automated fault model discretization for inversions for coseismic slip distributions 1 geoscientists increasingly rely on coseismic slip distributions inferred from geodetic observations to drive sophisticated models of the seismic cycle to date little work has been done on optimizing the parameterization of these fault models so that they reflect the resolving power of observed surface displacements the locations of noisy surface displacement observations are often widely scattered far from features we wish to analyze in the subsurface and result in highly variable model resolution with depth the few attempts to produce variably discretized fault planes are arduously constructed by hand and may not correctly reflect the ability of the data to resolve slip features motivated by the increasing size of geodetic data pools and the need for distributed slip models that accurately represent features the data can resolve we present a fully automated algorithm that iteratively adjusts the sizes of dislocations in a fault model we use the concept of smoothing scales derived from the model resolution matrix to resize dislocations so that each dislocation is sized appropriately given the area over which slip in that region of the fault would be smoothed we present a series of synthetic tests that utilize both sparse and dense data sets and we compare our variably discretized inversions to traditional regularly discretized inversions we also use our approach to invert for slip from geodetic observations of the 2004 mw 6 0 parkfield california earthquake and the 1995 mw 8 1 antofagasta chile earthquake

simulation of atmospheric radiocarbon during abrupt oceanic circulation changes trying to reconcile models and reconstructions abstract an abrupt increase in the atmospheric 14 c content at the beginning of the younger dryas about 13 000 years ago has been related to a slow down of the global oceanic circulation this has been well simulated by box models but the amplitude and timing of such a 14 c change could not be represented with dynamical models we have forced a climate model of intermediate complexity with a meltwater discharge to test three model parameters that have the potential to strongly influence the simulated 14 c change and may help us to reconcile the model results with reconstructions we find that a decrease of the tropical wind speed accompanying a slow down of the oceanic circulation largely amplifies the circulation induced 14 c change and brings it closer to the reconstructions second we find that vertical mixing in a dynamical ocean model leads to a substantial damping in the 14 c response of simple models third we demonstrate that neglecting radiocarbon reservoir age variations during abrupt climate change may lead to a substantial overestimate of atmospheric 14 c fluctuations reconstructed from paleoceanographic archives

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

the mera lahar deposit in the upper amazon basin transformation of a late pleistocene collapse at huisla volcano central ecuador abstract the sub andean zone east of the cordillera real ecuador and out to the amazon basin s western margin has been the depository of voluminous lahars related to volcanic activity in the andean highlands these lahars arrived to the sub andean zone via gravitational transport through narrow river canyons and emplaced volumes surpassing several cubic kilometers over robust inundation zones this paper discusses the origin flow route depositional zone terrace formation and geomorphic significance of the most important lahar deposit yet mapped in this region that of the mera lahar which likely formed from a late pleistocene collapse of huisla volcano followed by impounding by temporary dams behind drainage blocking debris avalanche deposits dad then subsequent rupture of the blockage the actual deposit of the mera lahar has a thickness between 30 and 70 m is mainly comprised of dad breccia is matrix supported c 70 of reddish gray color and is well consolidated based on geochemical and petrographic similarities huisla volcano s dad is the best candidate for the lahar s source huisla volcano is located some 90 km up valley of the bulk of mera lahar s mapped deposit clasts of mera lahar rocks and huisla s dad breccias have 57 61 wt sio2 corresponding to andesites of the calc alkaline series with mean values of 1 1 5 wt for k2o the mapped mera lahar deposit has an actual volume estimated in 1 2 km3 compared to its original estimated volume of 5 4 km3 cross sectional widths of 1 5 to 4 5 km span and extend laterally beyond the actual pastaza river channel where the lahar s deposition produced high standing isolated surfaces that are notable local geomorphic features of the upper sub andean zone the flow modeling program laharflow employing the modern landscape as the topographic base adequately simulates the flow route and inundation zones of the mera lahar

seismological and geodetic constraints on the 2011 mw5 3 trinidad colorado earthquake and induced deformation in the raton basin the raton basin of southern colorado and northern new mexico is an actively produced hydrocarbon basin that has experienced increased seismicity since 2001 including the august 2011 mw5 3 trinidad normal faulting event following the 2011 earthquake regional seismic observations were used to relocate 21 events including the 2011 main shock two foreshocks and 13 aftershocks additionally interferometric synthetic aperture radar insar observations of both the 2011 event and preevent basin deformation place constraint on the spatial kinematics of the 2011 event and localized basin subsidence due to ground water or gas withdrawal we find that the 2011 earthquake ruptured an 8 10 km long segment of a normal fault at depths of 1 5 6 0 km within the crystalline precambrian basement underlying the raton basin sedimentary rocks the earthquake also nucleated within the crystalline basement in the vicinity of an active wastewater disposal site the ensuing aftershock sequence demonstrated statistical properties expected for intraplate earthquakes though the length of the 2011 earthquake is unexpectedly long for an mw5 3 event suggesting that wastewater disposal may have triggered a low stress drop otherwise natural earthquake additionally preevent and postevent seismicity in the raton basin spatially correlates to regions of subsidence observed in insar time series analysis while these observations cannot discern a causal link between hydrocarbon production and seismicity they constrain spatial relationships between active basin deformation and geological and anthropogenic features furthermore the insar observations highlight the utility of space based geodetic observations for monitoring and assessing anthropogenically induced and triggered deformation

