the geological history of the ballydeenlea chalk breccia county kerry ireland the ballydeenlea chalk breccia co kerry occurs as an outlier surrounded by namurian rocks and is composed dominantly of namurian mudstone clasts with cretaceous campanian chalk acting as a matrix a new model is proposed for the formation of the deposit in which it is considered to be the remnant of a suite of sediments deposited at the foot of a submarine fault scarp active during the campanian in this model namurian mudstones comprised the active scarp and were redeposited by rockfall events these were mixed with unlithified chalk ooze derived from slumping from the upthrown side of the fault an organic maturation study of the ballydeenlea chalk breccia indicates a maximum burial depth of between 1 and 1 5 km suggesting uplift and erosion during the early tertiary

active deformation near the nicoya peninsula northwestern costa rica between 1996 and 2010 interseismic megathrust coupling 1 we use campaign and continuous gps measurements at 49 sites between 1996 and 2010 to describe the long term active deformation in and near the nicoya peninsula northwestern costa rica the observed deformation reveals partial partitioning of the cocos caribbean oblique convergence into trench parallel forearc sliver motion and less oblique thrusting on the subduction interface the northern costa rican forearc translates northwestward as a whole ridge block at 11 1 mm yr relative to the stable caribbean the transition from the forearc to the stable caribbean occurs in a narrow deforming zone of 16 km wide subduction thrust earthquakes take 2 3 of the trench parallel component of the plate convergence however surface deformation caused by interseismic megathrust coupling is primarily trench normal two fully coupled patches one located offshore nicoya centered at 15 km depth and the other located inland centered at 24 km depth are identified in nicoya with the potential to generate an mw 7 8 1950 type earthquake another fully coupled patch se of nicoya coincides with the rupture region of the 1990 nicoya gulf earthquake interface microearthquakes non volcanic tremor low frequency earthquakes and transient slow slip events generally occur in the intermediately to weakly coupled regions

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

tertiary uplift and inversion history in the north celtic sea basin and its influence on source rock maturity abstract tertiary uplift and basin inversion have been widely recognized in the area of the north celtic sea basin offshore ireland but the magnitude and timing of the various events have not been well documented an understanding of these events is important because recent basin history generally has a major influence on hydrocarbon source rock maturity levels a multi disciplinary approach was used to investigate the timing and nature of uplift in the north celtic sea basin involving seismic data interpretation well log correlation vitrinite reflectance measurement apatite fission track analysis and a cretaceous chalk group isopach and velocity study both regional uplift and compressive inversion can be interpreted to have occurred based on missing geological section compressive reactivation of earlier normal faults and basin centred uplift two tertiary erosion events are recognized a regional uplift in the palaeocene and compressive inversion characterized by basin doming and fault reversal probably associated with an oligo miocene phase of the alpine orogeny separating these was a period of basinal deposition in the eocene to oligocene a map of the magnitude of erosion generated as a result of the two events shows that the amount of uplift is quite variable in the northeast part of the basin where the later event was most severe uplift was as much as 1100 m reconstruction of the basin geometry before inversion together with thermal modelling at selected well locations suggests that upper jurassic source rocks reached maturity for oil generation only in the central portion of the basin whereas lower jurassic source rocks entered the gas window in much of the basin prior to tertiary uplift

a tremor and slip event on the cocos caribbean subduction zone as measured by a global positioning system gps and seismic network on the nicoya peninsula costa rica in may 2007 a network of global positioning systems gps and seismic stations on the nicoya peninsula of northern costa rica recorded a slow slip event accompanied by seismic tremor the close proximity of the nicoya peninsula to the seismogenic part of the cocos caribbean subduction plate boundary makes it a good location to study such events several centimeters of southwest motion were recorded by the gps stations over a period of several days to several weeks and the seismic stations recorded three distinct episodes of tremor during the same time span inversion of the surface displacement data for the depth and pattern of slip on the plate interface shows peak slip at a depth of 25 30 km downdip of the main seismogenic zone estimated temperatures here are 250 300 c lower than in other subduction zones where events of this nature have been previously identified there may also be a shallower patch of slip at 6 km depth these results are significant in that they are the first to suggest that slow slip can occur at the updip transition from stick slip to stable sliding and that a critical temperature threshold is not required for slow slip tremor and low frequency earthquake locations are more difficult to determine our results suggest they occur on or near the plate interface at the same depth range as the deep slow slip but not spatially colocated

