antarctic link to deep flow speed variation during marine isotope stage 3 in the western north atlantic the western boundary undercurrent wbuc off eastern america is an important component of the atlantic meridional overturning circulation and is the principal route for southward transport of north atlantic waters and southward return of southern source water ssw here a direct flow speed proxy mean grain size of the sortable silt is used to infer the vigour of flow of the palaeo wbuc at blake outer ridge odp site 1060 depth 3481 m during marine isotope stage mis 3 the overall shape of the flow speed proxy record shows a complex pattern of variability with generally more vigorous flow and larger scale flow variations between 35 and 60 ka than in the younger part of mis 3 and mis 2 b35 ka six events of reduced bottom flow vigour slow events ses occur these appear uncorrelated with heinrich events but are instead synchronous with the warming phases of antarctic warm events a 1 to a 4 with one new one a 1a and one poorly defined a 0 this indicates that antarctic climate exerts a stronger control on deep flow vigour in the north atlantic during mis 3 than northern hemisphere climate the correspondence of ses with antarctic warming suggests a weaker wbuc flow due to reduced volume flux at ssw source or reduced ssw density because the variability of the lower limb of the wbuc was not connected to sharp north atlantic changes in temperature it is unlikely that the dansgaard oeschger cycles were associated with a mode of moc variation involving wholeocean overturn but more likely with perturbations of only the shallow glacial gulf stream glacial northern source intermediate water cell nutrient proxies benthic carbon isotopes and cd ca of uvigerina peregrina at this site show similar trends to the grip 18 o record this correlation has previously been attributed mainly to hydrographic and flow changes but is here shown to be better explained by variations in surface ocean productivity and subsequent decomposition of 12 c rich organic material on the

blake outer ridge late neogene variability in paleoceanography and deep sea biota article i nfo carbon isotope and benthic foraminiferal data from blake outer ridge a sediment drift in the western north atlantic ocean drilling program sites 994 and 997 water depth 2800 m document variability in the relative volume of southern component scw and northern component waters ncw over the last 7 ma scw was dominant before 5 0 ma at 3 6 2 4 ma and 1 2 0 8 ma whereas ncw dominated in the warm early pliocene 5 0 3 6 ma and at 2 4 1 2 ma the relative volume of ncw and scw fluctuated strongly over the last 0 8 ma with strong glacial interglacial variability the intensity of the western boundary undercurrent was positively correlated to the relative volume of ncw values of total organic carbon toc were n1 5 in sediments older than 3 8 ma and not correlated to high primary productivity indicators thus may reflect lateral transport of organic matter toc values decreased during the intensification of the northern hemisphere glaciation nhg 3 8 1 8 ma benthic foraminiferal assemblages underwent major changes when the sites were dominantly under scw 3 6 2 4 and 1 2 0 8 ma coeval with the last global extinction of elongate cylindrical deep sea benthic foraminifera which has been linked to cooling increased ventilation and changes in the efficiency of the biological pump these benthic foraminiferal turnovers were neither directly associated with changes in dominant bottom water mass nor with changes in productivity but occurred during global cooling and increased ventilation of deep waters associated with the intensification of the nhg

source scaling relationship for m 4 6 8 9 earthquakes specifically for earthquakes in the collision zone of taiwan we investigated the source scaling of earthquakes mw 4 6 8 9 mostly from the taiwan orogenic belt and made a global compilation of source parameters to examine the scaling self similarity finite fault slip models 12 dip slip and 7 strike slip using mainly dense strong motion data and teleseismic data from taiwan were utilized seven additional earthquakes m 7 were included for further ex amination of scaling of large events we determined the effective length and width for the scaling study was m0 l 2 and m0 l 3 for the events less than and larger than the seismic moment of 10 20 nm respectively regardless of the fault types suggesting a nonself similar scaling for small to moderate events and a self similar scaling for large events although the events showed variation in stress drops with the exception of three events with high stress drops most of the events had stress drops of 10 100 bars the observed bilinear relation is well explained by the derived magnitude area equation of shaw 2009 when we considered only events with stress drops of 10 100 bars and a seismogenic thickness of 35 km the bilinear feature of the regressed magnitude area scaling holds for ruptured areas up to about 1000 km 2 for our seismogenic thickness of 35 km for the events having rupture areas larger than that the average slip becomes proportional to the rupture length the distinct high stress drop events from blind faults in the western foothill of taiwan yield local high peak ground accelerations pgas when compared to the next generation attenuation model regardless of the relative small magnitudes of these events the high pgas give the region higher seismic hazard potential and thus require special attention for seismic hazard mitigation

strike slip earthquakes on quasi vertical transcurrent faults inferences for general scaling relations the recent occurrence of several large strike slip earthquakes provides the opportunity to review and complement available data on the scaling of seismic moment mo with length of rupture l for large earthquakes depending on their tectonic setting and mechanism for strike slip earthquakes on quasi vertical transcurrent faults the mo versus l relation has a significant change of slope around mo 0 6 0 8 1020 n m and for larger earthquakes mo scales linearly with l this is compatible with models where slip is controlled by the width of the fault also it appears to be easier to categorize large earthquakes by their mechanism strike slip on vertical transcurrent fault versus pure thrust normal than their tectonic setting interplate intraplate

effect of thermal pressurization on radiation efficiency abstract the radiation efficiency r is an important parameter showing the source property it is strongly affected by the variation in shear stress with slip thermal pressurization is considered to be a significant mechanism in controlling such a variation thus influencing r in this study the formula of r as a function of slip on the basis of two end member models of thermal pressurization that is the adiabatic undrained deformation aud model and slip on a plane sop model proposed by rice 2006 is derived the controlling parameters of the aud and sop models are respectively c and l which are dependent on thermal mechanical and hydraulic parameters of fault rocks modeled results suggest that thermal pressurization controls the variation in shear stress with slip and thus influences the radiation efficiency results show that r increases with the increasing rate of r with is high at small and low at large this indicates that r varies very much with for small earthquakes and only slightly depends on for large events for the two end member models r increases with decreasing c or l when c l r is higher for the aud model than for the sop model the thermal pressurization model is also applied to investigate the shear stress slip function in a 5 5 km square covering a drilled site on the fault plane of the 1999 chi chi taiwan earthquake inferred from seismograms results show that the aod model is more appropriate to describe the inferred shear stress slip function than the sop model and the proposed model is a modified one from the aud model by including a small amount of loss of frictional heat from the slip zone during faulting

a centennial scale record of vegetation and climate variability from 312 to 240 ka marine isotope stages 9c a 8 and 7e from tenaghi philippon ne greece abstract based on a new centennial scale resolution pollen record from the terrestrial site of tenaghi philippon ne greece we report a series of high amplitude millennial scale forest expansion events during the interval from 312 to 240 ka equivalent to isotopic substages c a of marine isotope stage mis 9 mis 8 and the onset of mis 7e pollen based indices support the climatic interpretation of the forest expansion events as indicators of abrupt increases in temperature and moisture availability in the mediterranean region long term changes in vegetation cover and composition during the studied interval permit the definition of glacial substages early middle and late analogous to the glacial substages of the last climatic cycle within this framework forest expansion events occurred during the early glacial equivalent to mis 9c a and the later part of the middle glacial mid to late mis 8 but are absent from the early part of the middle glacial early mis 8 forest expansion events are also detected during the lateglacial and onset of mis 7 associated with a millennial scale climate oscillation across the glacial interglacial transition i e termination iii t iii a peak for peak match between forest expansion events and antarctic temperature maxima suggests interhemispheric coupling of millennial scale climate variability via global oceanic circulation change and synergistic variability in atmospheric circulation consistent with the bipolar see saw the resolution of our record mean 290 yr also permits the characterisation of climate evolution over the course of interstadial episodes following forest expansion events and highlights differences in the characteristics of early and middle glacial interstadials saw tooth vs plateau profile these differences point to an influence of long term boundary conditions especially global ice volume on the characteristics of millennial scale events

younger dryas style cooling events at glacial terminations i vi at odp site 658 associated benthic δ13c anomalies constrain meltwater hypothesis high resolution planktonic and epibenthic stable isotope records from ocean drilling program site 658 off northwest africa provide a basis for a detailed study of glacial terminations i vi during the last 650 000 years the duration of the terminations was about one half to one quarter of an orbital precession cycle 5800 10 700 years when its amplitude was high at low amplitudes the terminations lasted longer than half an obliquity cycle 29 000 years marked climatic rebounds similar to the younger dryas each with a duration of 1000 2500 years subdivided all six terminations into distinct steps a b and c important parts of the deglacial steps were as brief as 700 1000 years the speed of climatic change suggests that special associations existed between orbital forcing and inherent instability of the ice sheets in harmony with published models the more rapid pulses of glacial meltwater incursions to the northern north atlantic led to one or more brief short term shut downs of north atlantic deep water formation this process is reflected by pronounced benthic 13c minima that precisely coincide in most cases with the end of the 18o deglaciation steps and immediately terminate with succeeding younger dryas style cooling events thus we conclude that the rebounds resulted from a short term antecedent estuarine circulation regime in the north atlantic except for the younger dryas itself which succeeded the allerod with its well ventilated atlantic deepwater circulation and hence continues to be an enigma

carbonate dissolution on the muir seamount western north atlantic interglacial glacial changes abstract although the history of carbonate dissolution has been studied for many years few records of dissolution through an entire glacial cycle are available for the western north atlantic north american basin using 14 cores from the muir and siboney seamounts located about 240 km northeast of bermuda changes in carbonate dissolution were examined over the last 125 000 years the core depth range spans more than 3000 m 1780 m 4980 m insuring that major changes in dissolution will be recorded weight percent carbonate was plotted as a function of water depth for five stratigraphically defined levels to determine temporal changes in the sedimentary lysocline and calcite compensation depth ccd during the holocene the lysocline is located between 4050 m and 4350 m the ccd is not pre ent even in the deepest sample 4980 m the late glacial 18 000 years b p lysocline may have shoaled to about 2500 m whereas during early glacial time 72 000 years b p it deepened to about 3400 m the mid glacial carbonate maximum 60 000 years b p interstadial is marked by a deepening of the lysocline to about 3800 m during the entire glacial episode the ccd aappears to have remained fixed at 4650 m the last interglacial 125 000 years b p was a time favorable to carbonate preservation the lysocline was deeper than 4650 m the deepest core containing sediments of this age increased glacial dissolution appears to result from changes in deep circulation the establishment of the ccd during glacial time is interpreted as indicating increased antarctic bottom water flow the lysocline on the other hand may reflect the degree of stagnation of north atlantic deep water

