paleoceanographic evolution of north pacific surface water off japan during the past 150 000years abstract hydrographic variability in the mixed water region of the northwest pacific ocean at latitudes 35 40 n between the kuroshio extension and oyashio front causes complex upwelling leading to large primary productivity and thus great fishery resources we reconstructed the periodicity of the variability in north pacific intermediate water upwelling and surface ocean hydrography based on the high resolution analysis of diatom assemblages in seven cores representing the last 150 000 years we derived annual sea surface temperatures ssts through a diatom based proxy td the td derived annual ssts c are controlled by orbital forcing and show a reversed saw tooth in southern cores in contrast to a normal saw tooth pattern in the northern cores oceanic diatom abundances along the northern margin of the mixed water region are twice times as high as beneath the axis of the kuroshio extension and fluctuated in a revised saw tooth pattern with higher overall abundances interglacials after the last deglaciation annual ssts declined markedly during heinrich and bond events in the northern north atlantic when ice rafted detritus transported by icebergs was abundant wavelet analyses of the record of oceanic diatom abundances show significant variability at 2 0 kyr 2 to 5 6 kyr and 3 2 to 9 6 kyr periods wavelet analyses of the annual sst records show significant periodicity at 1 4 to 2 6 kyr 3 3 to 4 0 kyr 7 2 to 12 8 kyr cycles

the detection of low magnitude seismic events using array based waveform correlation summary it has long been accepted that occurrences of a known signal are most effectively detected by cross correlating the incoming data stream with a waveform template such matched signal detectors have received very little attention in the field of detection seismology because there are relatively few instances in which the form of an anticipated seismic signal is known a priori repeating events in highly confined geographical regions have been observed to produce very similar waveforms and good signals from events at a given site can be exploited to detect subsequent co located events at lower magnitudes than would be possible using traditional power detectors even greater improvement in signal detectability can be achieved using seismic arrays running correlation coefficients from single sensors can be stacked over an array or network to result in a network correlation coefficient displaying a significant array gain if two events are co located the time separating the corresponding patterns in the wave train as indicated by the cross correlation function is identical for all seismic stations and this property means that the correlation coefficient traces are coherent even when the waveforms are not we illustrate the power of array based waveform correlation using the 1997 august 16 kara sea event the weak event that occurred 4 hr after the main event was barely detected using an sta lta detector on the spits array but is readily detected by signal matching on a single channel the main event was also recorded by the far more distant norsar array but no conventional detection can be made for the second event a clear detection is however made when the correlation coefficient traces are beamformed over all sensors of the array we estimate the reduction in detection threshold of a test signal on a regional seismic array using waveform correlation by scaling down a master signal and immersing it into seismic noise we show that for this case waveform correlation using a single channel detects signals of approximately 0 7 orders of magnitude lower than is possible using an sta lta detector on the array beam waveform matching on the full array provides an additional improvement of approximately 0 4 magnitude units we describe a case study in which small seismic events at the barentsburg coal mine on spitsbergen were detected using the signals from a major rockburst as master waveforms many spurious triggers occurred in this study whereby short sections of signal exhibited coincidental similarity with unrelated incoming wave fronts we demonstrate how such false alarms can almost always be identified and screened out automatically by performing frequency wavenumber analysis upon the set of individual correlation coefficient traces

ground motion prediction equations in the san jacinto fault zone significant effects of rupture directivity and fault zone amplification we present a new set of ground motion prediction equations gmpes for horizontal peak ground acceleration peak ground velocity and 5 damped pseudo spectral acceleration psa developed for the san jacinto fault zone sjfz area besides using these equations to quantify seismic shaking in the area the results allow us to examine the physics and local properties controlling the observed ground motions the analyzed dataset includes 30 000 observations from 800 events spanning a magnitude range of 1 5 m 6 0 and recorded by up to 140 stations at epicentral distances ranging from essentially zero to 150 km the local gmpe is developed for the sjfz by applying classical regression techniques with predictive variables that include first distance and magnitude and then site characteristics rupture directivity and fault zone amplification the significance of these effects is determined by measuring the uncertainty reduction of the gmpe due to each factor the results show that in contrast to many regional studies traditional site characteristic has a relatively minor effect on peak amplitudes in our study area however rupture directivity is a significant factor controlling the amplitudes of ground motion even for small events the dense seismic network and newly developed directivity tool enable us to extract efficiently directivity effects with statistical significance using the ground motion dataset during the regression analysis process the obtained rupture directivities are consistent with the main focal mechanism orientations and surface trace orientations known from other studies and predictions for bimaterial ruptures in the trifurcation area of the sjfz fault zone amplification is a second important factor showing strong impact on the peak ground motion values with increasing role for the lower frequency range 10 hz examined in the 5 damped psa values we also observe signatures of large amplitude variances which indicate additional source related control on the distribution of amplitudes besides rupture directivity for aftershocks close in time and location to the m l 5 1 earthquake of march 2013 using the full set of records we present the most complete set of gmpes for the sjfz area including a higher amplitude prediction for regions in the direction of rupture

ice streams as the arteries of an ice sheet their mechanics stability and significance ice streams are corridors of fast ice flow ca 0 8 km year within an ice sheet and are responsible for discharging the majority of the ice and sediment within them consequently like the arteries in our body their behaviour and stability is essential to the well being of an ice sheet ice streams may either be constrained by topography topographic ice streams or by areas of slow moving ice pure ice streams the latter show spatial and temporal patterns of variability that may indicate a potential for instability and are therefore of particular interest today pure ice streams are largely restricted to the siple coast of antarctica and these ice streams have been extensively investigated over the last 20 years this paper provides an introduction to this substantial body of research and describes the morphology dynamics and temporal behaviour of these contemporary ice streams before exploring the basal conditions that exist beneath them and the mechanisms that drive the fast flow within them the paper concludes by reviewing the potential of ice streams as unstable elements within ice sheets that may impact on the earth s dynamic system d 2002 elsevier science b v all rights reserved

simulating the impact of freshwater inputs and deep draft icebergs formed during a mis 6 barents ice sheet collapse 1 an intermediate complexity climate model is used to simulate the collapse of the barents ice sheet during marine isotope stage 6 mis 6 140 ka b p with the purpose of investigating whether a mass input of freshwater from the collapse could have affected the convection and deep water formation in the north atlantic ocean further experiments used a coupled dynamic and thermodynamic iceberg model to determine the effects of deep draft icebergs rather than freshwater alone on the ocean circulation the results predict that the collapse of the barents ice sheet had a significant impact on the meridional overturning circulation in both the atlantic and pacific oceans freshwater fluxes have more of an impact on the atlantic overturning circulation during the actual release period compared to icebergs but the bergs induce effects over longer time scales even after the pulse is removed freshwater fluxes of 0 15 sverdrup sv and iceberg surges of 0 1 sv trigger significant changes in the global patterns particularly in the north pacific where there is strengthening of the overturning circulation at the expense of that in the north atlantic and associated increases in pacific sea surface temperatures these results highlight the importance of simulating not only the correct flux but also the form of the freshwater input from ice sheet collapses appropriately

response of interior north america to abrupt climate oscillations in the north atlantic region during the last deglaciation several broad scale climatic oscillations during the last deglaciation are well documented in regions around the north atlantic ocean this paper reviews empirical evidence for these deglacial climatic oscillations from non coastal north america and discusses implications for testing climatic simulations and for understanding the cause and transmittal mechanisms paleoclimatic interpretation of oxygen isotope records from several small sites in the eastern great lakes region indicates a classic deglacial climatic sequence that is comparable with records from europe and greenland the climatic events as interpreted from crawford lake oxygen isotopes include the bolling allerod boa warming at 12 700 14c bp a warm boa at 12 500 10 920 14c bp an intra allerod cold period shortly before 11 000 14c bp a cold younger dryas yd climate reversal at 10 920 10 000 14c bp the holocene warming at 10 000 14c bp a brief preboreal oscillation pb at 9650 14c bp and an early holocene cold event at 7500 14c bp 8200 cal bp some of these events were also evident from changes in upland and aquatic vegetation and sediment lithology the pronounced yd climatic reversal has been documented from pollen records along the ecotones at this time and from glacier readvances in the great lakes region along the rocky mountains from alberta to colorado the yd event is indicated by alpine glacier advance and or shift in timberline vegetation in minnesota and upper new york early holocene climatic instability is also suggested by oxygen isotope records and or varve thickness the regional variations in evidence for the yd and other events in north america suggest that climatic oscillations may have different expressions in paleo records depending on geographic location and characteristics of a particular site the extent and magnitude of these climatic oscillations across north america suggest that these oscillations are an expression of climatic change that was probably widespread rather than locally induced by a nearby glacier the location of these sites implies that climatic signals were likely carried over the northern hemisphere through the atmosphere as indicated by general circulation models we hypothesize that the lack of evidence for a cold yd in interior north america west of the great lakes region and east of the rocky mountains was caused by the trapping of cold arctic air mass north of the laurentide ice sheet and by uninterrupted northward expansion of warm caribbean air this strongly contrasted climate also produced non analogous biological assemblages

