coastal dune ridge systems as chronological markers of palaeoseismic activity a 650 yr record from southwest new zealand a study of two shore parallel dune ridge sequences in southwest new zealand shows that tectonic activity has been the primary controlling influence in their formation since at least ad 1450 the timing of dune building episodes at the mouths of the haast and okuru rivers was determined using the ages of colonizing trees episodic dune formation was indicated by clear discontinuities in tree ages with distinct cohorts having colonized successive newly formed dune ridge swale units at both sites four dune ridge swale units have formed since ad 1450 with each unit closely postdating an alpine fault rupture c ad 1460 c ad 1615 ad 1717 ad 1826 colonizing cohorts of trees started growing within 20 46 years after an earthquake at both sites and all known major regional earthquakes have resulted in a dunebuilding episode no other dunes are present at either site progradational coastal dune systems have potential as a tool for palaeoseismic studies in regions with high background levels of sedime

source parameters estimated from the aftershocks of the 1997 umbria marche italy seismic sequence we derived the source parameters of 563 aftershocks 1 4 m l 4 5 of the 1997 umbria marche seismic sequence by analyzing three component digital recordings of a temporary network and developed a local magnitude scale using the whole available data set more than 25 000 waveforms from synthetic wood anderson seismograms then considering a subnetwork composed of nine portable stations more than 12 000 earthquake spectra were corrected for the near surface attenuation parameter k and the path attenuation the corrected spectra were used to compute the seismic moment the source radius and stress drop assuming an 2 brune source model we calculate the relationship log m 17 46 1 12 m l between seismic moment and local magnitude for the studied area the source dimension versus seismic moment relationship did not show any breakdown in the similarity of the rupture process even when events of magnitude less than 2 2 the threshold value for the completeness of the considered catalog were considered the average stress drop obtained analyzing the s wave spectra was 38 10 bar and the source dimension ranged between about 40 and 500 m

source scaling of microearthquakes at mt etna volcano and in the calabrian arc southern italy microearthquake data recorded at mt etna volcano and in the calabrian arc southern italy have been used to study the scaling of the main source parameters after correction of the p wave displacement spectra for both path attenuation and the site amplification effects an inverse method has been applied to compute spectral parameters low frequency spectral level corner frequency and high frequency roll off results show that seismic moments m0 range from ca 1016 to 1021 dyne cm at mt etna and from ca 1017 to 1020 dyne cm in southern calabria corner frequencies range from ca 3 to 15 hz in both areas we found that the stress drop decreases from ca 100 to few bars with decreasing seismic moment a simple brune source model is not able to explain the source scaling because the typical fall off observed at higher frequencies 3 as an average is larger than that of brune s theory furthermore the relation between the seismic moment and the corner frequency points to a scaling law behaving as m0 c 4 5 and m0 c 3 6 on average at mt etna and in southern calabria respectively and higher for smaller events in both areas therefore the cube law m0 3 generally accepted for large earthquakes does not hold true for the analysed microearthquakes neither for those which occur along the tectonic structures of southern calabria or along those hosting the roots of the feeding system of the largest european volcano

ground penetrating radar and its use in sedimentology principles problems and progress abstract ground penetrating radar gpr also referred to as ground probing radar surface penetrating radar subsurface radar georadar or impulse radar is a noninvasive geophysical technique that detects electrical discontinuities in the shallow subsurface

estimation of source parameters of local earthquakes originated in shillong mikir plateau and its adjoining region of northeastern india abstract we estimate the source parameters seismic moment source radius stress drop and source displacement and scaling laws for local earthquakes that occurred in the shillong mikir plateau assam valley and arunachal himalaya in northeast india during 2001 2008 the source parameters were determined using the spectral analysis of p waves from the vertical component seismograms after correction for attenuation seismic moments are observed within the range from 9 51 10 12 to stress drop ranges from 4 10 5 to 9 10 7 pa for the brune model and 7 10 5 to 1 10 8 pa for the madariaga model seismic events in this study are prominent with an average stress drop of 0 1 10 mpa the effect of site geology may be a contributing factor for such a variation in stress drop source dimensions are however found to be smaller within the major part of the plateau it is suggested that local earthquakes in the region are associated with a brittle shear failure mechanism on fault segments and or the presence of weakened zones and earthquakes are triggered by low deviatoric stress empirical relations between m w m l and m 0 m l are developed leading to the future prediction of calibration coefficients for the local earthquakes in the shillong mikir plateau and its adjoining region online material tables of source parameters

