inversion of complex body waves we have developed a method that inverts seismic body waves to determine the mechanism and rupture pattern of earthquakes the rupture pattern is represented as a sequence of subevents distributed on the fault plane this method is an extension of our earlier method in which the subevent mechanisms were fixed in the new method the subevent mechanisms are determined from the data and are allowed to vary during the sequence when subevent mechanisms are allowed to vary however the inversion often becomes unstable because of the complex trade offs between the mechanism the timing and the location of the subevents many different subevent sequences can explain the same data equally well and it is important to determine the range of allowable solutions some constraints must be imposed on the solution to stabilize the inversion we have developed a procedure to explore the range of allowable solutions and appropriate constraints in this procedure a network of grid points is constructed on the i plane where and i are respectively the onset time and the distance from the epicenter of a subevent the best fit subevent is determined at all grid points then the correlation is computed between the synthetic waveform for each subevent and the observed waveform the correlation as a function of and i and the best fit mechanisms computed at each i grid point depict the character of allowable solutions and facilitate a decision on the appropriate constraints to be imposed on the solution the method is illustrated using the data for the 1976 guatemala earthquake

acceleration spectra for subduction zone earthquakes we estimate the source spectra of shallow earthquakes from digital recordings of teleseismic p wave groups that is p pp sp by making frequency dependent corrections for the attenuation and for the interference of the free surface the correction for the interference of the free surface assumes that the earthquake radiates energy from a range of depths we apply this spectral analysis to a set of 12 subduction zone earthquakes which range in size from ms 6 2 to 8 1 obtaining corrected p wave acceleration spectra on the frequency band from 0 01 to 2 0 hz seismic moment estimates from surface waves and normal modes are used to extend these p wave spectra to the frequency band from 0 001 to 0 01 hz the acceleration spectra of moderate subduction zone earthquakes that is earthquakes whose seismic moments are less than 1027 dyn cm exhibit square or brune type spectra while the acceleration spectra of large subduction zone earthquakes that is earthquakes whose seismic moments are greater than 1027 dyn cm exhibit intermediate slopes where u 5 4 for frequencies from 0 005 to 0 05 hz for this set of earthquakes spectral shape appears to be a discontinuous function of seismic moment using reasonable assumptions for the phase characteristics we transform the spectral shape observed for large earthquakes into the time domain to fit ekstrom s 1987 moment rate functions for the ms 8 1 michoacan earthquake of september 19 1985 and the ms 7 6 michoacan aftershock of september 21 1985

mapping the rupture process of moderate earthquakes by inverting accelerograms we present a waveform inversion method that uses recordings of small events as green s functions to map the rupture growth of moderate earthquakes the method fits p and s waveforms from many stations simultaneously in an iterative procedure to estimate the subevent rupture time and amplitude relative to the green s function event we invert the accelerograms written by two moderate parkfield earthquakes using smaller events as green s functions the first earthquake m 4 6 occurred on november 14 1993 at a depth of 11 km under middle mountain in the assumed preparation zone for the next parkfield main shock the second earthquake m 4 7 occurred on december 20 1994 some 6 km to the southeast at a depth of 9 km on a section of the san andreas fault with no previous microseismicity and little inferred coseismic slip in the 1966 parkfield earthquake the inversion results are strikingly different for the two events the average stress release in the 1993 event was 50 bars distributed over a geometrically complex area of 0 9 km2 the average stress release in the 1994 event was only 6 bars distributed over a roughly elliptical area of 20 km2 the ruptures of both events appear to grow spasmodically into relatively complex shapes the inversion only constrains the ruptures to grow more slowly than the s wave velocity but does not use smoothness constraints

teleseismic time functions for large shallow subduction zone earthquakes broadband vertical p wave records are analyzed from 63 of the largest shallow subduction zone earthquakes which have occurred in the circum pacific in the last 45 yr most of the records studied come from a common instrument the pasadena california benioff 1 90 seismometer propagation and instrument effects are deconvolved from the p wave records using a damped least squares inversion to obtain the teleseismic source time function the inversion has the additional constraint that the time function be positive everywhere the period band over which the time functions are considered reliable is from 2 5 to 50 sec fourier displacement amplitude spectra computed for each of the 1 90 p wave trains indicate spectral slopes measured between 2 and 50 sec of 1 0 to 2 25 with an average value of 1 5 these values assume an average attenuation of t 1 0 the seismic moments derived from the p wave time functions compare well with other published values for earthquakes having moments smaller than 2 5 10 28 dyne cm m w 8 2 because the 1 90 seismometer has little response at very long periods this technique underestimates the moments of the very largest events the time functions are characterized using five parameters 1 spectral slope between 2 and 50 sec 2 roughness of the time function 3 multiplicity of sources 4 pulse widths of individual sources and 5 overall signal duration the 63 earthquakes studied come from 15 subduction zones with a wide range in the ages of subducted lithosphere convergence rates and maximum size of earthquakes comparing the time function parameters with age rate and m w of the subduction zone does not yield obvious global trends however most of the subduction zones do behave characteristically and can be grouped accordingly

