stuck in the mud earthquake nucleation and propagation through accretionary forearcs 1 subduction zone earthquakes can propagate to the surface causing large seafloor displacements resulting in tsunamis this requires the earthquake to rupture through clay rich sediments of the accretionary wedge which are largely aseismic as found previously the frictional properties of a range of wet clays at low slip velocity are velocity strengthening thus inhibiting earthquake nucleation however at high slip velocity the same materials weaken almost immediately resulting in a negligible critical slip weakening distance and fracture energy we interpret this behaviour as rapid thermal pressurization of the pore fluid within the clay gouge the lack of fracture energy can explain how a large rupture propagating from depth might not be arrested by clay rich velocity strengthening sediments as is commonly seen the results suggest that generally earthquakes may be difficult to nucleate on mature faults dominated by clay but the propagation of earthquakes through these zones is energetically very favourable

the 5 september 2012 nicoya costa rica mw 7 6 earthquake rupture process from joint inversion of high rate gps strong motion and teleseismic p wave data and its relationship to adjacent plate boundary interface properties 1 on 5 september 2012 a large thrust earthquake mw 7 6 ruptured a densely instrumented seismic gap on the shallow dipping plate boundary beneath the nicoya peninsula costa rica ground motion recordings directly above the rupture zone provide a unique opportunity to study the detailed source process of a large shallow megathrust earthquake using very nearby land observations hypocenter relocation using local seismic network data indicates that the event initiated with small emergent seismic waves from a hypocenter 10 km offshore 13 km deep on the megathrust a joint finite fault inversion using high rate gps strong motion ground velocity recordings gps static offsets and teleseismic p waves reveals that the primary slip zone slip 1 m is located beneath the peninsula the rupture propagated downdip from the hypocenter with a rupture velocity of 3 0 km s the primary slip zone extends 70 km along strike and 30 km along dip with an average slip of 2 m the associated static stress drop is 3 mpa the seismic moment is 3 5 1020 nm giving mw 7 6 the coseismic large slip patch directly overlaps an onshore interseismic locked region indicated by geodetic observations and extends downdip to the intersection with the upper plate moho at deeper depths below the upper plate moho seismic tremor and low frequency earthquakes have been observed most tremor locates in adjacent areas of the megathrust that have little coseismic slip a region of prior slow slip deformation to the southeast also has no significant coseismic slip or aftershocks an offshore locked patch indicated by geodetic observations does not appear to have experienced coseismic slip and aftershocks do not overlap this region allowing the potential for a comparable size rupture offshore in the future

oxygen isotopic composition of multiple species of planktonic foraminifera recorders of the modern photic zone temperature gradient abundances of 12 species of planktonic foraminifera collected in two plankton tows from the east tropical atlantic are compared to the chlorophyll content and the temperature of the sea water from which they were collected as expected from previous work in the tropics all dominant tropical species occur in greatest abundance within the photic zone many species occur in greatest abundances in the seasonal thermocline in association with the maximum chlorophyll concentration while a few algal symbiont bearing species occur in greatest abundance in the mixed layer the 18o measurements of planktonic foraminifera shells from core top sediment samples confirm the vertical stratification within the photic zone that is suggested by the relationship between hydrography and abundances found in the plankton tows and found in the statistical study by ravelo et al 1990 comparison between the measured 18o values of planktonic foraminifera with the predicted 18o profiles of the overlying water column at three core locations indicate that species abundances in the sediment record the seasonally integrated conditions of the photic zone and suggests that the abundance of a species in the sediment depends on whether the preferred ecological conditions of that species may be found within the photic zone of the overlying water column sometime during the year species which calcify below the photic zone have only trace relative abundances finally it appears that the total range of 18o values of the dominant species approximates the predicted annual 18o of calcite range in the upper 80 m of the water column

millennial scale variability in western tropical atlantic surface ocean hydrography during the early pliocene abstract we use high resolution oxygen isotope data 18o from planktonic foraminifera in the western tropical atlantic ocean ocean drilling program leg 154 site 925 to investigate millennial scale climate variability during an interval of relative climate warmth the early pliocene for this purpose we have chosen a 100 kyr long time interval from 4 13 to 4 24 ma and subsampled it to obtain an average time step of 800 yr we reconstruct changes in upper ocean hydrography using the 18o values of globigerinoides sacculifer a mixed layer dweller and neogloboquadrina dutertrei a thermocline dweller their oxygen isotopic difference 18o is taken as a measure of the mixed layer to thermocline thermal gradient time series analysis indicates that significant concentration of variance exists in the g sacculifer and n dutertrei at sub milankovitch periods of between 8 and 4 kyr and in the 18o record between 13 and 8 kyr wavelet analysis illustrates that the suborbital variance is only present in the record when the amplitude of the precessional signal is large between 4 24 and 4 20 ma in this particular portion of the record however we observe positive 18o excursions in the individual 18o time series thus the suborbital periods evident in the spectra may reflect harmonics associated with asymmetrical time series because the excursions only occur when precession forcing is also strong we suggest that there is a relationship between the proxy records and climate although we cannot conclude that it is cyclical in nature the 18o record on the other hand is characterized by positive as well as negative excursions we observe significant concentration of variance close to half precession during the portion of the record when precession forcing is also strong which we believe reflects a close although nonlinear response of the western tropical surface ocean to low latitude insolation forcing