radiocarbon reservoir age of high latitude north atlantic surface water during the last deglacial the radiocarbon reservoir age of high latitude north atlantic ocean surface water is essential for linking the continental and marine climate records and is expected to vary according to changes in north atlantic deep water nadw production measurements from this region also provide important input and or tests of oceanic radiocarbon using 3 d global ocean circulation models here we present a surface water radiocarbon reservoir age record of the high latitude western north atlantic for the deglacial period via the use of fossil cold water corals growing in waters that are rapidly exchanged with nearby surface waters the reservoir age of high latitude north atlantic surface waters was computed from the radiocarbon age difference between our radiocarbon calibration record http radiocarbon ldeo columbia edu and our marine radiocarbon data 230th 234u 238u dates provide the absolute coral ages our high latitude north atlantic ocean reservoir age data combined with recalculated reservoir ages based on published coexisting terrestrial and marine material and vedde ash radiocarbon dates from central and eastern north atlantic show modern values 380 140 year n 14 during the bolling and allerod warm period and a 200 year increase in reservoir age 590 130 year n 10 during the entire younger dryas yd cold episode the reservoir age then decreased to 270 20 year n 2 at the preboreal yd transition although the dates are too sparse for us to be confident in this estimate we are not able to resolve the timing of the transition to increased reservoir ages from the mid allerod to the yd due to the relatively small change and correspondingly large uncertainty in the estimates the atmospheric 14c record derived from our atmospheric radiocarbon record displays a 40 per mil increase from 12 900 to 12 650 cal years bp coincident with the shift to high reservoir ages in the early yd cold event intrusion of 14c depleted antarctic intermediate water aaiw to the high latitude north atlantic and reduction of nadw formation are possible causes for the coincident shift to high reservoir ages in the north atlantic surface ocean and increased atmospheric 14c during the beginning of the yd event

locations and magnitudes of historical earthquakes in the sierra of ecuador 1587 1996 summary the whole territory of ecuador is exposed to seismic hazard great earthquakes can occur in the subduction zone e g esmeraldas 1906 mw 8 8 whereas lower magnitude but shallower and potentially more destructive earthquakes can occur in the highlands this study focuses on the historical crustal earthquakes of the andean cordillera several large cities are located in the interandean valley among them quito the capital 2 5 millions inhabitants a total population of 6 millions inhabitants currently live in the highlands raising the seismic risk at present precise instrumental data for the ecuadorian territory is not available for periods earlier than 1990 beginning date of the revised instrumental ecuadorian seismic catalogue therefore historical data are of utmost importance for assessing seismic hazard in this study the bakun wentworth method is applied in order to determine magnitudes locations and associated uncertainties for historical earthquakes of the sierra over the period 1587 1976 an intensity magnitude equation is derived from the four most reliable instrumental earthquakes mw between 5 3 and 7 1 intensity data available per historical earthquake vary between 10 quito 1587 intensity vi and 117 riobamba 1797 intensity iii the bootstrap resampling technique is coupled to the b w method for deriving geographical confidence contours for the intensity centre depending on the data set of each earthquake as well as confidence intervals for the magnitude the extension of the area delineating the intensity centre location at the 67 per cent confidence level 1 depends on the amount of intensity data on their internal coherence on the number of intensity degrees available and on their spatial distribution special attention is dedicated to the few earthquakes described by intensities reaching ix x and xi degrees twenty five events are studied and nineteen new epicentral locations are obtained yielding equivalent moment magnitudes between 5 0 and 7 6 large earthquakes seem to be related to strike slip faults between the north andean block and stable south america to the east while moderate earthquakes mw 6 seem to be associated with to thrust faults located on the western internal slopes of the interandean valley

motion of continental slivers and creeping subduction in the northern andes regions of intense continental deformation termed continental slivers have been identified in chile bolivia and ecuador analyses of gps data now identify another large sliver in peru the inca sliver that is moving away from a neighbouring sliver in ecuador implying that moving continental slivers control the deformation of almost the entire andean mountain range