persistent alluvial fanhead trenching resulting from large infrequent sediment inputs we present laboratory and field evidence that in mountainous catchment fan systems persistent alluvial fanhead aggradation and trenching may result from infrequent large sediment inputs we suggest that the river fan systems along the fault bounded range front of the western southern alps new zealand are likely to be in a dynamic equilibrium on 103 yr timescales superimposed on which their fanheads undergo long term cumulative episodic aggradation these fanheads are active only in rare events do not take part in the usual behaviour of the catchment fan system and require much longer to exhibit dynamic equilibrium than the rest of the fan these findings 1 increase our knowledge of the effects of extreme events on alluvial fan morphodynamics in humid climates 2 question the general applicability of inferring past climatic or tectonic regimes from alluvial fan morphology and stratigraphy and 3 provide a conceptual basis for hazard zonation on alluvial fans copyright 2006 john wiley sons ltd

source and qp parameters from pulse width inversion of microearthquake data in southeastern sicily italy 1 source and qp parameters were estimated from the inversion of first arrival p waveform durations of about 300 microearthquakes recorded at a digital seismic network operating in southeastern sicily the average risetime and pulse width at each station do not show large differences allowing us to exclude significant differential attenuation site effects a first qp estimate was obtained by applying the classical risetime method under the assumption of a point like source time function in order to investigate the effect of directivity due to the finiteness of seismic sources new nonlinear relationships based on a circular crack model rupturing at a constant velocity were numerically built these relationships were used to formulate a nonlinear inverse method for retrieving source radius dip and strike of the circular crack and qp parameters from the inversion of risetime and pulse width data the application of the method produced a better fit of the observed data and a qp value higher than that obtained by applying the risetime method the discrepancy between the different q estimates may be due to a trade off among source dimension and qp as we inferred from a test on a subset of low magnitude events ml 2 5 a good agreement with independent estimates of fault plane solutions as inferred from p polarities and s polarizations was found the estimated stress drops are generally very low 0 1 10 bars this suggests that the background seismic activity in southeastern sicily is related to fault segments and or weakened zones where great stress accumulations are hindered

attenuation and source properties at the coso geothermal area california we use a multiple empirical green s function method to determine source properties of small m 0 4 to 1 3 earthquakes and p and s wave attenuation at the coso geothermal field california source properties of a previously identified set of clustered events from the coso geothermal region are first analyzed using an empirical green s function egf method stress drop values of at least 0 5 1 mpa are inferred for all of the events in many cases the corner frequency is outside the usable bandwidth and the stress drop can only be constrained as being higher than 3 mpa p and s wave stress drop estimates are identical to the resolution limits of the data these results are indistinguishable from numerous egf studies of m 2 5 earthquakes suggesting a similarity in rupture processes that extends to events that are both tiny and induced providing further support for byerlee s law whole path q estimates for p and s waves are determined using the multiple empirical green s function megf method of hough 1997 whereby spectra from clusters of colocated events at a given station are inverted for a single attenuation parameter with source parameters constrained from egf analysis the estimates which we infer to be resolved to within 0 01 sec or better exhibit almost as much scatter as a function of hypocentral distance as do values from previous single spectrum studies for which much higher uncertainties in individual estimates are expected the variability in estimates determined here therefore suggests real lateral variability in q structure although the ray path coverage is too sparse to yield a complete three dimensional attenuation tomographic image we invert the inferred value for three dimensional structure using a damped least squares method and the results do reveal significant lateral variability in q structure the inferred attenuation variability corresponds to the heat flow variations within the geothermal region a central low q region corresponds well with the central high heat flow region additional detailed structure is also suggested