simulated variability of the atlantic meridional overturning circulation to examine the multi annual to decadal scale variability of the atlantic meridional overturning circulation amoc we conducted a four member ensemble with a daily reanalysis forced medium resolution global version of the isopycnic coordinate ocean model micom and a 300 years integration with the fully coupled bergen climate model bcm the simulations of the amoc with both model systems yield a long term mean value of 18 sv and decadal variability with an amplitude of 1 3 sv the power spectrum of the inter annual to decadal scale variability of the amoc in bcm generally follows the theoretical red noise spectrum with indications of increased power near the 20 years period comparison with observational proxy indices for the amoc e g the thickness of the labrador sea water the strength of the baroclinic gyre circulation in the north atlantic ocean and the surface temperature anomalies along the mean path of the gulf stream shows similar trends and phasing of the variability indicating that the simulated amoc variability is robust and real mixing indices have been constructed for the labrador the irminger and the greenland iceland norwegian gin seas while convective mixing in the labrador and the gin seas are in opposite phase and linked to the nao as observations suggest the convective mixing in the irminger sea is in phase with or leads the labrador sea newly formed deep water is seen as a slow anomalous cold and fresh plume flowing southward along the western continental slope of the atlantic ocean with a return flow of warm and saline water on the surface in addition fast travelling topographically trapped waves propagate southward along the continental slope towards equator where they go east and continue along the eastern rim of the atlantic for both types of experiments the northern hemisphere sea level pressure and 2 m temperature anomaly patterns computed based on the difference between climate states with strong and weak amoc yields a nao like pattern with intensified icelandic low and azores high and a warming of 0 25 0 5 c of the central north atlantic sea surface temperature sst the reanalysis forced simulations indicate a coupling between the labrador sea water production rate and an equatorial atlantic sst index in accordance with observations this coupling is not identified in the coupled simulation

changes in static stress on southern california faults after the 1992 landers earthquake the magnitude 7 5 landers earthquake of 28 june 1992 was the largest earthquake to strike california in 40 years the slip that occurs in such an earthquake would be expected to induce large changes in the static stress on neighbouring faults these changes in stress should in turn affect the likelihood of future earthquakes stress changes that load faults towards failure have been cited as the cause of small1 5 moderate6 and large7 earthquakes conversely those that relax neighbouring faults have been related to a decrease in seismicity5 here we use an elastic half space model8 to estimate the stress changes produced by the landers earthquake on selected southern california faults including the san andreas we find that the estimated stress changes are consistent with the triggering of four out of the five aftershocks with magnitude greater than 4 5 and that the largest changes 1 10 bar occurring on part of the san bernardino segment of the san andreas fault may have decreased the time to the next magnitude 8 earthquake by about 14 years

eustatic variations during the paleocene eocene greenhouse world we reconstruct eustatic variations during the latest paleocene and earliest eocene 58 52 ma dinoflagellate cysts grain size fractions and organic biomarkers in marine sections at four sites from three continents indicate an increased distance to the coast during the paleocene eocene thermal maximum petm the same trend is recognized in published records from other sites around the world together the data indicate a eustatic rise during the petm beginning 20 to 200 ka before the globally recorded negative carbon isotope excursion cie at 55 5 ma although correlations are tentative we recognize other global transgressions during chrons c25n and c24n the latter may be associated with eocene thermal maximum 2 53 5 ma or the x event 52 ma these results suggest a link between global sea level and hyperthermal intervals potentially because of the melting of small alpine ice sheets on antarctica thermal expansion of seawater or both however the early onset of sea level rise relative to the cie of the petm suggests contributions from other mechanisms perhaps decreasing ocean basin volume on sea level rise copyright 2008 by the american geophysical union

a common source rock for egyptian and saudi hydrocarbons in the red sea the northern red sea area hosts a classic triple junction of the red sea gulf of aqaba and gulf of suez rifted basins the sedimentary succession here can be divided into prerift pre miocene and synrift miocene and post miocene megasequences the prerift section has been penetrated in only a few wells drilled on the western egyptian side of the red sea whereas the synrift section is known on both the egyptian and the saudi sides of the red sea although the synrift units on both sides of the water are similar in facies thicknesses and depositional environments they have different stratigraphic nomenclatures the northern red sea consists of elongated troughs separated by elongated structural highs both of which trend northwest southeast gulf of suez trend these highs are dissected by cross elements trending northeast southwest gulf of aqaba trend and east northeast west southwest and are looked upon as strike slip faults dislocating these highs identified rich source rocks are present in the upper senonian carbonates the sudr and duwi formations on the western side of the sea the early miocene rudeis formation burqan group and the middle miocene kareem and belayim formations maqna group the pre miocene and the early miocene source rocks host oil prone kerogen whereas the middle and late miocene source rocks contain oil and gas prone kerogen all of these source rocks are sufficiently mature copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received january 18 1996 revised manuscript received october 11 1996 final acceptance march 21 1997 2faculty of science uae university p o box 17551 al ain united arab emirates we are especially grateful to the egyptian general petroleum corporation for supplying the materials and the necessary data on which the present work is based and the permission to publish it we also thank c g st c kendall and a e m nairn who read the early draft of this paper and offered valuable comments thanks to aapg reviewers d waples r j murris w maze and an anonymous reviewer for their constructive comments which we have used to improve our paper we acknowledge g cole bhp petroleum for granting permission to use some of his previous work

late cretaceous upwelling system along the southern tethys margin israel interrelationship between productivity bottom water environments and organic matter preservation organic rich upper cretaceous sequences in israel were deposited in an extensive highly productive upwelling linked system which prevailed along the southern tethys margin and lasted for 19 m y santonian to late maastrichtian an understanding of the spatial and temporal characteristics of this system was gained through detailed paleontological and geochemical analyses of subsurface sequences in two basins in israel representing an outer shefela and an inner zin facies belt the nature of the upwelling system and its effect on the sedimentary record is related to two basic environmental parameters namely paleoproductivity intensity and oxygen levels at the bottom the assessment of these parameters and their interrelationship has been performed through the development of paleontological foraminiferal criteria which are independent of the organic matter content following the establishment of these criteria it is concluded that the productivity reached its maximum intensity during the late campanian which was also the time of most notable differentiation between the center of the upwelling system in the inner belt and the less intense conditions in the outer basin this distribution is expressed in varied lithology organic rich carbonates phosphorites and siliceous rocks at the core of upwelling and a uniform lithology organic rich carbonates at the margin of this system the uniform lithology of the maastrichtian in both basins composed of organic rich carbonates is ascribed to a gradual weakening of productivity the bottom conditions in the inner belt during the late campanian the time of maximum surface productivity were near anoxic changing to more aerated dysaerobic conditions during the early maastrichtian in the outer belt a more aerated bottom dysaerobic prevailed throughout the late campanian to late maastrichtian the elevated organic matter content in both basins reflects the overall environment of high productivity its actual variations however seem to be unrelated to changes in surface productivity and bottom oxygen levels

icing the north atlantic there is debate over the causes of the large and abrupt climate changes that the north atlantic region has experienced in the past and may do in the future the driving forces of such changes might originate in the north atlantic itself or could be transmitted to the region from elsewhere new evidence on the extent and movement of the british ice sheet around the end of the last ice age supports the first contention and in particular implicates the advance and retreat of the laurentide ice sheet in causing some of the big climate jumps of the past

focal spot imaging based on zero lag cross correlation amplitude fields application to dense array data at the san jacinto fault zone we image the subsurface below a dense seismic array straddling the clark branch of the san jacinto fault zone in southern california the analysis is based on focal spots of surface waves associated with the zero lag amplitudes of noise cross correlations computed between all stations of the dense array local medium properties are inferred from the spatially variable focal spot size and shape based on the first zero crossing of amplitude versus distance distributions the method provides simultaneous estimates of wave speed apparent attenuation and anisotropy without solving a tomographic inverse problem the obtained images of the frequency dependent seismic velocity distributions are consistent with independent estimates from a far field rayleigh wave tomography we observe an anticorrelation between our apparent attenuation coefficient and seismic velocity and a fault parallel alignment of fast propagation directions with greater structural complexity to the southwest of the fault the results imply a complex fault zone structure including a waveguide to the northeast of the fault that is continuous across the observed depth range and a low velocity structure to the southwest associated with a shallow sedimentary basin

imaging widespread seismicity at midlower crustal depths beneath long beach ca with a dense seismic array evidence for a depth dependent earthquake size distribution we use a dense seismic array composed of 5200 vertical geophones to monitor microseismicity in long beach california poor signal to noise ratio due to anthropogenic activity is mitigated via downward continuation of the recorded wavefield the downward continued data are continuously back projected to search for coherent arrivals from sources beneath the array which reveals numerous previously undetected events the spatial distribution of seismicity is uncorrelated with the mapped fault traces or with activity in the nearby oil fields many events are located at depths larger than 20 km well below the commonly accepted seismogenic depth for that area the seismicity exhibits temporal clustering consistent with omori s law and its size distribution obeys the gutenberg richter relation above 20 km but falls off exponentially at larger depths the dense array allows detection of earthquakes two magnitude units smaller than the permanent seismic network in the area because the event size distribution above 20 km depth obeys a power law whose exponent is near one this improvement yields a hundred fold decrease in the time needed for effective characterization of seismicity in long beach