evidences of surface rupture associated with a low magnitude mw5 0 shallow earthquake in the ecuadorian andes this study analyzes surface displacements generated by a low magnitude crustal earthquake in the ecuadorian andes by combining analysis of sar interferometry geological field investigations and seismological data in march 2010 a significant surface faulting event occurred in the pisayambo area eastern cordillera along the major dextral fault zone bounding the north andean sliver and the south america plate interferograms were inverted to determine fault plane geometry and slip displacement distribution the event affected a 9 km long previously unknown fault referred as the laguna pisayambo fault lpf with purely dextral movement reaching 45 cm and concentrated in the top 3 km of the crust geological investigations confirm both the fault mechanism and the amplitude of displacements while these large displacements would be related to an event with a magnitude of 5 44 if using a standard crustal rigidity we show that they can be convincingly associated with an mw5 0 earthquake that occurred on 2010 03 26 reconciling the apparent differences in magnitude requires the existence of a low rigidity medium at shallow depths and or postseismic activity of the fault however considering only the latter hypothesis would imply an unusually active postseismic process in which 400 500 of the coseismic moment is released in the 6 days following the earthquake our observations highlight that the scaling laws relating surface observations to earthquake magnitude classically used for seismic hazard assessment should be carefully used this study also illustrates how systematic insar analysis even in places where no clues of ground deformation are present can reveal tectonic processes

interactions between volcanism and geodynamics in the southern termination of the ecuadorian arc abstract this study focuses on the construction and evolution through time of volcanic edifices located in the southern part of the ecuadorian arc with the objective to contribute to a better understanding of the interactions between magmatism slab geometry and the activity of tectonic faults our new groundmass k ar ages obtained for a dozen volcanoes from the southern quaternary arc are rather young without ages older than 800 ka and highlight an increasing volcanic activity between 300 and 100 ka these new temporal constraints suggest that a southward migration of the ecuadorian arc occurred during the last 600 ka we interpret this evolution as the result of major and recent geodynamic reorganization in ecuador related to the activation of lithospheric faults and to the flexure of the slab at depth following the inland prolongation of the grijalva fracture zone both phenomena could have been induced by the oblique subduction of the nazca plate towards the convex margin of the south american continent and the coupling of these two plates along the wadati benioff zone progressively intensified by the carnegie ridge subduction southward migration of the slab flexure at depth could have changed pressure and temperature conditions favoring the partial melting of the mantle wedge and magma genesis thereby inducing a southward migration of the ecuadorian arc volcanoes these results contribute therefore to a better knowledge of the current arc dynamics in the northern andes and provide insights into the use of geochronological data applied to volcanic rocks for studies of past tectonic activity in ecuador

glacial water mass geometry and the distribution of δ13c of σco2 in the western atlantic ocean 1 oxygen and carbon isotopic data were produced on the benthic foraminiferal taxa cibicidoides and planulina from 25 new piston cores gravity cores and multicores from the brazil margin the cores span water depths from about 400 to 3000 m and intersect the major water masses in this region these new data fill a critical gap in the south atlantic ocean and provide the motivation for updating the classic glacial western atlantic 13c transect of duplessy et al 1988 the distribution of 13c of co2 requires the presence of three distinct water masses in the glacial atlantic ocean a shallow 1000 m southern source water mass with an end member 13c value of about 0 3 0 5 vpdb a middepth 1500 m northern source water mass with an end member value of about 1 5 and a deep 2000 m southern source water with an end member value of less than 0 2 and perhaps as low as the 0 9 values observed in the south atlantic sector of the southern ocean ninnemann and charles 2002 the origins of the water masses are supported by the meridional gradients in benthic foraminiferal 18o a revised glacial section of deep water 13c documents the positions and gradients among these end member intermediate and deep water masses the large property gradients in the presence of strong vertical mixing can only be maintained by a vigorous overturning circulation