geodetic and seismic constraints on some seismogenic zone processes in costa rica new seismic and geodetic data from costa rica provide insight into seismogenic zone processes in central america where the cocos and caribbean plates converge seismic data are from combined land and ocean bottom deployments in the nicoya peninsula in northern costa rica and near the osa peninsula in southern costa rica in nicoya inversion of gps data suggests two locked patches centered at 14 2 and 39 6 km depth interplate microseismicity is concentrated in the more freely slipping intermediate zone suggesting that small interseismic earthquakes may not accurately outline the updip limit of the seismogenic zone the rupture zone for future large earthquakes at least over the short 1 year observation period we also estimate northwest motion of a coastal sliver block at 8 3 mm yr probably related to oblique convergence in the osa region to the south convergence is orthogonal to the trench cocos caribbean relative motion is partitioned here with 8 cm yr on the cocos panama block boundary including a component of permanent shortening across the fila costena fold and thrust belt and 1 cm yr on the panama block caribbean boundary the gps data suggest that the cocos plate panama block boundary is completely locked from 10 50 km depth this large locked zone as well as associated forearc and back arc deformation may be related to subduction of the shallow cocos ridge and or younger lithosphere compared to nicoya with consequent higher coupling and compressive stress in the direction of plate convergence

calculation of vitrinite reflectance from thermal histories a comparison of some methods vitrinite reflectance values ro calculated from commonly used methods are compared with respect to time invariant temperatures and constant heating rates two monofunctional methods one involving a time temperature index to vitrinite reflectance correlation tti ro and the other involving a log ro to depth correlation yield vitrinite reflectance values that are similar to those calculated by recently published arrhenius based methods such as easy ro the approximate agreement between these methods supports the perception that the easy ro algorithm is the most accurate method for the prediction of vitrinite reflectances throughout the range of organic maturity normally encountered however calibration of the e methods against vitrinite reflectance data from two basin sequences with well documented geologic histories indicates that although the easy ro method has wide applicability it slightly overestimates vitrinite reflectances in strata of low to medium maturity up to a ro value of 0 9 the two monofunctional methods may be more accurate for prediction of vitrinite reflectances in similar sequences of low maturity an older but previously widely accepted tti ro correlation consistently overestimates vitrinite reflectances with respect to other methods underestimation of paleogeothermal gradients in the original calibration of time temperature history to vitrinite reflectance may have introduced a systematic bias to the tti ro correlation used in this method also incorporation of tai thermal alteration index data and its conversion to ro equivalent values may have introduced inaccuracies

organic maturation levels thermal history and hydrocarbon source rock potential of the namurian rocks of the clare basin ireland abstract vitrinite reflectance data from two inland cored boreholes confirm high maturation levels throughout the onshore part of the irish clare basin and suggest erosion of 2 to 4 km of late carboniferous cover and elevated palaeogeothermal gradients in the carboniferous section the observed maturation gradients are fully consistent with the published hypothesis of a late carboniferous permian superplume beneath pangaea but local vertical reversals in gradients also suggest a complex thermal regime probably involving advective heating the uppermost visean lower namurian clare shale is laterally extensive and up to 300 m thick although this unit is post mature toc values of up to 15 suggest that it could have considerable hydrocarbon source rock potential in any less mature offshore parts of the basin

joint inversion of strong motion teleseismic geodetic and tsunami datasets for the rupture process of the 2011 tohoku earthquake 1 the 2011 tohoku earthquake was observed by dense strong motion teleseismic geodetic and tsunami networks we first inverted each of the datasets obtained by the networks separately for the rupture process of the earthquake we then performed checkerboard resolution tests for assessing the resolving power of these datasets in order to overcome the limited resolutions of the separate inversions and differences in their results we performed a quadruple joint inversion of all these data to determine a source model most suitable for explaining all the datasets in the obtained source model the maximum coseismic slip was approximately 35 m and the total seismic moment was calculated to be 4 2 1022 nm which yielded mw 9 0 the main rupture propagated not only in the strike direction but also in the dip direction and included both the deep area called the miyagi oki region and the compact shallow area near the japan trench

rupture processes of the 2012 september 5 mw 7 6 nicoya costa rica earthquake constrained by improved geodetic and seismological observations