landform development in a zone of active gedi fault eastern kachchh rift basin india abstract an earthquake of 2006 mw 5 7 occurred along east west trending gedi fault gf to the north of the kachchh rift basin in western india which had the epicenter in the wagad upland which is approximately 60 km northeast of the 2001 mw 7 7 earthquake site or epicenter development of an active fault scarp shifting of a river channel offsetting of streams and uplift of the ground indicate that the terrain is undergoing active deformation based on detailed field investigations three major faults that control uplifts have been identified in the gf zone these uplifts were developed in a step over zone of the gf and formed due to compressive force generated by left lateral motion within the segmented blocks in the present research a terrace sequence along the north flowing karaswali river in a tectonically active gf zone has been investigated reconstructions based on geomorphology and terrace stratigraphy supported by optical chronology suggest that the fluvial aggradation in the wagad area was initiated during the strengthening at 8 ka and declining 4 ka of the indian summer monsoon ism the presence of younger valley fill sediments which are dated 1 ka is ascribed to a short lived phase of renewed strengthening of ism before present day aridity based on terrace morphology two major phases of enhanced uplift have been estimated the older uplift event dated to 8 ka is represented by the tertiary bedrock surfaces which accommodated the onset of valley fill aggradation the younger event of enhanced uplift dated to 4 ka was responsible for the incision of the older valley fill sediments and the tertiary bedrock these ages suggest that the average rate of uplift ranges from 0 3 to 1 1 mm yr during the last 9 ka implying active nature of the area

simultaneous determination of site responses and source parameters of small earthquakes along the atotsugawa fault zone central japan velocity seismograms recorded at nine local stations from 102 small earthquakes on the atotsugawa fault zone central japan with seismic moment from 3 10 17 to 3 10 21 dyne cm are analyzed to obtain the s wave spectra a genetic algorithm is applied to determine the earthquake source parameters and site responses simultaneously the stability of both site responses and source parameters are experimentally tested as well as the effects of different q models the resulting source parameters show that the stress drops appear to vary systematically with the location of earthquakes events located on the mozumi fault or the junction of the mozumi and the atotsugawa faults have higher stress drops than those on the creeping section and southernmost part of the atotsugawa fault the relationship between seismic moment and corner frequency constructed by combining our results and those of iio 1986 for other regions in japan shows that a single scaling relation does not apply in a moment range of 10 10 to 10 25 dyne cm a steplike change in scaling relationship occurs between 5 10 18 and 5 10 20 dyne cm corresponding to corner frequencies between 15 and 25 hz this observation suggests that earthquakes are most likely a multihierarchical system divided by characteristic sizes according to aki9s 1980 model a characteristic source dimension 100 200 meters may represent a critical size of the barriers distributed in the fault zone at which the barrier effects are balanced by the dynamic effect of the source process

frictional properties and 3 d stress analysis of the southern alpine fault new zealand abstract new zealand s alpine fault af ruptures quasi periodically in large magnitude earthquakes paleoseismological evidence suggests that about half of all recognized af earthquakes terminated at the boundary between the central and south westland sections of the fault there fault geometry and the polarity of uplift change the south westland af exhibits oblique normal fault motion on a structure oriented 052 82 se that for at least 35 km along strike contains saponite rich principal slip zone gouges new hydrothermal friction experiments reveal that the saponite fault gouge is frictionally weak exhibiting friction coefficients between 0 12 and 0 16 for a range of temperatures t 25 210 c and effective normal stresses n 31 2 93 6 mpa the saponite gouge is rate strengthening in all velocity steps performed at velocities between 0 01 and 3 0 m s behavior conducive to aseismic creep a three dimensional stress analysis shows that the south westland af is favorably oriented with respect to the regional stress field for slip within the frictionally weak saponite fault gouge geometrically the fault is severely misoriented for slip in any fault forming materials with friction coefficients exceeding 0 5 the combination of weak gouges prone to aseismic creep strong asperities and low resolved shear stress may impede earthquake rupture propagation along the south westland alpine fault

carbon export from mountain forests enhanced by earthquake triggered landslides over millennia rapid ground accelerations during earthquakes can trigger landslides that disturb mountain forests and harvest carbon from soils and vegetation although infrequent over human timescales these co seismic landslides can set the rates of geomorphic processes over centuries to millennia however the long term impacts of earthquakes and landslides on carbon export from the biosphere remain poorly constrained here we examine the sedimentary fill of lake paringa new zealand which is fed by a river draining steep mountains proximal to the alpine fault carbon isotopes reveal enhanced accumulation rates of biospheric carbon after four large earthquakes over the past 1 100 years probably reflecting delivery of soil derived carbon eroded by deep seated landslides cumulatively these pulses of earthquake mobilized carbon represent 23 5 of the record length but account for 43 5 of the biospheric carbon in the core landslide simulations suggest that 14 5 million tonnes of carbon mtc could be eroded in each earthquake our findings support a link between active tectonics and the surface carbon cycle and suggest that large earthquakes can significantly contribute to carbon export from mountain forests over millennia large earthquakes export significant carbon from mountain forests over millennia according to analyses of sediments mobilized by earthquake triggered landslides in new zealand