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

paleoseismology and tectonic geomorphology of the pallatanga fault central ecuador a major structure of the south american crust the pallatanga fault pf is a prominent nne ssw strike slip fault crossing central ecuador this structure is suspected to have hosted large earthquakes including the 1797 riobamba event which caused severe destructions to buildings and a heavy death toll more than 12 000 people as well as widespread secondary effects like landsliding liquefaction and surface cracking the scope of this study is to evaluate the seismic history of the fault through a paleoseismological approach this work also aims at improving the seismotectonic map of this part of the andes through a new mapping campaign and finally aims at improving the seismic hazard assessment we show that the pf continues to the north of the previously mapped fault portion in the western cordillera rumipamba pallatanga portion into the inter andean valley riobamba basin field evidences of faulting are numerous ranging from a clear geomorphological signature to fault plane outcrops along the western side of the riobamba basin the strike slip component seems predominant along several fault portions with a typical landscape assemblage dextral offsets of valleys fluvial terrace risers and generation of linear pressure ridges in the core of the inter andean valley the main fault portion exhibits a vertical component along the c 100 m high cumulative scarp the presence of such an active fault bounding the western suburbs of riobamba drastically increases the seismic risk for this densely inhabited and vulnerable city to the east peltetec massif cordillera real the continuation of the pallatanga fault is suspected but not definitely proved yet based on the analysis of three trenches we state that the rumipamba pallatanga section of the pf experienced 4 maybe 5 holocene to historical strong events mw 7 the coseismic behavior of the fault is deduced from the occurrence of several colluvial wedges and layers associated with the fault activity and interbedded within the organic black soil sequence according to a series of 14c datings we document that these events occurred during the last 6500 years the clear deformation of the shallowest layer 14c 1633 ad is most likely associated with the 1797 riobamba earthquake after retrodeforming one of the 3 trenches we estimate coseismic vertical throws 0 70 to 0 90 m because of bad outcrop conditions we could not determine the horizontal component of slip and we used the slip vector determined in a previous work with a tectonic geomorphology study assuming this slip vector we obtain total coseismic offsets between 3 5 and 4 5 m indicative of earthquake magnitudes around c mw 7 5 the estimated recurrence time intervals range between 1300 and 3000 years indicating an average slip rate of c 2 5 mm a for the rumipamba pallatanga section of the fault

accuracy and resolution of alos interferometry vector deformation maps of the father s day intrusion at kilauea we assess the spatial resolution and phase noise of interferograms made from l band advanced land observing satellite alos synthetic aperture radar sar data and compare these results with corresponding c band measurements from european space agency remote sensing satellite ers based on cross spectral analysis of phase gradients we find that the spatial resolution of alos interferograms is 1 3times better than ers interferograms the phase noise of alos i e line of sight precision in the 100 5000 m wavelength band is 1 6times worse than ers 3 3 mm versus 2 1 mm in both cases the largest source of error is tropospheric phase delay vector deformation maps associated with the june 17 2007 father s day intrusion along the east rift zone of the kilauea volcano were recovered using just four alos sar images from two look directions comparisons with deformation vectors from 19 continuous gps sites show rms line of site precision of 14 mm and rms azimuth precision flight direction of 71 mm this azimuth precision is at least 4times better than the corresponding measurements made at c band phase coherence is high even in heavily vegetated areas in agreement with previous results this improved coherence combined with similar or better accuracy and resolution suggests that l band alos will outperform c band ers in the recovery of slow crustal deformation

longitudinal variation of the stratospheric quasi biennial oscillation the longitudinal dependence of interannual variations of tropical stratospheric wind is examined in a detailed general circulation model simulation and in the limited observations available a version of the skyhi model is run with an imposed zonally symmetric zonal momentum source that forces the zonal mean zonal wind evolution in the tropical stratosphere to be close to an estimate of the observed zonal wind based on radiosonde observations at singapore during the period 1978 99 this amounts to a kind of simple assimilation model in which only the zonal mean wind field in the tropical stratosphere is assimilated and other quantities are allowed to vary freely a total of five experiments were run one covering the full 1978 99 period and four for 1989 99 the results at and above about 30 hpa are fairly simple to characterize when the zonal mean wind near the equator at a particular level is easterly the monthly mean wind has only very small zonal contrasts when mean westerlies are present near the equator significant zonal asymmetries occur at low latitudes most notably easterly anomalies over south america and westerly anomalies in the eastern pacific region these anomalies generally display a continuous meridional phase propagation with the extratropical quasi stationary eddy field in the winter hemisphere the net result is a significantly weaker peak to peak amplitude of the quasi biennial oscillation qbo in zonal wind over the south american sector than over the rest of the equatorial band the zonal contrast in qbo amplitude near 10 hpa exceeds 10 in the lower stratosphere the zonal asymmetries in the prevailing wind are fairly small asymmetries seem to reflect the upward extension of the tropospheric walker circulation and are less strongly modulated by the quasi biennial oscillation in zonal mean circulation the model results were checked against limited station observations at nairobi 1 38s 36 78e singapore 1 48n 103 98e rochambeau 4 88n 52 48w and bogota 4 78n 74 18w overall reasonable agreement was found between the monthly mean zonal winds in the model simulation and these station data the low latitude wind field in monthly mean ncep gridded analyses was also examined these analyses have some obviously unrealistic features in the tropical stratosphere but some of the behavior seen in the skyhi model simulations can be identified as well in the ncep analyses

