regional variation of the ω upper bound magnitude of giii distribution in hindukush pamir himalaya and the adjacent regions a perspective on earthquake hazard the upper bound magnitude or maximum magnitude in 28 seismogenic source zones in the hindukush pamir himalaya and the adjacent regions have been computed with the help of a complete and homogeneous earthquake catalogue during the period 1900 2010 to estimate the earthquake hazards in the region the gumbel s third asymptotic distribution giii of extreme value method is used to estimate this parameter in this study a comparison of maximum magnitude obtained by giii distribution is carried out with kijko sellevoll method it is observed that the maximum earthquake magnitudes estimated by kijko sellevoll and giii methods are comparable to each other and the average of differences of their values is only 0 13 the results also estimate the most probable earthquake magnitude that can be expected in next 100 years m100 in all 28 seismogenic source zones an effort is made to make regression relations between and maximum magnitude estimated by kijko sellevoll method mmax ks and and maximum observed magnitude mmaxobs the estimated values exceeded the value of 7 00 in 15 and 8 00 in 5 of the 28 seismogenic source zones the geographical distribution of and m100 in 28 seismogenic source zones of the study region is visualized to analyze the localized seismicity parameters it is observed that earthquake hazard level varies spatially from one zone to another which suggests that examined region have high crustal heterogeneity and seismotectonic complexity

locating microseismic events using borehole data constraining microseismic hypocentres in and around hydrocarbon reservoirs and their overburdens is essential for the monitoring of deformation related to hydraulic fracturing production and injection and the assessment of reservoir security for co2 and wastewater storage microseismic monitoring in hydrocarbon reservoirs can be achieved via a variety of surface and subsurface acquisition geometries in this study we use data from a single subsurface vertical array of sensors we test an existing technique that uses a 1d velocity model to constrain locations by minimizing differential s to p arrival times for individual sensors we show that small errors in either arrival time picks or the velocity model can lead to large errors in depth especially near velocity model discontinuities where events tend to cluster to address this issue we develop two methods that use all available arrival times simultaneously in the inversion thus maximizing the number of potential constraints from n 2 to n where nis the number of phase picks the first approach minimizes all available arrival time pairs whilst the second approach the equal distance time edt method defines the hypocentre as the point where the maximum number of arrival time surfaces intersect we test and compare the new location procedures with locations using differential s to p times at each individual sensor on a microseismic data set recorded by a vertical array of sensors at the ekofisk reservoir in the north sea specifically we test each procedure s sensitivity to perturbations in measured arrival times and the velocity model using monte carlo analysis in general location uncertainties increase with increasing raypath length we show that errors in velocity model estimates are the most significant source of uncertainty in source location with these experiments our tests show that hypocentres determined by the new procedures are less sensitive to erroneous measurements and velocity model uncertainties thus reducing the potential for misinterpretation of the results

age and significance of sequence boundaries on jurassic and early cretaceous rifted continental margins the age and significance of sequence boundaries on jurassic to early cretaceous rifted continental margins in three ocean basins have been documented the margins are the santos basin in the south atlantic the grand banks in the north atlantic and the beaufort sea in the arctic ocean large industry data bases were used for the interpretation of each area megasequence boundaries separate the major phases of basin evolution for example syn rift and post rift boundaries developed with an average periodicity of 49 m y sequence boundaries define the component parts of each megasequence and developed with a modal periodicity of 10 15 m y out of 27 total boundary ages most 16 are developed on just one margin only two possible age ranges overlap on all three margins ighty percent of the megasequence boundaries and 50 of the sequence boundaries show a direct causal connection with coeval faulting and or folding the rest of the boundaries appear as unstructured surfaces separating transgressive and or regressive sedimentary wedges and are interpreted to result from changes in the rate of basin subsidence sediment input and long term eustatic sea level these data do not support theories advocating synchronous worldwide boundary development resulting from periodic short term falls in global eustatic sea level only in like basins of the same age with identical subsidence and sediment input rates are boundaries likely to develop synchronously hence the concept of global synchroneity of sequence boundary development may well be an illusion creat d by the similarity in age of the majority of basins studied as a result of this study it seems wise discard the global approach to basin analysis

borehole receiver orientation using a 3d velocity model the orientation of three component borehole geophones used for recording during a microseismic monitoring experiment is estimated the standard technology for deploying multi component geophones in a deep borehole is wireline based in which the azimuthal rotation of the geophone string cannot be controlled each receiver can have a different rotation angle that is compensated by the particle motion analysis of the direct p wave arrivals picked from a walk around vsp carried out in the proximity of the well knowing the orientation of borehole receivers is critical as inaccuracies lead to systematic errors in determining the hypocentral coordinates of microseismic events additional errors arise from over simplifications of p and s wave velocity earth models in this paper we propose a tomographic approach for improving the orientation estimates of borehole receivers based on hodogram analysis the initial velocity model built from well logs and upholes is refined by 3d tomographic inversion of walk around vsp data and some string shots fired in a nearby borehole taking into account ray bending the estimated errors due to local velocity anomalies can be reduced this makes our estimates of fracture orientation and microseismic hypocentres more reliable when borehole receivers are used in passive seismic surveys

seismic rupture patterns in oaxaca mexico the spatio temporal patterns of seismic activity for events with body wave magnitude mb 4 0 are investigated for the three most recent large earthquakes in the oaxaca region of southern mexico august 23 1965 ms 7 6 mw 7 5 august 2 1968 ms 7 1 mw 7 3 november 29 1978 ms 7 8 mw 7 6 a master catalogue of earthquakes is compiled for the analyses using the international seismological center isc catalogue supplemented by the national earthquake information service neis catalogue the events are then relocated with the joint hypocenter determination jhd method at this magnitude threshold we find that the aftershock zone of the 1965 earthquake was seismically quiescent for at least 20 months prior to the main event the 1968 earthquake was preceded by 1 year of foreshock type activity clustered in the aftershock zone the 1978 earthquake was preceded by 43 months of quiescence and one event mb 4 7 within the aftershock zone 4 months prior to the mainshock we also find that a segment of the subduction zone in oaxaca remains unbroken by these earthquakes in addition some catalogue problems are pointed out which are important to interpretations of seismicity patterns

