting mechanism along a plane dipping to the southeast which expresses extensional tectonics in the back arc behind the hellenic subduction zone the seismic moment of 3 9 10 27 dyn cm is the largest measured in the past 100 yr in the mediterranean basin a quantitative database of 68 values of tsunami run up was built through the systematic interview over the past 5 yr of elderly eyewitness residents of 16 aegean islands and the turkish coast of asia minor it confirms values of up to 20 m on the southern coast of amorgos 10 m on astypalaia and up to 14 m on the western coast of folegandros 80 km to the west of the epicentre these values largely in excess of the inferred seismic slip at the source and their concentration along isolated segments of fault are incompatible with the generation of the tsunami by the seismic dislocation and require an ancillary source in the form of a series of landslides triggered by the earthquake and or its main aftershocks a model confirmed by hydrodynamic simulations using both the dislocation source and models of landslide sources

asynchronous climate change between new zealand and the north atlantic during the last deglaciation climatic fluctuations recorded in antarctica and greenland during the last deglaciation 18 10 ka differ markedly in their timing it remains controversial whether local climate fluctuations recorded in southern mid latitudes relate primarily to northern or southern polar records we present multiproxy results from new zealand that show strong evidence for a minor cooling or slowdown in the rate of warming at the time of the north atlantic late glacial interstadial the younger dryas chronozone in new zealand was a period of resumed warming and increased westerly airflow differences between the hemispheres at this time were probably due to a reorganization of the thermohaline circulation system and associated changes in the meridional temperature gradient

geological nitrogen cycle and atmospheric n2 over phanerozoic time using the average nitrogen carbon ratio n c of sedimentary organic matter coal and volcanic metamorphic gases existing models of the carbon cycle have been used to calculate the fluxes of nitrogen to and from the atmosphere via the weathering burial and metamorphic volcanic decomposition of organic matter results indicate no appreciable change less than one percent of that present in the mass of atmospheric n 2 over phanerozoic time this is in sharp contrast to atmospheric o 2 which shows notable variations variation of the mass of o 2 but not that of n 2 must have led to variation in total atmospheric pressure with time results are not altered by considering n c ratios ten times higher than the average for sedimentary rocks nor by considering nitrogen release from silicate weathering the residence time of n 2 in the atmosphere relative to exchange with and storage in crustal rocks is estimated to be about one billion years

earth science mainly in the plain the finding that global mass loss from landscapes is dominated by physical erosion and chemical weathering from flat terrain rather than from mountains challenges our understanding of how earth s surface evolves

teleseismic estimates of radiated seismic energy the e m 0 discriminant for tsunami earthquakes we adapt the formalism of boatwright and choy for the computation of radiated seismic energy from broadband records at teleseismic distances to the real time situation when neither the depth nor the focal geometry of the source is known accurately the analysis of a large data set of more than 500 records from 52 large recent earthquakes shows that this procedure yields values of the estimated energy ee in good agreement with values computed from available source parameters for example as published by the national earthquake information center neic the average logarithmic residual being only 0 26 units we analyze the energy to moment ratio by defining log10 ee m0 for regular earthquakes this parameter agrees well with values expected from theoretical models and from the worldwide neic catalogue there is a one to one correspondence between values of that are deficient by one full unit or more and the so called tsunami earthquakes previously identified in the literature as having exceedingly slow sources and believed due to the presence of sedimentary structures in the fault zone our formalism can be applied to single station measurements and its coupling to automated real time measurements of the seismic moment using the mantle magnitude mm should significantly improve real time tsunami warning

distribution patterns of the elements in the ocean a synthesis the observed partition patterns of elements between a marine solid phase e g pelagic clays deep sea manganese nodules seamount manganese crusts and plankton and seawater can be to the first approximation explained by the james and healy adsorption model except for ce co mn pb and tl which are concentrated in the solid phase through oxidative uptake processes in other words the composition of seawater is mainly controlled by the compositions of source materials i e the crustal igneous rocks and primary magmatic volatiles and the physicochemical principles regulating the adsorption processes of various chemical species in seawater onto oceanic pelagic clays

the destructive 1946 unimak near field tsunami new evidence for a submarine slide source from reprocessed marine geophysical data the mw 8 6 earthquake in 1946 off the pacific shore of unimak island at the end of the alaska peninsula generated a far field tsunami that crossed the pacific to antarctica its tsunami magnitude 9 3 is comparable to the 9 1 magnitude of the 2011 tohoku tsunami on unimak island s pacific shore a runup of 42 m destroyed the lighthouse at scotch cap elsewhere localized tsunamis with such high runups have been interpreted as caused by large submarine landslides however previous to this study no landslide large enough to generate this runup was found in the area that is limited by the time interval between earthquake shaking and tsunami inundation at scotch cap reworking of a seismic reflection transect and colocated multibeam bathymetric surveys reveal a landslide block that may explain the 1946 high runup it is seaward of scotch cap on the midslope terrace and within the time limited area