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

evidence for changes in the north atlantic deep water linked to meltwater surges during the heinrich events abstract deep sea sediment records from north atlantic cores 40 n 55 n provide evidence of several massive iceberg discharges known as heinrich events during the last glacial period high resolution benthic 18 o and 13 c records from north atlantic sediment cores were used to monitor the impact of heinrich events on thermohaline circulation and to estimate the sensitivity of deep oceanic circulation to changes in freshwater input to the north atlantic surface waters our data indicate that major rearrangements of deep water masses were directly associated with these massive iceberg discharges to trace in detail the deep water conditions in the north atlantic benthic 13 c values in several cores were used to generate time slices before during and after heinrich event 4 dated at 35 ka bp although north atlantic deep water continued to form during the oxygen isotope stage 3 at 37 ka bp deep circulation was characterized by an increased incursion of deep waters of southern origin which reduced the 13 c composition of north atlantic deep waters particularly in the eastern atlantic basin north atlantic deep water production was reduced during heinrich layer 4 hl4 at 35 ka bp synchronously with the changes in the surface water hydrology deep convection processes may have occurred in areas not affected by the salinity decrease soon after hl4 33 ka bp the 13 c distribution was similar to that before the event similarly a rapid return to initial 13 c values was observed at the end of the most clearly defined heinrich events hl5 hl4 and hl1 comparison between deep circulation patterns corresponding to hl4 the last glacial maximum and heinrich event 1 indicates that each of these periods was characterized by a different circulation state associated with changes in convection sites

rupture process of the 2010 mw 7 8 mentawai tsunami earthquake from joint inversion of near field hr gps and teleseismic body wave recordings constrained by tsunami observations the 25 october 2010 mentawai tsunami earthquake mw 7 8 ruptured the shallow portion of the sunda megathrust seaward of the mentawai islands offshore of sumatra indonesia generating a strong tsunami that took 509 lives the rupture zone was updip of those of the 12 september 2007 mw 8 5 and 7 9 underthrusting earthquakes high rate 1 s sampling gps instruments of the sumatra gps array network deployed on the mentawai islands and sumatra mainland recorded time varying and static ground displacements at epicentral distances from 49 to 322 km azimuthally distributed tsunami recordings from two deepwater sensors and two tide gauges that have local high resolution bathymetric information provide additional constraints on the source process finite fault rupture models obtained by joint inversion of the high rate hr gps time series and numerous teleseismic broadband p and s wave seismograms together with iterative forward modeling of the tsunami recordings indicate rupture propagation 50 km up dip and 100 km northwest along strike from the hypocenter with a rupture velocity of 1 8 km s subregions with large slip extend from 7 to 10 km depth 80 km northwest from the hypocenter with a maximum slip of 8 m and from 5 km depth to beneath thin horizontal sedimentary layers beyond the prism deformation front for 100 km along strike with a localized region having 15 m of slip the seismic moment is 7 2 1020 n m the rupture model indicates that local heterogeneities in the shallow megathrust can accumulate strain that allows some regions near the toe of accretionary prisms to fail in tsunami earthquakes

supercycle at the ecuadorian subduction zone revealed after the 2016 pedernales earthquake large earthquakes are usually assumed to release all of the strain accumulated since the previous event implying a reduced seismic hazard after them however long records of seismic history at several subduction zones suggest supercycle behaviour where centuries long accumulated strain is released through clustered large earthquakes resulting in an extended period of enhanced seismic hazard here we combine historical seismology results present day geodesy data and dense local observations of the recent mw 7 8 2016 pedernales earthquake to reconstruct the strain budget at the ecuador subduction zone since the great 1906 earthquake we show that the pedernales earthquake involved the successive rupture of two patches on the plate interface that were locked prior to the earthquake and most probably overlaps the area already ruptured in 1942 by a similar earthquake however we find that coseismic slip in 2016 exceeds the deficit accumulated since 1942 the seismic moment of every large earthquake during the twentieth century further exceeds the moment deficit accumulated since 1906 these results together with the seismic quiescence before 1906 highlighted by historical records and marine palaeoseismology argue for an earthquake supercycle at the ecuador colombia margin this behaviour which has led to an enhanced seismic hazard for 110 years is possibly still going on and may apply to other subduction zones that recently experienced a great earthquake large earthquakes are often assumed to reset the seismic hazard of a region analysis of recent and historical seismicity in ecuador suggests that this region may experience clusters of large earthquakes and extended periods of high seismic hazard