large and primarily updip afterslip following the 2012 mw 7 6 nicoya costa rica earthquake we present detailed surface measurements of the first 3 5 years of postseismic deformation following the 5 september 2012 moment magnitude mw 7 6 nicoya costa rica earthquake the dominant signal in the first 2 5 years is uniform horizontal trenchward motion totaling 7 26 cm across 40 stations trenchward velocity is strongly diminished by mid 2014 and appears by 2016 to have begun reversing we invert the first 2 5 years to determine the corresponding afterslip on a detailed 3d interface results show significant afterslip both up and down dip of the main coseismic rupture zone with as much as 1 7 m of offset in two patches at 15 20 km depth and immediately up dip of the maximum coseismic slip this updip slip represents an important mechanism to address unrelieved interseismic locking although sufficient strain energy remains to generate up to a mw 7 1 event near the coastline the afterslip patches are anticorrelated with strongly clustered aftershocks at the same depth which is indicative of varying frictional behavior along strike an additional patch of slip is colocated with reoccurring slow slip events beneath the gulf of nicoya the magnitude of the observed slip however cannot be sufficiently explained by the known slow slip events ongoing measurements will be crucial to understanding the relocking process in nicoya

superficial simplicity of the 2010 el mayor cucapah earthquake of baja california in mexico the geometry of faults is usually thought to be more complicated at the surface than at depth and to control the initiation propagation and arrest of seismic ruptures the fault system that runs from southern california into mexico is a simple strike slip boundary the west side of california and mexico moves northwards with respect to the east however the m w 7 2 2010 el mayor cucapah earthquake on this fault system produced a pattern of seismic waves that indicates a far more complex source than slip on a planar strike slip fault here we use geodetic remote sensing and seismological data to reconstruct the fault geometry and history of slip during this earthquake we find that the earthquake produced a straight 120 km long fault trace that cut through the cucapah mountain range and across the colorado river delta however at depth the fault is made up of two different segments connected by a small extensional fault both segments strike n130 e but dip in opposite directions the earthquake was initiated on the connecting extensional fault and 15 s later ruptured the two main segments with dominantly strike slip motion we show that complexities in the fault geometry at depth explain well the complex pattern of radiated seismic waves we conclude that the location and detailed characteristics of the earthquake could not have been anticipated on the basis of observations of surface geology alone

persistent tremor within the northern costa rica seismogenic zone 1 we identify tremor using a spectral detection method and characterize its occurrence over a period of four years 2006 2009 in the vicinity of the nicoya peninsula costa rica although a few major tremor events accompanied by geodetic slow slip occur much of the tremor record consists of minor episodes with short duration and no detectable geodetic slip its persistent occurrence suggests that some portion of the interface is experiencing slow slip nearly continuously driving small patches to fail in accelerated slip locations indicate that much of the tremor occurs at shallow depth in freely slipping regions of the seismogenic zone this result is significant in that locations of slow slip and tremor at other subduction zones are largely limited to the downdip frictional transition tremor locations may help to refine the heterogeneous distribution of locked and freely slipping patches within the costa rica seismogenic zone

nicoya earthquake rupture anticipated by geodetic measurement of the locked plate interface part of the subduction zone plate interface beneath costa rica was previously locked which allowed strain to accumulate analyses using gps and geomorphic data show that almost the entire locked region ruptured during a megathrust quake in 2012 implying that plate interface mapping towards the end of the earthquake cycle can aid seismic hazard assessments

spatial correlation of interseismic coupling and coseismic rupture extent of the 2011 mw 9 0 tohoku oki earthquake 1 imaging the extent to which the rupture areas of great earthquakes coincide with regions of pre seismic interplate coupling is central to understanding patterns of strain accumulation and release through the earthquake cycle both geodetic and seismic estimates of the coseismic rupture extent for the march 11 2011 mw 8 9 9 0 earthquake tohoku oki earthquake may be spatially correlated 0 26 0 05 to 0 82 0 05 with a region estimated to be partially to fully coupled in the interseismic period preceding the earthquake though there is substantial variation in the estimated distribution and magnitude of coseismic slip the 400 km long region estimated to have slipped 4 m corresponds to an area of the subduction zone interface that was coupled at 30 of long term plate convergence rate with peak slip near a region coupled 80 the northern termination of rupture is collocated with a region of relatively low 20 interseismic coupling near the epicenter of the 1994 mw 7 6 sanriku oki earthquake and near a region of potential long term low coupling or ongoing slow slip slip on the subduction interface beneath the coastline 40 50 km depth is best constrained by the land based gps data and least constrained on the shallowest portion of the plate interface due to the 230 km distance between geodetic observations and the japan trench