links between climate and sea levels for the past three million years the oscillations between glacial and interglacial climate conditions over the past three million years have been characterized by a transfer of immense amounts of water between two of its largest reservoirs on earth the ice sheets and the oceans since the latest of these oscillations the last glacial maximum between about 30 000 and 19 000 years ago approximately 50 million cubic kilometres of ice has melted from the land based ice sheets raising global sea level by approximately 130 metres such rapid changes in sea level are part of a complex pattern of interactions between the atmosphere oceans ice sheets and solid earth all of which have different response timescales the trigger for the sea level fluctuations most probably lies with changes in insolation caused by astronomical forcing but internal feedback cycles complicate the simple model of causes and effects

ice sheet variability around the north atlantic ocean during the last deglaciation millennial scale variability in the flux of ice rafted detritus to north atlantic sediments during the last glacial period has been interpreted to reflect a climate forced increase in the discharge of icebergs from ice sheet margins surrounding the northern north atlantic ocean 1 but the relationship between ice sheet variability and climate change is not clear as both the sources of ice rafted detritus and the ice marginal processes are varied and complex 2 4 terrestrial records are helpful in unravelling this complexity because they can demonstrate the scale of ice sheet oscillations and whether the ice sheet or sector was advancing or retreating with respect to climate change here we constrain the age and anatomy of a prominent readvance of the british ice sheet in the northern irish sea region at similar to 14 14 c kyr bp similar to 16 4 calendar kyr bp the analysis indicates that the british ice sheet participated in an iceberg discharge episode known as heinrich event 1 comparison with other terrestrial and marine ice sheet records suggests that the dynamic collapse of the laurentide ice sheet beginning at 14 6 15 0 c 14 kyr bp1 4 similar to 17 2 17 6 calendar kyr bp 5 initiated varied responses from other ice sheet margins around the northern north atlantic region these observations support the argument that the release of icebergs and meltwater during heinrich event 1 disrupted the north atlantic thermohaline circulation 6 8 leading to a delay or reversal of deglaciation of the northern hemisphere and at least as far south as 40 degrees s for two to three thousand years 5 9 10 suggesting a climate forcing and response similar to that of the ensuing younger dryas cold snap 11 12

coupled climate and sea level changes deduced from huon peninsula coral terraces of the last ice age abstract huon peninsula papua new guinea is a tectonically unstable uplifting shoreline ringed by emergent coral terraces the terraces were formed during episodes of rapid sea level rise when corals constructed large discrete coral platforms that were subsequently uplifted uranium series ages of four prominent huon peninsula last glacial ois 3 coral terraces coincide with the timing of major north atlantic climate reversals at intervals of 6000 7000 yr between 30 000 yr and 60 000 yr ago terrace elevations when combined with uplift indicate 10 15 m high sea level excursions at these times we attribute the growth of the terraces directly to sea level rises arising from ice calving episodes from major north atlantic ice sheets and the antarctic ice sheet that precipitated extremes of cold climate called heinrich events these periods are associated with major discharges of land based ice and enhanced concentrations of ice rafted debris in deep sea cores sea levels at this time were 60 90 m lower than present

late holocene climate variability in the adriatic sea central mediterranean planktic and benthic foraminifera assemblages from a set of sediment cores collected on the adriatic shelf and the southern adriatic deep basin provide compelling evidence of submillennial scale environmental changes during the last 6000 years repeated peaks in globigerinoides sacculifer represent warm dry intervals including the mediaeval warm period the roman age the late bronze age and the copper age the last occurrence lo of g sacculifer 550 years bp approximates the base of the little ice age lia significant turnovers in the structure of the water column reflect changes in the rate of formation and depth of flow of the north adriatic dense water naddw and the levantine intermediate water liw about 7500 years bp the benthic oxygen isotope records mark the timing when the naddw formation intensified on the slope and shifted to its modern route about 5500 years bp when sea level reached its modern high stand oxygen isotope records of intermediate planktic dwellers indicate a northward intrusion of the liw on the slope the oscillating isotope trends during the last five millennia document a discontinuous invasion of liw into the central adriatic possibly reflecting short term climate changes with weakened liw production during colder and wetter intervals

theoretical limits on detection and analysis of small earthquakes we investigate theoretical limits on detection and reliable estimates of source characteristics of small earthquakes using synthetic seismograms for shear tensile dislocations on kinematic circular ruptures and observed seismic noise and properties of several acquisition systems instrument response sampling rate simulated source time functions for shear tensile dislocation events with different magnitudes static stress drops and rupture velocities provide estimates for the amplitude and frequency content of p and s phases at various observation angles the source time functions are convolved with a green s function for a homogenous solid assuming given p s wave velocities and attenuation coefficients and a given instrument response the synthetic waveforms are superposed with average levels of the observed ambient seismic noise up to 1 khz the combined seismograms are used to calculate signal to noise ratios and expected frequency content of p and s phases at various locations the synthetic simulations of signal to noise ratio reproduce observed ratios extracted from several well recorded data sets the results provide guidelines on detection of small events in various geological environments along with information relevant to reliable analyses of earthquake source properties

response of the san andreas fault to the 1983 coalinga nunez earthquakes an application of interaction based probabilities for parkfield 1 the parkfield cholame section of the san andreas fault site of an unfulfilled earthquake forecast in 1985 is the best monitored section of the world s most closely watched fault in 1983 the m 6 5 coalinga and m 6 0 nunez events struck 25 km northeast of parkfield seismicity rates climbed for 18 months along the creeping section of the san andreas north of parkfield and dropped for 6 years along the locked section to the south right lateral creep also slowed or reversed from parkfield south here we calculate that the coalinga sequence increased the shear and coulomb stress on the creeping section causing the rate of small shocks to rise until the added stress was shed by additional slip however the 1983 events decreased the shear and coulomb stress on the parkfield segment causing surface creep and seismicity rates to drop we use these observations to cast the likelihood of a parkfield earthquake into an interaction based probability which includes both the renewal of stress following the 1966 parkfield earthquake and the stress transfer from the 1983 coalinga events we calculate that the 1983 shocks dropped the 10 year probability of a m 6 parkfield earthquake by 22 from 54 22 to 42 23 and that the probability did not recover until about 1991 when seismicity and creep resumed our analysis may thus explain why the parkfield earthquake did not strike in the 1980s but not why it was absent in the 1990s we calculate a 58 17 probability of a m 6 parkfield earthquake during 2001 2011 index terms 7223 seismology seismic hazard assessment and prediction 7230 seismology seismicity and seismotectonics 7260 seismology theory and modeling keywords coalinga earthquake parkfield stress change earthquake probability seismicity rate

triggering of earthquake aftershocks by dynamic stresses it is thought that small static stress changes due to permanent fault displacement can alter the likelihood of or trigger earthquakes on nearby faults many studies of triggering in the near field particularly of aftershocks rely on these static changes as the triggering agent and consider them only in terms of equivalent changes in the applied load on the fault here we report a comparison of the aftershock pattern of the moment magnitude mw 7 3 landers earthquake not only with static stress changes but also with transient oscillatory stress changes transmitted as seismic waves that is dynamic stresses dynamic stresses do not permanently change the applied load and thus can trigger earthquakes only by altering the mechanical state or properties of the fault zone these dynamically weakened faults may fail after the seismic waves have passed by and might even cause earthquakes that would not otherwise have occurred we find similar asymmetries in the aftershock and dynamic stress patterns the latter being due to rupture propagation whereas the static stress changes lack this asymmetry previous studies have shown that dynamic stresses can promote failure at remote distances but here we show that they can also do so nearby

seismicity around parkfield correlates with static shear stress changes following the 2003 mw6 5 san simeon earthquake 1 earthquakes trigger other earthquakes but the physical mechanism of the triggering is currently debated most studies of earthquake triggering rely on earthquakes listed in catalogs which are known to be incomplete around the origin times of large earthquakes and therefore missing potentially triggered events here we apply a waveform matched filter technique to systematically detect earthquakes along the parkfield section of the san andreas fault from 46 days before to 31 days after the nearby 2003 mw6 5 san simeon earthquake after removing all possible false detections we identify 8 times more earthquakes than in the northern california seismic network catalog the newly identified events along the creeping section of the san andreas fault show a statistically significant decrease following the san simeon main shock which correlates well with the negative static stress changes i e stress shadow cast by the main shock in comparison the seismicity rate around parkfield increased moderately where the static stress changes are positive the seismicity rate changes correlate well with the static shear stress changes induced by the san simeon main shock suggesting a low friction in the seismogenic zone along the parkfield section of the san andreas fault

atmospheric transmission of north atlantic heinrich events this research was supported by the u s geological survey global change program and nsf under grants atm 9523584 atm 9632029 and ear 9725554

pyrolysis analyses and bulk kinetic models of the late cretaceous oil shales in jordan and their implications for early mature sulphur rich oil generation potential abstract in this study oil shale samples were collected from late cretaceous muwaqaar chalk marl formation mcm in jordan to study their petrologic and organic geochemical properties pyrolysis and bulk kinetic techniques were performed on the late cretaceous oil shales the results of this study were used to characterize the different organofacie types in the late cretaceous oil shales and their effect on the petroleum type generated during thermal maturation and the temperature of petroleum generation on the basis of the geochemical results the analysed late cretaceous oil shales contain predominantly type ii and rarely type i kerogens these kerogens are consistent with the high dominate of sapropel organic matter i e alginite and amorphous organic matter a good correlation is noted between increasing abundance of organic matter and the kerogen type that was derived from an open pyrolysis gas chromatography py gc the py gc data indicate the analysed oil shale samples contain heterogeneous organic matter of the kerogen type ii s it is interesting to know that this sulphur rich kerogen type ii s can generate high sulphur oils at low maturity ranges this is consistent with the predicted temperature petroleum generation from bulk kinetic models the bulk kinetic models in this study indicate that the main phase of petroleum formation from the thermally immature late cretaceous oil shales occur between 122 and 148 c these temperature values of the petroleum generation are generally consistent with the kerogen type ii s and further indicate that the analysed oil shale samples can generate sulfur rich oils at early stage of kerogen cracking