a probabilistic assessment of earthquake hazard parameters in nw himalaya and the adjoining regions the maximum likelihood estimation method is applied to study the geographical distribution of earthquake hazard parameters and seismicity in 28 seismogenic source zones of nw himalaya and the adjoining regions for this purpose we have prepared a reliable homogeneous and complete earthquake catalogue during the period 1500 2010 the technique used here allows the data to contain either historical or instrumental era or even a combination of the both in this study the earthquake hazard parameters which include maximum regional magnitude mmax mean seismic activity rate the parameter b or b log e of gutenberg richter g r frequency magnitude relationship the return periods of earthquakes with a certain threshold magnitude along with their probabilities of occurrences have been calculated using only instrumental earthquake data during the period 1900 2010 the uncertainties in magnitude have been also taken into consideration during the calculation of hazard parameters the earthquake hazard in the whole nw himalaya region has been calculated in 28 seismogenic source zones delineated on the basis of seismicity level tectonics and focal mechanism the annual probability of exceedance of earthquake activity rate of certain magnitude is also calculated for all seismogenic source zones the obtained earthquake hazard parameters were geographically distributed in all 28 seismogenic source zones to analyze the spatial variation of localized seismicity parameters it is observed that seismic hazard level is high in quetta kirthar sulaiman region in pakistan hindukush pamir himalaya region and uttarkashi chamoli region in himalayan frontal thrust belt the source zones that are expected to have maximum regional magnitude mmax of more than 8 0 are quetta southern pamir caucasus and kashmir himanchal pradesh which have experienced such magnitude of earthquakes in the past it is observed that seismic hazard level varies spatially from one zone to another which suggests that the examined regions have high crustal heterogeneity and seismotectonic complexity

eustatic sea level changes interpreted from seismic stratigraphy a critique of the methodology with particular reference to the north sea jurassic record seismic stratigraphic methods for interpreting eustatic sea level change are based on generalized stratigraphic models and chronostratigraphic interpretations that have not been substantiated by publication of the necessary basic supportive data chronostratigraphic correlations of sea level change curves between basins are based partly on circular reasoning onlap and offlap seismic models may not indicate sea level change but flexural subsidence facies shifts or changes in sea level in the opposite direction to that proposed resolution of some of these problems may be achieved by publication of basic data now in confidential industry files the widely acclaimed vail curves should not be used as templates for basin correlation until such data have been provided and such use should be supported by appropriate conventional lithostratigraphic and biostratigraphic documentation from each new basin where such data have been made available as with the north sea jurassic serious questions of interpretation are raised

seismic strain release along the middle america trench mexico we measure the seismic moment of five great ms 7 8 earthquakes from 1928 to 1942 along the mexican portion of the middle american trench directly from recorded seismograms and obtain considerably lower moment values than had previously been estimated from ms such direct moment determinations are inherently more reliable as the average seismic slip rate along this portion of the arc appears to be essentially constant these measurements of the past seismic moment are used to estimate that the current end of 1980 moment deficiency is 46 1027 dyne cm or an average slip of 97 cm along the arc although this is much lower than past estimates at the current rate of increase 1 6 1027 dyne cm yr 3 4 cm yr of seismic displacement the moment deficiency by 1985 will be the equivalent of five magnitude 8 earthquakes and by 1990 six such events the slip along this portion of the middle america trench arc appears to fit shimazaki and nakata s slip predictable model in which the size but not the time of occurrence of future large events may be estimated

current aspects of basin analysis abstract current research in basin analysis focuses on interdisciplinary integration of geodynamics mathematical and physical modelling and sedimentary geology these efforts are organized into a research framework emphasizing basin formation nature of the basin fill maturation diagenesis of the basin fill and timing of events research in geodynamics permits development of a proposed classification of sedimentary basins in which basin types are discriminated according to nature of the plate margin basin position on or within a tectonic plate nature of the crust and geodynamic models or known process of formation a summary of current research developments on sedimentary basin fills focuses on the interdisciplinary solutions developed to understanding carbonate distribution through time origin of black shales sea level history and global sedimentary cycles maturation of basin fills requires an understanding of both thermodynamic aspects of mineral phase changes and changing character of the chemistry of flow of water through porous sediments during basin evolution summary case histories from the illinois basin and the appalachian basin illustrate these approaches

sealevel curves based on seismic stratigraphy their chronostratigraphic significance abstract in recent years it has become popular to think of relative sealevel changes detectable from seismic stratigraphic analyses of continental margins as being responses to short term oscillations in global eustatic sealevel global sealevel has indeed fluctuated through time on a first order cycle with a wavelength of about 400 ma in response to plate tectonic processes especially those involving the accretion and fragmentation of supercontinents like pangaea the short term cycles of relative sealevel change detected from coastal onlap curves derived from seismic data on continental margins are more likely to be caused by interactions between thermotectonic subsidence the flexure of the lithosphere and this first order change in sealevel than by short term oscillatory changes in global eustatic sealevel thus records of changing coastal onlap are likely to differ from one basin to another depending on subsidence history continental margins with similar subsidence histories will have similar coastal onlap curves but it is unlikely that there will be any chronostratigraphic correspondance between coastal onlap curves from basins of very different subsidence histories except at times when there were large changes in ice volume as in the late cenozoic for instance it is concluded that supposedly global curves of sealevel derived from coastal onlap curves may have little or no chronostratigraphic significance

determination of s wave slowness from a linear array of borehole receivers summary locations of seismic events from a linear array of receivers may require determination of slowness vectors of arriving waves in an isotropic medium p waves are polarized along the slowness vector which enables direct determination of backazimuth i e azimuth to a source from a receiver from p wave polarization in contrast s waves usually have much larger signal to noise ratio than p waves but are polarized in a plane perpendicular to their slowness vectors which prevents direct determination of their backazimuth we have developed a novel technique to determine the slowness vector of s waves detected in a linear array of receivers in an isotropic medium we combine the s wave polarization measurement with the derivative of the s wave travel times along the array to obtain the full slowness vector and backazimuth the proposed method allows one to determine direction to sources of seismic events from a single linear array of receivers using only s waves this technique is not affected by sv waves which is shown by a test on a synthetic data set we also test the method on two real microseismic data sets from hydraulic fracturing treatments and show that it outperforms the backazimuth determination from p waves and from horizontal polarization of s waves

plate boundary tectonics global sea level changes and the development of the eastern south island continental margin new zealand southwest pacific the great south basin is a mid cretaceous continental margin rift related to the break up of the new zealand sector of gondwanaland syn rift cretaceous paleogene sediment accumulated up to a thickness of 8 km followed by post rift subsidence of the northwest and southeast basin margins to form the canterbury basin and campbell plateau respectively the sedimentary evolution of the eastern south island continental margin is described within the context of four megasequences containing eight regionally recognizable seismic sequences syn rift phases 1 2 non marine graben fill post rift phases 3 6 epeiric marine transgression paraconformity phase 7 mid oligocene maximum transgression and syn orogenic phase 8 plate boundary driven terrigenoclastic regression the successive phases of this overall transgressive regressive cycle can be equated with the natural and progressive development of the sedimentary sequence within known regional factors the eastern south island margin sequence forms an appropriate southern hemisphere test of the global sea level curves of vail et al 1977 and haq et al 1986 although eustatic sea level cycles may have played some part in the differentiation of transgressive phases 3 7 the stratigraphic sequence is adequately interpreted in terms of intrinsic basin evolution within a local tectonic context