implications for organic maturation studies of evidence for a geologically rapid increase and stabilization of vitrinite reflectance at peak temperature cerro prieto geothermal system mexico discussion a short term rapid heating and cooling of the rock in well m 94 below 1300 m was caused by a pulse of hot water passing through the edge of the cerro prieto mexico geothermal system below 1300 m the peak paleotemperatures were about 225 250 degrees c but equilibrium well log temperatures indicate a decrease to 150 210 degrees c at present this hot water pulse sharply increased vitrinite reflectance to levels comparable to those measured in the central part of the system even though studies of apatite fission track annealing indicate that the duration of heating was only 10 0 10 1 yr in m 94 in contrast to 10 3 10 4 yr in the central part of the system these data indicate that sedimentary organic matter chemically reacts quickly to temperature increases of about 125 degrees c above ambient even when the higher temperature existed for only 10 0 10 1 yr the quick change of the vitrinite reflectance geothermometer indicates that thermal maturation reactions can stabilize after a geologically short period of heating to a level consistent with peak temperature under moderate to high temperature diagenesis in open fluid rich geothermal systems cerro prieto is one of the most intensively studied and well known geothermal systems in the world thus data from cerro prieto are a benchmark to compare with the predictions of published thermal maturation models such as those formulated by j karweil n v lopatin and a k burnham and j j sweeney these thermal maturation models inaccurately predict duration of heating at cerro prieto the kinetic equations used in these models explicitly allow thermal maturation to continue indefinitely at peak temperature which does not seem to be the case at cerro prieto

petrological and chemical characteristics of liptinite rich coals from alberta canada a suite of liptinite rich coals from the lower cretaceous mannville group in the subsurface of alberta canada has been studied with respect to its organic petrology and organic geochemistry the samples are rich in fluorescing vitrinite perhydrous sporinite cutinite exsudatinite and bituminite rock eval analysis shows that the coals are enriched in hydrogen hydrogen index up to 320 mg hc g toc and depleted in oxygen oxygen index up to 11 mg co2 g toc the value of tmax ranges from 445 to 460 c indicating a late catagenic level of thermal maturity equivalent to ro 1 0 1 1 but the vitrinite reflectance is between 0 68 and 0 81 indicating that it is lowered by as much as 0 4 the pyrolysis chromatograms of the coal samples are dominated by substituted benzenes toluene and xylenes naphthalenes phenanthrenes substituted phenols cresols and small amounts of n alkanes in the range c20 gas chromatography mass spectrometry of the steranes and terpanes indicates little or no contribution of allochthonous bitumen to the coals in addition the mz 217 sterane traces are dominated by c29 compounds with little c27 and c28 this along with the high terpane to sterane ratio mz 191 to mz 217 8 8 indicates that the bitumen was generated from terrestrially derived organic matter the bitumen in the coals has most likely been autogenerated by the coals themselves in response to thermal stress the originally sapropelic coals were probably deposited in an anaerobic environment and were much enriched in hydrogen this study shows that terrigenous organic matter when associated with an anomalous liptinite content may have the potential to generate bitumen

large earthquake rupture process variations on the middle america megathrust the megathrust fault between the underthrusting cocos plate and overriding caribbean plate recently experienced three large ruptures the august 27 2012 m w 7 3 el salvador september 5 2012 m w 7 6 costa rica and november 7 2012 m w 7 4 guatemala earthquakes all three events involve shallow dipping thrust faulting on the plate boundary but they had variable rupture processes the el salvador earthquake ruptured from about 4 to 20 km depth with a relatively large centroid time of 19 s low seismic moment scaled energy release and a depleted teleseismic short period source spectrum similar to that of the september 2 1992 m w 7 6 nicaragua tsunami earthquake that ruptured the adjacent shallow portion of the plate boundary the costa rica and guatemala earthquakes had large slip in the depth range 15 to 30 km and more typical teleseismic source spectra regional seismic recordings have higher short period energy levels for the costa rica event relative to the el salvador event consistent with the teleseismic observations a broadband regional waveform template correlation analysis is applied to categorize the focal mechanisms for larger aftershocks of the three events modeling of regional wave spectral ratios for clustered events with similar mechanisms indicates that interplate thrust events have corner frequencies normalized by a reference model that increase down dip from anomalously low values near the middle america trench relatively high corner frequencies are found for thrust events near costa rica thus variations along strike of the trench may also be important geodetic observations indicate trench parallel motion of a forearc sliver extending from costa rica to guatemala and low seismic coupling on the megathrust has been inferred from a lack of boundary perpendicular strain accumulation the slip distributions and seismic radiation from the large regional thrust events indicate relatively strong seismic coupling near nicoya costa rica patchy zones of strong seismic coupling in the shallowest megathrust region along nicaragua and el salvador and small deeper patchy zones of strong seismic coupling near guatemala which can be reconciled with the geodetic observations as long as the strong coupling is limited to a small fraction of the megathrust area