maastrichtian to early paleocene sea level changes and climatic evolution on the southeastern tethys margin abstract an integrative multi proxy approach based on lithology microfacies bulk rock composition total organic carbon toc and 13ccarb was used to estimate southeastern tethys sea level fluctuations during the deposition of the maastrichtian danian oil shales in jordan clay mineral assemblages were used as proxies to determine climatic variation induced sediment supply during the cretaceous paleogene boundary k pg interval the results from two cores os 02 jafr basin southeast jordan os 28 azraq hamza basin central east jordan reveal four major intervals of distinctive bulk rock composition reflecting sea level changes interval i earliest maastrichtian with a low sea level and the formation of dolomites and a high detrital quartz input predates the oil shales intervals ii and iii in core os 02 and interval ii in core os 28 represent the highest relative sea level following the early maastrichtian sea level rise on the arabian platform intervals iii core os 02 and ii core os 28 coincide with the highest organic matter deposition interval iv core os 02 and intervals iii and iv core os 28 relate to the sea level regression transgression cycle in the latest maastrichtian through danian and are marked by a large drop in the toc content increased terrestrial influx during sea level lows is evident from two peaks intervals of major negative 13ccarb values in core os 28 based on clay mineralogy it can be differentiated between warm humid warm cool seasonally alternating and cool arid climates when bulk rock composition is used as a sea level proxy clay mineral assemblages from both cores reveal the dominance of warm and humid climate or alternatively warm cool seasonal alternations during high sea levels ii and iii core os 02 ii and iv core os 28 while periods of arid and cool climate correspond to lower sea levels the sea level changes and climatic variations deduced from the jordanian oil shale successions are in agreement with the long term variations from the egyptian western desert sections southeastern tethys and the tunisian el kef section southweastern tethys moreover the sea level changes identified relate to the regional changes on the arabian platform during the maastrichtian danian

coherent resonant millennial scale climate oscillations triggered by massive meltwater pulses the role of mean and stochastic freshwater forcing on the generation of millennial scale climate variability in the north atlantic is studied using a low order coupled atmosphere ocean sea ice model it is shown that millennial scale oscillations can be excited stochastically when the north atlantic ocean is fresh enough this finding is used in order to interpret the aftermath of massive iceberg surges heinrich events in the glacial north atlantic which are characterized by an excitation of dansgaard oeschger events based on model results it is hypothesized that heinrich events trigger dansgaard oeschger cycles and that furthermore the occurrence of heinrich events is dependent on the accumulated climatic effect of a series of dansgaard oeschger events this scenario leads to a coupled ocean ice sheet oscillation that shares many similarities with the bond cycle further sensitivity experiments reveal that the timescale of the oscillations can be decomposed into stochastic linear and nonlinear deterministic components a schematic bifurcation diagram is used to compare theoretical results with paleoclimatic data

origin sequence stratigraphy and depositional environment of an upper ordovician hirnantian deglacial black shale jordan the upper ordovician succession of jordan was located 60 s less than 100 km from the hirnantian ice sheet margin new graptolite dates indicate glaciation ended in jordan in the late hirnantian persculptus biozone the succession records two glacial advances within the ammar formation and the subsequent deglaciations organic rich black shales batra formation form part of the final deglacial transgressive succession that in filled an existing low stand glacial continental shelf topography the base of the black shale is coincident with the maximum flooding surface during transgression interfluves and sub basin margins were breached and black shale deposition expanded rapidly across the region the top of the black shales coincides with peak highstand the expanding puddle model sensu wignall for black shale deposition adapted for the peri glacial setting provides the best explanation for this sequence of events we propose a hypothesis in which anoxic conditions were initiated beneath the halocline in a salinity stratified water column a fresher surface layer resulted from ice meltwater generated during early deglaciation during the initial stages of marine incursion nutrients in the monimolimnion were isolated from the euphotic zone by the halocline increasing total organic carbon toc and 13corg up section indicates the organic carbon content of the shales was controlled mainly by increasing bioproductivity in the mixolimnion the strakhov model mixolimnion nutrient levels were sustained by a continual and increasing supply of meltwater derived nutrients modulated by obliquity changes in high latitude insolation anoxia was sustained over tens to hundreds of thousands of years the formation of black shales on the north gondwana shelf was little different to those observed in modern black shale environments suggesting that it was the nature of the ordovician seas that pre disposed them to anoxia

earthquake hazard after a mainshock in california after a strong earthquake the possibility of the occurrence of either significant aftershocks or an even stronger mainshock is a continuing hazard that threatens the resumption of critical services and reoccupation of essential but partially damaged structures a stochastic parametric model allows determination of probabilities for aftershocks and larger mainshocks during intervals following the mainshock the probabilities depend strongly on the model parameters which are estimated with bayesian statistics from both the ongoing aftershock sequence and from a suite of historic california aftershock sequences probabilities for damaging aftershocks and greater mainshocks are typically well constrained after the first day of the sequence with accuracy increasing with time

modelling iceberg trajectories sedimentation rates and meltwater input to the ocean from the eurasian ice sheet at the last glacial maximum we model iceberg flow paths from the eurasian ice sheet and the associated meltwater production and sedimentation rates within the norwegian greenland sea during the last glaciation results from a numerical ice sheet model an atmospheric general circulation model and an ocean general circulation model are collated and used to provide iceberg production rate wind field and surface current forcings to an iceberg trajectory model the iceberg model then determines how icebergs issuing from the eurasian ice sheet travel across the ocean and eventually melt in addition the release of iceberg sediments is also predicted the results show that iceberg trajectories are complex and that common features of iceberg movement are clustering in zones of convergence and exit into the north atlantic through the iceland faeroes channel eurasian icebergs do not penetrate into the interior of the arctic ocean the gathering of icebergs produces a complex meltwater pattern that does not follow the conceptual idea of decreasing meltwater production with distance from the ice sheet margin sedimentation results are compared with the meltwater configuration and are found to be a poor indicator of past zones of iceberg melt with zones of sedimentation extending significantly less far

diatom records in the quaternary marine sequences around the japanese islands abstract understanding the quaternary is a key to estimating what the earth s climate will be like in the future such studies demand high resolution analyses based on paleoclimatic proxy records of changing earth s orbital forcing and solar insolation that affect the climate system quaternary diatom biostratigraphy and paleoceanography have been well established based on the quaternary marine sequences obtained by piston coring and deep sea drilling around the japanese islands this paper firstly reviews the quaternary diatom datum levels that are directly tied to magnetic polarity and then the late pleistocene and holocene rhythmic fluctuations in td derived ssts c which correlate with the earth s orbital parameters and finally reveals the large and abrupt climatic changes that have occurred around the japanese islands on centennial to millennial time scales the main aim is to provide the results of td ssts c based on the late pliocene to pleistocene sequences from three holes obtained by deep sea drilling dsdp odp the main difference between td and twt is that twt gives 0 5 values to xt warm transitional taxa thalassiosira oestrupii is grouped with xt in twt but with warm water species in td differences between the twt and td ssts c curves at hole 436 are unremarkable the remarkable variations of paleo temperatures based on td ssts c show four conspicuous episodes which correspond to the double precession cycle of mis 11 in the japan sea the twt ratio remarkably decreases at 2 6 ma due to a large increase in cold water taxa and indicates the beginning of the glacial age defined as the pliocene pleistocene boundary both twt and td ssts c increase at 2 60 2 0 ma and coincide with the lithologic change from diatom bearing clay with few dark colored layers to fine grained sediments with distinct dark light colored cycles wavelet analysis of td ssts c at site 798 indicates a reversed saw tooth pattern of 48 to 24 ky periods during 1 2 0 7 ma and 24 to 12 ky periods during 0 7 0 ma resulting in a change from longer to shorter cycles these fluctuations correlate with the earth s orbital parameters and climatic changes on a millennial time scale

climatic and oceanographic changes in the northeast atlantic reflected by magnetic properties of sediments deposited on the portuguese margin during the last 340 ka abstract rock magnetic parameters measured along two giant piston cores md95 2040 40 34 n 9 51 w and md95 2042 37 47 n 10 09 w collected off the portuguese margin related to other proxy climatic data have been used to reconstruct magnetic mineralogical changes of in relation to environmental and climatic conditions over the north atlantic western europe and northwest africa during the last three climatic cycles since isotope stage 10 thin discrete layers containing coarse grains of titano magnetite are associated with events of iceberg discharge during heinrich events 1 6 heinrich quat res 29 1988 142 that have equivalent events in isotope stages 5 8 concentrations of fine grained ti magnetite and hematite goethite varying in phase opposition are directly linked with alternations of cold and warm climatic periods spectral analyses of the rock magnetic signals reveal milankovitch periods at 100 and 41 ka confirming the relationship with long term climatic changes at high latitudes the nature ti magnetite and size range of the finest ferrimagnetic fraction as well as its variation suggest a control by deep currents carrying a colloidal clayey fraction from remote sources iceland faeroes mid atlantic ridge variation of hematite goethite contents is linked with transport by rivers and winds from the neighbouring continent a tight correlation with the d o cycles in greenland ice records confirms that north atlantic oceanic regimes and continental wind regimes were strongly influenced by millennial scale climatic changes throughout the last 350 ka