topographic slope as a proxy for seismic site conditions and amplification we describe a technique to derive first order site condition maps directly from topographic data for calibration we use global 30 arc sec topographic data and v s 30 measurements here v s 30 refers to the average shear velocity down to 30 m aggregated from several studies in the u s as well as in taiwan italy and australia v s 30 values are correlated against topographic slope to develop two sets of parameters for deriving v s 30 one for active tectonic regions where topographic relief is high and one for stable shields where topography is more subdued by taking the gradient of the topography and choosing ranges of slope that maximize the correlation with shallow shear velocity observations we can recover to first order many of the spatially varying features of sitecondition maps developed for california our site condition map for the low relief mississippi embayment also predicts the bulk of the v s 30 observations in that region despite rather low slope ranges we find that maps derived from the slope of the topography is often well correlated with other independently derived regional scale site condition maps but the latter maps vary in quality and continuity and subsequently also in their ability to match observed v s 30 measurements contained therein alternatively the slope based method provides a simple approach to uniform site condition mapping

forcing of atlantic equatorial and subpolar millennial cycles by precession abundance cycles of the marine alga florisphaera profunda centered on a period of 7600 carbon 14 years 8400 calendar years are present in high resolution records from the equatorial atlantic spanning 0 to 45 000 years ago these cycles correlate with heinrich events 1 through 5 which document rapid changes in continental ice melting around the subpolar north atlantic these variations in f profunda are a direct response to modulation in zonal wind driven divergence produced by a precessional component of orbital variation during a time of reduced eccentricity modulation

pliocene shallow water paleoceanography of the north atlantic ocean based on marine ostracodes abstract middle pliocene marine ostracodes from coastal and shelf deposits of north and central america and iceland were studied to reconstruct paleotemperatures of shelf waters bordering portions of the western boundary current system including the gulf loop current florida current gulf stream and north atlantic drift factor analytic transfer functions provided pliocene august and february bottom water temperatures of eight regions from the tropics to the subfrigid the results indicate 1 meridional temperature gradients in the western north atlantic were less steep during the pliocene than either today or during late pleistocene isotope stage 5e 2 tropical and subtropical shelf waters during the middle pliocene were as warm as or slightly cooler than today 3 slightly cooler water was on the outer shelf off the southeastern and mid atlantic coast of the u s possibly due to summer upwelling of gulf stream water 4 the shelf north of cape hatteras north carolina may have been influenced by warm water incursions from the western edge of the gulf stream especially in summer 5 the northeast branch of the north atlantic drift brought warm water to northern iceland between 4 and 3 ma evidence from the iceland record indicates that cold east greenland current water did not affect coastal iceland between 4 and 3 ma 6 middle pliocene north atlantic circulation may have been intensified transporting more heat from the tropics to the arctic than it does today

tsunamis in the black sea comparison of the historical instrumental and numerical data 1 the tsunami hazard in the black sea is discussed by comparing historical instrumental data and numerical results there are 22 tsunami events in the black sea documented since the first century and nine of them have occurred in twentieth century the numerical simulations of tsunami propagation for the 1966 and 1939 events are performed by using the framework of the shallow water theory the instrumental data from tide gauge records are used to compare and validate the simulation results and estimate the wave motion at other locations where the instrumental data are unavailable the distribution of maximum positive tsunami amplitudes along the north and south coasts are obtained for each event the arrival time tsunami amplitudes and directivity of tsunamis in the black sea are studied the probable source and target areas of tsunamis are discussed

kinematic study of iquique 2014 mw 8 1 earthquake understanding the segmentation of the seismogenic zone abstract we study the rupture processes of iquique earthquake m w 8 1 2014 04 01 and its largest aftershock m w 7 7 2014 04 03 that ruptured the north chile subduction zone high rate global positioning system gps recordings and strong motion data are used to reconstruct the evolution of the slip amplitude rise time and rupture time of both earthquakes a two step inversion scheme is assumed by first building prior models for both earthquakes from the inversion of the estimated static displacements and then kinematic inversions in the frequency domain are carried out taken into account this prior information the preferred model for the mainshock exhibits a seismic moment of 1 73 1021 nm m w 8 1 and maximum slip of 9 m while the aftershock model has a seismic moment of 3 88 1020 m w 7 7 and a maximum slip of 3 m for both earthquakes the final slip distributions show two asperities a shallow one and a deep one separated by an area with significant slip deficit this suggests a segmentation along dip which might be related to a change of the dipping angle of the subducting slab inferred from gravimetric data along strike the areas where the seismic ruptures stopped seem to be well correlated with geological features observed from geophysical information high resolution bathymetry gravimetry and coupling maps that are representative of the long term segmentation of the subduction margin considering the spatially limited portions that were broken by these two earthquakes our results support the idea that the seismic gap is not filled yet