erosional response to northward propagating crustal thickening in the coastal ranges of the u s pacific northwest we measured basin scale erosion rates using cosmogenic 10 be concen trations in quartz from fluvial sediment in rivers draining the coastal mountain ranges of the u s pacific northwest between 40 and 47 n apparent erosion rates are 0 1 to 0 2 mm yr 1 throughout the oregon coast ranges north of 43 n and increase to the south to 0 6 to 1 1 mm yr 1 in the northern california coast ranges near 40 n we propose that these observations display the erosional response to northward migrating crustal thickening associated with subduction of the mendocino triple junction north south variations in erosion rate range elevation and metrics of landscape relief and steepness are consistent with the hypotheses that i their primary cause is northward migrating crustal thickening ii erosion rates are strongly controlled by topographic relief and weakly if at all controlled by climate and iii the dependence of erosion on relief is nonlinear and obeys a threshold relief relationship

nitrogen production from geochemical weathering of rocks in southwest montana usa 1 a 30 day time course laboratory weathering experiment was conducted using rock samples collected from the west fork of the gallatin river watershed wfw in southwestern montana usa the goal of these experiments was to quantify the amount of labile nitrogen in rock samples collected from the watershed and determine if chemical weathering is a source of dissolved nitrogen in stream water several rock samples investigated produced nitrate in significantly higher concentrations than the silica bead control p 0 05 and the data were consistent with elevated no3 concentrations measured in associated wfw streams isotopic analyses of 15n no3 in 22 stream water samples from the wfw and four rock water extracts from the laboratory experiments indicated that the isotopic composition of no3 was comparable with rocks and stream water samples in the same watershed and differed strongly from waters downstream of development we suggest that the no3 measured in wfw streams includes nitrogen derived from mineral dissolution products from soils and rock the results presented herein further indicate that rock weathering is a source of stream water n in the west fork watershed and inform water quality assessment total maximum daily load development and the relative influences of natural and anthropocentrically derived n sources across this developing mountain watershed

mm a variable period mantle magnitude this paper lays the theoretical groundwork for a variable period mantle magnitude mm based on the measurement of the spectral amplitude x of very long period rayleigh waves we retain the concept of magnitude by restricting ourselves to single station measurements ignoring the focal mechanism and the exact depth of the shallow earthquakes considered our measurements are made at a series of periods in all cases greater than 40 s and the largest value is retained this procedure effectively avoids the well known interference effects leading to saturation of magnitude scales defined at a fixed period two corrections are used a period dependent distance correction cd and a source correction cs also period dependent compensating for the variation of the excitation of rayleigh waves with period both of these corrections are fully predictable on the basis of standard surface wave excitation and dispersion theory the result is a formula of the type mm log10 x cd cs c0 in which all coefficients including the constant c0 are justifiable on sound theoretical grounds the analysis of a data set of 256 records from the broadband seismograph at papeete tahiti the ultra long period system at pasadena and stations of the geoscope network shows that the mean error in the estimation of the seismic moment is on the order of 0 1 0 2 units of magnitude with the standard deviation at each station also on the order of 0 2 units of magnitude no significant trend with either distance period or station can be identified the method can also be transposed to the time domain under some simple assumptions which are justifiable theoretically for typical teleseismic distances across the pacific basin both versions of the method lend themselves well to automation thus by providing a real time estimate of the seismic moment of distant earthquakes mm has considerable potential for tsunami warning purposes its concept can easily be extended to love waves and also to intermediate and deep earthquakes

minimal climatic control on erosion rates in the sierra nevada california climate is widely thought to regulate erosion rates but the relationships among precipitation temperature and erosion rate have remained speculative because long term erosion rates have been difficult to measure we used cosmogenic nuclides to measure long term erosion rates at climatically diverse sites in the sierra nevada california spanning 20 180 cm yr in annual precipitation and 4 15 8c in mean annual temperature average erosion rates vary by only 2 5 fold across these sites and are not correlated with climate indicating that climate only weakly regulates nonglacial erosion rates in mountainous granitic terrain

a discontinuous ca 80 ka record of late quaternary environmental change from lake omapere northland new zealand we present an integrated record of environmental change from lake omapere northland new zealand based on palaeolimnological analysis of a 7 m long core and eight adjunct cores spanning part of the last 80 calendar cal ka the chronology was developed using tephrochronology palaeomagnetism and radiocarbon dating together with climato and palyno stratigraphy two of 14 tephra layers in the cores provide markers for correlating the record with other new zealand climato stratigraphic sequences deep sea cores and the global marine isotope record pollen diatom palaeomagnetic sedimentologic and pigment analyses show that lake omapere currently 2 m deep has had a discontinuous history occupying a shallow basin perched partly within old basalt lavas the initial alkaline lake formed towards the end of mis 5a at ca 80 cal ka presumably because of blockage of local drainage of a swampy alluvial floodplain inundating peat deposits and forest trees including kauri agathis australis the lake filled rapidly to a level 1 2 m above that at present such filling was probably unrelated to climate but a subsequent phase of variable but generally falling lake levels and increasing dystrophy may have been climatically controlled commencing during mis 4 and culminating in periods early in mis 3 when the lake became swampy or dry conditions of non deposition or non preservation obtained for most of the period after ca 55 cal ka rotoehu ash until formation of the modern lake approximately 600 700 cal years ago or soon after as indicated by the presence of tephra 1 identified in part as kaharoa tephra ad 1314 near the top of the core the modern lake originated possibly through damming of the western outlet as a consequence of accelerated erosion accompanying earliest polynesian deforestation an interpretation supported by maori oral tradition the pollen record indicates that beech nothofagus presumably n truncata was much more common in northland during the last glacial and that for this region the relative abundance of nothofagus vs agathis pollen serves as a better indicator of cooler versus warmer intervals during the quaternary than the ratio of tree to non tree pollen however it seems likely that moisture balance was a more critical factor than temperature in vegetation composition and distribution particularly during the lgm and the long periods of hiatus may also be linked to a drier climate than present correlation coefficients between the pollen curves confirm that several tree species halocarpus bidwillii h biformis and phyllocladus alpinus previously palynologically concealed within generic taxonomic groups occurred about two degrees latitude further north and at a much lower altitude than their current limits during cooler or drier phases of the last glacial a temperature depression in northland of 4 c at various times during the last glacial is inferred from these range expansions nevertheless the persistence of widespread forest cover suggests that the late pleistocene climate of northland was less severe than for most of the rest of new zealand and strengthens the argument for a heightened temperature gradient across northern new zealand during the last glacial