oceanographic variations over the last 150 000 yr in the japan sea and synchronous holocene with the northern hemisphere abstract the paleo hydrography in the japan sea called a mini ocean was reconstructed based on the high resolution analysis of diatom assemblages over the period of 150 000 yr the decrease of diatom fertilization in the japan sea when it was isolated from surrounding seas due to the drop of sea level during the glacial to stadial phase resulted in dissolution and or extremely low diatom production in the northern cores in the subarctic water masses the annual td derived paleo ssts c were controlled by the fluctuations of 2 kyr and 4 kyr periods at intervals of 20 kyr and 40 kyr over the last 160 kyr bp respectively a 23 kyr cycle is recognized during the periods from 140 ka to 100 ka according to the wavelet analysis after temperature and sea level increased both at 133 128 ka 60 53 ka and 15 10 ka oceanic warm water diatom species predominated at 127 119 ka and after 9 cal ka in the interstadial phase at 21 3 16 9 ka and 12 9 9 8 ka sea level and salinity increased as the transgression developed at 10 0 7 0 ka the oceanic association shifted from cold water species in the stadial period to warm water ones in the interstadial phase the fluctuations of td derived ssts c on century to millennial time scales during the holocene are well correlated with abrupt climatic events that different paleoclimatic proxies record in many regions of the northern hemisphere

stochastic characterization of mesoscale seismic velocity heterogeneity in long beach california s u m m a r y earth s seismic velocity structure is heterogeneous at all scales andmapping that heterogeneity provides insight into the processes that create it at large scale lengths seismic tomography is used to map earth structure deterministically at small scale lengths structure can be imaged deterministically but because it is impractical to image short wavelength heterogeneity everywhere we often resort to statistical methods to depict its variability in this study we develop random field model representations of a 3 d p wave velocity model at long beach california estimated from dense array recordings of the ambient seismic wavefield we focus on heterogeneity at the mesoscale which is smaller than 10 km scale of regional tomography but larger than the micro scale of borehole measurements we explore four ellipsoidally anisotropic heterogeneity models including von karman gaussian self affine and kummer models based on their autocorrelation functions we find that the von karman model fits the imaged velocity model best among these options with a correlation length in the horizontal direction about five times greater than in the vertical direction and with strong small scale length variations we validate our results by showing that our model accurately predicts the observed decay of scattered waves in the coda of a nearby earthquake suggesting that quantitative measures of velocity variability will be useful for predicting high frequency ground motion in earthquakes

stratigraphy of the middle eocene lower oligocene successions in northwestern and eastern jordan abstract rocks of eocene and oligocene age consisting mainly of carbonate ramp facies are widely distributed in jordan but no previous stratigraphic works have dealt with the eocene oligocene contact stratigraphic analysis based on field exploration and detailed lithostratigrapic and biostratigraphic preliminary data detected a major hiatus that separates the middle eocene lutetian from the early oligocene rupelian in the studied exposures in the wadi el ghadaf and ash shunah areas of jordan our results reveal that the planktonic foraminifera turborotalia cerroazulensis pseudohastigerina spp p18 zone and the calcareous nannoplankton ericsnia subdisticha np21 zone of early oligocene age were recorded immediately above the morozovelloides lehneri e11 zone and the discoaster tanii nodifer np16 zone indicating a period of non deposition as a result of tectonic activity and or sea level changes a correlative hiatus and time gap were also reported in different parts of the arabian and african plates which representing the contemporaneous paleo high areas the presence of the early oligocene shallow marine calcareous planktonic assemblages indicates that shallow shelves of the tethys ocean occupied the paleotopographic lows of jordan with deepening of the depositional basin toward the north

evidence for millennial scale climate change during marine isotope stages 2 and 3 at little lake western oregon u s a pollen and geochemical data from little lake western oregon suggest several patterns of millennial scale environmental change during marine isotope stage mis 2 14 100 27 600 cal yr b p and the latter part of mis 3 27 600 42 500 cal yr b p during mis 3 a series of transitions between warm and cold adapted taxa indicate that temperatures oscillated by ca 2 4 c every 1000 3000 yr highs and lows in summer insolation during mis 3 are generally associated with the warmest and coldest intervals warm periods at little lake correlate with warm sea surface temperatures in the santa barbara basin changes in the strength of the subtropical high and the jet stream may account for synchronous changes at the two sites during mis 2 shifts between mesic and xeric subalpine forests suggest changes in precipitation every 1000 3000 yr increases in tsuga heterophylla pollen at 25 000 and 22 000 cal yr b p imply brief warmings minimum summer insolation and maximum global ice volumes during mis 2 correspond to cold and dry conditions fluctuations in precipitation at little lake do not correlate with changes in the santa barbara basin and may be explained by variations in the strength of the glacial anticyclone and the position of the jet stream c 2001 university of washington

characterizing the uppermost 100 m structure of the san jacinto fault zone southeast of anza california through joint analysis of geological topographic seismic and resistivity data

seismic tomography of the southern california plate boundary region from noise based rayleigh and love waves we use cross correlations of ambient seismic noise between pairs of 158 broadband and short period sensors to investigate velocity structure over the top 5 10 km of the crust in the southern california plate boundary region around the san jacinto fault zone sjfz from the 9 component correlation tensors associated with all station pairs we derive dispersion curves of rayleigh and love wave group velocities the dispersion results are inverted first for rayleigh and love waves group velocity maps on a 1 5 1 5 km2 grid that includes portions of the sjfz the san andreas fault saf and the elsinore fault we then invert these maps to 3d shear wave velocities in the top 7 km of the crust the distributions of the rayleigh and love group velocities exhibit 2 azimuthal anisotropy with fast directions parallel to the main faults and rotations in complex areas the reconstructed 3d shear velocity model reveals complex shallow structures correlated with the main geological units and strong velocity contrasts across various fault sections along with low velocity damage zones and basins the sjfz is marked by a clear velocity contrast with higher v s values on the ne block for the section se of the san jacinto basin and a reversed contrast across the section between the san jacinto basin and the saf velocity contrasts are also observed along the southern parts on the saf and the elsinore fault with a faster southwest block in both cases the region around the salton trough is associated with a significant low velocity zone strong velocity reductions following flower shape with depth are observed extensively around both the sjfz and the saf and are especially prominent in areas of geometrical complexity in particular the area between the sjfz and the saf is associated with an extensive low velocity zone correlated with diffuse seismicity at depth and a similar pattern including correlation with deep diffuse seismicity is observed on a smaller scale in the trifurcation area of the sjfz these results augment local earthquake tomography images that have low resolution in the top few km of the crust and provide important constraints for studies concerned with behavior of earthquake ruptures generation of rock damage and seismic shaking hazard in the region

eocene oil shales from jordan paleoenvironmental implications from reworked microfossils abstract reworked microfossils common in paleogene sediments in jordan are here used to reconstruct the depositional environment the reworked taxa which include both calcareous nannofossils and foraminifera of cretaceous and paleocene age were found in eocene oil shales the potential provenance of the reworked material and the underlying processes of the reworking are discussed we differentiate between a subaerial erosion of exposed hinterland strata and a submarine abrasion of sediments a total of 73 smear slides have been prepared to identify calcareous nannofossils another fifteen samples were analyzed for foraminifera the allochthonous calcareous nannofossil and foraminifera taxa can be linked to a lithified source which was eroded and transported with both calcitic lithic fragments and organic matter multiple factors controlling the transport of the reworked taxa during the time of deposition have been investigated for the jordanian oil shales climate changes are thought to be the cause for changes in the abundance patterns and in the composition of the reworked taxa the input of common autochthonous components during arid phases and more allochthonous sediment particles during humid periods filled the eocene sink a fall in relative sea level perhaps in combination with increased storm activity caused a transport of reworked material to deeper parts of the azraq hamza sub basin the relative sea level changes in turn were related to syndepositional movements redefining the shape of the azraq hamza sub basin and its internal fault block architecture

time reversal location of glacial earthquakes in 2003 ekstrom et al reported the detection and location of a new class of earthquakes occurring in the polar regions of the earth the proposed source mechanism involves large and sudden sliding motions of glaciers which gave the name glacial earthquakes to these events in this study we localize some of these earthquakes with a time reversal mirror trm algorithm which contrary to ordinary back projection methods does not involve testing each possible source location in trm localization an earthquake is located on the basis of only one 3 d spectral element simulation of seismic wave propagation by using the full complexity of recorded data as simultaneous time reversed sources we show that on the basis of this approach even glacial earthquakes with a faint signal can be correctly localized and that the pattern of the time reversed wavefield is coherent with the motion of glaciers down their valley