a time predictable model for earthquake generation in greece 20th century data have been used to determine repeat times t of main shocks in seven of the most active seismogenic sources of shallow earthquakes in greece it is observed that t depends on magnitude mp of the preceding main shock and not on the magnitude mf of the following main shock this means that the time predictable model and not the slip predictable model is valid for the main shocks of these sources a relation of the form log t cmp a fits the data while the parameter a depends on the seismicity of each source and on the minimum cutoff magnitude of the main shocks considered a representative of all sources value equal to 0 3 is found for parameter c when mp is surface wave magnitude and t is measured in yr

estimation of effective anisotropy simultaneously with locations of microseismic events passive seismic tomography in which the event locations and the velocity model are inferred simultaneously is seldom used to process microseismic surveys acquired in the oil and gas industry we discuss advantages of applying tomographic ideas to typical microseismic data recorded in a single nearly vertical well to monitor hydraulic stimulation of a shale gas reservoir microseismic events are conventionally located in the energy industry applications using a velocity model derived from sonic logs and perforation shots instead of fixing the model as is normally done we alter it while locating the events this added flexibility not only makes it possible to accurately predict traveltimes of the recorded p and s waves but also provides a convincing evidence for anisotropy of the examined shale formation while we find that velocity heterogeneity does not need to be introduced to explain the data acquired at each stage of hydraulic fracturing the obtained models are suggestive of possible time laps

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

an improved method for hydrofracture induced microseismic event detection and phase picking the ability to detect small microearthquakes and identify their p and s phase arrivals is a key issue in hydrofracture downhole monitoring because of the low signal to noise ratios s n an array based waveform correlation approach matched filter is applied to improve the detectability of smallmagnitudeeventswithmechanismsandlocationssimilar to a nearby master event after detecting the weak events a transformed spectrogram method is used to identify the phase arrivals the technique has been tested on a downhole monitoring data set of the microseismic events induced by hydraulic fracturing it is shown that for this case one event with a s n around 6 db which is barely detectable using an array stacked short time average long time average sta lta detector under a reasonable false alarm rate is readily detected on the array stacked correlation traces the transformedspectrogramanalysisofthedetectedeventsimproves p ands phasepicking

nonuniform seismic slip rates along the middle america trench revised estimates of seismic slip rates along the middle america trench are lower on the average than plate convergence rates but match them locally for example oaxaca along the cocos north american plate boundary this can be explained by nonuniformities in slip at points of aseismic ridge or fracture zone subduction for at least 81 yr and possibly several hundred years no major m sub s or 7 5 shallow earthquake is known to have occurred near the orozco fracture zone and tehuantepec ridge areas compared with the average recurrence periods for large earthquakes 33 8 yr since 1898 and 35 24 yr between 1542 and 1979 this suggests that either a large m or 8 4 event may be anticipated at such locations or that these are points of aseismic subduction large coastal terraces and evidence suggesting tectonic uplift are found onshore near the orozco fracture zone the larger discrepancy between plate convergence and seismic slip rates along the cocos carribbean plate boundary is more likely due to decoupling and downbending of the subducted plate we used the limited statistical evidence available to characterize both spatial and temporal deficiencies in recent seismic slip the observations appear consistent with a possible forthcoming episodemore of more intense seismic activity based on a series of comparisons with carefully delineated aftershock zones we conclude that the zones of anomalous seismic activity can be indentified by a systematic automated analysis of the worldwide earthquake catalog m sub b or 4 less

active rifting in southwestern mexico manifestations of an incipient eastward spreading ridge jump a major ongoing episode of continental rifting has formed a system of three intersecting grabens in the western mexican volcanic belt these structures may mark the initial stage of an eastward spreading ridge jump beneath continental crust eastward ridge segment jumps have been propagating northward along this part of the east pacific rise for the past 12 m y but this is the first plate boundary reorganization event to involve continental crust since the separation of baja california in the miocene since pliocene time small volumes of unusual alkaline magmas have erupted in the graben areas in close association with the more abundant subduction related calc alkaline magmas erupted from andesitic stratovolcanoes the alkaline magmas are varieties found in zones of active rifting elsewhere in the world

probabilistic appraisal of earthquake hazard parameters deduced from a bayesian approach in the northwest frontier of the himalayas a straightforward bayesian statistic is applied in five broad seismogenic source zones of the northwest frontier of the himalayas to estimate the earthquake hazard parameters maximum regional magnitude mmax value of g r relationship and seismic activity rate or intensity for this purpose a reliable earthquake catalogue which is homogeneous for mw 5 0 and complete during the period 1900 to 2010 is compiled the hindukush pamir himalaya zone has been further divided into two seismic zones of shallow h 70 km and intermediate depth h 70 km according to the variation of seismicity with depth in the subduction zone the estimated earthquake hazard parameters by bayesian approach are more stable and reliable with low standard deviations than other approaches but the technique is more time consuming in this study quantiles of functions of distributions of true and apparent magnitudes for future time intervals of 5 10 20 50 and 100 years are calculated with confidence limits for probability levels of 50 70 and 90 in all seismogenic source zones the zones of estimated mmax greater than 8 0 are related to the sulaiman kirthar ranges hindukush pamir himalaya and himalayan frontal thrusts belt suggesting more seismically hazardous regions in the examined area the lowest value of mmax 6 44 has been calculated in northern pakistan and hazara syntaxis zone which have estimated lowest activity rate 0 0023 events day as compared to other zones the himalayan frontal thrusts belt exhibits higher earthquake magnitude 8 01 in next 100 years with 90 probability level as compared to other zones which reveals that this zone is more vulnerable to occurrence of a great earthquake the obtained results in this study are directly useful for the probabilistic seismic hazard assessment in the examined region of himalaya

back azimuth constrained double difference seismic location and tomography for downhole microseismic monitoring abstract we have developed a new seismic tomography method back azimuth constrained double difference dd seismic tomography which is suitable for downhole microseismic monitoring of hydraulic fracturing the new method simultaneously locates microseismic events and determines three dimensional 3d vp and vs models for the fracturing zone using differential arrival times from pairs of events and event back azimuths in addition to absolute arrival times compared to the existing dd location and tomography method our method incorporates back azimuth information to better constrain microseismic event locations in the case of poor spatial station coverage such as the linear downhole seismic array generally used for microseismic monitoring by incorporating the relative arrival time and back azimuth information of events the extended dd method can provide better relative event locations and thus can better characterize the fracture distribution in addition to microseismic locations seismic velocity anomalies determined around the fracturing zone may also provide valuable information for fracture development due to the existence of fractures and fluids the seismic velocity is expected to be lower in the fractured zone compared to the surrounding regions therefore the area of low seismic velocity anomaly may be used as a proxy for the stimulated reservoir volume we have applied the new method to a downhole microseismic dataset from shale gas hydraulic fracturing the microseismic events are more accurately relocated than the conventional grid search location method and they are generally associated with low velocity anomalies