morphology of a submarine slide kitimat arm british columbia a digitally acquired scale corrected side scan sonar survey yielded high resolution imagery of a submarine landslide in british columbia the landslide in a fjord head setting at kitimat was last active in 1975 and created a wide area of deformed sea floor the sediment failure involved shallow rotational movements on the slopes of a fjord head delta marginal tearing translational sliding compressional folding and block gliding of fjord bottom marine clays the slide is shallow and elongate and appears to have been produced by failure in mobile low strength sediments

extreme inundation flows during the hokkaido nansei oki tsunami the tsunami generated by the july 12 1993 hokkaido nansei oki mw 7 8 earthquake produced in japan the worst local tsunami related death toll in fifty years with estimated 10 18m sec overland flow velocities and 30m runup these extreme values are the largest recorded in japan this century and are among the highest ever documented for non landslide generated tsunamis we model this event to confirm the estimated overland flow velocities and we find that given reasonable ground deformation data current state of the art shallow water wave models can predict tsunami inundation correctly including extreme runup current velocities and overland flow we find that even small local topographic structures affect the runup to first order and that the resolution of the bathymetric data is more important than the grid resolution our results qualitatively suggest that for this event coastal inundation is more correlated with inundation velocities than with inundation heights explaining also why threshold type modeling has substantially underpredicted coastal inundation for this and other recent events

the large andaman islands earthquake of 26 june 1941 why no significant tsunami we present a modern seismological study of the earthquake of 26 june 1941 in the andaman islands the largest pre 2004 event along that section of the india burma plate boundary despite a large conventional magnitude m text pas 8 1 it generated at best a mediocre tsunami for which no definitive quantitative reports are available we show that the 1941 earthquake took place under the andaman accretionary prism and consisted of a composite event whose nucleating phase had a strike slip mechanism incompatible with a data set of spectral amplitudes of mantle rayleigh and love waves combining this initial phase with a larger normal faulting mechanism can reconcile them with p wave first motions reports of subsidence on the eastern coast of the andaman islands and the small amplitudes of any putative tsunami the small tsunami results from a combination of that mechanism and of a source located under the islands themselves and in shallow water implying a reduction in amplitude under green s law when transitioning to a deeper basin

the behavior of nitrogen and nitrogen isotopes during metamorphism and mineralization evidence from the otago and alpine schists new zealand abstract metamorphism is a major mechanism for the re distribution of fluids and mass in the earth s crust with these processes most prominently highlighted by the occurrence of major gold resources within these terranes however although orogenic gold deposits have contributed over 20 of the global gold production their origins remain controversial the nitrogen concentration and isotopic composition of rocks and minerals are potentially powerful tracers of crustal metamorphism and mineralization but there have been few detailed applications of this approach to date although nitrogen isotopes have recently been used to elucidate the source of fluids in some neoarchean orogenic gold deposits and proterozoic to paleozoic mountain belts due to their age and geological complexity of these terranes major uncertainties as to the behavior of nitrogen remain the otago and alpine schists in the south island of new zealand comprise a large comparatively young the range of 15n values for mica and whole rock samples from the schists spans 0 2 to 7 0 and the nitrogen concentration from 23 to 3483 ppm sample provenance and rock type have minimal influence on the nitrogen concentration and isotopic value which appears to have been inherited from the original sedimentary kerogen there is no systematic variation between metamorphic temperature and 15n or n concentration in micas suggesting that there has been little discernible loss of 15n depleted fluids from silicates with increasing metamorphic temperature comparison of fluid mobile alkali element k rb and cs carbon and nitrogen whole rock concentrations indicates that for the otago and alpine schists in rocks up to upper greenschist facies significant nitrogen remains hosted in phases other than micas most likely poorly matured carbonaceous material samples from macraes flat a major gold producer have a similar range of 15n values to the host terrane but show distinctly higher nitrogen concentrations relative to unmineralized samples due to the incorporation of nitrogen from the mineralizing hydrothermal fluid this suggests that there is only a subtle metamorphic re distribution of nitrogen during mineralization albeit with minimal isotopic fractionation in the case of nitrogen at least the isotopic signatures of mineralized rocks support a metamorphic fluid source and are inconsistent with mantle or meteoric fluid reservoirs however due to the high relative abundance of nitrogen in sedimentary rocks compared to other potential reservoirs unless fluid fluxes are very large and well channeled nitrogen signatures are not sensitive recorders of fluid inputs from mantle magmatic or meteoric reservoirs conversely the absence of a sedimentary source nitrogen isotope signature similar to the host rock in an orogenic deposit would be a very strong indicator of an external exotic source for the mineralizing fluids