millennial scale changes of surface and deep water flow in the western tropical atlantic linked to northern hemisphere high latitude climate during the holocene there is increasing evidence that the preceding holocene climate was as unstable as the last glacial period although variations occurred at much lower amplitudes however low latitude climate records that confirm this variability are sparse here we present a radiocarbon dated holocene marine record from the tropical western atlantic aragonite dissolution derived from the degree of preservation of the pteropod limacina inflata records changes in the corrosiveness of the bottom water at the core site due to the changing influence of northern versus southern water masses the 18 o difference between the shallow living planktonic foraminifera globigerinoides sacculifer and the deep living globorotalia tumida is used as proxy for changes in the vertical stratification of the surface water hence the trade wind strength at this latitude we compared our data to high latitude records of the north atlantic region a good agreement is found between the aragonite dissolution and the strength in the island scotland overflow water which contributes significantly to the north atlantic deep water this suggests that large scale variations in the atlantic thermohaline circulation occurred throughout the holocene concurrently the comparison of our 18 o with the gisp2 glaciochemical records points to global holocene atmospheric reorganizations seen in both the tropics and high northern latitudes

millennial scale fluctuations in north atlantic heat flux during the last 150 000 years abstract surface water and deep ocean palaeoclimate records obtained from north atlantic core su90 03 40 n 32 w exhibit pronounced fluctuations at sub orbital time scales surface temperature variability in the mid latitude atlantic over the last 150 kyr is dominated by forcing at precession 21 kyr and semi precession harmonics 11 kyr abrupt changes in sea surface temperatures show that the northward transport of heat by the north atlantic current was curtailed during ice rafting events sea surface temperatures were about 12 c colder than modern values during the most intense cooling episodes associated with major ice rafting events heinrich events 1 4 6 and 11 and 10 c below modern values during the later part of isotope stage 3 40 30 ka during these cold intervals the north atlantic current was displaced to south of 40 n as the cold meltwaters penetrated southwards into what is now the subtropical ocean these changes in surface ocean heat exchange were most probably allied to a latitudinal migration and increase in zonality of atmospheric circulation patterns concurrent shifts in ird concentration sea surface temperatures and benthic 13 c values provide evidence of coupling between sea surface processes and the deep water circulation and suggest that decreases in surface temperature and salinity during ice rafting events culminated in a significant reorganisation of north atlantic deep water production

enhanced circulation during a warm period the early pliocene is the most recent interval in which equilibrium oceanic conditions can be studied in the context of global warmth relative to today to characterize thermohaline circulation during this warm period 4 4 3 1 ma we combined new benthic foraminiferal isotopic data from the southeast atlantic with published data and reconstructed pacific and atlantic ocean nutrient distributions the data indicate enhanced ventilation of the deep atlantic and intermediate pacific during the early pliocene enhanced ventilation implies that delivery of surface water to high latitudes in western boundary currents of north pacific and atlantic subtropical gyres was probably also enhanced future modeling of this warm period needs to reconcile reduced meridional surface temperature gradients with enhanced subtropical gyre and thermohaline circulation

local tsunami warnings perspectives from recent large events we demonstrate a flexible strategy for local tsunami warning that relies on regional geodetic and seismic stations through retrospective analysis of four recent tsunamigenic events in japan and chile we show that rapid earthquake source information provided by methodologies developed for earthquake early warning can be used to generate timely estimates of maximum expected tsunami amplitude with enough accuracy for tsunami warning we validate the technique by comparing to detailed models of earthquake source and tsunami propagation as well as field surveys of tsunami inundation our approach does not require deployment of new geodetic and seismic instrumentation in many subduction zones and could be implemented rapidly by national monitoring and warning agencies we illustrate the potential impact of our method with a detailed comparison to the actual timeline of events during the recent 2015 mw8 3 illapel chile earthquake and tsunami that prompted the evacuation of 1 million people

millennial scale changes in north atlantic deep water circulation during marine isotope stages 11 and 12 linkage to antarctic climate the time interval represented by marine isotope stages mis 11 and 12 ca 360 470 ka may contain the most extreme glacial and interglacial climate conditions of the late pleistocene sediments from the bermuda rise western north atlantic provide clues to the nature of climate variability during this period our geochemical records indicate that millennial scale climate instability and associated changes in north atlantic deep water nadw production occurred during both interglacial mis 11 and glacial mis 12 stage 12 is punctuated by a series of interstadial events that occurred at a 5 6 k y periodicity and the occurrence of ice rafted debris at various times during stage 12 indicates that icebergs were present at least as far south as 34 n during this glacial period within the limits of our correlation the atmospheric temperature changes recently reported for the vostok ice core for the stage 11 time period appear to be represented by coeval changes in nadw flow specifically warming in antarctica is associated with increased production of nadw