seismicity and tectonics of the rivera plate and implications for the 1932 jalisco mexico earthquake seismicity on and near the boundaries of the rivera plate is examined in order to determine the subduction regime of the rivera plate and its influence on the earthquake behavior of the northernmost section of the mid america trench in particular we address the question of a rivera cocos boundary there have been several large historic earthquakes in the coastal areas of the mexican states colima and jalisco but the last large event was in june 1932 the 1932 jalisco earthquake ms 8 1 the present quiescence has lasted longer than the average recurrence interval for the mexican subduction zone and the jalisco area is now categorized as a seismic gap however if subduction in this area is dominated by the motion of the rivera plate which is subducting at half the rate of the cocos plate the deficiency of earthquake activity may not be unusual in an attempt to better delineate the rivera cocos boundary intermediate sized earthquakes along and near the rivera fracture zone and the mid america trench were relocated with the joint epicenter determination method we found that in general the catalog locations are fairly accurate with the average change in epicenter upon relocation being 12 km seismicity along the rivera fracture zone follows the physiographic trend of the fracture zone but east of its intersection with the east pacific rise seismicity is more diffuse two intermediate sized earthquakes in this diffuse area have focal mechanisms suggesting that they represent rivera cocos boundary motion reexamination of arrival time data for the 1932 jalisco earthquake yields an epicenter at 19 57 n 104 42 w close to the boundary zone inferred from these two earthquakes we conclude that the possibility that the 1932 jalisco earthquake broke the northernmost section of the cocos north american plate interface as opposed to the rivera north american plate interface cannot be ruled out

out of our depth on the impossibility of fathoming eustasy from the stratigraphic record the evolution of a sedimentary basin s gross morphology depends upon 1 basement movement 2 sediment accumulation and compaction and 3 variations of eustasy with time thus if an accurate history of eustasy could be derived it would aid in our understanding of basin stratigraphy and help in the prediction of sediment geometry from described areas techniques which attempt to determine the magnitude of eustatic sea level excursions include the measurement of 1 the amount of sedimentary onlap onto the continental margins with and without the use of hypsometric curves 2 the thickness of marine sedimentary cycles and the elevation and distance between indicators of old strandlines 3 the perturbations on individual thermo tectonic subsidence curves and stacked crustal subsidence curves 4 the variations in deep ocean oxygen isotopes found in sediments and 5 the size of variables used in graphical and numerical simulations of basin fill in terms of tectonic behavior rates of sediment accumulation and eustasy which invert the problem to date a combination of the use of relative sea level charts derived from sediment onlap of the continental margin with dimensioning by oxygen isotopes responding to glacial events offers the best potential for relative tectono eustatic sea level curves but even this method can not produce a unique solution for absolute eustatic variations mathematical modelling shows that at best it is possible to obtain only the sum of tectonic basement subsidence and sea level variations from the above methods and at worst not even that simple a combination thus every proposed scheme to measure eustatic sea level excursions assumes some behavior for two of the three underlying processes tectonic movement of the basement sedimentary accumulation and eustatic sea level each scheme then determines the third process relative to the assumed model behavior of the other two it would seem that like king canute we cannot command the sea though we can still use undifferentiated relative tectono eustatic sea level curves to generate a family of solutions which are the product of a variety of absolute sea level curves and tectonic models each solution has then to be assessed in terms of geologic setting and the hypotheses it generates

testing for eustatic sea level control in the precambrian sedimentary record abstract stratigraphic successions are deposited under the influence of three primary controls which tend to vary systematically through time these controls are tectonism basin subsidence and uplift sea level change and sediment supply the development of sequence stratigraphy has enabled the introduction of systematic quantitative methods for the analysis of these controls the use of the sequence approach requires the establishment of a regional sequence framework and detailed chronostratigraphic control working with the phanerozoic record this approach has revealed a variety of sequence types reflecting long term tectonostratigraphic processes caused by continental rifting continental collisions and cratonic dynamic topography high frequency thrust loading cycles in foreland basins and high frequency cycles caused by orbital forcing glacioeustasy 104 5 year periodicity and eustasy driven by changing rates of sea floor spreading 107 8 year periodicity have emerged as two significant global processes documenting the sequence record in the precambrian has proved difficult owing to fragmentary preservation and structural deformation methods of dating are at present not precise enough to permit reliable regional correlation or testing of high frequency sequence generating mechanisms some studies of precambrian sequence architecture have been achieved but these indicate tectonic processes acting at a much slower rate than during the phanerozoic further analysis of this problem is required

historical seismicity and rates of crustal deformation along the margins of the ordos block north china earthquakes in china show an empirical relation between seismic moment m 0 and the areal distribution of modified mercalli intensities vi and viii log m 0 16 66 0 91 log a viii and log m 0 14 35 1 16 log a vi where a and m 0 are measured in squared kilometers and newton meter respectively the empirical relations may be used to estimate m 0 for historical earthquakes in china to within a factor of three on average when sufficient isoseismal data exist this observation and an extensive collection of isoseismal maps are used to estimate m 0 for large earthquakes that occurred along the margins of the ordos block during the last 700 yr focal parameters of the historical events are inferred from the orientation and displacements across quaternary faults average rates of crustal deformation are then estimated from the 700 yr historical record with formulas that relate the occurrence rate of seismic moment in a region to rates of crustal strain the shanxi and northern ningxia graben systems are situated along the eastern and northwestern edges of the ordos block respectively normal faults in the two systems trend northeasterly and are characterized by a component of right lateral slip the deformation resulting from slip during earthquakes in each of the respective fault systems is estimated at about 0 5 to 1 0 mm yr of both right lateral shear and north by northwest extension the weihe graben system bounds the southern edge of the ordos block strikes easterly and conjugate to the shanxi and northern ningxia fault systems and exhibits left lateral normal fault displacements the average rate of deformation across weihe is described by about 1 0 mm yr of north by northwest extension and 1 5 mm yr left lateral east west shear the hetao fault system delineates the northern edge of the ordos block and displays quaternary faults similar in orientation and mechanism to that observed in weihe although mapped faults in hetao exhibit evidence of quaternary displacement crustal deformation rates are not estimated because there exists no historical record of large earthquakes in the area in southern ningxia at the southwest boundary of the ordos block deformation occurs by slip on left lateral strike slip faults oriented in an easterly azimuth and thrust faults with strikes ranging from southeast to south the average deformation rate in southern ningxia is found to be about 4 0 mm yr of east by northeast contraction and 10 0 mm yr of left lateral shear deformation of each of the fault systems is consistent with a regional compressive stress that trends northeast and results in an average of about 3 0 mm yr each of contraction at n70 e and extension of n160 e across the entire region inasmuch as uncertainties in estimates of m0 for historical earthquakes are about a factor of three a similar uncertainty is attached to rates of crustal strain determined in this manner