the isc gem global instrumental earthquake catalogue 1900 2009 introduction abstract in this introductory article we give a general description of the isc gem global instrumental earthquake catalogue 1900 2009 we also provide the background for four further articles that describe the effort in collecting and digitizing parametric earthquake bulletin data as well as the methodologies developed to compute homogeneous earthquake parameters the result of the two and a half year project is a catalogue of approximately 20 000 large earthquakes covering 110 years with hypocentres and uncertainties computed using the same technique and velocity model we show that the overall homogeneity of the main earthquake parameters in the catalogue was achieved despite changes in instrumentation and routine measurement practices concurrent with developments in instrumental seismology from almost a ground level to its current state for each earthquake mw magnitude values and uncertainties were computed either based on available estimates of seismic moment or using new empirical relationships between mw ms and mb further important results of this project include the electronic availability of a considerable volume of seismic wave arrival time and amplitude measurements from early instrumental printed station bulletins these newly recovered amplitude measurements provided a basis for computation of many previously unavailable ms magnitudes with uncertainties in this article we describe why such a catalogue is required for a comprehensive assessment of global and regional seismic hazard we also describe other potential uses of the catalogue in many other fields of earth sciences we discuss the catalogue availability and lay out the plans of further development

distribution source and evolution of nitrate in a glacial till of southern alberta canada this paper addresses the distribution origin and controls upon nitrate in a 30 km2 area of the interior great plains region of southern alberta canada high concentrations of nitrate 100 mg l 1 no 3 n occurred in several isolated enclaves below the water table in brown weathered till nitrate concentrations of over 300 mg l 1 n were encountered in groundwater samples collected from these enclaves low nitrate concentrations 1 1 mg l 1 no 3 n were also encountered in the weathered till upgradient and downgradient of the nitrate enclaves groundwater samples collected from the underlying grey nonweathered till and bedrock had no 3 n concentrations of 1 1 mg l 1 through the application of geochemical no 3 n and nh 4 n studies environmental isotope studies tritium microbial analyses nitrifiers and laboratory experiments it was shown that the high nitrates found in the weathered till are the result of the oxidation of ammonium present within the tills it is postulated that this oxidation occurred during the holocene epoch when water tables were much lower than present day levels 5 18 m and 2 m below ground respectively through the use of eh measurements the enumeration of denitrifying bacteria and laboratory experiments the potential for denitrification was shown to exist below the present day water table in the weathered till as well as in the nonweathered till and bedrock isotopic data showed that less denitrification may be occurring within the nitrate enclaves than in adjacent downgradient areas

geological respiration of a mountain belt revealed by the trace element rhenium oxidation of rock derived petrogenic organic carbon ocpetro during weathering of sedimentary rocks is a major source of carbon dioxide co2 to the atmosphere this geological respiration is thought to be enhanced by physical erosion suggesting that mountain belts could release large amounts of co2 to counter the co2 sequestration achieved by the erosion riverine transfer and oceanic burial of organic carbon from the terrestrial biosphere however ocpetro oxidation rates in mountain belts have not been quantified here we use rhenium re as a proxy to track ocpetro oxidation in mountain river catchments of taiwan where existing measurements of physical erosion rate allow the controls on ocpetro oxidation to be assessed re has been shown to be closely associated with ocpetro in rocks and following oxidation during chemical weathering forms a soluble oxyanion reo4 which contributes to the dissolved load of rivers soils on meta sedimentary rocks in taiwan show that re loss is coupled to ocpetro loss during weathering confirming previous observations from soil profiles on sedimentary rocks elsewhere in taiwan rivers dissolved re flux increases with the catchment average sediment yield suggesting that physical erosion rate is a major control on ocpetro oxidation based on our current understanding of re mobility during weathering the dissolved re flux can be used to quantify an upper bound on the ocpetro oxidation rate and the associated co2 transfer the estimated co2 release from this mountain belt by ocpetro oxidation does not negate estimates of co2 sequestration by burial of biospheric oc offshore the findings are compared to oc transfers estimated for the himalaya where ocpetro oxidation in the mountain belt remains unconstrained together these cases suggest that mountain building in the tropics can result in a net sink of oc which sequesters atmospheric co2