a unified source model for the 2011 tohoku earthquake abstract the devastating 2011 tohoku earthquake was observed by dense networks of geophysical instruments a unified source model was constructed through joint inversion of teleseismic strong motion and geodetic datasets the result indicates that the earthquake consists of three main ruptures after small rupture in the initial 50 s the first rupture expanded at a slow speed of 1 8 km s to the northeast and east the second rupture began 20 s later at the slowest speed of 1 5 km s and became dominant with the largest slip of 36 m the third rupture then played the leading role propagating southward at a speed of 2 5 km s only the tsunami inversion requires an extension of the source fault to a shallow part between the first rupture area and the japan trench recovering tsunamigenic slips larger than 40 m the slow rupture speed and tsunamigenic slips can explain the features of the disaster by the earthquake

ostracod colour change by thermal alteration offshore ireland and western uk abstract ostracod colour changes from white to amber to red brown to black are principally interpreted to be the result of thermal alteration the changes in colour are thought to be caused by progressive carbon fixation of hydrocarbons derived from the surrounding sediments which invaded the ostracod shell exceptions to this scheme include faunas from organically poor limestones which remain white irrespective of the amount of heating and grey brown or yellow brown specimens coloured by the oxidation of diffuse pyrite thirty four exploration wells have been examined from the irish and western uk sectors and these have shown a progressive darkening of colours which is correlated with both burial depth and distance from igneous intrusions the fastnet basin and southern region of the north celtic sea exhibit higher colour change depth ratios to the porcupine basin and northern region of the north celtic sea basin implying greater palaeoheat flow in the former basins

trench breaching afterslip following deeper coseismic slip of the 2012 mw 7 6 costa rica earthquake constrained by near trench pressure and land based geodetic observations abstract large rupture of the shallowest portion of subduction thrust faults megathrusts such as during the 2011 moment magnitude m w 9 0 tohoku oki earthquake can generate the most devastating tsunamis however it remains unclear whether such trench breaching rupture is typical of other subduction earthquakes the main difficulty in answering this question is the common lack of near trench geodetic monitoring in subduction zones worldwide seafloor and sub seafloor fluid pressure measurements at two closely located borehole observatories in the middle america trench have provided clear evidence for the absence of trench breaching rupture during the 2012 m w 7 6 costa rica earthquake and for the presence of substantial trench breaching afterslip at slow rates after the rupture davis et al 2015 in this study we compare postseismic seafloor pressure change at the trench with coastal global navigation satellite system gnss displacements the same temporal characteristics of the deformation at the trench and coastal sites indicate that both offshore and onshore deformation were the consequence of afterslip that occurred over a wide spatial range updip of the rupture by determining the co and post seismic slip distributions and inferring the associated shear stress changes on the megathrust we show that the mechanical behaviour varies in the dip direction the slip behaviour of the shallow megathrust at costa rica is consistent with conventional conceptual models and contrasts with the behaviour of the shallowest megathrust during the tohoku oki event

inverse modelling of extension and denudation in the east irish sea and surrounding areas abstract epeirogenic uplift and denudation are difficult to quantify because unlike basin subsidence they do not leave an unambiguous record in recent years much research has been focussed on calculating regional denudation from sonic velocity measurements from vitrinite reflectance profiles and from fission track analyses here we show that inverse modelling of the remnant stratigraphy within extensional sedimentary basins yields estimates of denudation within a corridor which crosses the british isles for a variety of reasons these estimates are minima but they do broadly agree with those determined by inversion of vitrinite reflectance profiles our results also demonstrate that denudation estimates from fission track analyses are meaningful a combined stratigraphic and thermal indicator approach should now be used to map denudation across different continents