a probabilistic estimate of the most perceptible earthquake magnitudes in the nw himalaya and adjoining regions nw himalaya and its neighboring region 25 40 n and 65 85 e is one of the most seismically hazardous regions in the indian subcontinent a region that has historically experienced large to great damaging earthquakes in the present study the most perceptible earthquake magnitudes mp are estimated for intensity i vii horizontal peak ground acceleration a 300 cm s2 and horizontal peak ground velocity v 10 cm s in 28 seismogenic zones using the two earthquake recurrence models of kijko and sellevoll bulletin of the seismological society of america 82 1 120 134 1992 and gumbel s third asymptotic distribution of extremes giii both methods deal with maximum magnitudes the earthquake perceptibility is calculated by combining earthquake recurrence models with ground motion attenuation relations at a particular level of intensity acceleration and velocity the estimated results reveal that the values of mp for velocity v 10 cm s show higher estimates than corresponding values for intensity i vii and acceleration a 300 cm s2 it is also observed that differences in perceptible magnitudes calculated by the kijko sellevoll method and giii statistics show significantly high values up to 0 7 0 6 and 1 7 for intensity acceleration and velocity respectively revealing the importance of earthquake recurrence model selection the estimated most perceptible earthquake magnitudes mp in the present study vary from mw 5 1 to 7 7 in the entire zone of the study area results of perceptible magnitudes are also represented in the form of spatial maps in 28 seismogenic zones for the aforementioned threshold levels of intensity acceleration and velocity estimated from two recurrence models the spatial maps show that the quetta of pakistan the hindukush pamir himalaya the caucasus mountain belt and the himalayan frontal thrust belt kashmir kangra uttarkashi chamoli regions exhibit higher values of the most perceptible earthquake magnitudes mw 6 0 these spatially distributed values indicate good agreement with high seismic hazard zones in previously published hazard maps based on seismicity maximum expected earthquake magnitudes during specific time intervals and maximum expected acceleration these maps have useful implications in preparing earthquake selection criteria for the anti seismic design of non critical structures in the study region

stochastic slip predictable model for earthquake occurrences recent geophysical studies have indicated that an earthquake recurrence interval and the size of the preceding event are positively correlated this observation is the basis for the deterministic time predictable recurrence model of shimazaki and nakata using the basic assumptions of the time predictable recurrence model we develop a stochastic model of earthquake occurrence that incorporates temporal dependence this paper discusses the formulation of the model and the effect of including temporal dependence hazard estimates for a section of the san andreas fault near parkfield where data has suggested time predictable behavior are obtained for illustrative purposes comparisons are made with the poisson model results indicate that currently used poisson models may give lower estimates of the seismic hazard when there has been a seismic gap of the various sensitivity analyses performed it is observed that slip rate has the largest effect on exceedence probabilites computed from the stochastic time predictable model therefore accurate determinations of slip rates both seismic and aseismic can substantially reduce the uncertainty in seismic hazard estimates

a time and magnitude predictable model for generation of shallow earthquakes in the aegean area repeat times of strong shallow mainshocks have been determined by the use of instrumental and historical data for 68 seismogenic sources in the aegean and surrounding area 34 n 43 n 18 e 30 e for 49 of these sources at least two interevent times three mainshocks are available for each source by using the repeat times for these 49 sources the following relation has been determined log t t 0 36m min 0 35m p a wheret t is the repeat time measured in years m p the surface wave magnitude of the preceding mainshock mmin the magnitude of the smallest earthquake considered and a parameter which varies from source to source a multilinear correlation coefficient equal to 0 89 was determined for this relation

conditional probabilities for the recurrence of large and great interplate earthquakes along the mexican subduction zone abstract time dependent conditional probabilities for the recurrence of large and great interplate earthquakes along the mexican subduction zone are presented for time intervals of 5 10 and 20 yr duration i e 1986 1991 1986 1996 and 1986 2006 at present the central oaxaca 97 3 to 97 7 w ometepec san marcos 98 2 to 99 5 w and central guerrero 100 to 101 w segments stand out as having the highest probability for the recurrence of large and great earthquakes in the near future segmentation of the margin is delineated by the rupture zones of the most recent earthquakes occurring in each area for segments of the mexican margin with one or more known recurrence intervals probability estimates are based on the observed average recurrence time for each segment and the lognormal probability distribution function use of a generic distribution function nishenko and buland 1987 allows a more stable estimate of average recurrence times than are available from a few observations a long term prediction time window is also defined based on the 90 per cent confidence interval for our estimates of the recurrence time use of a predetermined confidence interval conveys valuable additional information as to the precision and information content of the forecast for those segments of the margin with only one prior event and hence no historically observed recurrence times repeat times are estimated by extrapolating the observed recurrence time behavior in oaxaca subject to the assumptions that recurrence time scales only as a function of the ratio of seismic displacement and convergence rate and that all events are characterized as simple sources i e involve the rupture of a single asperity

evidence for periodic seismicity in the inner aegean seismic zone the most complete and reliable data of strong m s 6 5 shallow h 70 km earthquakes which occurred in the inner aegean seismic zone have been utilized to describe its seismicity time variation during 1800 1986 by two independent statistical models the first is a sequentially stationary model of seismicity rates which shows that intervals of low seismicity rate lasting for some 37 years alternate with high rate intervals of 8 12 years duration the second model is a statistical model according which seismic energy released within 5 year time windows approximates a harmonic curve within a period of about 50 years this model is in agreement with the notion that the time series of strong earthquake occurrences in the inner aegean seismic zone consists of a random shocks withm s 6 5 6 8 and a nonrandom component m s 6 9 maxima and minima of the harmonic curve coincide with the high and low rate intervals respectively a model of regional stationary accumulation of thermal stresses along certain seismic belts and their cyclic relaxation may explain this periodicity