tsunami sedimentation associated with the 1923 kamchatka earthquake abstract the kuril kamchatka region is notorious for the occurrence of earthquake tsunamis and historical documents show that they have caused repeatedly considerable damage since the 1750s the great tsunami generated in april 1923 around the northern kamchatka trench flooded the coast of ust kamchatsk depositing a thin sand layer which is traceable up to 3 km or more inland beyond the present coastline local government documents indicate that the 1923 tsunami flooded low lying coastal areas covered by thick snow the unusual process of tsunami run up without loss of tractive load is interpreted to have resulted from the smoothing of fields by the ice covered surface we conclude that the tsunami flooded snowfields and deposited an extensive sheet of sand a mixture of snow and seawater flooded over the area and caused damage to vegetation

the tsunami earthquake of 1932 june 22 in manzanillo mexico seismological study and tsunami simulations summary we conduct a detailed seismological study of the large colima mexico earthquake of 1932 june 3 and of its aftershocks of june 18 and 22 the latter event iii generated a tsunami more devastating than that of the main shock despite much smaller seismic magnitudes thus qualifying as a so called tsunami earthquake relocation based on published arrival times shows that event iii took place up dip of the main shock the analysis of the spectral amplitude of mantle surface waves yields low frequency moments of 24 5 2 and 4 times 1027 dyn cm respectively with event iii featuring a moment growing with period which expresses the source slowness characteristic of tsunami earthquakes this is confirmed by a deficient energy to moment ratio as derived from high frequency p waves recorded at pasadena near field hydrodynamic simulations show that the effects of the main shock s tsunami are well modelled by a standard seismic source whereas the stronger tsunami from event iii can be modelled by rupture along a splay fault in a mechanically deficient material all our results then fit the model for tsunami earthquake aftershocks proposed for the kuril islands by fukao in 1979

combining constraints from tsunami modeling and sedimentology to untangle the 1969 ozernoi and 1971 kamchatskii tsunamis 1 large tsunamigenic earthquakes occurred in 1969 mw 7 7 and 1971 mw 7 8 along the bering sea and northernmost pacific coast of kamchatka both resultant tsunamis were recorded on tide gauges but only the 1969 tsunami has cataloged observations of runup and these observations are limited and questionable we used a combination of field mapping of tsunami deposits and tsunami modeling to augment this historical record we mapped tsunami deposits above a d 1956 and 1964 volcanic ash layers along more than 200 km of shoreline however the 1969 and 1971 tsunami deposits are not distinguishable in the field the distribution of tsunami deposit elevation has two latitudinal peaks from 58 to 57 sediment runup typically ranges from 2 to 4 m decreasing to the south from 57 to 56 sediment runup typically ranges from 3 to 6 m maximum more than 10 m increasing to the south models of local runup for the 1969 and 1971 tsunamis explain most of the sediment distribution differentiate the two tsunamis in some localities and elucidate the earthquakes focal mechanisms and rupture areas

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

shallow subduction zone earthquakes and their tsunamigenic potential summary we have examined the source spectra of all shallow subduction zone earthquakes from 1992 to 1996 with moment magnitude 7 0 or greater as well as some other interesting events in the period range 1 20 s by computing moment rate functions of teleseismic p waves after comparing the source spectral characteristics of tsunami earthquakes earthquakes that are followed by tsunamis greater than would be expected from their moment magnitude with regular events we identified a subclass of this group slow tsunami earthquakes this subclass consists of the 1992 nicaragua the 1994 java and the february 1996 peru earthquakes we found that these events have an anomalously low energy release in the 1 20 s frequency band with respect to their moment magnitude although their spectral drop ov is comparable to those of the other earthquakes from an investigation of the centroid and body wave locations it appears that most earthquakes in this study conformed to a simple model in which the earthquake nucleates in a zone of compacted and dehydrated sediments and ruptures up dip until the stable sliding friction regime of unconsolidated sediments stops the propagation sedimentstarved trenches e g near jalisco can produce very shallow slip because the fault material supports unstable sliding the slow tsunami earthquakes also ruptured up dip however their centroid is located unusually close to the trench axis the subduction zones in which these events occurred all have a small accretionary prism and a thin layer of subducting sediment ocean surveys show that in these regions the ocean floor close to the trench is highly faulted we suggest that the horst and graben structure of a rough subducting oceanic plate will cause contact zones with the overriding plate making shallow earthquake nucleation and up dip propagation to the ocean floor possible the rupture partly propagates in sediments making the earthquake source process slow two factors have to be considered in the high tsunami generating potential of these events first the slip propagates to shallow depths in low rigidity material causing great deformation and displacement of a large volume of water second the measured seismic moment may not represent the true earthquake displacement because the elastic constants of the source region are not taken into account in the standard cmt determination