empirical green s functions from small earthquakes a waveform study of locally recorded aftershocks of the 1971 san fernando earthquake seismograms from 52 aftershocks of the 1971 san fernando earthquake recorded at 25 stations distributed across the san fernando valley are examined to identify empirical green s functions and characterize the dependence of their waveforms on moment focal mechanism source and recording site spatial variations recording site geology and recorded frequency band recording distances ranged from 3 0 to 33 0 km hypocentral separations ranged from 0 22 to 28 4 km and recording site separations ranged from 0 185 to 24 2 km the recording site geologies are diorite gneiss marine and nonmarine sediments and alluvium of varying thicknesses waveforms of events with moment below about 1 5 1021 dyn cm are independent of the source time function and are termed empirical green s functions waveforms recorded at a particular station from events located within 1 0 to 3 0 km of each other depending upon site geology with very similar focal mechanism solutions are nearly identical for frequencies up to 10 hz there is no correlation to waveforms between recording sites at least 1 2 km apart and waveforms are clearly distinctive for two sites 0 185 km apart the geologic conditions of the recording site dominate the character of empirical green s functions even for source spatial separations of up to 20 0 km the empirical green s functions at a particular site are consistent in frequency content amplification and energy distribution therefore it is shown that empirical green s functions can be used to obtain site response functions the observations of empirical green s functions are used as a basis for developing the theory for using empirical green s functions in deconvolution for source pulses and synthesis of seismograms of larger earthquakes

modelling of active lineaments for predicting a possible earthquake scenario around dehradun garhwal himalaya india abstract the doon valley which consists of the doon gravels and siwalik rocks is surrounded by the main boundary thrust mbt in the north the main frontal thrust mft mohand thrust and bhimgoda thrust in the south the ganga tear fault in the east and the yamuna tear fault in the west lineaments identified from the aerial photographs show that a few of them trend parallel to the himalayan orogen and the others are transverse to it the effect of the neotectonic activity is clearly reflected in the doon valley implying that the doon valley is tectonically unstable today and that the possibility of earthquakes in this region cannot be ruled out the ruptures along identified active lineaments are modelled three dimensionally peak accelerations are obtained by using a methodology based on the semi empirical method of irikura which was used by midorikawa the efficacy of this modelling technique for the himalayan region is established by simulating peak ground accelerations for the uttarkashi earthquake of 20 october 1991 and comparing it with recorded one a seismic study of the region shows that it is prone to moderate as well as great earthquakes the technique of midorikawa has been applied for the preparation of zonation maps in this seismically active region two different zonation maps showing respectively the effects of moderate as well as great earthquakes in this region are presented in this paper the zonation map for moderate earthquakes shows that the region can experience peak ground accelerations around 310 cm s2 this value is close to the peak ground acceleration of 304 cm s2 recorded for the uttarkashi earthquake ms 7 1 at uttarkashi station which is about 60 km north of dehradun the prepared map shows that among all identified active lineaments rupture along four lineaments can cause major damage in the region among these four three lineaments are transverse to the major tectonic zones viz the mft and mbt in the region and one extends along the mft lying south of dehradun the zonation map for great earthquakes m 8 has been prepared by modelling a rupture in the central gap region of the himalaya seven different possibilities of rupture nucleation within the rupture plane are modelled and a zonation map containing three different zones is prepared the prepared zonation map for this worst possible scenario shows that cities like tehri uttarkashi srinagar deoprayag pauri and dehradun fall within zone 1 and can experience ground accelerations bigger than 600 cm s2 the region like hardwar and rishikesh fall within zone 2 and can experience ground accelerations around 300 cm s2 the zonation map shows that tehri can experience accelerations up to 0 84g and this value is comparable with that obtained by other researchers this study confirms that for very long periods the destruction in the region will be dominantly affected by ruptures having longer lengths and least effected by shorter ruptures therefore special consideration about the longer ruptures should be taken while considering effect of earthquake hazards in this region

the rupture process and asperity distribution of three great earthquakes from long period diffracted p waves moment tensor source mechanisms for the largest twenty nine shallow earthquakes from 1981 m s 6 5 have been determined using long period rayleigh wave spectra and p wave first motions recorded by the international deployment of accelerograms ida global digital seismic network gdsn and world wide standardised seismic network wwssn these are compared with the centroid moment tensor mechanisms presented by dziewonski and woodhouse which were obtained in a contrasting manner in most cases the source is well represented by a single double couple mechanisms with good agreement of scalar moment and orientation between the two studies apparent mismatches for other cases may be interpreted in terms of source complexity we emphasise the objectivity of comparing moment tensor elements apparent discrepancies in the moment and orientation of double couple fault plane solutions are usually due to differences in the mxz and myz moment tensor elements which are poorly constrained by long period data

routine estimation of earthquake source complexity the 18 october 1992 colombian earthquake we describe two methods suitable for routine application to tele seismic recordings that characterize the time history of seismic events stacking short period signals from large regional arrays provides stable estimates of high frequency radiation from the source and an empirical green s function decon volution procedure extracts reliable broadband time functions suitable for anal ysis of faulting complexity and the spatio temporal extent of rupture combined these procedures characterize the source radiation of large events ms 7 be tween 200 and 0 5 sec periods