monitoring of active tectonic deformations in the longitudinal valley eastern taiwan using persistent scatterer insar method with alos palsar data abstract this paper presents new observation of the interseismic deformation along the longitudinal valley eastern taiwan that represents a major tectonic boundary of the taiwan collision zone we investigate the southern part of the valley from rueisuei to taitung latitude 23 5 n 22 7 n which is the part of the valley where interseismic surface creep has already been observed at some points of the longitudinal valley fault lvf a persistent scatterer sar interferometry approach stamps is applied using ten l band sar images from alos satellite acquired over the period 2007 2010 interferograms from l band data show a dramatic improvement of coherence in comparison to previous studies using c band ers data the density of measurement resulting from stamps processing is the highest achieved so far in the area about 40 55 points per km2 for a total of 77 000 points allowing a continuous view of the deformation along the valley and also giving information on its borders central range and coastal range the most striking feature of the resulting mean velocity map is a clear velocity discontinuity localized in a narrow band 0 1 1 km along the lvf and responsible for up to 3 cm yr velocity offset along the radar line of sight which is attributed to shallow interseismic creep insar results are in good agreement with continuous gps measurements over the same period 0 3 cm yr rms the density of measurement allows us to improve fault trace map along the creeping section of the lvf with accuracy of about 100 m and to find new field evidences of the fault activity in some places our trace differs significantly hundreds of meters from previous published traces the creep rate shows significant variations along the fault at the southern end of the valley the deformation is distributed on several structures including the luyeh strand and drops significantly south of the peinanshan however there are discrepancies with previous studies made from ers data over the period 1993 1999 that remain to be investigated the mean velocity for each point of measure and the improved faults trace are provided as supplementary data

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

distribution of dissolved and particulate230th and232th in seawater from the gulf of mexico and off cape hatteras as measured by sims we present vertical and horizontal profiles of dissolved and particulate230th and232th concentrations in seawater from shelf and slope areas of the gulf of mexico and off cape hatteras in the middle atlantic bight as measured by secondary ion mass spectrometry sims and compare the partitioning of long lived230th between particles and seawater with that of short lived234th concentrations of dissolved and particulate230th and232th in surface seawater decreased from near shore to off shore in the gulf of mexico demonstrating terrestrial input to the surface waters vertical profiles indicate that lateral transport as well as surface inputs e g fluvial and aeolian and bottom sediment resuspension could be an important source of230th and232th in ocean margin regions sea water samples collected off cape hatteras contained significantly higher dissolved and particulate230th and232th concentrations than those found in the open gulf of mexico likely the distributions of230th and232th in seawater off cape hatteras are to a large extent controlled by terrestrial particles in contrast in situ production for230th and scavenging are the major processes regulating the concentrations of dissolved230th and232th in the open gulf of mexico the observed negative correlation between log kd particle solution distribution coefficient and log cp concentration of suspended particulate matter for234th and230thxs in both study areas demonstrated a particle concentration effect down to very low cp concentrations 20 g l based on the230th inventory in situ production and the small estimated surface input the overall residence time of230th in the water column at a slope station in the gulf of mexico is calculated to be about 5 yr

deep sea corals evidence periodic reduced ventilation in the north atlantic during the lgm holocene transition abstract nine new intermediate water ages estimated with coupled uranium series and radiocarbon measurements on deep sea corals from the northeastern atlantic are presented together with six intermediate and deep water ages from the western north atlantic adkins et al science 280 1998 725 728 and one from the equatorial atlantic mangini et al nature 392 1998 347 348 they span the time period from 15 400 to 560 yr ago and show abrupt variations of intermediate and deep water ages from 270 up to 2320 yr both major pulses of meltwater discharge mwp 1a following heinrich event 1 and mwp 1b after the younger dryas cold event are followed by enhanced supply of southern source water at intermediate depths in the north atlantic together with reduced formation of well ventilated glacial north atlantic intermediate water 1000 2000 m this result gives strong support to numerical models predicting fast and sharp increase of bottom water age in the atlantic triggered by pulses of freshwater discharge into the north atlantic rahmstorf nature 372 1994 82 85 stocker and wright radiocarbon 40 1998 359 366

slip on the superstition hills fault and on nearby faults associated with the 24 november 1987 elmore ranch and superstition hills earthquakes southern california alignment arrays and creepmeters spanning several faults in southern california recorded slip associated with the 24 november 1987 elmore ranch and superstition hills earthquakes no precursory slip had occurred on the superstition hills fault up to 27 october 1987 when the last measurement before the earthquakes was made about 23 days before the earthquake dextral creep events of about 13 mm and 0 5 mm may have occurred simultaneously on the imperial and southern san andreas faults respectively but the tectonic origin of the smaller event is questionable within 12 hr after the superstition hills earthquake 20 9 cm of dextral slip occurred on the main fault trace at the superstition hills alignment array and 39 8 cm of dextral slip was recorded over the entire 110 m width of the array despite this initial wide distribution of slip nearly all of the postseismic slip is occurring on the main fault trace as of 3 august 1988 the alignment array had recorded a total of 80 2 cm of dextral slip as of 5 days after the earthquakes 65 to 80 per cent of the total slip measured by the alignment array had occurred on discrete mappable fractures in addition the two earthquakes triggered slip on the coyote creek fault the southern san andreas fault and on the imperial fault telemetered data from creepmeters on the southern san andreas and imperial faults indicate that triggered slip began there within 3 min or less of each of the two earthquakes additional triggered slip occurred on the imperial fault beginning 3 5 hr after the second earthquake