probabilistic assessment of earthquake hazard in gujarat and adjoining region of india the gujarat and adjoining region falls under all four seismic zones v iv iii and ii of the seismic zoning map of india and is one of the most seismically prone intracontinental regions of the world it has experienced two large earthquakes of magnitude m w 7 8 and 7 7 in 1819 and 2001 respectively and several moderate earthquakes during the past two centuries in the present study the probability of occurrence of earthquakes of m 5 0 has been estimated during a specified time interval for different elapsed times on the basis of observed time intervals between earthquakes using three stochastic models namely weibull gamma and lognormal a complete earthquake catalogue has been used covering the time interval of 1819 to 2006 the whole region has been divided into three major seismic regions saurashtra mainland gujarat and kachchh on the basis of seismotectonics and geomorphology of the region the earthquake hazard parameters have been estimated using the method of maximum likelihood the logarithmic of likelihood function ln l is estimated and used to test the suitability of models in three different regions it was found that the weibull model fits well with the actual data in saurashtra and kachchh regions whereas lognormal model fits well in mainland gujarat the mean intervals of occurrence of earthquakes are estimated as 40 455 20 249 and 13 338 years in the saurashtra mainland gujarat and kachchh region respectively the estimated cumulative probability probability that the next earthquake will occur at a time later than some specific time from the last earthquake for the earthquakes of m 5 0 reaches 0 9 after about 64 years from the last earthquake 1993 in saurashtra about 49 years from the last earthquake 1969 in mainland gujarat and about 29 years from the last earthquake 2006 in the kachchh region the conditional probability probability that the next earthquake will occur during some specific time interval after a certain elapsed time from last earthquake is also estimated and it reaches about 0 8 to 0 9 during the time interval of about 57 to 66 years from the last earthquake 1993 in saurashtra region 31 to 51 years from the last earthquake 1969 in mainland gujarat and about 21 to 28 years from the last earthquake 2006 in kachchh region

inversion of microseismic data for triclinic velocity models modern downhole microseismic surveys often employ geometries in which ray trajectories generated by a collection of locatable events provide full polar and azimuthal coverage making it possible to estimate the in situ seismic anisotropy we show that traveltimes and particle motions of the direct p and shear waves acquired in such geometries can constrain stiffness tensors of triclinic media while obtaining all 21 stiffness coefficients of a homogeneous triclinic space simultaneously with locating pertinent microseismic events from data recorded in a single vertical well is relatively straightforward the same methodology does not necessarily succeed in layered formations because the combination of their vertical heterogeneity and azimuthal anisotropy might invalidate the commonly adopted approximation of the event azimuths by those of the p wave polarization vectors when the event azimuths cannot be derived from the particle motions traveltimes observed in two or more wells are required to locate the events and build layered triclinic or higher symmetry azimuthally anisotropic velocity models as our numerical tests indicate the multi well event location methods are expected to perform better than their single well counterparts because they rely solely on triangulation and eliminate the usually pronounced azimuthal uncertainties in the event locations that stem from noises adversely affecting hodogram analysis

comparison of surface and borehole locations of induced seismicity monitoring of induced microseismic events has become an important tool in hydraulic fracture diagnostics and understanding fractured reservoirs in general we compare microseismic event and their uncertainties using data sets obtained with surface and downhole arrays of receivers we first model the uncertainties to understand the effect of different acquisition geometries on location accuracy for a vertical array of receivers in a single monitoring borehole we find that the largest part of the final location uncertainty is related to estimation of the backazimuth this is followed by uncertainty in the vertical position and radial distance from the receivers for surface monitoring the largest uncertainty lies in the vertical position due to the use of only a single phase usually p wave in the estimation of the event location in surface monitoring results lateral positions are estimated robustly and are not sensitive to the velocity model in this case study we compare event location solutions from two catalogues of microseismic events one from a downhole array and the second from a surface array of 1c geophone our results show that origin time can be reliably used to find matching events between the downhole and surface catalogues the locations of the corresponding events display a systematic shift consistent with a poorly calibrated velocity model for downhole dataset for this case study locations derived from surface monitoring have less scatter in both vertical and horizontal directions

probabilistic assessment of earthquake recurrence in northeast india and adjoining regions northeast india and adjoining regions 20 32 n and 87 100 e are highly vulnerable to earthquake hazard in the indian sub continent which fall under seismic zones v iv and iii in the seismic zoning map of india with magnitudes m exceeding 8 7 and 6 respectively it has experienced two devastating earthquakes namely the shillong plateau earthquake of june 12 1897 mw 8 1 and the assam earthquake of august 15 1950 mw 8 5 that caused huge loss of lives and property in the indian sub continent in the present study the probabilities of the occurrences of earthquakes with magnitude m 7 0 during a specified interval of time has been estimated on the basis of three probabilistic models namely weibull gamma and lognormal with the help of the earthquake catalogue spanning the period 1846 to 1995 the method of maximum likelihood has been used to estimate the earthquake hazard parameters the logarithmic probability of likelihood function ln l is estimated and used to compare the suitability of models and it was found that the gamma model fits best with the actual data the sample mean interval of occurrence of such earthquakes is estimated as 7 82 years in the northeast india region and the expected mean values for weibull gamma and lognormal distributions are estimated as 7 837 7 820 and 8 269 years respectively the estimated cumulative probability for an earthquake m 7 0 reaches 0 8 after about 15 16 2010 2011 years and 0 9 after about 18 20 2013 2015 years from the occurrence of the last earthquake 1995 in the region the estimated conditional probability also reaches 0 8 to 0 9 after about 13 17 2008 2012 years in the considered region for an earthquake m 7 0 when the elapsed time is zero years however the conditional probability reaches 0 8 to 0 9 after about 9 13 2018 2022 years for earthquake m 7 0 when the elapsed time is 14 years i e 2009

regional time predictable modeling in the hindukush pamir himalayas region abstract the seismic characteristic of hindukush pamir himalaya hph and its vicinity is very peculiar and has experienced many widely distributed large earthquakes recent work on the time dependent seismicity in the hindukush pamir himalayas is mainly based on the so called regional time predictable model which is expressed by the relation log t cm p a where t is the inter event time between two successive main shocks of a region and m p is the magnitude of the preceded main shock parameter a is a function of the magnitude of the minimum earthquake considered and of the tectonic loading and c is positive 0 3 constant in 90 of the cases with sufficient data parameter c was found to be positive which strongly supports the validity of the model in the present study a different approach which assumes no prior regionalization of the area is attempted to check the validity of the model nine seismic sources were defined within the considered region and the inter event time of strong shallow main shock were determined and used for each source in an attempt at long term prediction which show the clustering and occurrence of at least three earthquakes of magnitude 5 5 m s 7 5 giving two repeat times satisfying the necessary and sufficient conditions of time predictable model tp model further using the global applicability of the regional time and magnitude predictable model the following relations have been obtained log t t 0 19 m min 0 52 m p 0 29 log m 0 10 63 and m f 1 31 m min 0 60 m p 0 72 log m 0 21 01 where t t is the inter event time measured in years m min the surface wave magnitude of the smallest main shock considered m p the magnitude of preceding main shock m f the magnitude of the following main shock and m 0 the moment rate in each source per year these relations may be used for seismic hazard assessment in the region based on these relations and taking into account the time of occurrence and the magnitude of the last main shock in each seismogenic source time dependent conditional probabilities for the occurrence of the next large m s 5 5 shallow main shocks during the next 20 years as well as the magnitudes of the expected main shocks are determined