early onset and tropical forcing of 100 000 year pleistocene glacial cycles between 1 5 and 0 6 myr ago the period of the earth s glacial cycles changed from 41 kyr the period of the earth s obliquity cycles to 100 kyr the period of the earth s orbital eccentricity1 2 which has a much smaller effect on global insolation the timing of this transition and its causes pose one of the most perplexing problems in palaeoclimate research3 here we use complex demodulation to examine the phase evolution of precession and semiprecession cycles the latter of which are phase coupled to both precession and eccentricity in the tropical and extra tropical atlantic ocean we find that about 1 5 myr ago tropical semiprecession cycles with periods of about 11 5 kyr started to propagate to higher latitudes coincident with a growing amplitude envelope of the 100 kyr cycles evidence from numerical models suggests that cycles of about 10 kyr in length may be required to explain the high amplitude of the 100 kyr cycles4 combining our results with consideration of a modern analogue we conclude that increased heat flow across the equator or from the tropics to higher latitudes around 1 5 myr ago strengthened the semiprecession cycle in the northern hemisphere and triggered the transition to sustained 100 kyr glacial cycles

earthquake magnitude calculation without saturation from the scaling of peak ground displacement gps instruments are noninertial and directly measure displacements with respect to a global reference frame while inertial sensors are affected by systematic offsets primarily tilting that adversely impact integration to displacement we study the magnitude scaling properties of peak ground displacement pgd from high rate gps networks at near source to regional distances 10 1000 km from earthquakes between mw6 and 9 we conclude that real time gps seismic waveforms can be used to rapidly determine magnitude typically within the first minute of rupture initiation and in many cases before the rupture is complete while slower than earthquake early warning methods that rely on the first few seconds of p wave arrival our approach does not suffer from the saturation effects experienced with seismic sensors at large magnitudes rapid magnitude estimation is useful for generating rapid earthquake source models tsunami prediction and ground motion studies that require accurate information on long period displacements

persistent suborbital climate variability in marine isotope stage 5 and termination ii new surface water records from two high sedimentation rate sites located in the western subtropical north atlantic near the axis of the gulf stream provide clear evidence of suborbital climate variations through marine isotope stage mis 5 persisting even into the warm peak of the interglaciation substage 5e we found that the amplitude of suborbital climate oscillations did not vary significantly for the whole of mis 5 implying that ice volume has little or no influence on the amplitude of suborbital climate variability in this region although some records suggest that longer suborbital variations 4 10 kyr during mis 5 are linked to deepwater changes none of the existing records is of sufficient resolution to assess if a linkage occurred for oscillations shorter than 4 kyr however when examined in conjunction with published data from the norwegian sea new evidence from the subpolar north atlantic suggests that coupled surface deepwater oscillations occurred during the penultimate deglaciation this supports the hypothesis that during glacial and deglacial times ocean ice interactions and deepwater variability amplify suborbital climate change at higher latitudes we suggest that during the penultimate deglaciation the north atlantic deepwater source varied between nordic sea and open north atlantic locations in parallel with surface temperature oscillations

millennial scale climate change and oceanic processes in the late pliocene and early pleistocene we generated 200 500 year resolution records of oceanic processes in the north atlantic ocean drilling program site 983 60 24 n 23 38 w 1983 meters water depth for intervals in the latest pliocene 1 86 1 93 ma and the earliest pleistocene 1 75 1 83 ma in order to examine the linkages between millennial scale variations in the ocean and background glacial interglacial climate change within glacial intervals we find evidence for variations similar to those observed in the late pleistocene we find discrete ice rafted debris ird events that reoccur every 2 5 kyr these events are preceded by a short cooling and accompanied by a reorganization of glacial deep waters the timing of ird events in the late pliocene and early pleistocene intervals is similar to that of dansgaard oeschger cycles but we find no ird events comparable in timing to late pleistocene heinrich events although interglacial intervals are much more stable we do find evidence for low amplitude variations in deep water properties that reoccur every 2 kyr within interglacial intervals the similarity between our late pliocene early pleistocene records and late pleistocene records implies that the mechanism driving millennial scale variations cannot be uniquely attributed to the strongly nonlinear linkage between climate and insolation and the large ice sheets of the late pleistocene

extreme runup from the 17 july 2006 java tsunami 1 the 17 july 2006 magnitude mw 7 8 earthquake off the south coast of western java indonesia generated a tsunami that effected over 300 km of coastline and killed more than 600 people with locally focused runup heights exceeding 20 m this slow earthquake was hardly felt on java and wind waves breaking masked any preceding withdrawal of the water from the shoreline making this tsunami difficult to detect before impact an international tsunami survey team was deployed within one week and the investigation covered more than 600 km of coastline measured tsunami heights and run up distributions were uniform at 5 to 7 m along 200 km of coast however there was a pronounced peak on the south coast of nusa kambangan where the tsunami impact carved a sharp trimline in a forest at elevations up to 21 m and 1 km inland local flow depth exceeded 8 m along the elevated coastal plain between the beach and the hill slope we infer that the focused tsunami and runup heights on the island suggest a possible local submarine slump or mass movement