the largest instrumentally recorded earthquake in taiwan revised location and magnitude and tectonic significance of the 1920 event summary the ryukyu subduction is known to generate very few earthquakes in its central segment contrarily to its two extremities we focus in this study on the southernmost part of the ryukyu subduction zone offshore east taiwan our first task was to build a homogeneous earthquake cataloguefortheperiod1900 2007 thenewcatalogueprovideshomogenized m

middle pleistocene variations in palaeoclimate palaeoenvironment and vegetation of the las tablas de daimiel national park spain the middle pleistocene palaeoclimate and palaeoenvironment evolution of the las tablas de daimiel wetlands is described using a combination of sedimentology pollen and d 13 c and d 18 o isotopic records of unit b of core lt 199906 this unit mostly contains fluvial and palustrine sediments u th and amino acid racemization aar dating and a comparison of the d 18 o curve of unit b with oceanic records suggests that unit b spans the period from the end of marine isotope stage mis 10 340 ka to the first stages of mis 7 ca 210 ka mis 9 was characterised by a regional vegetation dominated by cupressaceae with pinus as a tree element the water level was high and temperatures were very probably higher than during the holocene mis 8 and the first substages of mis 7 7e 7d and 7c were dominated by xerophilous steppe vegetation in lowlands elevations around 610 m above sea level near to the wetland at higher altitudes far away from the wetland there were fewer pinus than in mis 9 and a greater presence of warm temperate and cool climate tree elements the aquatic system in mis 9 became shallower with eutrophication and the accumulation of organic matter occurring temperatures were similar to or lower than those of the holocene copyright 2011 john wiley sons ltd

suborbital scale surface and deep water records in the subtropical north atlantic implications on thermohaline overturn abstract we reconstruct millennial scale variations in sea surface hydrography and deep water flow in the northwestern subtropical atlantic ocean drilling program leg 172 sites 1056 and 1063 with a focus on marine isotope stage mis 9 together with published records from this region the new data also afford a longer term perspective on millennial scale changes in meridional overturning circulation spanning two full interglacial intervals mis 9 and 11 as well as two full glacial intervals mis 10 and 12 planktic foraminiferal 18o values indicate relatively stable conditions during the peak warmth of mis 9 but three large cold excursions disrupt the otherwise smooth transition toward glacial mis 8 there is no unique response in the site 1063 benthic foraminiferal 13c values that would suggest a concomitant decrease in the relative flux of nadw during these events similarly there is no persistent correlation between millennial scale variations in surface and deep water hydrography over the entire mis 8 13 interval while millennial scale variations at the sea surface are most pronounced during glacial intervals and the transitions toward glacial intervals millennial scale variations in the deep water hydrography tend to be largest during the warm periods this observation supports that rapid changes in thermohaline circulation are sensitive to driving forces other than those directly related to ice sheet size time series analysis shows that spectral power in the benthic foraminiferal 13c record contains periodicities related to the second 10 kyr and fourth harmonics 5 kyr of precession in this record 20 kyr pointing to the importance of tropical processes

depth profiles of δ13c in bottom water and core top c wuellerstorfi on the ontong java plateau and emperor seamounts we have measured the carbon isotopic composition of dissolved inorganic carbon in bottom waters of the ontong java plateau western equatorial pacific and on the northern emperor seamounts northwest pacific each of these locations is several hundred miles from the nearest geochemical ocean sections study geosecs stations and the observed 13c values at each site differ substantially from regionally averaged geosecs 13c profiles we discuss the possible causes of these differences including horizontal variability near bottom effects and problems with the pacific geosecs 13c data we also measured the isotopic composition c and o of core top c wuellerstorfi from a depth transect of cores at each location the 18o data are used to verify that our samples are holocene comparison of foraminiferal and bottom water 13c values shows that this species faithfully records bottom water 13c at both sites and demonstrates that there is no depth related artifact in the dissolved inorganic carbon c wuellerstorfi 13c relationship at these sites

synergistic approach for mapping debris covered glaciers using optical thermal remote sensing data with inputs from geomorphometric parameters abstract debris cover on glacier boundaries critically impedes the global inventorying of glaciers and confounds most of the techniques developed for semi automated mapping of glaciers debris on the glacier referred as supraglacial debris and that occurring outside the glacier boundaries referred as periglacial debris being derived from a common source i e the valley rock tend to have a similar spectral response in the reflection region which renders them mutually indistinguishable however there exist temperature differences between them this aspect has been considered in this remote sensing based study to distinguish between the supraglacial and periglacial debris in a test area in the chenab basin himalayas by inclusion of thermal infrared tir bands in remote sensing data processing a synergistic multisensor approach for the delineation of debris covered glacier boundaries is used here which integrates the inputs from thermal terra aster sensor and optical irs p6 awifs sensor remote sensing data multispectral classification techniques and the dem derived geomorphometric parameters the results of this study corroborate earlier findings on utilization of temperature differences as one of the parameters in glacial studies the proposed synergistic approach therefore appears useful in accurate mapping of debris covered glaciers in the himalayan region

deepwater source variations during the last climatic cycle and their impact on the global deepwater circulation the degree of similarity of the 13c records of the planktonic foraminiferal species n pachyderma and of the benthic foraminiferal genus cibicides in the high latitude basins of the world ocean is used as an indicator of the presence of deepwater sources during the last climatic cycle whereas continuous formation of deep water is recognized in the southern ocean the norwegian sea stopped acting as a sink for surface water during isotope stage 4 and the remainder of the last glaciation however deep water formed in the north atlantic south of the norwegian sea during the last climatic cycle as early as isotope substage 5d and this area was also the only active northern source during stages 4 2 a detailed reconstruction of the geographic distribution of 13c in benthic foraminifera in the atlantic ocean during the last glacial maximum shows that the most important deepwater mass originated from the southern ocean whereas the glacial north atlantic deep water cannot be traced south of 40 n at shallower depth an oxygenated 13c rich intermediate water mass extended from 45 n to 15 s in the pacific ocean a ventilation higher than the modern one was also found in open ocean in the depth range 700 2600 m and is best explained by stronger formation of intermediate water in high northern latitudes

sortable silt and fine sediment size composition slicing parameters for palaeocurrent speed and palaeoceanography fine sediment size 63 ixm is best measured by a sedimentation technique which records the whole size distribution repeated size measurement with intermediate steps of removal of components by dissolution allows inference of the size distribution of the removed component as well as the residue in this way the size of the biogenic and lithogenic noncarbonate fractions can be determined observations of many size distributions suggest a minimum in grain size frequency curves at 8 to 10 ixm the dynamics of sediment erosion deposition and aggregate breakup suggest that fine sediment behavior is dominantly cohesive below 10 1xm grain size and noncohesive above that size thus silt coarser than 10 ixm displays size sorting in response to hydrodynamlc processes and its properties may be used to infer current speed silt that is f mer than 10 ixm behaves in the same way as clay 2 xm useful parameters of the distribution are the 10 63 ixm mean size and the percentage 10 63 ixm in the fine fraction we cannot use size distributions to distinguish the nature of the currents therefore to infer water mass advection speeds i e the mean kinetic energy of the flow ku regions of high eddy kinetic energy ke must be avoided at the present such abyssal regions lie under the high surface k e of major current systems gulf stream kuroshio agulhas antarctic circmpolar current and brazil falldand currents in the argenthe basin this is probably a satisfactory guide for the pleistocene with regard to the carbonate subfraction of the size spectrum size modes due to both cocco iths and foramlnlferal fragments can be recognized and analyzed with the boundary between them again at about 10 lm the flux of less than 10 lm carbonate at pelagic sites above the lysocline is another candidate for a productivity indicator

caco3 dissolution in sediments of the ceara rise western equatorial atlantic we have used porewater sampling by in situ techniques including whole core squeezing as well as by shipboard sectioning and whole core squeezing to estimate the rates of sedimentary organic matter oxidation and caco3 dissolution at seven sites on the ceara rise in the western equatorial atlantic ocean porewater no3 profiles at all sites show a pattern indicative of active organic matter oxidation in the upper 15 20 cm of the sediments and in a buried organic rich layer the organic c oxidation rate generally decreases with increasing water depth from a value of 22 mol cm2 y at the shallowest site 3279 m to 14 mol cm2 y at the deepest site 4675 m over this depth range the bottomwaters vary from moderately supersaturated with respect to calcite to strongly undersaturated high resolution alkalinity profiles measured in porewaters collected by in situ whole core squeezing yield estimated ca2 fluxes of 11 mol cm2 y at a site located at the depth of the calcite saturation horizon and 7 6 zmol cm2 y at a moderately undersaturated site ca2 fluxes calculated from profiles in porewaters collected by relatively coarse resolution in situ sampling methods clearly indicate that there is caco3 dissolution above the calcite saturation horizon the dissolution of aragonite may contribute to the dissolution flux at the shallowest site these ca2 fluxes as well as fluxes estimated from a model of sedimentary organic matter oxidation and calcite dissolution indicate that 36 66 of the caco3 rain to the seafloor dissolves at sites at and above the calcite saturation horizon while 52 75 of the rain dissolves at sites below this depth when these results are incorporated into the oceanic caco3 budget of milliman 1993 they indicate that 35 of caco3 production is preserved in the deep sea they suggest a caco3 accumulation rate that is 27 lower than that estimated by milliman 1993 our corg oxidation caco3 dissolution model indicates that a large fraction of the caco3 dissolution that is occurring on the ceara rise is attributable to the neutralization of metabolic acids produced during organic matter oxidation the efficiency with which organic matter oxidation dissolves caco3 that is the ratio caco3 dissolution attributable to organic matter oxidation organic matter oxidation rate generally increases as degree of undersaturation of bottomwaters increases however there are deviations from the general trend that can be attributed to site to site variations in the kinetics of organic matter oxidation and calcite dissolution this result indicates that the dissolution of caco3 as a result of organic matter oxidation in the deep sea may mask the effects of variations in surface water caco3 productivity and bottomwater chemistry on the accumulation rate of caco3 in deep sea sediments