teleseismic and strong motion source spectra from two earthquakes in eastern taiwan the 20 may and 14 november 1986 hualien earthquakes occurred in a seismically active region of taiwan locally determined focal mechanisms and aftershock patterns from the taiwan telemetered seismographic network indicate that both earthquakes occurred on steeply dipping reverse faults that trend nne this agrees with teleseismic first motion data for the may event but not for the november event this discrepancy is due to a moderate foreshock before the november event surface wave analysis gives a solution for the november event of dip 57 rake 100 and strike 43 which is similar to the locally reported focal mechanism the seismic moment of the november event is m 0 1 7 10 27 dynecm and the magnitudes determined from wwssn data are m b 6 4 m s 7 3 teleseismic source spectra show that the two events also have similar spectral signatures above 0 15 hz reference acceleration spectra are computed from the average teleseismic source spectra and compared to the averaged acceleration spectra computed from strong motion stations for both events correlations between the spectral amplitudes of the strong motion spectra obtained from the main portion of the smart 1 array and the teleseismically estimated reference spectra are poor above 0 2 hz data from the hard rock site situated outside of the basin indicates that amplification of the ground motion between 0 17 1 7 hz is due to the alluvial valley where the smart 1 array is located the amplitude of the observed spectrum is five times the reference spectrum at the hard rock site this is consistent with similar observations from the 1985 michoacan and 1983 akita oki earthquakes the analysis of these and more teleseismic and strong motion records will lead to a better understanding of the relationship between their spectra

the earthquake sequence of november 1987 and march 1988 in the gulf of alaska a new insight new information has been obtained by reanalyzing the rupture process of three large strike slip earthquakes that occurred in the gulf of alaska on november 17 and 30 1987 and march 6 1988 we used spectral analysis of p waves complemented with a simple technique for inverting body waves using a fixed source mechanism our results show that the ms 7 0 event of november 17 which can be considered to be a foreshock to the november 30 event consisted of two pulses of large seismic moment release the first one with a duration of 15 sec coincides with those obtained by other studies the second which occurs 20 sec after the first arrival is clearly visible on the records but was not previously reported the ms 7 4 earthquake of november 30 is a complex event that ruptured on a fault plane trending north south the ms 7 7 shock of march 6 1988 was a simple event along the same north south trend south of the november events p wave far field spectra exhibit an 1 intermediate trend between the usual 0 and 2 slopes this trend is due to rupture along a long narrow fault so the corner frequency associated with this intermediate trend is related to the reciprocal of rupture propagation time we suggest that these events were due to a tear in the pacific plate

comparison of strong motion spectra with teleseismic spectra for three magnitude 8 subduction zone earthquakes we studied strong motion spectra observed for three m w 7 8 to 8 0 earthquakes the 1985 michoacan mexico 1985 valparaiso chile and 1983 akita oki japan earthquakes we determined the decay of spectral amplitude with distance from the station considering different measures of distance from a finite fault we compared strong motion spectra fourier acceleration spectra observed for these three earthquakes with those estimated from the source spectrum determined from teleseismic p waves we scaled the teleseismic source spectra to produce reference strong motion spectra at periods from 1 to 10 sec using a simple physical model of far field s body waves from a point source recorded at the surface of a homogeneous half space for all three earthquakes the reference spectral amplitudes at periods of 1 to 5 sec are about half the observed ones at distances of about 50 km the difference increases as the distance increases at distances of 200 to 300 km the reference spectrum is about 1 10 of the observed one the difference between the reference and the observed spectrum is attributed to the contribution of phases other than direct s waves and to site response we applied corrections for the finiteness spatial extent of the source using a simple model of rupture propagation on a dipping two dimensional fault including the source finiteness did not improve the estimate substantially at periods from 1 to 20 sec but it modeled significant changes in the signal duration as a function of azimuth for the 1985 michoacan earthquake our results can be used to establish empirical relations between the observed spectra and the half space responses depending on the distance and the site condition if such empirical relations can be established source spectra determined from teleseismic records may be used to estimate strong motions

estimates of 1 hz maximum acceleration in bulgaria for seismic risk reduction purposes abstract the regional seismic hazard in bulgaria is assessed using a deterministic approach which computes synthetic seismograms at a set of grid points the input for this computation is represented by available source and structural models a set of simplified structural models is proposed for bulgaria and assigned to a number of regional polygons the set of seismic sources are parametrized using the knowledge about the focal mechanisms the seismogenic areas and the regional seismicity a map of the maximum ground acceleration amax is chosen to represent the shakeability and the seismic hazard the most dangerous area of the country is confirmed as southwestern bulgaria

long period ground motion at bedrock level in delhi city from himalayan earthquake scenarios delhi the capital of india is prone to severe seismic hazards not only from local events but also from himalayan earthquakes at distances of 250 300 km standard techniques are not sufficiently reliable to completely characterize the seismic hazards in this case due to the difficulty of predicting the occurrence of earthquakes frequency magnitude relations and of properly treating the propagation of their effects attenuation laws especially their long period components in order to give a sound description of the seismic ground motion due to an earthquake in such a given range of distances and magnitudes we use modelling techniques developed from physics of the seismic source generation and propagation processes such models take into account the directivity effect of rupture propagation and the attenuation of long period ground motions the generated ground motion scenarios permit us to build a very important knowledge base to be fruitfully used by civil engineers since long period ground motions especially if amplified by deep sedimentary basins can represent a severe threat for large scale structures e g lifelines and bridges and tall buildings which are widespread in fast growing megacities in this study we simulate the ground motion at bedrock level in delhi city for an earthquake scenario corresponding to a source of mw 8 0 located in the central seismic gap of himalayas at an epicentral distance of about 300 km from delhi city by means of several parametric studies we simulate the time histories using size scaled point source space and time scaled point source and extended source models together with the complete time histories displacements velocities and accelerations from which the peak amplitudes have been extracted we have also used the displacement response spectrum to characterize the seismic input at delhi not only is the displacement response spectrum of great significance to modern displacement based design engineering approaches but it is probably the best parameter by which to characterize the destructiveness potential of earthquakes located at such great distances from the target sites of the order of 300 km since the energy of the seismic input is mainly concentrated at long periods in general greater than 1 s and it cannot be determined by straightforward integration of velocity or acceleration response spectra