global variations of stress drop for moderate to large earthquakes 1 we investigate the global variation of earthquake stress drops using spectra of about 2000 events of mb 5 5 between 1990 and 2007 we use an iterative least squares method to isolate source displacement spectra from travel path and receiver contributions based on a convolutional model the observed p wave source spectra are corrected with a globally averaged empirical correction spectrum and estimates of near source attenuation assuming a brune type source model we estimate corner frequencies and compute stress drops stress drop estimates for individual earthquakes range from about 0 3 to 50 mpa but the median stress drop of about 4 mpa does not vary with moment implying earthquake self similarity over the mw 5 2 to 8 3 range of our data a comparison of our results with previous studies confirms this observation over most of the instrumentally observable magnitude range while the absolute values of our estimated stress drops depend upon the assumed source model we identify relative regional variations of stress drop that are robust with respect to the processing parameters and modeling assumptions which includes an inherent assumption of constant rupture velocity we find a dependence of median stress drop on focal mechanism with a factor of 3 5 times higher stress drops for strike slip earthquakes and also find a factor of 2 times higher stress drops for intraplate earthquakes compared to interplate earthquakes

circum pacific seismic potential 1989 1999 the seismic potential for 96 segments of simple plate boundaries around the circum pacific region is presented in terms of the conditional probability for the occurrence of either large or great interplate earthquakes during the next 5 10 and 20 years i e 1989 1994 1989 1999 and 1989 2009 this study represents the first probabilistic summary of seismic potential on this scale and involves the comparison of plate boundary segments that exhibit varying recurrence times magnitudes and tectonic regimes presenting these data in a probabilistic framework provides a basis for the uniform comparison of seismic hazard between these differing fault segments as well as accounting for individual variations in recurrence time along a specific fault segment and uncertainties in the determination of the average recurrence time

evidence for serpentinization of the forearc mantle wedge along the nicoya peninsula costa rica 1 characterizing the hydration state of the forearc mantle wedge yields valuable information on frictional stability at the downdip edge of subduction megathrusts simultaneous inversion of p and s wave arrival times collected as part of the costa rica seismogenic zone experiment yields 1d and 3d p and s wave velocity models vp and vs for the nicoya peninsula segment of the middle america trench nicoya peninsula 1d velocity models show similar velocity gradients to country wide 1d velocity models from 5 30 km depth but diverge at expected moho depths due to proximity to the subducting cocos plate 3d vp values range from 7 2 7 6 km sec in the forearc mantle wedge receiver functions computed at global seismic network station jts in northwestern costa rica confirm these vp values yield vp vs of 1 85 and place the continental moho at 36 4 km depth vp and vp vs are consistent with 15 25 serpentinization of the forearc mantle wedge

slip distribution of the february 27 2010 mw 8 8 maule earthquake central chile from static and high rate gps insar and broadband teleseismic data 1 the shallow depth underthrust earthquake of february 27 2010 mw 8 8 ruptured the subduction plate interface in central chile between 34 s and 38 s we retrieve the spatial and temporal distribution of slip during this mega earthquake through a joint inversion of teleseismic records insar and high rate gps hrgps data additionally our model is shown to agree with broadband surface waves rupture initiated at about 32 km depth and propagated bilaterally resulting in two main slip zones located ssw and nne of the hypocenter nucleation did not take place within or at the edge of one of these main asperities but in between during the first 30s slip propagated predominantly southwards later on the rupture evolved more slowly and more symmetrically eventually the northern asperity became predominant with maximum slip reaching about 20 m most of the seismic moment was released within 110s a relatively short time explained by the bilateral propagation the overall average rupture velocity is 2 6 km s but propagation occurred initially faster towards the south 3 2 km s large slip did not reach the trench a result consistent with the moderate size of the tsunami down dip rupture stopped at about 50 km depth in agreement with the lower limit of the locked zone inferred by ruegg et al 2009 from pre seismic gps data