spatial mapping of earthquake hazard parameters in the hindukush pamir himalaya and adjacent regions implication for future seismic hazard abstract the study deals spatial mapping of earthquake hazard parameters like annual and 100 years mode along with their 90 probability of not being exceeded nbe in the hindukush pamir himalaya and adjoining regions for this purpose we applied a straightforward and most robust method known as gumbel s third asymptotic distribution of extreme values giii a homogeneous and complete earthquake catalogue during the period 1900 2010 with magnitude mw 4 0 is utilized to estimate these earthquake hazard parameters an equal grid point mesh of 1 longitude x 1 latitude is chosen to produce detailed earthquake hazard maps this performance allows analysis of the localized seismicity parameters and representation of their regional variations as contour maps the estimated result of annual mode with 90 probability of nbe is expected to exceed the values of mw 6 0 in the sulaiman kirthar ranges of pakistan and northwestern part of the nepal and surroundings in the examined region the 100 years mode with 90 probability of nbe is expected to exceed the value of mw 8 0 in the hindukush pamir himalaya with caucasus mountain belt the sulaiman kirthar ranges of pakistan northwestern part of the nepal and surroundings the kangra himanchal pradesh and kashmir of india the estimated high values of earthquake hazard parameters are mostly correlated with the main tectonic regimes of the examined region the spatial variations of earthquake hazard parameters reveal that the examined region exhibits more complexity and has high crustal heterogeneity the spatial maps provide a brief atlas of the earthquake hazard in the region

recognition and documentation of depositional sequences from outcrop an example from the aptian and albian on the eastern margin of the wessex basin stratigraphic data relating to the aptian and albian sediments around folkestone in southeast england on the eastern margin of the wessex basin are plotted graphically to illustrate biostratigraphic gaps and condensed intervals these are then used to suggest candidate sequence boundaries notated lg1 4 and gl 3 which are named after the lower greensand and gault the biostratigraphic subzones apparently unrepresented in the area are lg1 obsoletus and bodei lg2 gracite and debile lg3 schrammeni gl bulliensis candidate sequence boundaries g2 cristatum subzone and g3 auritus subzone are erosion surfaces correlating with probable biostratigraphic gaps elsewhere in the basin the age of lg4 is uncertain but must lie within the mammillatum superzone all candidate sequence boundaries correspond closely to those predicted by recent global sea level cycle charts and additionally there is a close match between predicted maximum flooding surfaces and the occurrence of condensed intervals most of the candidate sequence boundaries could have been formed as a result of rapid and at least regionally extensive relative sea level falls but the sedimentological contexts of lg3 and gl suggest that these may have been generated by transgression related sediment condensation the minor sequence boundary in the loricatus zone intermedius subzone illustrated in the cycle charts cannot be unambiguously recognized at outcrop in the folkestone area additional sequence boundaries not shown in the cycle charts may also be present in the wessex basin

reconstructing first order changes in sea level during the phanerozoic and neoproterozoic using strontium isotopes the eustatic sea level curves published in the seventies and eighties have supported scientific advances in the earth sciences and the emergence of sequence stratigraphy as an important hydrocarbon exploration tool however validity of reconstructions of eustatic sea level based on sequence stratigraphic correlations has remained controversial proposed sea level curves differ because of site to site changes in local tectonics depositional rates and long wavelength dynamic topography resulting from mantle convection in particular the overall amplitude of global phanerozoic long term sea level is poorly constrained and has been estimated to vary between 400 m above present day sea level to 50 m below present day sea level to improve estimates of past sea level we explore an alternative methodology to estimate global sea level change we utilise the phanerozoic neoproterozoic 87sr 86sr record which at first order represents the mix of inputs from continental weathering and from mantle input by volcanism by compensating for weathering with estimates of runoff from a 3d climate model geoclimtec a corrected 87sr 86sr record can be obtained that solely reflects the contribution of strontium from mantle sources at first order the flux of strontium from the mantle through time is due to increases and decreases in the production of oceanic crust through time therefore the changing levels of mantle derived strontium can be used as a proxy for the production of oceanic lithosphere by applying linear oceanic plate age distributions we compute sea level and continental flooded area curves we find that our curves are generally within the range of previous curves built on classical approaches a phanerozoic first order cyclicity of 250 myr is observed that may extend into the neoproterozoic the low frequency i e on the order of 10 to 100 my sea level curve that we propose while open for improvement may be used as baseline for refined sequence stratigraphic studies at a global and basin scale

hydraulic stimulation of natural fractures as revealed by induced microearthquakes carthage cotton valley gas field east texas we produced a high resolution microseismic image of a hydraulic fracture stimulation in the carthage cotton valley gas field of east texas we improved the precision of microseismic event locations four fold over initial locations by manually repicking the traveltimes in a spatial sequence allowing us to visually correlate waveforms of adjacent sources the new locations show vertical containment within individual targeted sands suggesting little or no hydraulic communication between the discrete perforation intervals simultaneously treated within an 80 m section treatment i e fracture zone lengths inferred from event locations are about 200 m greater at the shallow perforation intervals than at the deeper intervals the highest quality locations indicate fracture zone widths as narrow as 6 m similarity of adjacent source waveforms along with systematic changes of phase amplitude ratios and polarities indicate fairly uniform source mechanisms fracture plane orientation and sense of slip over

characterization of fractures and faults a multi component passive microseismic study from the ekofisk reservoir fractures and faults within a reservoir can provide important pathways for the movement of reservoir fluids understanding the character and properties of these features on a range of length scales can be vital for the efficient exploitation of natural resources whether it be enhanced oil and gas recovery the safe storage of co2 o r better exploitation of geothermal heat the monitoring of microseismicity within a reservoir illuminates active faults but these events can be also used to characterize fracture networks through measurements of seismic anisotropy in this study we use microseismic data acquired over an 18 day period in april 1997 at the ekofisk oil field in the north sea using the analysis of seismic multiplets we delineate a number of sub vertical tectonic faults which are consistent with previous core data analysis and seismic reflection work we use shear wave splitting measurements which are indicative of fracture induced seismic anisotropy to infer the orientation of aligned aseismic fracture sets within the reservoir the estimated fracture dip and strike from the shear wave splitting analysis are consistent with the active tectonic fractures characterized by the multiplets but this analysis also illuminates spatial variations in fracture properties such monitoring on a longer term and with multiple wells is a promising tool for better understanding fracture and fault controlled flow within reservoirs