dynamics of atlantic water advection to the norwegian greenland sea a time slice record of carbonate distribution in the last 300 ky abstract short term variability in volume and configuration of atlantic water advection to the norwegian greenland sea ngs has recently been identified as a new and significant element for northern hemisphere glacial interglacial climatic fluctuations the amount of salt heat and moisture transferred by atlantic waters to the high arctic effectively influences northern hemisphere climates and is critical for the overall oceanic turnover rate in particular determining the extent and duration of atlantic water intrusions in the ngs is essential because of 1 its effect on the climate of the nordic continents and 2 its trigger function on the stability of the ice sheets with a weak inflows of atlantic water during glacials promoting an increase in ice volume by moisture supply to polar areas and b positive feed back mechanisms of atlantic water intrusions during ice sheet decay in this study the dynamics of surface water mass regimes in the ngs have been reconstructed for the past 300 ky by means of time slice compilations of calcium carbonate distribution and micropaleontologic proxies in addition carbonate preservation records are used to quantify deep water ventilation and production rates in contrast to the climap scenario but in accordance with many recent publications results of this study indicate that atlantic water advection was also a common feature during most glacial periods but varied strongly in volume and configuration significant modes recognized are 1 the full interglacial mode with a wide inflow of warm atlantic waters covering a broad area in the eastern sector of the ngs and extending far north combined with excellent carbonate preservation and very efficient deep water formation stages 1 and 5 5 1 2 the moderate interglacial mode with a rather small extension of atlantic waters along a narrow corridor in the southeastern sector of the ngs but still very efficient deep water exchange stages 9 isotopic events 7 5 7 3 7 1 5 3 and 5 1 3 pronounced cool phases during interglacials with only a very narrow inflow of atlantic waters into the southeastern ngs while the coastal areas off norway were still affected by iceberg drift substages 7 4 and 5 2 carbonate preservation records indicate ongoing deep water formation in the ngs 4 the normal glacial mode characterized by a variable but persistent inflow of cool temperate atlantic water lower stage 8 repetitively during stages 6 4 3 1 and 2 carbonate preservation records indicate ongoing deep water formation in the ngs 5 short glacial and deglacial periods characterized by episodic high inputs of ird evidenced by a wide coverage of diamicton deposition and strong carbonate dissolution e g episodically within stages 10 6 and 2 the 6 5 4 3 and 2 1 transitions some of these ngs diamicton layers correlate with heinrich layers in the north atlantic but generally ngs diamicton layers occur more frequently than heinrich layers the role of atlantic water influence during these events remains enigmatic but atlantic water influence is frequently found just above and below these sections a scenario with rapid ice sheet disintegration induced by atlantic water advection via increase of the thermal regime along the ice margin possibly triggered by small scale sea level rise might be envisaged more obviously the short term cessation of deep water formation in the ngs as evidenced by the dissolution spikes may be correlated with contemporaneous ventilation minima in the north atlantic

contrasting patterns of early twenty first century glacier mass change in the himalayas glaciers are among the best terrestrial climate indicators an important water resource in mountains1 2 and a major contributor to global sea level rise3 4 in the hindu kush karakoram himalaya region hkkh a paucity of appropriate glacier data has prevented a comprehensive assessment of current regional mass balance5 however there are indirect evidences of a complex pattern of glacial responses5 8 in reaction to heterogeneous climate change signals9 here we provide the first coherent data set of detailed glacier thickness changes over the hkkh during 2003 2009 by combining satellite laser altimetry and a global elevation model in the eastern central and south western parts of the hkkh glacier wastage is widespread with regional thinning rates up to 0 66 0 09 m a 1 in the jammu kashmir region conversely in the karakoram glaciers are close to balance with only a slight thinning of 0 07 0 04 m a 1 regionally averaged thinning rates under debris mantled ice are similar to those of clean ice despite insulation by debris covers the 2003 2008 specific mass balance for our hkkh study region is 0 21 0 05 m a 1 water equivalent we significantly less negative than the global average of 0 7 m a 1 we for glaciers and ice caps4 10 this difference is mainly an effect of the balanced glacier mass budget in the karakoram the corresponding hkkh sea level contribution is 0 035 0 009 mm a 1 amounting to 1 of the present day sea level rise11 our 2003 2008 mass budget of 12 8 3 5 gt a 1 is more negative than recent satellite gravimetry based estimates of 5 6 gt a 1 over 2003 2010 ref 12 for the mountain catchments of the indus and ganges basins13 the glacier imbalance contributes 3 5 and 2 0 respectively to the annual average river discharge13 and up to 10 for the upper indus basin14

paleoceanographic significance of sediment color on western north atlantic drifts ii late pliocene pleistocene sedimentation abstract color variations were interpreted in paleoceanographic terms for the late pliocene pleistocene sediments recovered by odp leg 172 on deep sea drifts at blake bahama outer ridge and northeastern bermuda rise the color derived parameters used in interpretation included predicted carbonate content terrigenous fluxes and hematite content abundance of upper carboniferous spores indicates that the hematite is probably derived from the permo carboniferous red beds of the canadian maritimes in the last 800 kyr sedimentation pattern changes on the blake bahama outer ridge were determined by the sediment delivery to the deep basin as well as circulation changes sediment delivery increased during glacials especially during the last 500 kyr and particularly since stage 6 a fundamental change in the thermohaline circulation occurred at about 500 ka corresponding to the end of the mid pleistocene transition period at the onset of the predominant 100 kyr climate cyclicity sedimentation related to wbuc had intensified at that time and had become more focused at depths below 3000 m changes in hematite content and sedimentation rate show a pulse of sediment via the st lawrence outlet at the pliocene pleistocene boundary suggesting that a likely change in the hydrography physiography of the laurentide ice sheet could have been involved in the climatic and ocean circulation changes at that time

empirical relationships between aftershock zone dimensions and moment magnitudes for plate boundary earthquakes in taiwan in this study we establish the empirical relationships between the spatial dimensions of the aftershock zones and moment magnitudes m w for the taiwan region the length l and width w of the aftershock zone of an earthquake is measured by the major and minor axes respectively of the ellipse of a two dimensional gaussian distribution of one day aftershocks our data is composed of 649 mainshocks depth 70 km m w 4 0 7 6 between 1990 and 2011 the relationships between aftershock zone dimensions and m w were obtained by least squares method with the corresponding uncertainties estimated by bootstrap our study confirms that aftershock zone dimensions are independent of faulting types and the seismic moment is proportional to l 3 the ratio w l increases slightly with m w and is independent of faulting types together with previous study our results suggest that earthquakes of both small m w 4 0 and large m w 7 0 magnitudes have similar focal zone geometrical parameters by using the m w s relation where the aftershock zone area s is estimated from l and w we also provide an independent examination of the variations in the median stress drop we find that the median stress drops of strike slip earthquakes are higher than those of thrust events moreover the median stress drops are independent of the moment magnitudes for normal and strike slip events but decrease for large thrust events these results are consistent with the latest global observations regardless of faulting types the median stress drop decreases for larger 6 m w 7 6 and relatively deep depth 60 70 km earthquakes online material effect of up dip rupture propagation on estimated maximum slip duration details on teleseismic and geodetic stations and figures of far field displacements temporal change in slip and snapshots of the semblance value distribution

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

fluctuations in deep western north atlantic circulation on the blake outer ridge during the last deglaciation variations in the mean grain size of the detrital silt fraction from four piston cores along a depth transect on the blake outer ridge were used to examine paleocirculation patterns and intensity between 2650 and 3818 m for the late pleistocene and holocene prior to 12 kyr circulation was focused on the upper part of the ridge above 2700 m and may have corresponded to enhanced levels of intermediate water production in the north atlantic deepwater circulation during deglaciation underwent a two step decrease to minimum speeds from 15 5 to 13 5 kyr followed by a three step increase to maximum speeds at 10 kyr minima in circulation at 13 5 and 12 kyr can be directly associated with oxygen isotopic evidence for advection of reduced salinity surface water to the north atlantic additional circulation minima at 15 and 10 5 kyr may also be the result of reduced salinity from high latitude meltwater discharge evidence for a drop to moderate circulation intensity during the holocene is supported by isolated geochemical records but could also be explained by decoupling of ocean ventilation rates from bottom circulation or a change in sediment provenance at the end of deglaciation

flow of glaciar moreno argentina from repeat pass shuttle imaging radar images comparison of the phase correlation method with radar interferometry high resolution radar images of glaciar moreno argentina acquired by the shuttle imaging radar c sir c on 9 and 10 october 1994 at 24 cm wavelength l band are utilized to map the glacier velocity both interferometrically and using the phase correlation method the precision of the interferometric ice velocities is 1 8 cm d 1 6 m a 1 1 the phase correlation method measures ice velocity with a precision of 14 cm d 1 50 m a 1 with image data at a 6 m sample spacing acquired 1 day apart averaged strain rates are measured with a precision of 10 4 d 1 at a 240 m sample spacing with the phase correlation method and 10 5 d 1 with radar interferometry the phase correlation method is less precise than radar interferometry but it performs better in areas of rapid flow is more robust to temporal changes in glacier scattering and measures the glacier velocity in two dimensions with only one image pair using this technique we find that glaciar moreno flows at 400 m a 1 in the terminal valley and 800 m a 1 at the calving front in agreement with velocities recorded a decade ago assuming steady state flow conditions the vertical strain rates measured by sir c are combined with prior data on mass ablation to estimate the glacier thickness and ice discharge the calculated discharge is 0 6 0 2 km3 ice a 1 at 300 m elevation and 1 1 0 2 km3 ice a 1 at the equilibrium line elevation 1150 m which yields a balance accumulation of 6 1m ice a 1