nitrogen isotope compositions of metasedimentary rocks in the catalina schist california implications for metamorphic devolatilization history abstract in the catalina schist subduction zone metamorphic complex california metasedimentary rocks show a decrease in n concentration and an increase in 15nair with increasing metamorphic grade lowest grade lawsonite albite rocks contain 632 185 ppm n with 15 n 1 9 0 6 whereas highgrade amphibolite equivalents contain 138 76 ppm n with 15 n 4 3 0 8 loss of n accompanied devolatilization reactions that evolved h2o rich c o h s n fluids through consumption of chlorite and phengitic white mica and production of mineral assemblages containing muscovite biotite garnet and kyanite whole rock n concentrations of up to 200 ppm in veins and pegmatites produced during high p t metamorphism reflect the redistribution of n during devolatilization and partial melting of the metasedimentary rocks bulk fluid rock n isotope fractionations 15n 15nfluid 15nrock of 1 5 1 were calculated with the rayleigh distillation equation taking into account variability in rock composition by comparison of samples with similar k2o concentrations these fractionations are similar to but slightly lower than published calculated fractionations for n2 nh4 exchange at the temperature range of 350 600 c over which most of the devolatilization occurred in the catalina schist approximately 3 4 to 2 25 the n systematics appear to be explained by n2 nh4 exchange and a devolatilization process intermediate in behavior to batch volatilization and rayleigh distillation the observed shifts in n concentration and 15n cannot be explained by nh3 nh4 exchange at these temperatures using the equilibrium models the distillation devolatilization process implicated in this study may govern the behavior of other trace elements partitioned into hydrous fluids during devolatilization e g b cs u similarity of the calculated fluid 15n 1 5 to 5 5 with compositions of natural gases inferred to be derived from metasedimentary sources indicates the possibility of using n as a tracer of large scale volatile transport

effects of bathymetry on tsunami propagation application of ray tracing to tsunamis ray tracing of seismic surface waves is applied to tsunami propagation to examine bathymetric effect along its propagation path computations are made for trans pacific tsunamis and for near field tsunamis in the japan sea for tsunamis across the pacific ocean the comparison to a uniform ocean shows that focusing and defocusing due to bathymetry are significant for some combinations of source and receiver for example the refraction of rays is predominant at the east pacific rise for the tsunami from chile the tsunamis in the japan sea are strongly affected by the shallow yamato rise the predicted arrival time and amplitude distribution generally agree with the observations from an actual tsunami since the computation can be made very quickly the method is useful for preliminary analysis of tsunami propagation such as in an operational warning system or in the determination of computational area for finite difference computation

hikurangi margin tsunami earthquake generated by slow seismic rupture over a subducted seamount abstract tsunami earthquakes generate much larger tsunami than their surface wave magnitude would suggest and are a problem for tsunami warning systems they are often not accompanied by intense or even strong ground shaking and hence do not provide a natural warning for self evacuation the lesser known 1947 offshore poverty bay and tolaga bay earthquakes along the east coast of the north island new zealand share many characteristics with other well known tsunami earthquakes including low amplitude shaking long durations and anomalously large tsunami however these two new zealand events are rare in that their source area has been imaged directly by long offset 2d seismic reflection profiles in this contribution we propose a source model for the 1947 offshore poverty bay tsunami earthquake recognising that the hypocentre occurs in a region where seismic reflection and magnetic data support the existence of a shallow m 7 earthquakes with complex low velocity rupture scenarios that enhance tsunami waves and their role in seismic hazard should not be under estimated

use of the mantle magnitude m m for the reassessment of the moment of historical earthquakes the mantle magnitudemm is used on a dataset of more than 180 wavetrains from 44 large shallow historical earthquakes to reassess their moments which in many cases had been previously estimated only on the basis of the earthquake s rupture area we provide 27 new or revised values ofmo based on the spectral amplitudes of surface waves recorded at a number of stations principally uppsala and pasadena among them and most significantly we document a large low frequency component to the source of the 1923 kanto earthquake the low frequency seismic moment is 2 9 1028 dyn cm in accord with geodetic observations on the other hand we revise downwards the seismic moment of the 1906 ecuador event which did not exceed 6 1028 dyn cm

near field survey of the 1946 aleutian tsunami on unimak and sanak islands the 1946 aleutian earthquake stands out among tsunamigenic events because it generated both very high run up near the earthquake source region and a destructive trans pacific tsunami we obtained new data on the distribution of its tsunami in the near field along south facing coasts between unimak pass on the west and sanak island on the east by measuring the height of driftwood and beach materials that were deposited by the tsunami above the extreme storm tide level our data indicate that 1 the highest measured run up which is at the scotch cap light house was 42 m above tide level or about 37 m above present storm tide elevation 2 run up along the rugged coast from scotch cap for 12 km northwest to sennett point is 12 18 m and for 30 km east of scotch cap to cape lutke it is 24 42 m 3 run up along the broad lowlands bordering unimak bight is 10 20 m and inundation is locally more than 2 km 5 run up diminishes to 8 m or less at the southeast corner of unimak island 6 no evidence was found for run up above present storm tides about 4 5 m above mllw on the ikatan peninsula or areas along the coast to the west and 7 run up above storm tide level in the sanak island group is restricted to southwest facing coasts of sanak long and clifford islands where it is continuous and locally up to 24 m high generation of the tsunami by one or more major earthquake triggered submarine landslides near the shelf edge south of unimak island seems to be the only viable mechanism to account for the data on wave arrival time run up heights and distribution as well as for unconfirmed anecdotal reports of local postquake increases in water depth and diminished bottom fisheries productivity a preliminary hydrodynamic simulation of the local tsunami propagation and run up using a dipolar model of a possible landslide off davidson bank provides an acceptable fit to the characteristics of the distribution of local run up with a value at 34 m at the scotch cap lighthouse