seismic velocity structures in the southern california plate boundary environment from double difference tomography summary we present tomographic images of crustal structures in the southern california plate boundary area with a focus on the san jacinto fault zone sjfz based on double difference inversions of earthquake arrival times absolute arrival times of 247 472 p and 105 448 s wave phase picks for 5493 earthquakes recorded at 139 stations in southern california are used starting with a layered 1 d model and continuing in later iterations with various updated initial models we invert the data for vp and vs in a 270 km long 105 km wide and 35 km deep volume around the sjfz using a spatially variable grid with higher density around the sjfz the examined volume stretches from cajon pass to the northernmost imperial fault zone and includes portions of the southern san andreas fault saf the elsinore fault and the brawley seismic zone in the salton trough because differential traveltimes used in the double difference inversions are most sensitive to near source structures we obtain high resolution around the earthquake sources after 30 iterations we improve the average traveltime misfit by a factor of 16 though ray coverage is limited at shallow depths we obtain detailed images of seismic velocities from 3 to 20 km throughout much of the study area our final velocity results show zones of low velocity and anomalous vp vs ratios associated with various fault strands and sedimentary basins along with clear velocity contrasts across the sjfz and the southern saf the velocity reductions in fault zone regions are generally highest in geometrically complex areas up to 30 50 per cent in the top few kilometres are higher for vs than for vp and follow a flower type pattern with depth in the central section of the sjfz from the san jacinto valley to the trifurcation area the northeast side of the fault has generally higher seismic velocities than the southwest block the obtained contrasts of vp are more persistent and higher up to 20 per cent than the contrasts of vs up to 15 per cent although the differences may stem at least partially from the higher resolution of vp images in the sjfz sections to the northwest and southeast there are patches with reversed velocities contrasts especially in the shallow crust near the san jacinto valley and other basins along the banning fault there is no clear velocity contrast for the southern saf the northeast side has generally lower seismic velocities in the seismogenic zone with patches of contrast reversals in the shallow crust in the brawley seismic zone the northeast side has somewhat lower velocities in the 20 km section near the southern saf and higher velocities farther to the southwest the imaged features have important implications for various aspects of earthquake and crustal dynamics in the region

a methodological approach towards high resolution surface wave imaging of the san jacinto fault zone using ambient noise recordings at a spatially dense array we present a new technique for deriving detailed information on seismic velocities of the subsurface material from continuous ambient noise recorded by spatially dense seismic arrays this method uses iterative double beamforming between various subarrays to extract surface wave contributions from the ambient noise data in complex environments with unfavourable noise source distributions the iterative double beamforming extraction makes it possible to retrieve large amounts of rayleigh wave traveltime information in a wide frequency band the method is applied to data recorded by a highly dense nodal array with 1108 vertical geophones centred on the damage zone of the clark branch of the san jacinto fault zone south of anza california the array covers a region of 650 700 m 2 with instrument spacing of 10 30 m and continuous recording at 500 samples s 1 over 30 d in 2014 using this iterative double beamforming on subarrays of 25 sensors and cross correlations between all of the station pairs we separate surface waves from body waves that are abundant in the raw cross correlation data focusing solely on surface waves maps of traveltimes are obtained at different frequencies with unprecedented accuracy at each point of a 15 m spacing grid group velocity inversions at 2 4 hz reveal depth and lateral variations in the structural properties within and around the san jacinto fault zone in the study area this method can be used over wider frequency ranges and can be combined with other imaging techniques such as eikonal tomography to provide unprecedented detailed structural images of the subsurface material

locating hydrothermal acoustic sources at old faithful geyser using matched field processing in 1992 a large and dense array of geophones was placed around the geyser vent of old faithful in the yellowstone national park to determine the origin of the seismic hydrothermal noise recorded at the surface of the geyser and to understand its dynamics old faithful geyser ofg is a small scale hydrothermal system where a two phase flow mixture erupts every 40 to 100 min in a high continuous vertical jet using matched field processing mfp techniques on 10 min long signal we localize the source of the seismic pulses recorded at the surface of the geyser several mfp approaches are compared in this study the frequency incoherent and frequency coherent approach as well as the linear bartlett processing and the non linear minimum variance distorsionless response mvdr processing the different mfp techniques used give the same source position with better focalization in the case of the mvdr processing the retrieved source position corresponds to the geyser conduit at a depth of 12 m and the localization is in good agreement with in situ measurements made at old faithful in past studies

reducing marine and warm climate conditions during the late cretaceous and their influence on organic matter enrichment in the oil shale deposits of north jordan abstract late cretaceous oil shales located in the yarmouk sub basin north jordan were analysed using techniques of organic and inorganic geochemistry coupled with a microfossil study results of this study were used to reconstruct the paleoenvironmental and paleoclimatic conditions during the late cretaceous and to investigate their influence on organic matter enrichment of the oil shale deposits the analysed oil shales have high toc and s total content values in the ranges of 2 11 12 85 wt and 1 83 8 81 wt respectively the high s total content and its relation with toc values indicate that the sulfur is associated with organic matter and that the oil shales were deposited in a marine environment under reducing conditions this is shown by petrographic observation and supported by biomarker distributions the microscopic investigation indicated that the oil shales contain abundant liptinitic materials i e alginite and amorphous organic matter and planktonic foraminifera the presence of these sapropelic materials and planktonic foraminifera assemblages further suggests a marine origin biomarker distributions are also known to reflect dominantly marine plankton algal and microorganisms source input water column stratification and low oxygen reducing conditions are indicated by narrow pr ph values relatively high v ni elemental ratios and the presence of gammacerane reducing conditions contribute to preservation of organic matter warm water periods during the late cretaceous are also indicated by dominant occurrences of warm water index microfossil taxa the warm climate combined with elevated phosphorus p are the major causes of excessive algae growth and led to enhanced biological productivity within the photic zone of the water column during deposition of the oil shale deposits this increased bio productivity in combination with good preservation of organic matter are the main mechanisms of organic matter enrichment within the late cretaceous oil shales in the north jordan

sequence stratigraphic context and organic geochemistry of palaeogene oil shales jordan abstract the potential oil shales of the palaeogene muwaqqar chalk marl and umm rijam chert limestone formations are investigated from a subsurface location in the west of jordan detailed organic geochemistry data is placed in the context of a sequence stratigraphic framework derived from vertical foraminiferal biofacies and lithological changes and biostratigraphically calibrated using planktonic foraminiferal biozonation this shows that the transgressive systems tract of a selandian p4 probably p4a sequence has the best potential in the studied section to generate oil if subjected to induced pyrolysis a ypresian no older than e2 transgressive sequence has some potential whilst highstand systems tracts offer the least potential both the sequence model and oil shale potential compares well with equivalent age sediments in egypt and highlights that whilst the maastrichtian portion of the muwaqqar chalk marl formation is often regarded as the key interval for oil shale prospectivity parts of the paleocene succession also have some potential

fluvial discharge and sea level changes controlling black shale deposition during the paleocene eocene thermal maximum in the dababiya quarry section egypt abstract the formation of black shales along the tethyan margins at the paleocene eocene thermal maximum petm 55 ma may have been an important feedback mechanism to reduce the warming by excess carbon burial however the detailed evolution of sediment redox conditions during this event is still poorly constrained we address this issue by a high resolution mineralogical and geochemical investigation of the outer neritic dababiya quarry petm section in central egypt which serves as the global boundary stratotype section and point for the base of the eocene there the base of the petm beds corresponds to the onset of sediment lamination indicative of oxygen deficiency at the seafloor the absence of calcium carbonate and a major increase in phyllosilicate abundance and change in detritus sensitive trace elements is indicative of severe carbonate dissolution in addition to enhanced fluvial input erosion of coastal low lands and deposition during low or slightly rising sea level subsequently fully anoxic conditions were established for a short period during the peak phase of the petm as recorded by the strong relative enrichment of redox sensitive trace elements and organic carbon compared to background sediments the decoupling of the fe and mo contents from the detrital fraction may even indicate that euxinic conditions existed with free hydrogen sulfide in the water column concurrent to the onset of anoxia high carbonate and quartz contents as well as high elemental ratios of si al suggest a major drop of siliciclastic sediment supply sediment starvation most likely caused by a rapid sea level rise the final recovery phase of the petm is associated with a progressive restoration of the pre petm siliciclastic sedimentation temporary seasonal anoxic to dysoxic conditions and high phosphorus enrichment followed by carbonate dominated sedimentation and the return to well oxygenated conditions we conclude that after a period of strong fluvial discharge several parameters inherent to the petm e g warming water column stratification and enhanced fluvial discharge may have contributed to the development of anoxia and increased the burial efficiency of organic carbon by reducing water column oxygenation the temporal coincidence of sediment starvation and onset of black shale deposition during the petm suggests that a rapid sea level rise was an additional important triggering factor therefore our results support not only current views that tethyan continental shelf areas may have acted as large carbon sinks during the petm but also indicate that transgressions may have provided an important feedback mechanism for organic carbon drawdown during hyperthermal events

a triple sea ice state mechanism for the abrupt warming and synchronous ice sheet collapses during heinrich events 1 abrupt switch like changes in sea ice cover are proposed as a mechanism for the large amplitude abrupt warming that seemed to have occurred after each heinrich event sea ice changes are also used to explain the colder than ambient glacial conditions around the time of the glacier discharge the abrupt warming events occur in this mechanism owing to rapid sea ice melting which warmed the atmosphere via the strong sea ice albedo and insulating feedbacks such abrupt sea ice changes can also account for the warming observed during dansgaard oeschger events the sea ice changes are caused by a weak order of 5 sv response of the thermohaline circulation thc to glacier discharges the main point of this work is therefore that sea ice may be thought of as a very effective amplifier of a weak thc variability explaining the abrupt temperature changes over greenland synchronous ice sheet collapses from different ice sheets around the north atlantic indicated by some proxy records are shown to be possible via the weak coupling between the different ice sheets by the atmospheric temperature changes caused by the sea ice changes this weak coupling can lead to a nonlinear phase locking of the different ice sheets which therefore discharge synchronously it is shown that the phase locking may also lead to precursor glacier discharge events from smaller ice sheets before the laurentide ice sheet discharges the precursor events in this mechanism are the result rather than the cause of the major glacier discharges from the laurentide ice sheet