recession of the southern part of barnes ice cap baffin island canada between 1961 and 1993 determined from digital mapping of landsat tm changes along the margin of the southern half of the 5900 km 2 barnes ice cap have been assessed using 1993 landsat tm imagery in comparison with digitized 1 50 000 nts maps based on 1961 photogrammetry the average recession over the 183 km long southern perimeter was found to be at least 4 m a 1 with no significant difference between the southeast and southwest sectors viewed in conjunction with the sustained retreat previously reported for the northwest margin these results indicate that a general reduction in the size of barnes ice cap is occurring the present retreat phase began under a regional climate warming in the late 19th to early 20th century period and continues while the record of the ablation season temperature since the midcentury has not shown any significant trend

recent volume loss of british columbian glaciers canada 1 we use the shuttle radar topography mission srtm data and digital terrain models from aerial photography to quantify the change of glacier volume in british columbia bc canada for the period 1985 1999 we note substantial elevation bias in the srtm elevations typically on the order of 12 m km 1 the bias corrected thinning rate is 0 78 0 19 m a 1 which yields an annual volume loss of 22 48 5 53 km 3a 1 this rate of glacier volume loss is 65 of the estimate uncorrected for elevation bias 34 7 km 3a 1 and cautions against the use of uncorrected srtm data for glacier change studies glacier recession in bc could account for ca 0 67 0 12 mm of sea level rise over the period 1985 1999 0 05 0 009 mm yr 1 or about 8 3 of the contribution from mountain glaciers and ice caps the recent rate of glacier loss in the coast mountains 17 0 km 3a 1 is approximately double that observed for the previous two decades

the influence of organic matter diagenesis on caco3 dissolution at the deep sea floor abstract in situ benthic flux chamber measurements were performed at seafloor locations in the atlantic and pacific oceans where the bottomwaters were supersaturated approximately saturated and undersaturated with respect to calcite there was no evidence of significant dissolution at or above the saturation horizon below the saturation horizon however significant benthic fluxes of titration alkalinity and calcium out of the sediments were observed indicating appreciable dissolution where observed the rate of dissolution is consistent with a rate expression of reaction order 4 5 and a rate constant in the range of 0 05 to 0 5 per day a numerical simulation was constructed to represent organic matter and caco3 diagenesis at the seafloor at the supersaturated and near saturation sites the model over predicts the influence of metabolically produced co2 on the extent of caco3 dissolution it is possible that these results can be reconciled by a better understanding and parameterization of organic matter mineralization and porewater transport processes in surface sediments the primary factors to be considered include 1 the oxidation state of the carbon being oxidized 2 the vertical distribution of oxidation rates including the role of doc in sediment remineralization 3 the influence of nondiffusive transport of near surface porewaters and 4 the influence of episodic depositional events on organic and inorganic carbon cycling

the effect of slip variability on earthquake slip length scaling summary there has been debate on whether average slip d in long ruptures should scale with rupture length l o rwith rupture width w this scaling discussion is equivalent to asking whether average stress drop w hich is sometimes considered an intrinsic frictional property of af ault is approximately constant over a wide range of earthquake sizes in this paper we examine slip length scaling relations using a simplified 1 d model of spatially heterogeneous slip the spatially heterogeneous slip is characterized by a stochastic function with a fourier spectrum that decays as k w here k is the wavenumber and is a parameter that describes the spatial smoothness of slip we adopt the simple rule that an individual earthquake rupture consists of only one spatially continuous segment of slip i e earthquakes are not generally separable into multiple disconnected segments of slip in this model the slip length scaling relation is intimately related to the spatial heterogeneity of the slip linear scaling of average slip with rupture length only occurs when is about 1 5 which is a relatively smooth spatial distribution of slip we investigate suites of simulated ruptures with different smoothness and we show that faults with large slip heterogeneity tend to have higher d l ratios than those with spatially smooth slip the model also predicts that rougher faults tend to generate larger numbers of small earthquakes whereas smooth faults may have a uniform size distribution of earthquakes this simple 1 d fault model suggests that some aspects of stress drop scaling are a consequence of whatever is responsible for the spatial heterogeneity of slip in earthquakes

western north atlantic evidence for millennial scale changes in ocean circulation and climate two late quaternary series of high resolution percent carbonate data from western north atlantic sediment drifts bermuda rise and bahama outer ridge show millennial scale oscillations superimposed on the familiar longer period oscillations of orbital origin the dominant high frequency oscillation in these records has a quasi period of about 4000 years these percent caco3 changes most likely result from the influence of climate change on the flux of terrigenous material from eastern canada the resuspension of continental margin sediment by deep eddy kinetic energy and carbonate dissolution sediment is transported to the bermuda rise by deep recirculating gyres and to the bahama outer ridge by the deep western boundary current system stable isotope results on foraminifera across several of these oscillations from interstadial climate conditions and from a glacial inception display variability similar to that of percent caco3 oxygen isotope ratios of planktonic foraminifera suggest large variations in near surface temperature and or salinity and carbon isotope ratios of benthic foraminifera indicate that there were significant oscillations in the flux of north atlantic deep water nadw these data support models which couple surface ocean conditions in the north atlantic production of nadw north atlantic heat flux and evidence for temperature oscillations in ice cores

trends in caribbean paleoproductivity related to the neogene closure of the central american seaway abstract this study tests the hypothesis that the late miocene to early pliocene constriction and closure of the central american seaway cas connecting the tropical atlantic and east quatorial pacific eep caused a decrease in productivity in the caribbean due to decreased coastal upwelling and an end to the connection with high productivity tropical pacific waters the present study compared paleoceanographic proxies for the interval between 8 3 and 2 5 ma in 47 samples from south caribbean odp site 999 with published data on eep dsdp site 503 proxies for site 999 include the relative abundance of benthic foraminiferal species representing bottom current velocity and the flux of organic matter to the sea floor the ratio of infaunal epifaunal benthic foraminiferal species and benthic foraminifer accumulation rates bfars in addition we calculated resistant planktic foraminifers species and used the previously published sand fraction and benthic carbon isotope values from site 999 during early shoaling of the isthmus 8 3 7 9 ma the caribbean was under mesotrophic conditions with little ventilation of bottom waters and low current velocity the pre closure interval 7 6 4 2 ma saw enhanced seasonal input of phytodetritus with even more reduced ventilation and enhanced dissolution between 6 8 and 4 8 ma during the post closure interval 4 2 2 5 ma in the caribbean paleoproductivity decreased current velocity was reduced and ventilation improved while the seasonality of phytodetrital input was reduced dramatically coinciding with the establishment of the atlantic pacific salinity contrast at 4 2 ma our data support the hypothesis that late miocene constriction of the cas at 7 9 ma and its closure at 4 2 ma caused a gradual decrease in paleoproductivity in the caribbean consistent with decreased current velocity and seasonality of the phytodetrital input

scaling relations of earthquake source parameter estimates with special focus on subduction environment abstract earthquake rupture length and width estimates are in demand in many seismological applications earthquake magnitude estimates are often available whereas the geometrical extensions of the rupture fault mostly are lacking therefore scaling relations are needed to derive length and width from magnitude most frequently used are the relationships of wells and coppersmith 1994 derived on the basis of a large dataset including all slip types with the exception of thrust faulting events in subduction environments however there are many applications dealing with earthquakes in subduction zones because of their high seismic and tsunamigenic potential there are no well established scaling relations for moment magnitude and length width for subduction events within this study we compiled a large database of source parameter estimates of 283 earthquakes all focal mechanisms are represented but special focus is set on large subduction zone events in particular scaling relations were fitted with linear least square as well as orthogonal regression and analyzed regarding the difference between continental and subduction zone oceanic relationships additionally the effect of technical progress in earthquake parameter estimation on scaling relations was tested as well as the influence of different fault mechanisms for a given moment magnitude we found shorter but wider rupture areas of thrust events compared to wells and coppersmith 1994 the thrust event relationships for pure continental and pure subduction zone rupture areas were found to be almost identical the scaling relations differ significantly for slip types the exclusion of events prior to 1964 when the worldwide standard seismic network was established resulted in a remarkable effect on strike slip scaling relations the data do not show any saturation of rupture width of strike slip earthquakes generally rupture area seems to scale with mean slip independent of magnitude the aspect ratio l w however depends on moment and differs for each slip type

reply to comment on on scaling relations for large earthquakes by romanowicz and rundle from the perspective of a recent non linear diffusion equation linking short time deformation to long time tectonics

aftershock zone scaling we investigate the distribution of aftershock zones for large earthquakes scalar seismic moment m 10 19 5 n m moment magnitude m 7 mainshocks are selected from the harvard centroid moment tensor catalog and aftershocks are selected from the preliminary determination of epicenters neic catalog the aftershock epicenter maps are approximated by a two dimensional gaussian distribution the major ellipse axis is taken as a quantitative measure of the mainshock focal zone size the dependence of zone length l on earthquake size is studied for three representative focal mechanisms thrust normal and strike slip although the numbers of mainshocks available for analysis are limited maximum a few tens of events in each case all earthquakes show the same scaling m l 3 no observable scaling break or saturation occurs for the largest earthquakes m 10 21 n m m 8 therefore it seems that earthquake geometrical focal zone parameters are self similar

abyssal currents and advection of resuspended sediment along the northeastern bermuda rise abstract an integrated study using current meters time series nephelometers and water samplers for measurements of particulate matter concentration revealed an intense nepheloid layer centered on the slopes of the eastward scarp the northeastern boundary of the bermuda rise these slopes also contained extensive furrows truncated seismic reflectors and wisconsin age and older surface sediments the abyssal circulation in this region appears to be accelerated when it encounters the steep topography of the eastward scarp eroding sediments creating the erosional furrows and moving eroded sediment upslope instruments on top of the bermuda rise recorded episodic events benthic storms where particle concentrations at 25 m above the bottom increased from a background level of 60 g 1 1 to maximum of 251 g 1 1 and current velocities were nearly 20 cm s 1 net transport of both water and entrained sediment was to the west northwest during the largest benthic storm water temperature decreased by 0 1 c consistent with a 300 600 m upslope transport of water and resuspended sediments from the upper slopes of the eastward scarp when currents carry resuspended sediment over the rim of the eastward scarp to the plateau region the current slows depositing its sediment load thus the plateau is growing upwards slowly at the expense of the surrounding scarps