sequence stratigraphic analysis in deep water underfilled nw european passive margin basins sequence stratigraphic analysis is now carried out routinely on mesozoic cenozoic sedimentary basins with a view to understanding their post rift stratal geometries and predicting facies architecture the conventional method embodies two concepts the physical division of strata into unconformity bounded units and their genetic interpretation on the assumption that hierarchical changes in sea level represent the primary control on sedimentary architecture the genetic model is reflected in a complex descriptive terminology and derives from the development of the method in shallow water basins where the results of analyses typically accord with geological data constraints applied to deep water underfilled basins however the sea level assumption yields results that are unsatisfactory and in many cases misleading reflecting the influence of additional controls including tectonic movements deep sea currents and climate e g glaciation on stratal geometries and facies architecture this is illustrated by comparative analyses of examples from the deep water cenozoic basins of the nw european atlantic passive margin which contain a set of seismic megasequences bounded by unconformable to conformable surfaces correlative from shelf to slope to basinal settings the deep water successions contain regional locally diachronous submarine unconformities that were generated in response to changes in deep water current circulation and slope processes rather than subaerial erosion these bound aggradational contourite drifts that include upslope accretion against basin margins the deep water successions interfinger at two levels with seaward prograding shelf slope wedges that reflect differential tectonic movements involving coeval uplift and subsidence the youngest wedges formed in the last 4 ma and record seaward progradation of the margin by up to 100 km overprinting high amplitude variations in sea level and coeval with changes in deep ocean currents sediment supply by fluvial sources gave way in the pleistocene to direct glacial sediment supply to the slope in all these instances the stratal geometries and facies architecture cannot be attributed to a simple lowering of regional sea level but instead reflect a complex interplay of controlling factors including tectonic movements changes in sediment supply deep water current activity and climate in addition to sea level sequence stratigraphic analysis in such settings must recognise and evaluate alongslope downslope and vertical components of sediment supply

data acquisition design for microseismic monitoring microseismic monitoring of hydraulic well treatments is one of the most useful seismic techniques that can aid the development of tight gas and shale gas fields the main challenge in these fields is an extremely low formation permeability which lies in the microdarcy or even nanodarcy range and requires thousands of closely spaced wells to drain the reservoir for example the barnett field in texas usa has more than 12 000 producing wells depending on the specifics of a given reservoir it might be developed via vertical or slanted or horizontal wells or any combination thereof such varied well geometries and relatively small well spacing provide ample opportunities for microseismic surveys

the regional time and magnitude predictable model and its application to the alpine himalayan belt abstract the regional time and magnitude predictable model has been introduced and has been shown to be appropriate to describe the behaviour in the occurrence of mainshocks the model implies that the magnitude of the preceding mainshock in a seismogenic region that is the largest earthquake during a seismic excitation governs the time of occurrence and the magnitude of the expected mainshock in this region this model has been applied in 149 seismogenic regions of the alpine himalayan seismic belt the model probability for the occurrence of the next very strong main shock ms 6 5 during the decade 1993 2002 as well as the magnitude of this shock in each of these regions have been calculated furthermore two tests have been performed to check the validity of this model these tests have shown the reliability of the model and its superiority compared to the classical time independent model

locating microearthquakes induced by hydraulic fracturing in crystalline rock microearthquakes induced by hydraulic fracturing in crystalline rock at a depth of 3 5 km were located with a precision of better than 30 m to obtain information about the geometry and dimensions of the fracture system produced the induced microseismicity was monitored by a network of five vorehole seismic stations a total of about 800 induced events were reliably located from arrival times event locations show a tabular distribution that strikes 350 sup 0 and dips 65 sup 0 east subparallel to the injection well the injection was intended to produce a fracture system that would hydraulically connect two subparallel wells a lack of fluid communication between them is consistent with a lack of induced microearthquakes near the target wellbore the 150 m thickness of the zone of seismicity far exceeds the relative locational uncertainties the injected fluid appears to have stimulated a zone of rock rather than simply a single fracture the distribution of microseismic events presumably envelopes the zone of fluid paths created by the fracture experiment

synchronous global sequence boundaries sedimentary sequences in marine basins develop in response to relative changes in sea level sequence development in individual basins may be satisfactorily explained by a combination of tectonic subsidence and long period changes in global sea level it has been argued however that apparently synchronous shoreline shifts in widely separated basins require actual fluctuations in the global sea level curve with a period of 1 10 m y we suggest a mechanism for producing synchronous relative sea level changes in widely separated and geologically independent basins without producing changes in all basins and without requiring short period fluctuations in the global sea level curve the same mechanism can produce nonsynchronous but related shoreline shifts in separate bas ns while the rate of global sea level change remains constant

an earthquake doublet in ometepec guerrero mexico on june 7 1982 an earthquake doublet occurred in a gap near ometepec guerrero mexico which had been given a high seismic potential the two earthquakes first event m s 6 9 m b 6 0 16 3 n 98 4 w d 25 km second event m s 7 0 m b 6 3 16 4 n 98 5 w d 8 km of the doublet occurred within five hours of each other we determine the source parameters of these events by inverting surface wave data at a period of 256 s the results are for the first event strike 116 dip 77 slip 88 and seismic moment of 2 8 10 26 dyne cm and for the second event strike 116 dip 78 slip 89 and seismic moment of 2 8 10 26 dyne cm modeling of long period p waves suggests that the first event has a depth of 20 km and is represented by a single trapezoidal source time function with an effective duration of 6 s the second event is best modeled by two sources at depths of 15 and 10 km the combined effective source duration time for the two sources is about 10 s the ratio of the seismic moment obtained from body waves to that from surface waves is 0 5 for the first event and 1 for the second adding the seismic moment of the two events and considering the first week aftershock area 3200 km 2 the stress drop is 4 bars these results suggest that the first event that involved a deeper asperity caused an incremental stress change large enough to trigger the second event if the two events of the doublet broke distinct areas of the subduction zone the coseismic slip is 0 58 m and accounts for about 25 of the total plate motion between the cocos plate and the north america plate accumulated since the last large earthquake in the region other doublets similar to the ometepec doublet have occurred along the middle america trench during the past 70 years a regional distribution of comparable size asperities may be responsible for this relatively frequent occurrence of doublets and for the simplicity of earthquakes in the region the high convergence rate which produces rapid strain accumulation and short recurrence intervals for large earthquakes and the smooth sea floor subducted along the middle america trench may contribute to the homogeneous distribution of comparable size asperities we found a relation log t 1 3 log m 0 t is the average recurrence time and m 0 is the average seismic moment for large earthquakes along the subduction zone in the guerrero oaxaca region where the convergence rate and the properties of the subducted plate are considered relatively uniform a simple asperity model predicts this relation