slip history of the 2003 san simeon earthquake constrained by combining 1 hz gps strong motion and teleseismic data 1 the slip history of the 2003 san simeon earthquake is constrained by combining strong motion and teleseismic data along with gps static offsets and 1 hz gps observations comparisons of a 1 hz gps time series and a co located strong motion data are in very good agreement demonstrating a new application of gps the inversion results for this event indicate that the rupture initiated at a depth of 8 5 km and propagated southeastwards with a speed 3 0 km sec with rake vectors forming a fan structure around the hypocenter we obtained a peak slip of 2 8 m and total seismic moment of 6 2 10 18 nm we interpret the slip distribution as indicating that the hanging wall rotates relative to the footwall around the hypocenter in a sense that appears consistent with the shape of the mapped fault trace index terms 1242 geodesy and gravity seismic deformations 7205 7212 seismology earthquake ground motions and engineering 8123 tectonophysics dynamics seismotectonics citation ji c k m larson y tan k w hudnut and k choi 2004 slip history of the 2003 san simeon earthquake constrained by combining 1 hz gps strong motion and teleseismic data geophys res lett 31 l17608 doi 10 1029 2004gl020448

the recurrence time of dansgaard oeschger events and limits on the possible periodic component abstract by comparing the high resolution isotopic records from the greenland ice core project grip and the north greenland ice core project ngrip ice cores the common climate signal in the records has been approximately separated from local noise from this an objective criterion for defining dansgaard oeschger do events is achieved the analysis identifies several additional short lasting events increasing the total number of do events to 27 in the period 12 90 kyr before present bp the quasi regular occurrence of the do events could indicate a stochastic or coherent resonance mechanism governing their origin from the distribution of waiting times a statistical upper bound on the strength of a possible periodic forcing is obtained this finding indicates that the climate shifts are purely noise driven with no underlying periodicity

decay of aftershock density with distance does not indicate triggering by dynamic stress the most predictable earthquakes are aftershocks which invariably follow mainshocks so what triggers aftershocks it was recently argued controversially that the decay of aftershocks with distance from the main earthquake could only be explained by dynamic triggering keith richards dinger and colleagues have tested this hypothesis and conclude that the observed decay can be better explained by static triggering resolving whether static or dynamic stress triggers most aftershocks and subsequent mainshocks is essential to understand earthquake interaction and to forecast seismic hazard it has recently been argued that the decay of aftershocks with distance from the main earthquake could be explained only by dynamic triggering this hypothesis has now been tested the conclusion being that the observed decay can be better explained by static triggering resolving whether static1 2 3 or dynamic4 5 6 7 8 stress triggers most aftershocks and subsequent mainshocks is essential to understand earthquake interaction and to forecast seismic hazard9 felzer and brodsky10 examined the distance distribution of earthquakes occurring in the first five minutes after 2 m 3 and 3 m 4 mainshocks and found that their magnitude m 2 aftershocks showed a uniform power law decay with slope 1 35 out to 50 km from the mainshocks from this they argued that the distance decay could be explained only by dynamic triggering here we propose an alternative explanation for the decay and subject their hypothesis to a series of tests none of which it passes at distances more than 300 m from the 2 m 3 mainshocks the seismicity decay 5 min before the mainshocks is indistinguishable from the decay five minutes afterwards indicating that the mainshocks have no effect at distances outside their static triggering range omori temporal decay the fundamental signature of aftershocks is absent at distances exceeding 10 km from the mainshocks finally the distance decay is found among aftershocks that occur before the arrival of the seismic wave front from the mainshock which violates causality we argue that felzer and brodsky10 implicitly assume that the first of two independent aftershocks along a fault rupture triggers the second and that the first of two shocks in a creep or intrusion driven swarm triggers the second when this need not be the case

biostratigraphy and depositional setting of maastrichtian eocene oil shales from jordan abstract large distance correlation of sedimentary organic rich facies units in jordan has been established by means of calcareous nannofossil biostratigraphy based on a biostratigraphic framework a better understanding of the deposition and distribution of maastrichtian to eocene oil shales is obtained a total of 812 samples representing 29 wells located across jordan were studied for calcareous nannofossil biostratigraphy the results reveal major regional changes in paleogeography leading to a change in oil shales distribution in time the tectonic settings have been determined for four different oil shale sequences of maastrichtian paleocene early eocene and middle eocene age large variations in thickness over short distances indicate syndepositional subsidence control in several fault bound sedimentary sub basins during the early maastrichtian transgression a thick oil shale dominated succession was accumulated in the south of jordan this transgression continued into the paleocene as represented by a thick sequence of oil shales in nannofossil zone np 3 in the late paleocene the gradual progradation of the oil shale facies from south to north coincided with an uplift of the sirhan sub basin in east jordan accordingly the oil shale distribution varies locally and shows a scattered geographic distribution in the late paleocene an up to 60 m thick succession of early eocene oil shales was found in central jordan localized restricted conditions which prevailed during the ypresian lutetian transition nannofossil zone np 14 were caused by the subsidence of the azraq hamza and sirhan sub basins these movements resulted in thick oil shale accumulation in the southeastern and central parts of jordan a gradual relative sea level fall during the bartonian resulted in a prograding and thinning of the oil shale facies from west to east in central jordan

computing a large refined catalog of focal mechanisms for southern california 1981 2010 temporal stability of the style of faulting using the method developed by hardebeck and shearer 2002 2003 termed the hash method we calculate focal mechanisms for earthquakes that occurred in the southern california region from 1981 to 2010 when available we use hypocenters refined with differential travel times from waveform cross correlation using both the p wave first motion polarities and the s p amplitude ratios computed from three component seismograms we determine mechanisms for more than 480 000 earthquakes and analyze the statistical features of the whole catalog we filter the preliminary catalog with criteria associated with mean nodal plane uncertainty and azimuthal gap and obtain a high quality catalog with approximately 179 000 focal mechanisms as more s p amplitude ratios become available after 2000 the average nodal plane uncertainty decreases significantly compared with mechanisms that include only p wave polarities in general the parameters of the focal mechanisms have been stable during the three decades the dominant style of faulting is high angle strike slip faulting with the most likely p axis centered at n5 e for earthquakes of m 2 5 events using the 210 moment tensor solutions in tape et al 2010 as benchmarks we compare the focal plane rotation angles of common events in the catalog seventy percent of common earthquakes match well with rotation angles less than the typical nodal plane uncertainty the common events with relatively large rotation angles are either located around the edge of the scsn network or poorly recorded

traces of ancient geysers preserved in the travertine of siwaqa jordan conditions of their formation a pleistocene travertine quarrying on a hill in siwaqa area central jordan excavated solid well stratified travertine beds of about 12 m in thickness the fabric and composition of the travertine indicate original deposition from hot spring water at present the area and its surrounding are devoid of any perennial water except for periodic flood flows that collect at siwaqa dam 4 5 km to the west of the quarry area joining the catchment of the river mujib the travertine overlies combusted oil shale the exposed hot spring travertine consists predominantly of well bedded limestone interrupted by horizons of chaotic angular debris indicating ejection from below such as those produced by geysers the article discusses the origins of the mottled and angular rock fragments their transportation due to explosive geyser the conditions and possible causes that produced the pressures leading to steam outbreaks and are responsible for the observed redistribution of travertine layers

repeated enrichment of trace metals and organic carbon on an eocene high energy shelf caused by anoxia and reworking petroleum source rocks are strongly enriched in organic carbon oc and their trace metal tm contents often reach low grade ore levels the mechanisms leading to these coenrichments are important for understanding how extreme environmental conditions support the formation of natural resources we therefore studied organic rich eocene marls and limestones oil shale from the central jordan amzaq hazra subbasin part of a cretaceous paleogene shelf system along the southern neo tethys margin geochemical analyses on two cores show highly dynamic depositional conditions consistent with sedimentological and micropaleontological observations maximum and average contents respectively in oc 26 and 10 wt sulfur 7 and 2 4 wt phosphorus 10 and 2 wt molybdenum 400 and 130 ppm chromium 500 and 350 ppm vanadium 1600 and 550 ppm and zinc 3800 and 900 ppm are exceptional in particular without any indication of hydrothermal or epigenetic processes we propose a combination of two processes physical reworking of oc and metal rich 30 material from locally exposed cretaceous paleogene sediments as supported by reworked nannofossils and high marine productivity fueled by chemical remobilization of nutrients and metals on land that sustained anoxic sulfidic conditions burial of high quality organic matter hydrogen index 600 700 mghc goc was related to strongly reducing conditions punctuated by only short lived oxygenation events and to excess h2s promoting organic matter sulfurization these processes likely caused the oc and tm coenrichments in a high energy shallow marine setting that contradicts common models for black shale formation but may explain similar geochemical patterns in other black shales