evidence for different scaling of earthquake source parameters for large earthquakes depending on faulting mechanism scaling relationships between seismic moment rupture length and rupture width have been examined for this purpose the data from several previous studies have been merged into a database containing more than 550 events for large earthquakes a dependence of scaling on faulting mechanism has been found whereas small and large dip slip earthquakes scale in the same way the self similarity of earthquakes breaks down for large strike slip events furthermore no significant differences in scaling could be found between normal and reverse earthquakes and between earthquakes from different regions since the thickness of the seismogenic layer limits fault widths most strike slip earthquakes are limited to rupture widths of between 15 and 30 km while the rupture length is not limited the aspect ratio of dip slip earthquakes is similar for all earthquake sizes hence the limitation in rupture width seems to control the maximum possible rupture length for these events the different behaviour of strike slip and dip slip earthquakes can be explained by rupture dynamics and geological fault growth if faults are segmented with the thickness of the seismogenic layer controlling the length of each segment strike slip earthquakes might rupture connected segments more easily than dip slip events and thus could produce longer ruptures than dip slip events of the same width

multi decadal glacier surface lowering in the antarctic peninsula from approximately 400 glaciers of the western antarctic peninsula no in situ records of mass balance exist and their recent contribution to sea level is consequently poorly constrained we seek to address this shortcoming by using surface elevations from usgs and bas airborne 1948 2005 and aster spaceborne 2001 2010 stereo imagery combined by using a rigorous semi automated registration approach to determine multi decadal glacier surface elevation changes in the western antarctic peninsula for 12 glaciers all observed glaciers show near frontal surface lowering and an annual mean lowering rate of 0 28 0 03 m yr at the lower portion of the glaciers during the 4 decades following the mid 1960s with higher rates for the glaciers in the north west parts of the antarctic peninsula increased lowering of up to 0 6 m yr can be observed since the 1990s in close correspondence to increased atmospheric positive degree days in all cases surface lowering reduces to zero within 5 km of the glacier front at around 400 m altitude this lowering may have been at least partially compensated for by increased high altitude accumulation

earthquake scaling fault segmentation and structural maturity abstract slip and length measurements on earthquakes suggest large stress drop variability we analyze an extended set of slip length measurements for large earthquakes m 6 to seek for the possible origin s of this apparent variability we propose that such variability arises from earthquakes breaking a variable number of major fault segments that number depends on the strength of the inter segment zones which itself depends on the structural maturity of the faults we propose new d max l parameterizations based on that idea of multiple segment ruptures in such parameterizations each broken segment roughly scales as a crack while the total multi segment rupture does not stress drop on individual segments is roughly constant only varying between 3 5 to 9 mpa the slight variation that is still observed depends on fault structural maturity more mature faults have lower stress drops than immature ones the new d max l functions that we propose reduce uncertainties with respect to available relationships they thus provide a more solid basis to estimate seismic hazard by integrating fault properties revealed by geological studies

pacific caco3 preservation and δ18o since 4 ma paleoceanic and paleoclimatic implications the pliocene pleistocene history of caco3 preservation in the central equatorial pacific is reconstructed from a suite of deep sea cores and is compared to fluctuations in global ice volume inferred from 18o records the results are highlighted by 1 a strong covariation between caco3 preservation and ice volume over 104 to 106 year time scales 2 a long term increase in ice volume and caco3 preservation since 3 9 ma demonstrated by a deepening of the lysocline and the carbonate critical depth 3 a dramatic shift to greater caco3 preservation at 2 9 ma 4 distinctive ice volume growth and caco3 preservation events at 2 4 ma which are associated with the significant intensification of northern hemisphere glaciation 5 a mid pleistocene transition to 100 kyr cyclicity in both caco3 preservation and ice volume and 6 a 600 kyr brunhes dissolution cycle superimposed on the late pleistocene glacial interglacial 100 kyr cycles caco3 preservation primarily reflects the carbonate chemistry of abyssal waters and is controlled by long term 106 year and short term 104 to 105 year biogeochemical cycling and by distinct paleoclimatic events we attribute the long term increase in caco3 preservation primarily to a fractionation of caco3 deposition from continental shelf to ocean basin and secondarily to a gradual rise in the riverine and glaciofluvial flux of ca on shorter time scales the fluctuations in caco3 preservation slightly lag ice volume fluctuations and are attributed to climatically induced changes in the circulation and chemistry of pacific deep water

a reappraisal of large earthquake scaling abstract twelve years ago i pointed out that observations indicate that the slip in large earthquakes scales with their length rather than their width as expected from the canonical model romanowicz 1992 has recently argued that more recent data show that the opposite is true which has obliged me to re examine the question i point out here a defining flaw in her analysis in that she allowed mo the moment at the cross over from small to large earthquakes to be a free variable in her curve fitting whereas this parameter can be defined independently when this parameter is independently fixed i find that the up dated data set confirms my earlier conclusion that for large crustal earthquakes m0 scales with l 2 a little over a decade ago i pointed out that obser vations indicate that the slip in large earthquakes scales with their rupture length scholz 1982 several sub sequent papers provided additional data supportive of this view chen and molnar 1983 shimazaki 1986 scholz et al 1986 large earthquakes are defined in this con text as those that rupture the entire seismogenic thick ness w0 and are thus constrained to propagate farther in a horizontal direction only for crustal earthquakes w0 is nearly constant 15 km so this scaling conflicts with conventional models of earthquakes such as dislocation models because they predict that slip scales with width which is invariant for these earthquakes i offered two alternative ways to interpret these observations one is that such conventional w models are correct but that stress drop could no longer be regarded as scale invariant but must scale with fault length as an alternative i sug gested the possibility of what i termed an l model in which slip intrinsically scales with fault length this created a minor crisis in seismology which has yet to be resolved it is no exaggeration to say that my l model suggestion has not attracted a noticeable coterie of admirers nor has my other suggestion and there has been no other model proposed in the interim that ex plains the observed l scaling although heaton 1990 has suggested a way in which length may scale with stress drop a variation of my w model scaling alternative in the face of this an alternative is to question the obser vations which is what romanowicz 1992 has recently chosen to do in her interpretation of an updated data set she concluded that seismic moment m0 scales lin early with rupture length l for large earthquakes which is consistent with w models and implies that slip u is scale invariant for large crustal earthquakes this great discrepancy with the earlier result she implies is due to the presence of superior modern measurements in the updated data set this issue has major implications both practical and theoretical and merits some debate here i present my own reappraisal of the data in which the conclusions are very different reappraisal of the data romanowicz s conclusions were based on a log log plot of m0 versus l for a data set of strike slip earth quakes she showed that the data in this figure could be better fit by two straight lines one with slope 3 in the lower scale range and one with slope 1 in the upper scale range than with a single line of slope 2 for small earth quakes which grow in both dimensions with l w m0 should scale with l 3 for large earthquakes where w has saturated at w0 and growth only occurs in the l di rection m0 should scale with l according to conven tional models hence the problem produced by my ob servation that m0 scales with l 2 for those events superficially then it appears that she has resolved the issue the problem however is that she has allowed the cross over length l which separates small from large earthquakes to be a free variable in her curve fitting ex ercise she thus obtains a cross over moment of 0 6 to 0 8 x 1020 n m which is appropriate for a rupture length of 60 to 70 km by adding an additional free parameter to the curve fitting one would expect a much better fit to be achieved the question is whether such a step is justified if small earthquakes grow with l w then the transition to large earthquakes defined as an event that ruptures the entire seismogenic thickness would be l w0 10 to 20 km for the data being studied this may be checked observationally because large earth quakes almost invariably nucleate near the base of the seismogenic layer das and scholz 1983 it follows that the transition to large earthquakes is at the length at which one begins to consistently see surface ruptures inspec tion of the earthquakes in romanowicz s 1992 figure 215

a 1 0 myr record of glacial north atlantic intermediate water variability from odp site 982 in the northeast atlantic changes in the intermediate water structure of the north atlantic were reconstructed using benthic foraminiferal 13c at ocean drilling program odp site 982 for the past 1 0 myr during most terminations of the late pleistocene melting of icebergs and low salinity surface waters caused production of glacial north atlantic intermediate water to cease resulting in decreased ventilation of the middepth north atlantic poor ventilation of intermediate water masses lasted well into some interglacial stages until upper north atlantic deep water nadw production resumed under full interglacial conditions the magnitude of benthic 13c minima and ice rafted debris maxima at terminations at site 982 generally match the degree of glacial suppression of nadw inferred from site 607 these processes may be related and controlled by the spatial and seasonal extent of sea ice cover during glaciations in the nordic seas

analysis of the relationship between seismic moment and fault length for large crustal strike slip earthquakes between 1977 92 we have used an uniform data set to determine the scaling relation between seismic moment m0 and fault length for 34 large crustal strike slip earthquakes in the period 1977 92 the seismic moments used were obtained by the centroid moment tensor analysis the aftershocks of each event were relocated in this study and the fault length estimated from their spatial extent for large events we find that in spite of some scatter in the data the trend of this uni form data set indicates that m0 c 2 our data set does not show any obvious change of slope around m0 6 8 x 102o n m as was seen in a previous non uniform data set in

mass loss of greenland s glaciers and ice caps 2003 2008 revealed from icesat laser altimetry data 1 the recently finalized inventory of greenland s glaciers and ice caps gic allows for the first time to determine the mass changes of the gic separately from the ice sheet using space borne laser altimetry data corrections for firn compaction and density that are based on climatic conditions are applied for the conversion from volume to mass changes the gic which are clearly separable from the icesheet i e have a distinct ice divide or no connection lost 27 9 10 7 gt a 1 or 0 08 0 03 mm a 1 sea level equivalent sle between october 2003 and march 2008 all gic including those with strong but hydrologically separable connections lost 40 9 16 5 gt a 1 0 12 0 05 mm a 1 sle this is a significant fraction 14 or 20 of the reported overall mass loss of greenland and up to 10 of the estimated contribution from the world s gic to sea level rise the loss was highest in southeastern and lowest in northern greenland