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

decorrelation of l band and c band interferometry over vegetated areas in california temporal decorrelation is one of the main limitations for recovering interseismic deformation along the san andreas fault system using interferometric synthetic aperture radar to assess the improved correlation properties of l band with respect to c band we analyzed l band advanced land observation satellite alos interferograms with a range of temporal and spatial baselines over three vegetated areas in california and compared them with corresponding c band european remote sensing satellite ers interferograms over the highly vegetated northern california forests in the coast range area alos remains remarkably well correlated over a 2 year period whereas an ers interferogram with a similar temporal and spatial baseline lost correlation in central california near parkfield we found a similar pattern in decorrelation behavior which enabled the recovery of a fault creep and a local uplifting signal at l band that was not apparent at c band in the imperial valley in southern california both alos and ers have low correlation over farmlands alos has lower correlation over some sandy surfaces than ers probably due to low signal to noise ratio in general l band interferograms with similar seasonal acquisitions have higher correlation than those with dissimilar season for both l and c band correlation over vegetated areas decreases with time for intervals less than 1 year and then remains relatively constant at longer time intervals the decorrelation time for l band is more than 2 years in the forest in california whereas that for c band is less than 6 months overall these results suggest that l band interferograms will reveal near fault interseismic deformation once sufficient data become available

long term afterslip of the 2004 m 6 0 parkfield california earthquake implications for forecasting amount and duration of afterslip on other major creeping faults abstract we present the longest record of surface afterslip on a continental strike slip fault for the 2004 m 6 0 parkfield california earthquake from which we can derive critical information about the duration and predictability of afterslip relevant to urban displacement hazard applications surface slip associated with this event occurred entirely postseismically along the interseismically creeping 0 6 1 5 cm yr main trace of the san andreas fault using the first year of afterslip data the program after correctly predicted the cumulative surface afterslip maximum 35 cm eventually attained by 1 yr postearthquake observed afterslip had accumulated to only 74 of its modeled final value u f in units of length the 6 yr data suggested final slip would be reached everywhere by 6 12 yrs parkfield s afterslip lasted much longer 6 12 yrs than afterslip following a 2014 m 6 0 event in napa california where no interseismic creep was known and its afterslip neared completion 97 of u f by 1 yr the uncertainty in u f for the napa event fell to 2 cm in only three months versus in 2 yrs for the parkfield event mostly because duration of the power law stage of afterslip at parkfield is much longer 1000 493 1666 days versus 100 35 421 days for napa because the urban hayward fault near san francisco california like the parkfield section exhibits interseismic creep in a similar geological regime significant afterslip might last for up to a decade following an anticipated m 6 7 earthquake potentially delaying postearthquake recovery electronic supplement tables of afterslip observations and coefficients for computing afterslip

the 1992 nicaragua earthquake a slow tsunami earthquake associated with subducted sediments the 1992 nicaragua earthquake was a tsunami earthquake that is it generated tsunamis disproportionately large for its surface wave magnitude m s the moment magnitude m w determined from long period 250 s surface waves was 7 6 significantly larger than the 20 s m s of 7 this m s m w disparity is also characteristic of tsunami earthquakes the nicaragua earthquake is the first tsunami earthquake to be captured by modern broadband seismic networks allowing us to present here seismograms of sufficiently high quality to make inferences about the rupture mechanisms we conclude that the nicaragua earthquake was a slow thrust earthquake which occurred on the subduction interface between the cocos and north american plates and because of the absence of sediments on the trench floor offshore of nicaragua the slip propagated up dip all the way to the ocean bottom exciting large tsunamis the occurrence of slip on a plate interface filled with soft subducted sediments caused the rupture process to be slower than in ordinary subduction zone thrust earthquakes our results reinforce the idea that tsunami warning systems using long period 100 s waves are necessary to reduce the hazard from this type of earthquake