estimation of response spectra of earthquake ground motion based on an attenuation equation with detailed analysis of source and site effects characterized green s function method cgfm a new approach for estimating the response spectra of earthquake ground motion has been proposed by oji et al 2012 the cgfm is based on the concept that the spatial average of estimated results is equal to a conventional attenuation model the site specific deviations can be modeled by the source rupture effects such as directivity pulses and radiation patterns which are represented by the frequency dependent factors obtained from a superposition of simple characterized waveforms obeying the omega square model in this article we expand the cgfm to include nonlinear site response at a specific site this response is calculated using the estimated time history of ground motion on the engineering basement from the response spectrum and the simulated phase waveform obtained by the original cgfm the proposed cgfm is verified by comparing the estimated results with the records from the 1995 kobe and the 2007 chuetsu oki earthquakes japan

tracking unilateral earthquake rupture by p wave polarization analysis summary rapid estimation of earthquake rupture propagation is essential to declare an early warning for tsunami generating earthquakes an increasing number of seismological methods have been developed to determine rupture parameters such as length velocity and propagation direction especially since the occurrence of the sumatra andaman earthquake that resulted in a devastating tsunami in the indian ocean region here we present a new method to follow the rupture process in near real time by a polarization analysis of local and regional p phases that permits a faster determination of rupture properties than using teleseismic records the new technique has the capability to provide detailed information in less than 10 min originally the method stems from a single station earthquake location method and is expanded here to monitor p phase polarization variations through time as the earthquake source moves away from the hypocentre the backazimuth of an incoming p phase is expected to change accordingly with polarization analysis we may be able to monitor the temporal change in p wave backazimuth to follow the rupture process in near real time three component p phases are scanned to determine the azimuthal variation as a function of time the backazimuth of a moving rupture front is determined by the first eigenvector of the covariance matrix the linearity of the particle motion is used as a measure of the quality of the data seismic stations at local and regional distances are used we tested the new method with a theoretical simulation and observed seismograms of the sumatra andaman earthquake 2004 december 26 mw 9 3 and we were able to follow the rupture for the first 200 s for larger ruptures stations at more than 30 epicentral distances would be required the method is also successfully applied to the wenchuan earthquake 2008 may 12 mw 8 0

estimation of near source ground motions from a teleseismically derived rupture model of the 1989 loma prieta california earthquake abstract a rupture model for the 1989 loma prieta earthquake obtained from inversion of teleseismic body waves is used to calculate the mainshock near source strong ground motions the effectiveness of both synthetic and empirical aftershock green9s functions is evaluated in terms of velocity response spectra over the period range from 0 1 to 10 sec a strictly deterministic approach is used in the simulation of near source ground motion with both the synthetic and aftershock green9s functions a deterministic method has advantages in that it is simple to apply and there is no stochastic element to introduce variability in the solution response spectral values are very sensitive to the choice of the mainshock source time function using a 1 0 sec triangular time function obtained from the teleseismic study gives good estimates of response spectra from 1 to 2 sec period for aftershock green9s functions and from 1 to 10 sec period for synthetic green9s functions the limited long period response of the aftershock summations is due to the restricted bandwidth of the recording sensor using a 0 5 sec kostrov time function extends the bandwidth of validity of the aftershock summations to 0 1 to 2 sec period and the synthetic green9s function summations to 0 3 to 10 sec period the limited short period bandwidth of the synthetic green9s function summations is due to the lower frequency content 5 hz and absence of accurate high frequency propagation effects in the synthetic seismograms although the teleseismic study could not distinguish between a 1 0 sec triangular time function and a 0 5 sec kostrov time function we feel justified in using the kostrov function because it lies within our broader knowledge of earthquake source time functions

rupture process of the 2004 sumatra andaman earthquake the 26 december 2004 sumatra andaman earthquake initiated slowly with small slip and a slow rupture speed for the first 40 to 60 seconds then the rupture expanded at a speed of about 2 5 kilometers per second toward the north northwest extending 1200 to 1300 kilometers along the andaman trough peak displacements reached 15 meters along a 600 kilometer segment of the plate boundary offshore of northwestern sumatra and the southern nicobar islands slip was less in the northern 400 to 500 kilometers of the aftershock zone and at least some slip in that region may have occurred on a time scale beyond the seismic band

the rupture process of the 1976 mindanao earthquake the large mindanao earthquake mw 8 1 of august 16 1976 presents a complex rupture history the epicenter of this earthquake is located at the southern end of the 160 80 km2 aftershock area and the thrust mechanism with a shallow ne dipping plane indicates the subduction of the north celebes sea beneath mindanao we have characterized both temporally and spatially the rupture process of this event by deconvolving the source time functions from long period p wave seismograms at 20 azimuthally well distributed stations the seismic moment is released in a jagged fashion in two main pulses the observable directivity associated with these two pulses of moment release defines three segments on the fault 1 from 0 to 54 km n nw of the epicenter with of the moment release and an apparent rupture velocity of 2 0 km s 2 from 54 to 72 km n nw of the epicenter with low to no resolvable moment release and an apparent rupture velocity of 0 8 km s and 3 from 72 to 157 km n nw of the epicenter with of the moment release and a rupture velocity of 3 3 km s although the overall moment release is comparable in the first and second pulses the second pulse has a substantially higher rupture velocity and a higher level of short period radiation the sharp truncation of the second pulse generates the largest amplitudes in the p wave seismograms and is interpreted as the abrupt termination of the rupture front against mindanao island 160 km n nw of the epicenter an additional third pulse of moment release after the dominant truncation is identified at stations to the nw and se this additional moment release is located on a separate fault to the west which is probably strike slip in nature and related to a large strike slip aftershock along the coast of mindanao the jagged multiple event moment release of the mindanao earthquake is in sharp contrast to the smooth rupture of the 1979 colombia subduction zone earthquake mw 8 2 which resulted from the rupture of a single large asperity 60 km although these two earthquakes are both underthrusting events they occur in very different tectonic settings the mindanao earthquake occurred at a relatively young subduction zone in a region with rapidly evolving plate boundaries whereas the colombia earthquake occurred at a well established plate boundary