estimates of strain due to brittle faulting sampling of fault populations abstract the geometry of sampling domains is a first order consideration in the characterization of brittle fault populations in most cases descriptions of fault size distributions based on map cross section traverse or borehole data systematically underestimate the number of small faults present in a volume the geometry of sampling domains may be accounted for using an empirical proportionality between fault displacement and trace length estimates of strain in which the sampling geometry is considered suggest that small faults accommodate a significant portion of the total strain due to the brittle faulting process

changes in grain size and magnetic fabric at blake bahama outer ridge during the late pleistocene marine isotope stages 8 10 abstract odp sites 1055 1062 on the blake bahama outer ridge bbor are characterized by high sedimentation rates which allow high resolution analyses to reconstruct the behavior of the deep western boundary current dwbc as a function of depth along the bbor the odp sites provide an intermediate and deep water transect from 1800 to 4760 m water depths we focused on the time interval from 350 to 250 ka marine isotope stages mis 10 2 8 3 grain size and magnetic properties were analyzed with centennial to millennial scale time resolution integrating the results of grain size analyses lightness and magnetic properties the changes in the vertical position and the intensity of the dwbc core were inferred during glacial periods mis 10 2 and 8 4 8 3 the dwbc core was located at around 2200 m water depth whereas it deepened to 3000 m or more during warm periods interglacial stage 9 3 and interstadial 8 5 between these periods the dwbc core moved to shallower depth 2500 3000 m and its intensity increased which generally provided coarser sediments to a broad depth range from 2100 to 4800 m furthermore the magnetic properties imply that the dwbc supplied carbonate material other than terrigenous sediments to the deeper sites during mis 9 the depositional processes at site 1062 are characterized by sudden influxes of fine carbonate rich sediments which gradually decreased with time paleocurrent directions inferred from the direction of the great axis of the magnetic fabric are consistent with the modern topography at sites 1055 1056 1058 and 1060 during the relatively warm period from stages 9 3 to 8 5 at site 1062 the deepest site which exhibits a mud wave field the inferred flow direction is parallel to the bathymetric contours during warm periods while the nearly cross wave direction seemingly dominated during the other periods it appears that topographic position may have affected the scattering of azimuth plots moreover there is a possibility that the changes in flow direction correlate with climate changes

three dimensional glacial flow and surface elevation measured with radar interferometry outlet glaciers which serve to drain ice from ice sheets seem to be dynamically less stable in north greenland than in south greenland1 2 3 storstrommen a large outlet glacier in northeastern greenland which surged between 1978 and 1984 ref 2 has been well studied in general neither glacier surge mechanisms nor the geographical distribution of the surges are well known conventional satellite radar interferometry can provide large scale topography models with high resolution4 and can measure the radar line of sight component of ice flow vectors5 but cannot map full vector flow fields here we present an interferometry method that combines observations from descending and ascending satellite orbits which assuming ice flow parallel to the topographic surface allows us to use the differing view angles to estimate full three dimensional surface flow patterns the accuracy of our technique is confirmed by the good agreement between our radar based flow model and in situ global positioning system gps reference data at storstrommen radar measurements such as these made regularly and at high spatial density have the potential to substantially enhance our understanding of glacier dynamics and ice sheet flow as well as improve the accuracy of glacier mass balance estimates

pleistocene fluctuations in the western boundary undercurrent on the blake outer ridge the mean grain size of the detrital silt fraction was analyzed in two piston cores from the crest of the blake outer ridge using electronic particle analysis the resultant profiles in the two cores are highly correlatable and are interpreted to reflect the paleospeed of the western boundary undercurrent wbuc for the past 90 kyr the record can be divided into three periods the first encompasses the past 12 000 years and begins with an abrupt acceleration marking the transition from slow glacial to more vigorous holocene conditions the later holocene is a period of strong but variable flow the second period extends from 30 to 12 10 years and is characterized by a steady reduction of wbuc strength through the last ice age the current continued to decelerate until 12 10 years when the polar front finally retreated northward past the passages connecting the norwegian sea to the north atlantic the third period from 30 to about 90 10 years was a time of strong and variable flow that was independent of the glacial interglacial signal that is seen in the oxygen isotope record during this time the core of maximum flow appears to have shifted up and down the flank of the blake outer ridge and may have been influenced as much by salinity as by temperature variations in the source areas of the wbuc

earthquake scaling relations for mid ocean ridge transform faults 1 a mid ocean ridge transform fault rtf of length l slip rate v and moment release rate can be characterized by a seismic coupling coefficient ae at where ae v is an effective seismic area and at l3 2v 1 2 is the area above an isotherm tref a global set of 65 rtfs with a combined length of 16 410 km is well described by a linear scaling relation 1 ae at which yields 0 15 0 05 for tref 600 c therefore about 85 of the slip above the 600 c isotherm must be accommodated by subseismic mechanisms and this slip partitioning does not depend systematically on either v or l rtf seismicity can be fit by a truncated gutenberg richter distribution with a slope 2 3 in which the cumulative number of events n0 and the upper cutoff moment mc dcac depend on at data for the largest events are consistent with a self similar slip scaling dc ac1 2 and a square root areal scaling 2 ac at1 2 if relations 1 and 2 apply then moment balance requires that the dimensionless seismic productivity 0 0 atv should scale as 0 at 1 4 which we confirm using small events hence the frequencies of both small and large earthquakes adjust with at to maintain constant coupling rtf scaling relations appear to violate the single mode hypothesis which states that a fault patch is either fully seismic or fully aseismic and thus implies ac ae the heterogeneities in the stress distribution and fault structure responsible for relation 2 may arise from a thermally regulated dynamic balance between the growth and coalescence of fault segments within a rapidly evolving fault zone

pattern identification in the dynamic fingerprint of seismically active zones abstract the aim of this paper is to present a methodology designed to characterize seismically active areas from the point of view of their dynamic fingerprints which rely on space time aspects of seismicity patterns according to this methodology earthquake events are represented as points in phase space which leads to an events thread connecting the points in their temporal sequence a multi scale analysis procedure is applied to the events thread and scaling exponents are identified the proposed framework considers projections of the events thread corresponding to different spatial orientations for each orientation the events thread is characterized from the point of view of signal persistence the resulting persistence diagrams portray anisotropy aspects of the dynamic fingerprint the identification of anisotropic properties of the dynamic fingerprint provides a new perspective on seismically active zones complementing the information from geological and geophysical studies the paper describes the proposed methodological framework and presents applications focusing on two different regions the aleutian arc and hawaii

depositional changes along the blake bahama outer ridge deep water transect during marine isotope stages 8 to 10 links to the deep western boundary current odp sites 1055 1062 recover a bathymetric transect from 1800 to 4800 water depth in the subtropical nw atlantic carolina slope blake bahama outer ridge this sediment drift region is known for high deposition rates 40 cm kyr and offers the excellent opportunity to investigate the history of water mass circulation and chemistry as well as depositional changes during the quaternary a late pleistocene time interval from 250 to 350 kyr marine isotope stages 8 10 was investigated with centennial to millennial scale time resolution stable isotope records of benthic foraminifera provide new detailed insights on variations in climate and deep water ventilation the 13c records indicate well ventilated north atlantic water masses between 2200 and 3000 m water depth during the time interval from stage 9 to interstadial 8 5 during the glacial stages 8 4 and 10 2 however the decrease in 13c reflects an extension of nutrient rich antarctic bottom water aabw up to 2200 m water depth this is paralleled by a shoaling of the lysocline as indicated by the carbonate records a comparison between carbonate dissolution proxies points out that the carbonate dissolution at the hemipelagic sites was not only influenced by the different carbonate ion concentration of the water masses aabw contra north atlantic deep water but also by the organic carbon flux to the sea floor especially at the shallower sites whereby the decay of organic matter enhanced carbonate dissolution in the sediments additionally the varying depth position and strength of the deep western boundary current dwbc plays an important role on the depositional system along the blake bahama outer ridge comparisons between current intensities as inferred from grain size analyses sand and carbonate contents suggest that high intensities of the dwbc during cold stages caused an erosion of the fine carbonate and an enrichment of the sand fraction at shallower depth during warm stages the main core of dwbc moved to greater depth and allowed the settling of finer material at shallower depth synchronously this led to an increased supply of carbonate and extremely high carbonate concentrations below 3500 m water depth

the glaciers climate change initiative methods for creating glacier area elevation change and velocity products glaciers and their changes through time are increasingly obtained from a wide range of satellite sensors due to the often remote location of glaciers in inaccessible and high mountain terrain satellite observations frequently provide the only available measurements furthermore satellite data provide observations of glacier characteristics that are difficult to monitor using ground based measurements thus complementing the latter in the glaciers cci project of the european space agency esa three of these characteristics are investigated in detail glacier area elevation change and surface velocity we use a data from optical sensors to derive glacier outlines b digital elevation models from at least two points in time c repeat altimetry for determining elevation changes and d data from repeat optical and microwave sensors for calculating surface velocity for the latter the two sensor types provide complementary information in terms of spatio temporal coverage while c and d can be generated mostly automatically a and b require the intervention of an analyst largely based on the results of various round robin experiments multi analyst benchmark studies for each of the products we suggest and describe the most suitable algorithms for product creation and provide recommendations concerning their practical implementation and the required post processing for some of the products area velocity post processing can influence product quality more than the main processing algorithm

scaling differences between large interplate and intraplate earthquakes a study of large intraplate earthquakes with well determined source parameters shows that these earthquakes obey a scaling law similar to large interplate earthquakes in which m 0 l 2 or u l where l is rupture length and u is slip in contrast to interplate earthquakes for which 1 10 5 for for the intraplate events 6 10 5 which implies that these earthquakes have stress drops about 6 times higher than interplate events this result is independent of focal mechanism type this implies that intraplate faults have a higher frictional strength than do plate boundaries and hence that faults are velocity or slip weakening in their behavior this factor may be important in producing the concentrated deformation that creates and maintains plate boundaries