structural asperity focusing locking and earthquake slip along the nicoya megathrust costa rica on 5 september 2012 a moment magnitude 7 6 earthquake occurred along the locked megathrust interface directly beneath the nicoya peninsula in costa rica the event was anticipated given the history of frequent large earthquakes and recent gps results strain accumulation observed before and coseismic slip observed during the earthquake create a novel and important data set offering a unique look at the strain and locking behavior around a large megathrust environment given this geodetic data and a newly developed regional 3 d subduction interface we develop a regionally appropriate finite element model to evaluate the role of interface topography in generating interseismic locking and ultimately coseismic slip following the 2012 earthquake we find that the interface is most strongly coupled in a patch immediately beneath the central portion of nicoya in an area where a topographic high in the downgoing cocos plate is resisting further subduction this zone is the dominant slip environment in the 2012 earthquake reevaluation of the interseismic locking over 62 years before the most recent event finds that the total accumulated moment potential m0 3 48 1020 n m well matches the total moment release in the 2012 rupture found here m0 3 73 1020 n m mw 7 68 with rupture extending to the se outside of the strongly locked region possibly as early afterslip in contrast to a prior study little locking is required immediately offshore nicoya a conclusion important for understanding the rupture area of the 2012 event regional tsunami potential and relation with regionally observed shallow slow slip events

apatite fission track results from ireland and the porcupine basin and their significance for the evolution of the north atlantic abstract apatite fission track analysis was applied to samples from the irish mainland and exploration boreholes 13 3 1 26 26 1 and 26 28 1 in the northern porcupine and donegal basins to study the regional thermal and tectonic history of the irish continental margin samples from the irish mainland have apatite ages ranging from 301 25 to 56 5 ma with mean track lengths in the range 13 89 0 25 to 11 19 0 22 m and indicate higher temperatures during the middle jurassic about 160 180 ma and during the late cretaceous to early tertiary about 50 80 ma these two periods of increased palaeotemperatures correlate with major reorganizations in plate movements and suggest that uplift and erosion after the maximum palaeotemperatures was achieved as a consequence of a variation in the regional pattern of crustal stress the results from borehole 26 28 1 indicate that within the resolution of the data all samples are presently at their maximum post depositional burial temperatures to produce the mean track length results in the range 11 24 0 49 to 11 81 0 20 m from borehole 26 26 1 it is necessary to invoke post palaeocene geothermal gradients in excess of 50 c km increased relative to the present day gradient 28 c km similar increased geothermal gradients are recognized during the early tertiary in adjacent sedimentary basins and may be explained as a result of heat advection by gravity driven fluid flow established in response to tectonic uplift of the basin margins

aftershocks of the 2012 mw 7 6 nicoya costa rica earthquake and mechanics of the plate interface abstract subduction of the cocos plate beneath the nicoya peninsula costa rica generates large underthrusting earthquakes with a recurrence interval of about 50 yrs the most recent of these events occurred on 5 september 2012 m w 7 6 a vigorous sequence of more than 6400 aftershocks was recorded by a local seismic network within the first four months after the mainshock we determine locations and focal mechanisms for as many aftershocks as possible with m 1 5 occurring within the first nine days of the mainshock all aftershocks with m 3 through the end of 2012 and all events with m 4 through the end of 2015 we determine faulting geometries using regional full waveform moment tensor mt inversion for the largest events m 4 and p wave first motion polarities for smaller events producing a mechanism catalog with 347 earthquakes sixty percent of these events are identified as underthrusting and their locations are compared with spatial distributions of mainshock slip afterslip prior interplate seismicity and slow slip phenomena to better understand the mechanical behavior of the plate interface most of the aftershocks on the megathrust occur up dip of the coseismic slip where afterslip is large and between coseismic slip and shallow slow slip patches the pattern of interplate seismicity during the interseismic period is similar to that for the aftershocks but does not extend to as great a depth the coseismic slip extends even deeper than the interplate aftershocks suggesting that the mainshock ruptured a strongly locked patch driving down dip slip into the conditionally stable part of the deep plate interface that also hosts slow slip about 80 of the aftershocks have one nodal plane oriented favorably to promote failure from static stress changes following the mainshock and early afterslip whereas most others occur in regions of large afterslip electronic supplement tables of hypocenter location and focal mechanisms and selection criteria for underthrusting events and figures showing the gutenberg richter distribution regional moment tensor inversion spatial distribution of earthquake activity and temporal distribution of underthrusting events