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

transition from marine to fluvial dominated sediment supply at shoalhaven prograded barrier southeastern australia abstract prograded barriers are depositional coastal landforms which have the potential to reveal changes in the primary drivers of coastal evolution within their varied morphology beach ridges and intervening swales preserve paleoenvironmental records of coastal processes relative sea level and storm events optically stimulated luminescence osl dating of quartz grains airborne lidar derived morphology and sediment texture and mineralogy reveal four different periods of morpho sedimentary progradation history in the shoalhaven barrier system in southeastern australia the barrier is composed of approximately 40 ridges that occupy an area of 15 2 km2 comprising an estimated sand volume of approximately 88 000 000 m3 above mean sea level osl dating of ten samples taken from a 940 m long transect across the holocene system indicated that the barrier prograded at a slow rate of approximately 0 12 m yr from 6130 330 to 2400 130 years ago and subsequently at a higher rate of 0 22 m yr until 600 130 years ago more recently an increase in historical accumulation and progradation rates has favoured development of an anomalously high foredune fronting the system with the formation of lower ridges in the past two centuries increasing angularity and feldspar content observed via scanning electron microscope sem and determined using x ray diffraction xrd analysis respectively imply a transition in sediment supply progradation has been sustained through delivery and reworking of marine sediments from offshore following the marine transgression subsequently augmented by fluvial sands discharged to the coast by the shoalhaven river the adjustment in progradational rates and sediment provenance influenced the morphology and spacing of individual ridges and the regressive system as a whole average progradation rates for the shoalhaven barrier revised from those previously reported using radiocarbon dating are considered lower than most of barriers studied in similar coastal environments around australia indicating the different ways that similar progradation systems have evolved

excitation of short period body waves by great earthquakes short period seismograms from large earthquakes are generally complex and are hard to fourier analyze an innovation of spectral analysis has been made for wwssn short period seismograms the parameters necessary for the analysis are dominant frequency 0 maximum amplitude amax and a characteristic duration of complicated wave packets spectrum of short period seismograms y is shown to be approximated as y 1 07 0amax the spectrum after correcting for the effects of geometrical spreading unelastic attenuation instrumental response and crustal magnifications is used to retrieve a short period seismic moment m1 of earthquake sources the method has been applied to more than 900 short period seismograms from 79 large earthquakes throughout the world these earthquakes cover the seismic moment m0 from 7 5 1029 to 7 5 1024 dyne cm m1 would not be saturated in this range although body wave magnitude usually is a relation of m0 m12 is obtained for the present data set a relation between m1 and redetermined body wave magnitude m b is also shown log m1 1 24 m b 17 9 where mb is obtained from maximum amplitudes of p wavetrains the analysis method is based on an extension of algorithm of earthquake magnitude determination however it has a potential beyond the body wave magnitude as m1 is related closely to the source excitation of short period seismic waves it is one of the key parameters in understanding the fracture mechanisms of irregular faults

recent large earthquakes along the middle american trench and their implications for the subduction process several large shallow earthquakes ms 7 0 have occurred along the middle american trench since the installation of the wwssn network included are the 1965 1968 and 1978 oaxaca events the 1970 chiapas event the 1973 colima event and the 1979 petatlan event these earthquakes have been studied in an attempt to identify similarities and differences between them that may lead to a better understanding of fracture and subduction processes the events have seismic moments ranging from 1 0 1027 dyne cm for the 1968 event to 3 2 1027 dyne cm for the 1978 event all events are of predominantly thrust type consistent with subduction to the northeast of the cocos plate body waves for the 1965 1968 1978 and 1979 events along the trench indicate rather simple faulting processes these events all had focal depths of 15 to 20 km and stress drops of the order of 10 bars the 1970 and 1973 events the easternmost and westernmost respectively of the events studied here are located close to triple junctions for the cocos north america caribbean plates 1970 and the cocos north america rivera plates 1973 these two events generated more complex body waves than the oaxaca and petatlan quakes this source complexity may have been related to the more complicated tectonics near the 1970 and 1973 epicenters this may offer a new perspective to viewing source complexity in relation to subduction zones