on scaling of earthquake faults abstract scaling relations among seismic moment m 0 average displacement rupture width w and rupture length l of earthquake faults are studied mainly using the data base of earthquake source parameters compiled by wells and coppersmith 1994 results show that seismic moment scales with rupture length approximately as m 0 l 2 rupture width is independent of rupture length for large earthquakes average displacement relates to rupture length approximately as l and the average displacement is independent of rupture width consequently the l model proposed by scholz 1982 is more appropriate than the w model suggested by romanowicz 1992 to describe the scaling of earthquake faults

size distributions for large and small earthquakes small and large earthquakes obey different scaling laws and inhabit distinct populations both characterized by power laws with different exponents when considering earthquakes on a single fault or fault segment the one large earthquake that occurs during a seismic cycle is discontinuous with the population of small earthquakes here it is shown that these two observations together with the scaling laws are self consistent when proper account is taken of the size distribution of faults

comparison of satellite derived with ground based measurements of the fluctuations of the margins of vatnajokull iceland 1973 92 vatnajokull iceland is the earth s most studied ice cap and represents a classical glaciological field site on the basis of s palsson s seminal glaciological field research in the late 18th century since the 19th century vatnajokull has been the focus of an array of glaciological studies by scientists from many nations including many remote sensing investigations since 1951 landsat derived positions of the termini of 11 outlet glaciers of vatnajokull were compared with frontal positions of six of these 11 outlet glaciers determined by field observations during the period 1973 92 the largest changes during the 19 year period 1973 92 occurred in the large lobate surge type outlet glaciers along the southwestern western and northern margins of vatnajokull tungnaarjokull receded 1413 112 m 1380 1 m from ground observations and bruarjokull receded 1975 191 m 2096 5 m from extrapolated ground observations between 1973 and 1992 satellite images can be used to delineate glacier margin changes on a time lapse basis if the glacier margin can be spectrally discriminated from terminal moraines and sandur deposits and if the advance recession is larger than maximum image pixel size local knowledge of glaciers is critically important however in the accurate delineation of glacier margins on landsat images

north atlantic thermohaline circulation during the past 20 000 years linked to high latitude surface temperature during a surface cooling event 10 000 to 12 000 years ago higher cd ca and lower 13c 12c ratios are observed in benthic foraminifera shells from rapidly accumulating western north atlantic sediments data from sediment cores show that marked nutrient depletion of intermediate waters occurs in association with reduced glacial north atlantic deep water flux it is proposed that cold high latitude sea surface temperatures enhance intermediate water formation at the expense of deep water formation

transport and bottom boundary layerobservations of the north atlantic deep western boundary current at the blake outer ridge abstract the north atlantic deep western boundary current dwbc was surveyed at the blake outer ridge over 14 days in july and august 1992 to determine its volume transport and to investigate its bottom boundary layer bbl this site was chosen because previous investigations showed the dwbc to be strong and bottom intensified on the ridge s flanks and to have a thick bbl the primary instrument used was the absolute velocity profiler a free falling velocity and conductivity temperature depth device in two sections across the width of the dwbc volume transports of 17 1 sv and 18 1 sv were measured for all water flowing equatorward below a potential temperature of 6 c 1 sv 1 10 6 m 3 s 1 transport values were derived using both absolute velocities and avp referenced geostrophic velocities and were the same within experimental uncertainty good agreement was found between our results and historical ones when both were similarly bounded and referenced although this was a short term survey the mean of a 9 day time series of absolute velocity profiles was the same as the means of year long current meter records at three depths in the same location a turbulent planetary bbl was found everywhere under the current the thickness of the bottom mixed layer bml where concentrations of density nutrients and suspended sediments were vertically uniform was asymmetrical across the current and up to 5 times thicker than the bbl there was no velocity shear above the bbl within the thicker bmls and the across slope density gradient was very small the extra thick bml is perhaps maintained by a combination of processes including turbulence downwelling ekman transport a weak up slope return flow above the bbl and buoyant convection from the bbl into the bml the frictional bottom stress was mostly balanced by a down stream change in the current s external potential energy evidenced by a drop in the velocity core of the current

mass loss of larsen b tributary glaciers antarctic peninsula unabated since 2002 ice mass loss continues at a high rate among the large glacier tributaries of the larsen b ice shelf following its disintegration in 2002 we evaluate recent mass loss by mapping elevation changes between 2006 and 2010 11 using differencing of digital elevation models dems the measurement accuracy of these elevation changes is confirmed by a null test subtracting dems acquired within a few weeks the overall 2006 2010 11 mass loss rate 9 0 2 1 gt a 1 is similar to the 2001 02 2006 rate 8 8 1 6 gt a 1 derived using dem differencing and laser altimetry this unchanged overall loss masks a varying pattern of thinning and ice loss for individual glacier basins on crane glacier the thinning pulse initially greatest near the calving front is now broadening and migrating upstream the largest losses are now observed for the hektoria green glacier basin having increased by 33 since 2006 our method has enabled us to resolve large residual uncertainties in the larsen b sector and confirm its state of ongoing rapid mass loss

relationship between seismic moment and source duration for seismogenic earthquakes in taiwan implications for the product of static stress drop and the cube of rupture velocity a systematic analysis of the source duration and seismic moment m0 for seismogenic earthquakes mw 5 5 7 1 in the taiwan region was completed by using a teleseismic p wave inversion method irrespective of the source self similarity the m0 relationship derived in this study had a power law form namely m0 3 under the assumption that vr3 is constant following a circular fault model static stress drop vr rupture velocity for taiwan s earthquakes the derived m0 relationship not only provides information to predict the source duration of large earthquakes but also probes the rupture features of seismogenic earthquakes that is there are different rupture patterns for earthquakes but the product vr3 remains nearly constant

glacier surface velocities in alpine terrain from optical satellite imagery accuracy improvement and quality assessment the worldwide retreat of mountain glaciers has important consequences for the water food and power supply of large and densely populated areas in south and central asia successful mitigation of the hydrological impacts on societies as well as assessing glacier related hazards require large scale monitoring of glacier dynamics however detailed glaciological data from the asian highlands are lacking due to its size and difficult accessibility we have applied a novel technique for precise orthorectification co registration and sub pixel correlation of advanced spaceborne thermal emission and reflection radiometer aster satellite imagery to derive surface velocities of himalayan glaciers our approach allows for the correction of offsets due to attitude effects and sensor distortions as well as elevation errors if a digital elevation model dem from the shuttle radar topography mission srtm was used for orthorectification after post processing the error on the displacements is on the order of 2 4 m per correlation translated into annual velocities this error is reduced increased when the correlated images are more less than a year apart through application of a filtering procedure and several quality tests the consistency of the results is validated to provide confidence in the remotely sensed velocity measurements despite the lack of ground control this novel approach allows fast easy and economically viable acquisition of detailed glaciological data in areas of difficult access and provides a means for large scale monitoring of glaciers in high mountainous terrain

controls on modern carbonate preservation in the southern florida straits abstract the water masses in the florida straits and bahamas region are important sources for the northern atlantic surface ocean circulation in this study we analyse carbonate preservation in surface sediments located above the chemical lysocline in the florida straits and bahamas region and discuss possible reasons for supralysoclinal dissolution calcite dissolution proxies such as the variation of the foraminiferal assemblage fragmentation index benthic foraminifera index and resistance index displayed a good preservation in both areas the pteropod species limacina inflata showed very good preservation in sediments of inter platform channels from the great bahama bank providence channel exuma sound above the aragonite lysocline supralysoclinal aragonite dissolution however was observed at two water depth levels 800 1000 m and below 1500 m in the florida straits our observations suggest that the supralysoclinal dissolution in the florida straits is due to the degradation of organic material the presence of antarctic intermediate water aaiw may be a contributing factor for the significant aragonite dissolution in 800 1000 m the comparison of modern preservation patterns of the surface sediments with hydrographical measurements shows that the l inflata dissolution index ldx might be an adequate proxy to reconstruct paleo water mass conditions in an area which is highly saturated with respect to calcium carbonate

climatic effects of reduced arctic sea ice limits in the giss ii general circulation model in this paper we present results of an atmospheric general circulation model gcm experiment in which arctic sea ice limits were substantially reduced in all months march sea ice limits were set equivalent to modern september limits and all sea ice was removed in september sea ice coverage for other months varied between these two extremes this climate sensitivity experiment makes predictions about mean northern hemisphere atmospheric conditions including temperature pressure wind patterns and precipitation consistent with these boundary constraints the major effects of reduced sea ice limits are observed in winter they include large regional warming of the circum arctic region northward migration of the icelandic low pressure system and strengthening of the azores high changes in net heating over the north atlantic ocean suggest that increases in sea surface temperatures and salinities in this region would also accompany reductions in arctic sea ice limits in the wind field a weakening of the polar easterlies and an intensification of cyclonic circulation over the norwegian greenland sea suggest that surface water exchange between the atlantic and arctic would increase when sea ice limits are reduced however zonally averaged changes in strength of the westerlies or upper level jet stream are minimal the late pliocene cooling of the north atlantic ocean and north american arctic margin may have been linked in part to the development of perennial sea ice cover

comment on on scaling relations for large earthquakes by b romanowicz and j b rundle from the perspective of a recent nonlinear diffusion equation linking short time deformation to long time tectonics

ice loss rates at the northern patagonian icefield derived using a decade of satellite remote sensing abstract we use a satellite based survey of glacier surface elevation changes speeds and surface melt conditions between 2000 and 2011 to quantify mass loss from the northern patagonian icefield npi chile a history of ice elevation change is found by differencing aster digital elevation models dems relative to a void filled version of the dem collected by the shuttle radar topography mission srtm in february 2000 thinning rates have accelerated at lower elevations while above the equilibrium line altitude ela recent thinning rates are not significantly different from those observed in previous studies a volumetric change of 4 06 0 11 km 3 yr is found by summing surface elevation changes over all glaciers in the npi this is regarded as a lower bound because volume loss due to frontal retreat and sub aqueous melting is not included this volume change is converted to a mass loss of 3 40 0 07 gt yr taking into account density differences above and below the equilibrium line we find that the npi is providing at least 0 009 0 0002 mm yr to ongoing sea level change in agreement with previous estimates sub pixel offset tracking of aster image pairs is used to produce glacier displacements over intervals typically ranging from 6 days to 18 months the first whole icefield composite velocity map is presented the terminus of the san rafael glacier on the western side of the npi sustained a peak calving front speed of 19 7 1 2 m day for 7 days in the austral fall of 2007 passive microwave observations indicate that the surface of the accumulation basin of the glacier was wet during this period of rapid motion suggesting that the fast speed may be a consequence of a rise in sub glacial water pressure sourced from melt or rainwater making its way to the glacier bed and reducing basal friction several other outlet glaciers including the benito and hpn1 glaciers on the isolated western side of the icefield accelerated while thinning between 2007 and 2011 marked acceleration also occurred after 2007 at the front of the san quintin glacier the largest outlet glacier of the npi the paucity of thickness measurements at the outlet glaciers means it is impossible to accurately gauge the mass flux of the icefield and thus give a full estimate of the mass balance