slow slip events in costa rica detected by continuous gps observations 2002 2011 1 a network of continuously recording gps stations has operated in the nicoya peninsula of northern costa rica since 2002 we processed all available data from this network for the period of 2002 2011 to investigate the occurrence of slow slip events sse on the subduction interface between the cocos and caribbean plates in order to overcome signal masking by high levels of tropospheric noise we developed a new technique that facilitates detection of transient events in the presence of noise we identified five significant sses during the 2002 2011 period with event middle times in 2003 2005 2007 2009 and 2011 with an average recurrence interval of 21 6 months time series analysis shows that transient deformation imparts a signature similar to random walk removal of the sses and regional common mode errors from the time series reduced velocity uncertainty by nearly an order of magnitude limited available data for the 2003 2005 and 2011 events preclude detailed characterization of these events however good spatiotemporal coverage of the 2007 and 2009 events suggest that both events had irregular duration and distribution in the 2007 event slow slip started in the northwest coastal area and migrated southeastward over a period of 1 month the 2009 event had a significantly longer event duration and larger surface displacement stations in the northwest area observed two separate sses in 2008 6 and 2009 4 correlating well with the tremor episodes offshore indicating a shallow sse slip patch with shorter recurrence interval significant differences between the 2009 and 2007 events lead us to question the simple recurrence interval model for the sse in nicoya

the thermal setting of carboniferous basins in relation to the variscan orogeny in central and western europe abstract the coal basins at the variscan front in western europe provided the first examples of prefolding coalification that was linked to an early high geothermal history the coalification occurred almost contemporaneous with sedimentation and prior to folding the examination of a number of basins from southwestern britain to poland suggests a generalization of this coalification scheme and an extension of it to the inner variscan parts of the rhenish and harz massifs the latter form with the coal basins a repetition of similar troughs from the first flysch deposits up to the last molasse deposits intermontane coal basins of various types in this belt also reveal coalification linked to high geothermies concomitant to variscan sedimentation although sometimes ending during folding conversely the great platforms surrounding the orogen only display normal burial coalification with the exception of isolated structures that were active during and mostly after the variscan period the variscan range was recently interpreted as having been formed under a double influence crustal extensions in the framework of insular arcs and continental collisions that were responsible for folding high paleogeothermal flows are characteristic of the former so they accompanied the formation of subsidence basins

trace element distribution across calcite veins a tool for genetic interpretation abstract profiles of sr ca mg ca and ba ca in two sets of calcite veins within chalks of senonian age in the judean desert israel were utilized to identify both the system in which the calcite vein crystallized and the source of the indurating solution the mg ca sr ca and ba ca profiles in veins located at the dead sea rift boundary were different from profiles in veins located away from the rift boundary na ca distribution on the other hand was affected by a post crystallization source in both localities it is suggested that during the first stage of vein growth mg ca sr ca and ba ca profiles in the veins closer to the rift boundary were affected by the dolomitized country rock the sr ca and mg ca profiles in the veins are too high to be explained by a congruent dissolution of the country rock during the second stage of their growth therefore it is suggested that the solution which precipitated the veins during their second stage of growth obtained its high trace element content either from incongruent dissolution of the country rock or more likely from intrusion of post dolomitization rift water during the second stage of vein growth the ba ca profile in this type of veins was determined by partial dissolution of barite in contrast to veins located at the rift boundary the mg ca sr ca and ba ca profiles in veins located away from the rift boundary were mainly determined by the mode of calcite crystallization i e open vs closed system it seems that trace metal distribution across calcite veins in the judean desert can be related to epigenetic processes such as intrusion of rift waters as well as regional and local tectonic activities

slip history and dynamic implications of the 1999 chi chi taiwan earthquake we investigate the rupture process of the 1999 chi chi taiwan earthquake using extensive near source observations including three component velocity waveforms at 36 strong motion stations and 119 gps measurements a three plane fault geometry derived from our previous inversion using only static data ji et al 2001 is applied the slip amplitude rake angle rupture initiation time and risetime function are inverted simultaneously with a recently developed finite fault inverse method that combines a wavelet transform approach with a simulated annealing algorithm ji et al 2002b the inversion results are validated by the forward prediction of an independent data set the teleseismic p and sh ground velocities with notable agreement the results show that the total seismic moment release of this earthquake is 2 7 10 20 n m and that most of the slip occurred in a triangular shaped asperity involving two fault segments which is consistent with our previous static inversion the rupture front propagates with an average rupture velocity of 2 0 km s 1 and the average slip duration risetime is 7 2 s several interesting observations related to the temporal evolution of the chi chi earthquake are also investigated including 1 the strong effect of the sinuous fault plane of the chelungpu fault on spatial and temporal variations in slip history 2 the intersection of fault 1 and fault 2 not being a strong impediment to the rupture propagation and 3 the observation that the peak slip velocity near the surface is in general higher than on the deeper portion of the fault plane as predicted by dynamic modeling