global ice volume fluctuations north atlantic ice rafting events and deep ocean circulation changes between 130 and 70 ka multiproxy data from north atlantic deep sea sediment core neap18k provide a detailed record of climate through oxygen isotope stage ois 5 seven distinct large scale episodes of ice rafting c25 c19 were identified between 126 and 70 ka global ice volume reconstructions based on high resolution benthic 18 o records indicate that major ice rafting events were not confined to ice volume maxima at ois 5d and 5b but also occurred during periods of ice sheet growth and disintegration however iceberg discharges were restricted to times when sea levels were 40 65 m below present values ice rafting episode c25 the first large scale cooling of mid atlantic surface waters after the last interglacial occurred during the gradual buildup of continental ice sheets at the ois 5e 5d transition major ice sheet collapses allied to ice rafting events c24 and c21 were associated with rapid sea level increases of 20 and 40 m respectively suborbital climatic fluctuations in the neap18k sedimentary record denoted by prominent 7 5 4 5 and 3 k y cyclicities appear to correlate with both greenland atmospheric temperatures and changes in thermohaline circulation patterns inferred from benthic 13 c values and hence provide clear evidence of a highly interconnected north atlantic climatic regime during ois 5

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

early pliocene climate a perspective from the western equatorial atlantic warm pool high resolution 3 4 kyr planktonic stable isotope stratigraphies from site 925 drilled on ceara rise ocean drilling program leg 154 are used to investigate the role of the western equatorial atlantic sea surface hydrography in early pliocene 3 2 4 7 ma climate change oxygen isotope results from globigerinoides sacculifer a mixed layer dweller suggest that equatorial sea surface temperatures were cooler than today by 2 3 c consistent with relatively strong northward advection of heat away from the equator oxygen isotope results from neogloboquadrina dutertrei suggest that over the long term this thermocline dweller tracks global ice volume fluctuations stable isotope gradients between the two planktonic species throughout the entire interval imply a stable warm pool in the western equatorial atlantic we observe a rapid 3 4 kyr decrease in g sacculifer and the n dutertrei 18o values at 4 36 ma that may reflect a freshening of the sea surface a direct response to a southward displacement of the intertropical convergence zone and perhaps an indirect response to restricted flow through the central american seaway

the 25 october 2010 mentawai tsunami earthquake mw 7 8 and the tsunami hazard presented by shallow megathrust ruptures the 25 october 2010 mentawai indonesia earthquake m w 7 8 ruptured the shallow portion of the subduction zone seaward of the mentawai islands off shore of sumatra generating 3 to 9 m tsunami run up along southwestern coasts of the pagai islands that took at least 431 lives analyses of teleseismic p sh and rayleigh waves for finite fault source rupture characteristics indicate 90 s rupture duration with a low rupture velocity of 1 5 km s on the 10 dipping megathrust with total slip of 2 4 m over an 100 km long source region the seismic moment scaled energy release is 1 4 10 6 lower than 2 4 10 6 found for the 17 july 2006 java tsunami earthquake m w 7 8 the mentawai event ruptured up dip of the slip region of the 12 september 2007 kepulauan earthquake m w 7 9 and together with the 4 january 1907 m 7 6 tsunami earthquake located seaward of simeulue island to the northwest along the arc demonstrates the significant tsunami generation potential for shallow megathrust ruptures in regions up dip of great underthrusting events in indonesia and elsewhere

diffuse spectral reflectance as a proxy for percent carbonate content in north atlantic sediments diffuse reflectance records from fern drift in the north atlantic faithfully record sediment percent carbonate a high resolu tion reflectance based age model for these sediments derived from an orbitally tuned age model for western equatorial atlantic ceara rise sediments was generated by spectral frequency mapping power spectra of the fern drift record indicate statistically significant sub milankovitch cyclicity at 7 6 8 4 and 4 8 6 1 kyr we infer that these 8 and 5 kyr cycles document a linkage between north and equa torial atlantic climate given our ability to correlate these records these climate cycles influence atlantic basin carbonate prior to the intensification of northern hemisphere glaciation and thus must arise from some portion of the climate system other than the dynamics of large ice sheets the presence of these peaks which could be related to equatorial clipped precession implies a possible non linear response to milankovitch forcing abstract diffuse reflectance records from feni drift in the north atlantic faithfully record sediment percent carbonate a high resolu tion reflectance based age model for these sediments derived from an orbitally tuned age model for western equatorial atlantic ceara rise sediments was generated by spectral frequency mapping power spectra of the feni drift record indicate statistically significant sub milankovitch cyclicity at 7 6 8 4 and 4 8 6 1 kyr we infer that these 8 and 5 kyr cycles document a linkage between north and equa torial atlantic climate given our ability to correlate these records these climate cycles influence atlantic basin carbonate prior to the intensification of northern hemisphere glaciation and thus must arise from some portion of the climate system other than the dynamics of large ice sheets the presence of these peaks which could be related to equatorial clipped precession implies a possible non linear response to milankovitch forcing