changes in east atlantic deepwater circulation over the last 30 000 years eight time slice reconstructions using 95 epibenthic 13c records eight time slices were reconstructed to trace the distribution of east atlantic deepwater and intermediate water masses over the last 30 000 years our results show that there have been three distinct modes of deepwater circulation near the stage 3 2 boundary the origin of north atlantic deep water nadw was similar to today mode 1 however after late stage 3 the source region of the nadw end member shifted from the norwegian greenland sea to areas south of iceland mode 2 a reduced nadw flow persisted during the last glacial maximum with constant preformed 13c values the nutrient content of nadw increased markedly near the azores fracture zone from north to south probably because of the mixing of upwelled antarctic bottom water aabw from below which then advected with much higher flux rates into the northeast atlantic later the spread of glacial meltwater over the north atlantic led to a marked short term ventilation minimum below 1800 m about 13 500 14c years ago mode 3 the formation of nadw recommenced abruptly north of iceland 12 800 12 500 years ago and reached a volume approaching that of the holocene in the younger dryas 10 800 10 350 years b p another short term shutdown of deepwater formation followed between 10 200 and 9 600 years b p linked to a further major meltwater pulse into the atlantic each renewal of deepwater formation led to a marked release of fossil co2 from the ocean the likely cause of the contemporaneous 14c plateaus over the last 9000 years deepwater circulation varied little from today apart from a slight increase in aabw about 7000 14c years ago it is also shown that the oxygenated mediterranean outflow varied largely independent of the variations in deepwater circulation over the last 30 000 years

higher order interrelations between seismogenic structures and earthquake processes abstract aki k 1992 higher order interrelations between seismogenic structures and earthquake processes in t mikumo k aki m ohnaka l j ruff and p k p spudich guest editors earthquake source physics and earthquake precursors tectonophysics 211 1 12 to advance our understanding of higher order smaller scale interrelations between the fault zone structure and the earthquake process we start with the observation that the source parameters of major california earthquakes deviate systematically from the self similarity this departure from the self similarity is interpreted in terms of both the specific barrier model and the asperity model the asperity model however is found to be inconsistent with the following observations 1 sharp impulsive displacements waveform in the direction perpendicular to the fault trace 2 the complementary relationship between fault slip and aftershock and 3 existence of barriers in the creeping segment of the san andreas fault the application of the specific barrier model on the other hand leads to a predominant subevent crack size of a few hundred meters in the creeping segment this result is consistent with the negative correlation between coda q 1 and b value observed in the stone canyon area for 1 5 3 temporal increase in coda q 1 is sometimes accompanied by an increase in the rate of surface deformation but not always so this is attributed to the erratic coupling between the creeping brittle region and the overlying brittle region the applicability of the conclusions obtained from california earthquakes to other regions is investigated using the observed scaling laws of seismic source spectra and it is suggested that the crack size of the creeping brittle zone may vary regionally from a few hundred meters to a few kilometers as an alternative to the widely held view that the aseismic creep in the plate boundary may occur as a giant slow earthquake our result suggests that it may be occurring as small fractures with scale lengths from a few hundred meters to a few kilometers

magnitude distributions and slip scaling of heterogeneous seismic sources abstract a series of numerical experiments have been conducted to explore effects of strength heterogeneity and rupture propagation upon the average slip and magnitude distributions of earthquakes alternative rupture processes were represented by two possible sets of rules controlling rupture propagation ruptures were run on faults having strong patches that break to form subevents with various assumed stress drops the subevents have a truncated power law size distribution the rules controlling rupture propagation in combination with the subevent stress drop have a strong effect upon the magnitude distribution the most realistic rupture model favors ruptures whose length and width are comparable and produces an increase in b value for events above magnitude 7 5 magnitude distributions similar to observations of global seismicity are produced by models with subevents that have a stress drop near 100 mpa the relationship between seismic moment and rupture area also agrees with observations of events not from subduction zones when the same model that fits the global magnitude distribution is adapted for a narrower fault width

changes in glacier extent in the eastern pamir central asia determined from historical data and aster imagery abstract historical surveys and recent satellite imagery are used to map and assess glacier recession in the eastern pamir over the last three decades for this study we used topographic maps of 1 100 000 scales published in 1943 and 1970 air photos from 1978 and 1990 space images from russian satellites in 1972 1978 1980 and 1990 and aster data for 2001 climatic records from the fedtchenko glacier station 4156 m a s l 38 83 n 72 22 e and murgab meteorological station 3576 m a s l 38 17 n 73 97 e are used for analysis of the climate conditions in the region changes in the area of 5 glaciers and terminus positions of 44 glaciers in the eastern pamir reveal an accelerating trend since the end of the 1970s through 2001 as a continuation of glacier wastage and retreat since at least the end of the little ice age the glacier area decreased 7 8 during 1978 1990 and 11 6 in 1990 2001 this corresponds with documented changes in other mountain and subpolar regions in the northern hemisphere and specifically in central asia glacier changes in the eastern pamir are a response to increasing summer temperatures we find decreases in glacier area and retreat of glacier fronts increased debris covered area and the appearance of new lakes

classification of seismic strain estimates in the mediterranean region from a bootstrap approach summary the uncertainty that may affect seismic strain estimates in the mediterranean is investigated using a distribution free numerical approach based on the bootstrap resampling technique applied to more than 2000 seismic source mechanisms of shallow earthquakes that occurred from the azores to iran in the period 1905 1999 this analysis shows that the short time interval covered by the available data set may be the main source of uncertainty on long term strain estimates since it could imply a biased representation of contributions from large earthquakes our results also indicate that as a possible consequence of this bias the condition of strain field uniformity is poorly verified in most of the zones considered the confidence limits obtained for scalar strains and directions of principal strain axes indicate that both the amount and the style of seismic deformation are poorly defined for roughly half of the zones considered mostly located in the western and central mediterranean area these results suggest that one should be cautious in using seismic strain estimates when not accompanied by satisfactorily uncertainty evaluation

time scale for adjustment of glaciers to changes in mass balance the length of time tm over which a glacier responds to a prior change in climate is investigated with reference to the linearized theory of kinematic waves and to results from numerical models we show the following tm may in general be estimated by a volume time scale describing the time required for a step change in mass balance to supply the volume difference between the initial and final steady states the factor f in the classical estimate of m l u where i is glacier length and u is terminus velocity has a simple geometrical interpretation ft is the ratio of thickness change averaged over the full length i to the change at the terminus although both u and f relate to dynamic processes local to the terminus zone the ratio f u and therefore tm are insensitive to details of the terminus dynamics in contrast to conclusions derived from some simplified kinematic wave models a more robust estimate of tm independent of terminus dynamics is given by tm h b where h is a thickness scale for the glacier and b is the mass balance rate negative at the terminus we suggest that tm for mountain glaciers can be substantially less than the 1o2 103 years commonly considered to be theoretically expected

on the recent elevation changes at the flade isblink ice cap northern greenland 1 we have used radar altimeter 2 ra 2 onboard esa s envisat and geosciences laser altimeter system glas onboard nasa s icesat to map the elevation change of the flade isblink ice cap fiic in northern greenland based on ra 2 data we show that the mean surface elevation change of the fiic has been near zero 0 03 0 03 m a between fall 2002 and fall 2009 we present the elevation change rate maps and assess the elevation change rates of areas above the late summer snow line 0 09 0 04 m a and below it 0 16 0 05 m a the glas elevation change rate maps show that some outlet glaciers previously reported to have been in a surge state are thickening rapidly using the ra 2 measured average elevation change rates for different parts of the ice cap we present a mass change rate estimate of 0 0 0 5 gt a for the fiic we compare the annual elevation changes with surface mass balance smb estimates from a regional atmospheric climate model racmo2 we find a strong correlation between the two r 0 94 and p 0 002 suggesting that the surface elevation changes of the fiic are mainly driven by net smb the correlation of modeled net smb and measured elevation change is strong in the southern areas of the fiic r 0 97 and p 0 0005 but insignificant in the northern areas r 0 38 and p 0 40 this is likely due to higher variability of glacier flow in the north relative to the south

note on scaling of peak ground acceleration and peak ground velocity with magnitude summary the theoretical scaling of near field peak ground acceleration and peak ground velocity with moment magnitude mw is found using an l model of rupture this scaling matches well with the magnitude scaling of recent attenuation relations

an inventory and morphometric analysis of british columbia glaciers canada we describe an automated method to generate an inventory of glaciers and glacier morphometry from a digital topographic database containing glacier boundaries and a digital elevation model for british columbia canada the inventory contains over 12 000 glaciers with a total cumulative area that exceeds 25 000 km 2 based on mapping from aerial photographs circa the mid 1980s we use the inventory to examine dimensional characteristics among glaciers namely the scaling relations between glacier length width and area glacier length is a good predictor of glacier area and its predictive ability improves when glaciers are stratified by the number of up valley accumulation basins the spatial pattern of glacier mid range altitude parallels glaciation limits previously mapped for british columbia and similarly reflects large scale controls of orographic precipitation and continentality the inventory is also used to refine models that relate glacier mid range and terminus altitudes to regional position aspect and in the case of terminus altitudes an index of glacier shape relations between glacier altitude limits and controlling spatial and topographic factors are used to make further climatic and mass balance inferences from the glacier inventory