evidence from the high latitude north atlantic for variations in antarctic intermediate water flow during the last deglaciation we present evidence that the characteristic chemical signature based on coupled benthic foraminiferal cd ca and d13c of antarctic intermediate waters aaiw penetrated throughout the intermediate depths of the atlantic basin to the high latitude north atlantic during the abrupt cooling events of the last deglaciation heinrich 1 and the younger dryas aaiw may play the dynamic counterpart to the bipolar seesaw when near freezing salty bottom waters from the antarctic aabw sluggishly ventilate the deep ocean our data reinforce the concept that interglacial circulation is stabilized by salinity feedbacks between salty northern sourced deep waters nadw and fresh southern sourced waters aabw and aaiw further the glacial ocean may be susceptible to the more finely balanced relative densities of nadw and aaiw due to either freshwater input or a reversal of the salinity gradient such that the ocean is poised for nadw collapse via a negative salinity feedback the unstable climate of the glacial period and its termination may arise from the closer competition for ubiquity at intermediate depths between northern and southern sourced intermediate waters

earthquake deformation cycle on the san andreas fault near parkfield california six moderate earthquakes are thought to have ruptured the parkfield segment of the san andreas fault since 1857 the similar characteristics of the three seismically recorded events together with the quasi regular 22 year recurrence interval have led to the forecast of a similar event in 1988 5 years in this study the potential for the hypothesized earthquake is assessed by estimating the time required for interseismic straining to recover the strain energy released by the most recent june 1966 parkfield earthquake for a simple model of the earthquake cycle this interval is proportional to the ratio of the 1966 seismic moment to the interseismic moment deficit rate baseline lengths measured before and after the 1966 earthquake are inverted to estimate the magnitude and distribution of the combined coseismic and transient postseismic slip although the geodetic data determine only broad spatial averages of the fault slip they do require that slip at depth exceeded the surface offsets measured in 1966 inversions with extreme prior models are calculated to assess the range of seismic moment and moment deficit rates consistent with the available geodetic data inversions assuming only that the slip distributions are to some degree smooth yield strain energy recovery intervals of 14 25 years extreme values range from as little as 6 years to as much as 29 years in comparison historic recurrence intervals of parkfield earthquakes range from 12 to 32 years these results are consistent with the expectation of a magnitude 5 6 earthquake near parkfield by 1993

a new view for the geodynamics of ecuador implication in seismogenic source definition and seismic hazard assessment a new view of ecuador s complex geodynamics has been developed in the course of modeling seismic source zones for probabilistic seismic hazard analysis this study focuses on two aspects of the plates interaction at a continental scale a age related differences in rheology between farallon and nazca plates marked by the grijalva rifted margin and its inland projection as they subduct underneath central ecuador and b the rapidly changing convergence obliquity resulting from the convex shape of the south american northwestern continental margin both conditions satisfactorily explain several characteristics of the observed seismicity and of the interseismic coupling intermediate depth seismicity reveals a severe flexure in the farallon slab as it dips and contorts at depth originating the el puyo seismic cluster the two slabs position and geometry below continental ecuador also correlate with surface expressions observable in the local and regional geology and tectonics the interseismic coupling is weak and shallow south of the grijalva rifted margin and increases northward with a heterogeneous pattern locally associated to the carnegie ridge subduction high convergence obliquity is responsible for the north andean block northeastward movement along localized fault systems the cosanga and pallatanga fault segments of the north andean block south american boundary concentrate most of the seismic moment release in continental ecuador other inner block faults located along the western border of the inter andean depression also show a high rate of moderate size earthquake production finally a total of 19 seismic source zones were modeled in accordance with the proposed geodynamic and neotectonic scheme

ten year recurrence time between two major earthquakes affecting the same fault segment earthquake ruptures stop when they encounter barriers impeding further propagation these barriers can theoretically originate from changes of geometry or nature of the seismic faults or from a strong lowering of the tectonic stresses typically due to the occurrence of a recent major earthquake we show here that this latter mechanism can be ineffective at stopping rupture expansion the 17 november 2013 magnitude 7 8 scotia sea earthquake has propagated into a 100 km long zone already ruptured 10 years ago by a magnitude 7 6 earthquake given the plate velocities between scotia and antarctic plates 8 9 mm yr simple recurrence models would have predicted that the segment affected by the 2003 earthquake could not be reruptured by a major earthquake during several hundreds of years this earthquake pair indicates that the variations of the tectonic stress during the seismic history of the fault are small compared to the stresses dynamically generated by a large earthquake