revel a model for recent plate velocities from space geodesy 1 we present a new global model for recent plate velocities revel describing the relative velocities of 19 plates and continental blocks the model is derived from publicly available space geodetic primarily gps data for the period 1993 2000 we include an independent and rigorous estimate for gps velocity uncertainties to assess plate rigidity and propagate these uncertainties to the velocity estimates the velocity fields for north america eurasia and antarctica clearly show the effects of glacial isostatic adjustment and australia appears to depart from rigid plate behavior in a manner consistent with the mapped intraplate stress field two thirds of tested plate pairs agree with the nuvel 1a geologic 3 myr average velocities within uncertainties three plate pairs caribbean north america caribbean south america and north america pacific exhibit significant differences between the geodetic and geologic model that may reflect systematic errors in nuvel 1a due to the use of seafloor magnetic rate data that do not reflect the full plate rate because of tectonic complexities most other differences probably reflect real velocity changes over the last few million years several plate pairs arabia eurasia arabia nubia eurasia india move more slowly than the 3 myr nuvel 1a average perhaps reflecting long term deceleration associated with continental collision several other plate pairs including nazca pacific nazca south america and nubia south america are experiencing slowing that began 25 ma the beginning of the current phase of andean crustal shortening

nitrogen isotope record of fluid rock interactions in the skiddaw aureole and granite english lake district the skiddaw granite and its contact metamorphic aureole in the english lake district provide an excellent opportunity to test the capability of the n isotope system to trace devolatilization and large scale transfer of crustal fluids in the aureole skiddaw group metasedimentary rocks with relatively uniform lithology and major element compositions show a dramatic decrease in n content toward the granite contact from or 800 ppm at distances 2 5 km from the contact to 1 5 km these rocks have extremely uniform delta 15 n air near 3 7 per mil whereas closer to the contact or 1 km delta 15 n is shifted to higher values up to 8 7 per mil the coupled decreases in n content and increases in delta 15 n are compatible with the removal of n having low delta 15 n in fluids during continuous prograde devolatilization reactions involving the break down of white mica and the stabilization of biotite cordierite and andalusite bearing assemblages in the same metasedimentary rocks the lack of obvious trends in major element concentrations including sio 2 tio 2 sio 2 al 2 o 3 and the ratios of other major oxides to tio 2 and al 2 o 3 with distance from the granitic contact is consistent with minimal change in major element composition during the contact metamorphism ratios of whole rock n b rb and ba concentrations to whole rock k 2 o content are believed to reflect the differing fluid mica partitioning and involving varying relative proportions of white mica and biotite of these trace elements during devolatilization reactions greisenized skiddaw granite from a borehole is enriched in n range of 17 225 ppm for whole rocks and white mica separates relative to the unaltered granite whole rock 30 ppm and has delta 15 n of 1 0 to 4 8 per mil the n concentrations and delta 15 n of the wall rocks and greisenized granites combined with c isotopic data carbonate and carbonaceous matter for the same rocks are consistent with the mobilization of fluids having low delta 15 n and delta 13 c pdb values from the devolatilized aureole into the cooling intrusive body such transport is consistent with the predictions of recent theoretical models of late stage hydrothermal evolution in cooling intrusive systems

the 2010 mw 7 8 mentawai earthquake very shallow source of a rare tsunami earthquake determined from tsunami field survey and near field gps data 1 the mw 7 8 october 2010mentawai indonesia earthquake was a tsunami earthquake a rare type of earthquake that generates a tsunami much larger than expected based on the seismicmagnitude itproducedalocallydevastatingtsunami withrunupcommonlyinexcess of 6 m we examine this event using a combination of high rate gps data from instruments located on the nearby islands and a tsunami field survey the gps displacement time series are deficient in high frequency energy and show small coseismic displacements 16 m our modeling results show that the combination of the small gps displacements and large tsunami can only be explained by high fault slip at very shallow depths far from the islands and close to the oceanic trench inelastic uplift of trench sediments likely contributed to the size of the tsunami recent results for the 2011 mw 9 0 tohoko oki earthquake have also shown shallow fault slip but the results from our study which involves a smaller earthquake provide much stronger constraints on how shallow the rupture can be with the majority of slip for the mentawai earthquake occurring at depths of 6 km this result challenges the conventional wisdom that the shallow tips of subduction megathrusts are aseismic and therefore raises important questions both about the mechanical properties of the shallow fault zone and the potential seismic and tsunami hazard of this shallow region

the 26 5 ka oruanui eruption new zealand an introduction and overview abstract the 26 5 ka oruanui eruption from taupo volcano in the central north island of new zealand is the largest known wet eruption generating 430 km3 of fall deposits 320 km3 of pyroclastic density current pdc deposits mostly ignimbrite and 420 km3 of primary intracaldera material equivalent to 530 km3 of magma erupted magma is 99 rhyolite and 90 pdc deposits range from mm to cm thick ultra thin veneers enclosed within fall material to 200 m thick ignimbrite in proximal areas the farthest travelled 90 km most energetic pdcs velocities 100 m s 1 occurred during phase 8 but the most voluminous pdc deposits were emplaced during phase 10 grain size variations in the pdc deposits are complex with changes seen vertically in thick proximal accumulations being greater than those seen laterally from near source to most distal deposits modern lake taupo partly infills the caldera generated during this eruption a 140 km2 structural collapse area is concealed beneath the lake while the lake outline reflects coeval peripheral and volcano tectonic collapse early eruption phases saw shifting vent positions development of the caldera to its maximum extent indicated by lithic lag breccias occurred during phase 10 the oruanui eruption shows many unusual features its episodic nature wide range of depositional conditions in fall deposits of very wide dispersal and complex interplay of fall and pdc activity