mid holocene enso issues in quantitative model proxy data comparisons 1 evaluation of climate model simulations using observed data contributes to the assessment of confidence in model predictions of future climate change the mid holocene represents an opportunity to evaluate model simulations of el nino southern oscillation enso in comparison with coral proxy evidence of reduced enso amplitude quantitative comparisons between coral records and model output have been limited by 1 the use of different measures of enso amplitude 2 possible sampling of natural variability in short records and 3 uncertainty about the stationarity of the relationship between central pacific sea surface temperature sst variability and enso signals at the coral site we examine these issues using modern and fossil coral records from the western pacific and model simulations of preindustrial and mid holocene climate as a measure of enso amplitude the standard deviation is found to be preferable to event frequency or size as event based measures are highly dependent on the choice of threshold and may be unreliable for a small number of events model enso amplitude is found to be strongly dependent on the choice of averaging period with calendar year averages smoothing the seasonal enso signal a relatively robust relationship between sst variability in the nino3 4 region and the enso sst and precipitation anomalies archived in corals is demonstrated for the instrumental period and for a set of model simulations remaining uncertainty about changes in enso teleconnections under paleoclimate conditions implies the need for additional proxy records from enso sensitive regions before quantitative reconstructions of enso amplitude can be used to evaluate model sensitivity

slip on the san andreas fault at parkfield california over two earthquake cycles and the implications for seismic hazard parkfield california which experienced m 6 0 earthquakes in 1934 1966 and 2004 is one of the few locales for which geodetic observations span multiple earthquake cycles we undertake a comprehensive study of deformation over the most recent earthquake cycle and explore the results in the context of geodetic data collected prior to the 1966 event through joint inversion of the variety of parkfield geodetic measurements trilateration two color laser and global positioning system including previously unpublished two color data we estimate the spatial distribution of slip and slip rate along the san andreas using a fault geometry based on precisely relocated seismicity although the three most recent parkfield earthquakes appear complementary in their along strike distributions of slip they do not produce uniform strain release along strike over multiple seismic cycles since the 1934 earthquake more than 1 m of slip deficit has accumulated on portions of the fault that slipped in the 1966 and 2004 earthquakes and an average of 2 m of slip deficit exists on the 33 km of the fault southeast of gold hill to be released in a future perhaps larger earthquake it appears that the fault is capable of partially releasing stored strain in moderate earthquakes maintaining a disequilibrium through multiple earthquake cycles this complicates the application of simple earthquake recurrence models that assume only the strain accumulated since the most recent event is relevant to the size or timing of an upcoming earthquake our findings further emphasize that accumulated slip deficit is not sufficient for earthquake nucleation online material model fault geometry fit to the data for the inversions and model resolution

seismically damaged regolith as self organized fragile geological feature 1 the s wave velocity in the shallow subsurface within seismically active regions self organizes so that typical strong dynamic shear stresses marginally exceed the coulomb elastic limit the dynamic velocity from major strike slip faults yields simple dimensional relations the near field velocity pulse is essentially a love wave the dynamic shear strain is the ratio of the measured particle velocity over the deep s wave velocity the shallow dynamic shear stress is this quantity times the local shear modulus the dynamic shear traction on fault parallel vertical planes is finite at the free surface coulomb failure occurs on favorably oriented fractures and internally in intact rock i obtain the equilibrium shear modulus by starting a sequence of earthquakes with intact stiff rock extending all the way to the surface the imposed dynamic shear strain in stiff rock causes coulomb failure at shallow depths and leaves cracks in it wake cracked rock is more compliant than the original intact rock cracked rock is also weaker in friction but shear modulus changes have a larger effect each subsequent event causes additional shallow cracking until the rock becomes compliant enough that it just reaches coulomb failure over a shallow depth range of tens to hundreds of meters further events maintain the material at the shear modulus as a function where it just fails the formalism provided in the paper yields reasonable representation of the s wave velocity in exhumed sediments near cajon pass and the san fernando valley of california a general conclusion is that shallow rocks in seismically active areas just become nonlinear during typical shaking this process causes transient changes in s wave velocity but not strong nonlinear attenuation of seismic waves wave amplitudes significantly larger than typical ones would strongly attenuate and strongly damage the rock

tremor reveals stress shadowing deep postseismic creep and depth dependent slip recurrence on the lower crustal san andreas fault near parkfield 1 the 2003 magnitude 6 5 san simeon and the 2004 magnitude 6 0 parkfield earthquakes induced small but significant static stress changes in the lower crust on the central san andreas fault where recently detected tectonic tremor sources provide new constraints on deep fault creep processes we find that these earthquakes affect tremor rates very differently consistent with their differing transferred static shear stresses the san simeon event appears to have cast a stress shadow north of parkfield where tremor activity was stifled for 3 6 weeks in contrast the 2004 parkfield earthquake dramatically increased tremor activity rates both north and south of parkfield allowing us to track deep postseismic slip following this event rates initially increased by up to two orders of magnitude for the relatively shallow tremor sources closest to the rupture with activity in some sources persisting above background rates for more than a year we also observe strong depth dependence in tremor recurrence patterns with shallower sources generally exhibiting larger less frequent bursts possibly signaling a transition toward steady creep with increasing temperature and depth

full 3 d tomography for crustal structure in southern california based on the scattering integral and the adjoint wavefield methods we have successfully applied full 3 d tomography f3dt based on a combination of the scattering integral method si f3dt and the adjoint wavefield method aw f3dt to iteratively improve a 3 d starting model the southern california earthquake center scec community velocity model version 4 0 cvm s4 in f3dt the sensitivity frechet kernels are computed using numerical solutions of the 3 d elastodynamic equation and the nonlinearity of the structural inversion problem is accounted for through an iterative tomographic navigation process more than half a million misfit measurements made on about 38 000 earthquake seismograms and 12 000 ambient noise correlagrams have been assimilated into our inversion after 26 f3dt iterations synthetic seismograms computed using our latest model cvm s4 26 show substantially better fit to observed seismograms at frequencies below 0 2 hz than those computed using our 3 d starting model cvm s4 and the other scec cvm cvm h11 9 which was improved through 16 iterations of aw f3dt cvm s4 26 has revealed strong crustal heterogeneities throughout southern california some of which are completely missing in cvm s4 and cvm h11 9 but exist in models obtained from previous crustal scale 2 d active source refraction tomography models at shallow depths our model shows strong correlation with sedimentary basins and reveals velocity contrasts across major mapped strike slip and dip slip faults at middle to lower crustal depths structural features in our model may provide new insights into regional tectonics when combined with physics based seismic hazard analysis tools we expect our model to provide more accurate estimates of seismic hazards in southern california

relative sea level changes during the cretaceous in israel detailed lithologic microfaunal and biometric investigations using relative abundances diversity indexes and duration charts of ostracods and foraminifera allowed the recognition of sea level changes during the cretaceous of israel three major transgressive regressive sedimentation cycles occur on the northwest margins of the arabian craton these cycles are the neocomian aptian which is mostly terrigenous sediments the albian turonian which is basin marls and platform carbonates and the senonian which is uniform marly chalks the cycles are separated by two major regional unconformities the aptian albian and turonian coniacian boundaries the sedimentary cycles are related to regional tectonic and volcanic events and eustatic changes the paleodepth curve il ustrates the gradual sea level rise reaching its maximum during the late cretaceous with conspicuous advances during the late aptian late albian cenomanian early turonian early santonian and early campanian major lowstands occur at the aptian albian cenomanian turonian turonian coniacian and campanian maastrichtian boundaries this model for israel agrees well with other regional and global sea level fluctuations four anoxic events black shales accompanying transgressions correspond to the cretaceous oceanic record we hypothesize the presence of mature oil shales in the present day eastern mediterranean basin close to allochthonous reef blocks detached from the cretaceous platform

investigating microearthquake finite source attributes with iris community wavefield demonstration experiment in oklahoma author posting the authors 2018 this article is posted here by permission of the royal astronomical society for personal use not for redistribution the definitive version was published in geophysical journal international 215 2018 1072 1087 doi 10 1093 gji ggy203

zooming in on heinrich layers theories explaining the origin of the abrupt massive discharges of ice rafted detritus ird into the glacial north atlantic the heinrich layers hls generally point to the laurentide ice sheet as the sole source of these events until it was found that the irds also originated from icelandic and european ice sheets bond and lotti 1995 snoeckx et al 1999 grousset et al 2000 this apparent contradiction must be reconciled as it raises fundamental questions about the mechanism s of hl origin we have analyzed two 12 cm thick hls in an ultrahigh resolution mode 1 2 century intervals in a mid atlantic ridge piston core the 18o record n pachyderma left coiling reveals strong excursions induced by the melting of the icebergs these excursions are associated with a strong decrease in the amount of planktic foraminafersand with a 3 c cooling of the surface waters counts of coarse detrital grains reveal that ird are deposited according to a typical sequence 1 volcanic glass 2 quartz and feldspars 3 detrital carbonate that implies a chronology in the melting of the differentpan atlantic ice sheets sr and nd isotopic composition confirm that in both heinrich layers h1 and h2 precursor ird came from first europe iceland followed then by laurentide derived ird an internal cyclicity can be identified during h1 and h2 about four to six major abrupt discharges occurred roughly on a century timescale the 13c and 15n records reveal that dominant inputs of continent derived organic matter are associated with ird within the hls hiding the plankton productivity signal