eruptive history of chimborazo volcano ecuador a large ice capped and hazardous compound volcano in the northern andes abstract new fieldwork radiometric and whole rock chemical data permit the reconstruction of the main eruptive stages of the chimborazo compound volcano the highest summit of the northern andes chimborazo is composed of three successive edifices the basal edifice ch i was active from 120 to 60 ka and resulted in a large mostly effusive edifice which was built up during two stages of cone building terminating with the formation of a dome complex this edifice was affected by a huge sector collapse around 65 60 ka which produced a major debris avalanche that spread out into the riobamba basin covering about 280 km2 with an average thickness of 40 m and a total volume of 10 12 km3 after the emplacement of the riobamba debris avalanche eruptive activity resumed at the eastern outlet of the avalanche scar and was responsible for the construction of a less voluminous intermediary edifice ch ii whose current remnants are the politecnica and martinez peaks this edifice developed from 60 to 35 ka lastly eruptive activity shifted to the west leading to the construction of the morphologically well preserved young cone ch iii which currently forms the highest summit whymper the average eruptive rate of chimborazo volcano is 0 5 0 7 km3 ka however looking at the three successive edifices individually we estimate that there has been a progressive decrease in magma output rate from the basal edifice 0 7 1 0 km3 ka through the intermediary edifice 0 4 0 7 km3 ka to the young cone 0 1 km3 ka however during the main cone building stages the peak eruption rates are markedly higher indicating significant variations in the magma output rate during the lifespan of this arc volcano during the holocene the chimborazo eruptive activity consisted of small volume explosive events that occurred at quite regular intervals between about 8000 and 1000 yr ago since the last eruption occurred between the early part of the 5th century and the end of the 7th century and the average time interval between the events is about 1000 yr chimborazo must be considered as a potentially active volcano the presence of a thick ice cap covering the summit its steep flanks and its position above the populated lowland area of riobamba and ambato are factors that result in a high potential risk

synchronous radiocarbon and climate shifts during the last deglaciation radiocarbon data from the cariaco basin provide calibration of the carbon 14 time scale across the period of deglaciation 15 000 to 10 000 years ago with resolution available previously only from holocene tree rings reconstructed changes in atmospheric carbon 14 are larger than previously thought with the largest change occurring simultaneously with the sudden climatic cooling of the younger dryas event carbon 14 and published beryllium 10 data together suggest that concurrent climate and carbon 14 changes were predominantly the result of abrupt shifts in deep ocean ventilation

subduction of the eastern panama basin and seismotectonics of northwestern south america spreading along the cocos nazca plate boundary since the breakup of the farallon plate in the miocene has resulted in the formation of the panama basin and a complex interaction of plates in and near northwestern south america current plate boundaries have been defined and segments of subducted lithosphere identified through selection of hypocentral locations of earthquakes considering only well located events and through focal mechanism determinations the existence of relict plate boundaries bathymetric features and the panamanian isthmus has affected the subduction process of the nazca plate beneath south america and determined the present day configuration of the subducting lithospheric plate there is no single triple junction separating the caribbean south american and nazca plates instead the panamanian isthmus and surrounding areas are accommodating east west compression and a lesser degree of north south compression along a series of thrust faults striking nw to ne and the andean ranges of ecuador colombia and venezeula are moving as a block nne relative to the rest of the south american plates along a system of faults following the front of the eastern cordillera the subducted portions of the panama basin and old farallon plate have become segmented into three pieces recognized in this study from north to south they are 1 a bucaramanga segment continuous with the caribbean seafloor northwest of colombia 2 a cauca segment continuous with oceanic crust nazca plate currently being subducted beneath south america at the colombia ecuador trench and 3 an ecuador segment at the northern end of the subducted lithospheric plate which is dipping at a small angle to the east beneath northern peru the segmentation of the subducted plate can be explained by the buoyancy of bathymetric features which have been partially subducted

displacement and geometrical characteristics of earthquake surface ruptures issues and implications for seismic hazard analysis and the process of earthquake rupture there now exist about three dozen historical earthquakes for which in vestigators have constructed maps of earthquake rupture traces accompanied by de scriptions of the coseismic slip observed along the fault strike the maps and slip distributions are compiled here to place observational bounds on aspects of seismic hazard analysis and fault mechanics analysis leads to an initial statistical basis to predict the end points of rupture and the amount of surface slip expected at sites along the strike during earthquakes on mapped faults the observations also give support to the ideas that there exists a process zone or volume of about 3 4 km in dimension at the fronts of large laterally propagating earthquake ruptures within which stress changes may be sufficient to trigger slip on adjacent faults and that the ultimate length of earthquake ruptures is controlled primarily by the geometrical complexity of fault traces and variations in accumulated stress levels along faults that arise due to the location of past earthquakes to this may be added the observation that the form of earthquake surface slip distributions is better described by asymmetric rather than symmetric curve forms and that earthquake epicenters do not appear to correlate in any systematic manner to regions of maximum surface slip observed along strike online material maps of surface ruptures digitized values and curve fits to surface slip distributions and notes and references for tables 1 and 2