the 25 october 2010 mentawai tsunami earthquake from real time discriminants finite fault rupture and tsunami excitation 1 the moment magnitude 7 8 earthquake that struck offshore the mentawai islands in western indonesia on 25 october 2010 created a locally large tsunami that caused more than 400 human causalities we identify this earthquake as a rare slow source tsunami earthquake based on 1 disproportionately large tsunami waves 2 excessive rupture duration near 125 s 3 predominantly shallow near trench slip determined through finite fault modeling and 4 deficiencies in energy to moment and energy to duration cubed ratios the latter in near real time we detail the real time solutions that identified the slow nature of this event and evaluate how regional reductions in crustal rigidity along the shallow trench as determined by reduced rupture velocity contributed to increased slip causing the 5 9 m local tsunami runup and observed transoceanic wave heights observed 1600 km to the southeast

fast identification of near trench earthquakes along the mexican subduction zone based on characteristics of ground motion in mexico city abstract we explore the versatility of three parameters computed from recordings at station cu located in mexico city 300 600 km from the trench for quick detection 7 min after the origin time of near trench earthquakes for potential use in tsunami warning the parameters are 1 e r the ratio of total to high frequency energy 2 sa 6 the pseudoacceleration response spectrum with 5 damping at 6 s normalized by peak ground acceleration pga and 3 r esn the pga residual with respect to a newly derived ground motion prediction equation at cu because near trench earthquakes are relatively deficient in high frequency radiation we expect e r and sa 6 to be relatively large and r esn to be negative for such events tests on cu recordings of 65 interface earthquakes occurring along the mexican subduction zone 4 8 m w 8 0 270 r 615 km show that if e r 100 sa 6 0 70 and r esn 0 then the earthquake is near the trench such an event has greater tsunami potential and produces low acceleration few misidentifications and missed events are probably a consequence of poor location although unusual depth and source characteristics may also be responsible in some cases online material data used for the construction of ground motion prediction equation gmpe at station cu mexico city

attenuation relations of strong ground motion in japan using site classification based on predominant period a spectral acceleration attenuation model for japan is presented in the present study the data set includes a very large number of strong ground motion records up to the 2003 off tokach main and aftershocks site class terms instead of individual site correction terms are used the site classes of recording stations are from a recent study on site classification for strong motion recording stations in japan according to a classification scheme that has been used in japanese engineering design the use of site class terms enables tectonic source type effects to be identified and accounted for in the present model the effects of a faulting mechanism for crustal earthquakes also are accounted for for crustal and interface earthquakes a simple form of an attenuation model with respect to distance is able to capture the main strong motion characteristics and achieves unbiased estimates for subduction slab events a simple distance modification factor is employed to achieve plausible and unbiased predictions the effects of source depth tectonic source type and faulting mechanism of crustal earthquakes are significant the need for magnitude squared terms is evaluated and the use of magnitude squared terms reduces the interevent error further

on the use of high resolution topographic data as a proxy for seismic site conditions vs30 an alternative method has recently been proposed for evaluating global seismic site conditions or the average shear velocity to 30 m depth v s 30 from the shuttle radar topography mission srtm 30 arcsec digital elevation models dems the basic premise of the method is that the topographic slope can be used as a reliable proxy for v s 30 in the absence of geologically and geotechnically based site condition maps through correlations between v s 30 measurements and topographic gradient here we evaluate the use of higher resolution 3 and 9 arcsec dems to examine whether we are able to resolve v s 30 in more detail than can be achieved using the lower resolution srtm data high quality dems at resolutions greater than 30 arcsec are not uniformly available at the global scale however in many regions where such data exist they may be employed to resolve finer scale variations in topographic gradient and consequently v s 30 we use the u s geological survey earth resources observation and science eros data center s national elevation dataset ned to investigate the use of high resolution dems for estimating v s 30 in several regions across the united states including the san francisco bay area in california los angeles california and st louis missouri we compare these results with an example from taipei taiwan that uses 9 arcsec srtm data which are globally available the use of higher resolution ned data recovers finer scale variations in topographic gradient which better correlate to geological and geomorphic features in particular at the transition between hills and basins warranting their use over 30 arcsec srtm data where available however statistical analyses indicate little to no improvement over lower resolution topography when compared to v s 30 measurements suggesting that some topographic smoothing may provide more stable v s 30 estimates furthermore we find that elevation variability in canopy based srtm measurements at resolutions greater than 30 arcsec are too large to resolve reliable slopes particularly in low gradient sedimentary basins