paleoanthropological significance and morphological variability of the human bones and teeth from tabon cave abstract tabon cave is one of the few archaeological sites in island southeast asia which provided upper pleistocene homo sapiens fossils the published osteological material consists in one frontal bone and three mandibular fragments discovered during 1960 fieldworks as well as 11 new human remains unearthed during 2000 2001 excavations however recent efforts to recover and centralize the considerable amount of archaeological specimens and data from 1960s excavations revealed that an unexpected huge number of human bone remains were excavated during this period the collection preserved in the national museum of the philippines includes currently at least 483 human bone remains we propose here a preliminary review of the anatomical representation of the human bones from this collection and a first large scale comparative morphometric analysis focusing on the crown dimensions of six permanent first upper molars um1 this first overview revealed an extreme fragmentation of the bones of the collection resulting in a poorly indicative mni from the bones bearing sufficient diagnostic morphology few immature individuals are present in the assemblage refitting of specimens and observation of broken surfaces indicated that ancient human activity in the cave anterior to the excavation was likely to be an important taphonomic factor of fragmentation of the assemblage our comparative analysis including 339 um1 revealed that two um1 from tabon cave have unusual large dimensions outside the range of variation of submodern southeast asians sean molars of our sample four other um1 from tabon fall in or close to the variability of the philippines negritos we show also that the morphological disparity encountered among the um1 from tabon cave is higher than in other archaeological sites and submodern populations of our sample this confirms previous publications that emphasized important morphological variations and proposed the hypothesis of the presence of two morphotypes although chrono stratigraphic information is lacking because of the disturbed stratigraphic context in which almost the totality of the bones was unearthed unpublished reports and field documents show that robert fox head of the 1960s excavations considered that an important part of this collection might have a pleistocene age given the scarcity of the pleistocene homo sapiens fossil record in island southeast asia sea part of this collection might improve significantly our knowledge of the morphological relatedness and variability of the upper pleistocene homo sapiens in the region

moment spectra in a simple model of an earthquake fault the behavior of a simple one dimensional homogeneous deterministic model of an earthquake fault is examined on the timescale of the rupture process the model generates a complex spatial and temporal distribution of events from a frictional instability i measure the frequency spectra of the moment release rate for events of different sizes and observe power laws for the spectra a bend in the spectra of large events is also observed the paper concludes with a discussion of how these results may be relevant to real earthquake faults

source spectra of great earthquakes teleseismic constraints on rupture process and strong motion short period body waves recorded at teleseismic distances from great earthquakes provide information about source rupture processes and strong motions first we examine mostly wwssn records of 19 earthquakes of moment magnitude m w of 6 5 to 9 5 four parameters are measured from the short period p wave train the maximum amplitude the period at maximum amplitude the time between the first arrival and when the maximum amplitude is attained and coda length an extension m b of the teleseismic magnitude m b is defined using the maximum amplitude of the entire short period p wave rather than the amplitude achieved in the first few p wave cycles a least squares fit to the data yields the following relationship between m b and m w m b 0 53 m w 2 70 for m w 6 5 to 9 5 the time from the first arrival until the maximum amplitude is achieved and the coda length are roughly proportional to m w but are further interpreted by a simple asperity model of the rupture process these data support that short period waves are on average generated preferentially in the same regions of the fault plane as long period waves with periods of 10 to 50 sec we analyze the spectra of short and intermediate period teleseismic gdsn records for seven earthquakes with m w s of 6 4 to 7 8 and hand digitized short period wwssn records of the 1971 san fernando earthquake significant differences exist between the spectra of different events due partly to variations in tectonic setting or seismic coupling using the digital data we also investigate the relationship between time domain amplitude and spectral amplitude for short period p waves from our empirical relation between spectral amplitude and time domain amplitude we estimate the spectral amplitudes implied by the m b data we compare our results to the 2 and gusev spectral models neither model can completely represent the data nevertheless we consider the 2 model a useful reference model for comparing different events the average source spectrum of six large events with m w 7 4 to 7 8 does not have the spectral structure suggested by gusev an application to strong motion modeling is presented in which a 1971 san fernando teleseismic short period record is summed up to simulate teleseismic records produced by five great earthquakes the summation procedure matches the moment of the event to be simulated and includes rupture propagation fault plane roughness and randomness the m b data provide an important constraint on the summation procedures thus constrained this summation procedure can be more confidently used with near field strong motion records as green s functions to predict strong motions from great earthquakes

source process of the chiapas mexico intermediate depth earthquake mw 7 2 of 21 october 1995 abstract on 21 october 1995 we recorded with a local array an earthquake that occurred at a depth of 165 km in the subduction zone of chiapas the harvard focal mechanism solution indicates a normal fault responding to the down dip tension of the subducted oceanic crust this is the first intermediate depth earthquake well recorded with accelerographs and seismometers in southeastern mexico peak ground accelerations pga range from 21 to 436 cm sec 2 at hypocentral distances of 174 to 256 km respectively the recorded pgas are larger than those of the copala guerrero earthquake of 14 september 1995 which was a shallow 16 km thrust fault with a similar magnitude m w 7 4 the large pga generated by the chiapas earthquake are probably due to an enhancement of the signals produced by the up ward intraslab propagation of energy and are similar to those observed from other intermediate depth earthquakes in the subduction zone of japan molas and yamazaki 1995 the duration of the strongest shaking increases from about 10 sec in the southeast at the town of san vicente close to the tacana volcano to nearly 20 sec in the northwest in the city of tuxtla gutierrez located near the epicenter teleseismic p wave inversion using the harvard focal mechanism solution indicates that the seismic moment was released in three events with a total duration of about 20 sec the results of the inversion indicate that the rupture propagated from the northwest to the southeast along a 30 km distance from spectral analysis we calculate a total seismic moment release of 5 2 0 5 10 19 n m equivalent to an m w 7 1 magnitude event using three sources with an average depth of 150 km we were able to reach a reasonable match of the first 40 sec of the displacement records recorded at the broadband seismic stations of huatulco huig and pinotepa nacional pnig for the station located in tuxtla gutierrez tuxd we used two sources since only the first 5 sec were modeled the amplitude spectrum at teleseismic distances follows a typical brune9s 1970 2 model we obtained a corner frequency of 0 045 hz from the spectra which is equivalent to a source radius of 15 km and a stress drop of 65 bars assuming a circular fault