geochemical and tectonic uplift controls on rock nitrogen inputs across terrestrial ecosystems rock contains 99 of earth s reactive nitrogen n but questions remain over the direct importance of rock n weathering inputs to terrestrial biogeochemical cycling here we investigate the factors that regulate rock n abundance and develop a new model for quantifying rock n mobilization fluxes across desert to temperate rainforest ecosystems in california usa we analyzed the n content of 968 rock samples from 531 locations and compiled 178 cosmogenically derived denudation estimates from across the region to identify landscapes and ecosystems where rocks account for a significant fraction of terrestrial n inputs strong coherence between rock n content and geophysical factors such as protolith i e parent rock grain size and thermal history are observed a spatial model that combines rock geochemistry with lithology and topography demonstrates that average rock n reservoirs range from 0 18 to 1 2 kg n m 3 80 to 534 mg n kg 1 across the nine geomorphic provinces of california and estimates a rock n denudation flux of 20 92 gg yr 1 across the entire study area natural atmospheric inputs 140 gg yr 1 the model highlights regional differences in rock n mobilization and points to the coast ranges transverse ranges and the klamath mountains as regions where rock n could contribute meaningfully to ecosystem n cycling contrasting these data to global compilations suggests that our findings are broadly applicable beyond california and that the n abundance and variability in rock are well constrained across most of the earth system

diagenesis of ammonium during hydrocarbon maturation and migration wilcox group louisiana u s a abstract as organic matter matures n is released in the reduced form as nh4 and substitutes for k in clay minerals as oil forms an abundance of n is generated coincident with the formation of authigenic illite this study suggests that nh4 released from organic matter during maturation migrates through sandstones together with the pore fluids and volatile phases generated from the migrating crude oil this causes anomalously high nh4 substitution in authigenic illites fixed nh4 concentrations in illite are a product of both hydrocarbon maturation and migration concentrations of fixed nh4 from organic rich mudstones in two wilcox group oil fields show a general increase with depth coincident with increasing organic maturation reservoir sandstones containing crude oils have fixed nh4 concentrations as much as two times those of the mudstones when values are normalized to the quantity of clay minerals fixed nh4 concentrations in the gaseous portion of the reservoir are three times as high two out of five sandstones from a dry hole adjacent to a producing oil field contain anomalously high 2 above mean concentrations of fixed nh4 with respect to total organic centent this together with a high production index and hydrogen index in those units suggests that migrating hydrocarbons may have influenced the fixed nh4 concentrations

worldwide distribution of continental rock lithology implications for the atmospheric soil co2 uptake by continental weathering and alkalinity river transport to the oceans 1 the silicate rock weathering followed by the formation of carbonate rocks in the ocean transfers co2 from the atmosphere to the lithosphere this co2 uptake plays a major role in the regulation of atmospheric co2 concentrations at the geologic timescale and is mainly controlled by the chemical properties of rocks this leads us to develop the first world lithological map with a grid resolution of 1 1 this paper analyzes the spatial distribution of the six main rock types by latitude continents and ocean drainage basins and for 49 large river basins coupling our digital map with the gem co2 model we have also calculated the amount of atmospheric soil co2 consumed by rock weathering and alkalinity river transport to the ocean among all silicate rocks shales and basalts appear to have a significant influence on the amount of co2 uptake by chemical weathering

source discriminants for near field tsunamis summary we present numerical simulations of tsunami run up in the near field for a data set of 72 models of sources involving both seismic dislocations and landslides by varying one by one the parameters describing the source and the receiving beach we are able to separate their individual influence on the amplitude and distribution of run up which we characterize by forming several dimensionless parameters principally the ratio i 2 of its maximum amplitude to its lateral extent along the beach we find that i 2 remains less than 10 4 for seismic dislocation sources but is greater than this threshold for all physically realistic models of underwater landslides thus it can be used as a discriminant for the nature of the source of a near field tsunami for seismic dislocations we also consider the ratio i 1 of maximum run up to seismic slip on the fault plane and validate numerically the previously suggested rule of thumb that this ratio cannot be much greater than 1 in the case of underwater landslides we show that the distribution of near field run up is primarily controlled by the 2 d wall of water displaced on the ocean surface as an initial condition to the simulation and is practically independent of its extension in the third dimension perpendicular to the beach we apply this approach to nine profiles of tsunami run up obtained experimentally during recent field surveys and show that our method successfully identifies the 1998 papua new guinea tsunami as having been generated by an underwater landslide thus confirming the results of shipboard and hydroacoustic investigations it also strongly suggests a similar mechanism for the generation of the near field aleutian tsunami of 1946 april 1