the 17 july 2006 java tsunami earthquake the 17 july 2006 java earthquake involved thrust faulting in the java trench and excited a deadly tsunami 5 8 m that inundated the southern coast of java the earthquake s size estimates vary significantly with seismic wave period very long period signals 300 500 s indicate a seismic moment of 6 7 10 20 nm m w 7 8 m s 20 s 7 2 m b 1 s 6 2 while shaking intensities 3 10 hz were mmiv the large tsunami relative to ms characterizes this event as a tsunami earthquake like previous tsunami earthquakes the java event had an unusually low rupture speed of 1 0 1 5 km s and occurred near the up dip edge of the subduction zone thrust fault most large aftershocks involved normal faulting the rupture propagated 200 km along the trench with several pulses of shorter period seismic radiation superimposed on a smooth background rupture with an overall duration of 185 s

abrupt climate events 500 000 to 340 000 years ago evidence from subpolar north atlantic sediments subpolar north atlantic proxy records document millennial scale climate variations 500 000 to 340 000 years ago the cycles have an approximately constant pacing that is similar to that documented for the last glacial cycle these findings suggest that such climate variations are inherent to the late pleistocene regardless of glacial state sea surface temperature during the warm peak of marine isotope stage 11 mis 11 varied by 0 5 to 1 c less than the 4 to 4 5 c estimated during times of ice growth and the 3 c estimated for glacial maxima coherent deep ocean circulation changes were associated with glacial oscillations in sea surface temperature

millennial scale climate instability during the early pleistocene epoch climate proxy records of the past 100 000 years show that the earth s climate has varied significantly and continuously on timescales as short as a few thousand years 1 7 similar variability has also recently been observed for the interval 340 500 thousand years ago8 these dramatic climate shifts expressed most strongly in the north atlantic region may be linked to and possibly amplified by alterations in the mode of ocean thermohaline circulation4 5 6 7 8 9 here we use sediment records of past iceberg discharge and deep water chemistry to show that such millennial scale oscillations in climate occurred over one million years ago this was a time of significantly different climate boundary conditions not only was the early pleistocene epoch generally warmer but global climate variations were governed largely by changes in earth s orbital obliguity our results suggest that such millennial scale climate instability may be a pervasive and long term characteristic of earth s climate rather than just a feature of the strong glacial interglacial cycles of the past 800 000 years

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

the first since 1960 a large event in the valdivia segment of the chilean subduction zone the 2016 m7 6 melinka earthquake abstract we present results for joint kinematic inversion of high rate gps strong motion and insar data for the 2016 m7 6 melinka earthquake we show that the source is a compact 35 s long rupture with 5 0 0 15 m of peak slip we find the melinka earthquake occurs inside the slip region for the 1960 m9 5 valdivia earthquake and within the highly locked portion of the megathrust inferred from inter seismic velocity analysis we show that there is very modest post seismic deformation at a nearby gps site qlln and argue that this indicates the melinka earthquake ruptures within the intermediate portion of the megathrust and is an isolated asperity surrounded by locked velocity weakening material further we find that the peak slip observed during this earthquake is larger than what has been accumulated in the intervening 57 years since the 1960 rupture and conclude that at least in the area of the melinka earthquake this is indicates that the 1960 valdivia event might not have used all the slip deficit available on the megathrust

climate stability during the pliocene warm period 1 we present a high resolution climate record from a sediment core spanning an 80 kyr interval of time during the mid pliocene epoch when warmer conditions and lower global ice volume prevailed worldwide oxygen and carbon isotope analyses were made on benthic and planktonic foraminifera from odp site 981 in the north atlantic the amplitude and approximate recurrence interval of suborbital variations in these records are comparable to those of holocene and marine isotope stage 11 mis 11 records from the north atlantic we conclude that the mid pliocene warm interval was a time of relative climatic stability these results suggest that warmer climatic conditions alone may not necessarily enhance variability in the climate system a finding that may facilitate predictions of 21st century climatic response to anthropogenic warming

slab2 a comprehensive subduction zone geometry model subduction zones are home to the most seismically active faults on the planet the shallow megathrust interfaces of subduction zones host earth s largest earthquakes and are likely the only faults capable of magnitude 9 ruptures despite these facts our knowledge of subduction zone geometry which likely plays a key role in determining the spatial extent and ultimately the size of subduction zone earthquakes is incomplete we calculated the three dimensional geometries of all seismically active global subduction zones the resulting model called slab2 provides a uniform geometrical analysis of all currently subducting slabs