the rupture process of the great 1979 colombia earthquake evidence for the asperity model we have determined the asperity distribution in the segment of the ecuador colombia subduction zone that was ruptured by the 1979 mw 8 2 and 1958 mw 7 7 earthquakes for the 1979 earthquake we are able to document directivity in the p wave source time functions and consequently have spatially located the moment release by combining results from both p wave and surface wave directivity we have defined three regions 1 from 0 to 56 km northeast of the epicenter with low moment release and a small seismic displacement 2 the asperity from 56 to 116 km northeast of the epicenter with most of the moment release and a displacement of 6 m and 3 a small displacement region from 116 to 180 240 km northeast of the epicenter thus the 1979 rupture zone is composed of an asperity 60 km in length bounded by two weak small displacement regions the displacement at the asperity is equal to the cumulative tectonic displacement between 1979 and 1906 the year of the previous great earthquake in this segment the 1958 earthquake is characterized by the rupture of a small asperity length scale approximately 25 km in the epicentral region the 1958 event continued to rupture past this small epicentral asperity and stopped near the epicenter of the following 1979 event this detailed study of the spatial variation in moment release offers strong support for the asperity model of large earthquake occurrence

depth estimates of large earthquakes on the island of hawaii since 1940 although hypocenters of earthquakes on the island of hawaii are now routinely assigned to within 5 km depth was a poorly determined parameter until the early 1960 s however the 1950 1960 period was very active both in volcanic eruptions and large earthquakes source depths for the 12 largest hawaiian earthquakes magnitude 6 or greater since 1940 are estimated from the ratios of body and surface wave amplitudes recorded at pasadena california excitation functions for rayleigh waves are calculated as a function of source depth for the two dominant periods in the pasadena records 8s and 20s theoretical body wave amplitudes are determined from synthetic seismograms calculated ratios are very sensitive to source depth for example amplitudes of 8 s rayleigh waves diminish by a factor of 300 between depths of 10 km and 50 km this is a much larger effect than the fault geometry which we estimate to be a factor of 4 between representative focal mechanisms estimated depths for post 1960 earthquakes agree fairly well with the instrumental depths in general large earthquakes near the volcanic flanks and fault systems are shallow 20 km two earthquakes of magnitude 6 occurred under the volcanoes mauna loa in 1950 and kilauea in 1951 they preceded major eruptions by 3 days and 14 months respectively and had the largest depth estimates at 40 55 km and 35 50 km ms values assigned from global amplitudes are compared with those assigned from pasadena amplitudes alone for 70 events in 1973 1974 with 5 1 m s 6 0 the global values are only slightly larger 0 05 magnitude units than the pasadena values indicating that pasadena amplitudes are on the average representative of the event magnitude

source mechanism of two 1994 intermediate depth focus earthquakes in guerrero mexico abstract in may and december 1994 two medium size intermediate depth focus earthquakes occurred in guerrero mexico eastward of the rupture area of the great michoacan earthquake of september 19 1985 even though these are not major earthquakes 6 4 m w they were widely felt through central and southern mexico with minor damage at zihuatanejo and acapulco located along the pacific coast and mexico city both earthquakes separated by 100 km have similar focal depths and magnitudes however their focal mechanisms based upon the polarities of first arrivals show some differences the may earthquake shows a clear normal faulting mechanism 307 55 108 whereas the december earthquake mechanism solution suggests an initial thrust faulting 313 62 98 process although previous analysis including local and teleseismic stations reported a normal faulting for the december earthquake we find that modeling using the cmt focal mechanism solution fails to reproduce the first 5 sec of the observed p wave signal at the nearest broadband station 168 km and the s wave polarity at two strong ground motion local stations 32 53 km in fact the best fit for these stations is obtained using the thrust focal mechanism calculated from the first motion method seismic moment value and rupture duration time deduced from the teleseismic spectral analysis are 2 0 10 18 n m and 6 9 sec for the may event 2 8 10 18 n m and 7 1 sec for the december earthquake from the inferred seismic moment an average of 15 bars for both earthquakes is obtained inversion of teleseismic p wave data indicates a better fit using the cmt focal mechanism solution normal faulting than the first motion mechanism for both earthquakes although the adjustment9s differences are small for the may event for this earthquake the rupture consisted of two sources separated by 7 sec starting at a depth of 40 km and then propagating downdip reaching a depth of 60 km the december earthquake however released all its energy at a depth of 50 km in two main sources separated by 10 sec the non double couple components values are 0 004 and 0 01 for the may and december events respectively indicating that the december shock has a small contribution of non double couple radiation that could be the result of a changing mechanism this result agrees with the hypothesis that a slab subducting at a shallower angle our case is associated with the existence of random subfaults with different fault orientations from a tectonic point of view the complexity of the december earthquake could be the result of the observed complexity of the stress distribution around 101 w and the existence of compressional events beneath the normal faulting earthquakes near the coastline this feature permits the flexural stresses associated to the slab bending upward to become subhorizontal at the guerrero region we conclude that the may earthquake corresponds to a pure normal faulting whereas the december shock is a complex event with a variable fault geometry

complexity of rupture in large strike slip earthquakes in turkey complexity of rupture propagation has an important bearing on the state of stress along the earthquake fault plane and on the prediction of strong ground motion in the near field by studying far field body waveforms recorded by wwssn long period seismograms it has been possible to investigate the degree of complexity of several turkish earthquakes the results which are obtained by matching synthetic p waveforms to observed data indicate that the july 22 1967 mudurnu valley earthquake m s 7 1 is a complex event which can be explained by the superposition of elementary sources with variable amplitudes and source time sequence history in this regard it is very similar to the february 4 1976 guatemala earthquake m s 7 5 a comparison of these two events indicates that their source time series ranges from 5 to ca 20 s and regardless of the total moment of the earthquake the moment of the individual events is bounded at around 5 10 26 dyn cm the november 24 1976 e turkey earthquake m s 7 3 on the other hand has a complexity which cannot be explained by such a simple model in this respect it may be more similar to the tangshan china earthquake and as such may involve significant thrust normal or other complications to its faulting mechanism than the strike slip mechanism of the p wave first motion data the source time history for the 1967 mudurnu valley event is used to illustrate its significance in modeling strong ground motion in the near field the complex source time series of the 1967 event predicts greater amplitudes 2 5 larger in strong ground motion than a uniform model scaled to the same size for a station 20 km from the fault such complexity is clearly important in understanding what strong ground motion to expect in the near field of these and other continental strike slip faults such as the san andreas

inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 imperial valley california earthquake a least squares point by point inversion of strong ground motion and teleseismic body waves is used to infer the fault rupture history of the 1979 imperial valley california earthquake the imperial fault is represented by a plane embedded in a half space where the elastic properties vary with depth the inversion yields both the spatial and temporal variations in dislocation on the fault plane for both right lateral strike slip and normal dip slip components of motion inversions are run for different fault dips and for both constant and variable rupture velocity models effects of different data sets are also investigated inversions are compared which use the strong ground motions alone the teleseismic body waves alone and simultaneously the strong ground motion and teleseismic records the inversions are stabilized by adding both smoothing and positivity constraints the moment is estimated to be 5 0 10 25 dyne cm and the fault dip 90 5 dislocation in the hypocentral region south of the united states mexican border is relatively small and almost dies out near the border dislocation then increases sharply north of the border to a maximum of about 2 m under interstate 8 dipslip motion is minor compared to strike slip motion and is concentrated in the sediments the best fitting constant rupture velocity is 80 per cent of the local shear wave velocity however there is a suggestion that the rupture front accelerated from the hypocenter northward the 1979 imperial valley earthquake can be characterized as a magnitude 5 earthquake at the hypocenter which then grew into or triggered a magnitude 6 earthquake north of the border

global omori law decay of triggered earthquakes large aftershocks outside the classical aftershock zone 1 triggered earthquakes can be large damaging and lethal as evidenced by the1999 shocks in turkey and the 2001 earthquakes in el salvador in this study earthquakes with ms 7 0 from the harvard centroid moment tensor cmt catalog are modeled as dislocations to calculate shear stress changes on subsequent earthquake rupture planes near enough to be affected about 61 of earthquakes that occurred near defined as having shear stress change 0 01 mpa the ms 7 0 shocks are associated with calculated shear stress increases while 39 are associated with shear stress decreases if earthquakes associated with calculated shear stress increases are interpreted as triggered then such events make up at least 8 of the cmt catalog globally these triggered earthquakes obey an omori law rate decay that lasts between 7 11 years after the main shock earthquakes associated with calculated shear stress increases occur at higher rates than background up to 240 km away from the main shock centroid omori s law is one of the few time predictable patterns evident in the global occurrence of earthquakes if large triggered earthquakes habitually obey omori s law then their hazard can be more readily assessed the characteristic rate change with time and spatial distribution can be used to rapidly assess the likelihood of triggered earthquakes following events of ms 7 0 i show an example application to the m 7 7 13 january 2001 el salvador earthquake where use of global statistics appears to provide a better rapid hazard estimate than coulomb stress change calculations

estimation of source parameters and scaling relations for moderate size earthquakes in north west himalaya abstract the scaling relation and self similarity of earthquake process have been investigated by estimating the source parameters of 34 moderate size earthquakes m b 3 4 5 8 occurred in the nw himalaya the spectral analysis of body waves of 217 accelerograms recorded at 48 sites have been carried out using in the present analysis the brune s 2 model has been adopted for this purpose the average ratio of the p wave corner frequency fc p to the s wave corner frequency fc s has been found to be 1 39 with fc p fc s for 90 of the events analyzed here this implies the shift in the corner frequency in agreement with many other similar studies done for different regions the static stress drop values for all the events analyzed here lie in the range 10 100 bars average stress drop value of the order of 43 19 bars for the region this suggests the likely estimate of the dynamic stress drop which is 2 3 times the static stress drop is in the range of about 80 120 bars this suggests the relatively high seismic hazard in the nw himalaya as high frequency strong ground motions are governed by the stress drop the estimated values of stress drop do not show significant variation with seismic moment for the range 5 10 14 2 10 17 n m this observation along with the cube root scaling of corner frequencies suggests the self similarity of the moderate size earthquakes in the region the scaling relation between seismic moment and corner frequency m o f c 3 3 47 10 16 n m s 3 estimated in the present study can be utilized to estimate the source dimension given the seismic moment of the earthquake for the hazard assessment the present study puts the constrains on the important parameters stress drop and source dimension required for the synthesis of strong ground motion from the future expected earthquakes in the region therefore the present study is useful for the seismic hazard and risk related studies for nw himalaya