application of ground penetrating radar imaging to deepwater turbidite outcrops ground penetrating radar gpr provides a high resolution image of bed scale features within the interior of an outcrop this geophysical technique has been used successfully in fluvial deltaic sequences but its successful use in deepwater deposits is less documented the present paper demonstrates the ability of gpr to define the nature of channel margins and to distinguish internal channel facies at turbidite outcrops in wyoming cretaceous lewis shale usa profiles obtained behind the lewis shale outcrops show channel fills having complex slumped margins between channel sandstones and adjacent levee thin beds as well as onlap of sandstone beds onto the channel margins within the channel fill facies distinguished by gpr vary from interbedded debris flows and turbidites on one side of a channel to cross bedded sandstones on the other side lateral accretion surfaces and onlap features which cannot be observed at the outcrop scale are present on gpr profiles they may represent cross channel sediment transport and deposition within a sinuous channel these examples suggest that when used together with geologic mapping photomosaics and available behind outcrop drilling and logging gpr surveys spanning large outcrops may provide valuable sub seismic scale architectural information for building more robust 3 d models of deepwater reservoirs q 2003 elsevier ltd all rights reserved

lake sediments record cycles of sediment flux driven by large earthquakes on the alpine fault new zealand large earthquakes in mountain regions commonly trigger extensive landsliding and are important drivers of erosion but the contribution of this landsliding to long term erosion rates and seismic hazard remains poorly understood here we show that lake sediments record postseismic landscape response as a sequence of turbidites that can be used to quantify erosion related to large moment magnitude m w 7 6 earthquakes on the alpine fault new zealand alpine fault earthquakes caused a threefold increase in sediment flux over the 50 yr duration of each postseismic landscape response this represents considerable delayed hazard following earthquake induced strong ground motion earthquakes were responsible for 27 of the sediment flux from the lake catchment over the past 1100 yr leading us to conclude that alpine fault earthquakes are one of the most important drivers of erosion in the range front of the southern alps

lake sediments record high intensity shaking that provides insight into the location and rupture length of large earthquakes on the alpine fault new zealand abstract understanding the seismic hazard posed by large earthquakes requires paleoseismic investigation because most faults have not ruptured repeatedly during the period of historic records however determining the location and length of fault ruptures using paleoseismic data remains challenging our study demonstrates that lake sediments record the high intensity shaking that occurs proximal to fault rupture allowing the location and length of ruptures to be reconstructed in two lakes adjacent to the alpine fault new zealand seismic shaking is recorded as subaqueous mass wasting derived turbidites formed by coseismic subaqueous slope failures which are overlain by sets of hyperpycnites representing elevated fluvial sediment fluxes from earthquake induced landslides precise radiocarbon age models show that shaking events are synchronous between the two lake sites and correlate with the timing of known alpine fault earthquakes modelled shaking intensities for the last two alpine fault earthquakes show that subaqueous mass wasting occurs when shaking intensities exceed modified mercalli scale mm vi vii and that fluvial sediment fluxes from earthquake induced landslides occur when shaking intensities exceed mm ix the data demonstrate that lake records distinguish between strong mm vi and violent mm ix shaking at a lake site the ability to map the spatial extent of mm ix shaking provides new insights into the timing and extent of rupture for the last five earthquakes on the alpine fault the study demonstrates that lake deposits constrain the spatial extent of rupture during large earthquakes and may yield long records of the spatial and temporal patterns of fault rupture

time domain inversion of gpr data containing attenuation resulting from conductive losses many seismic data processing and inversion techniques have been applied to ground penetrating radar gpr data without including the wave field attenuation caused by conductive ground neglecting this attenuation often reduces inversion resolution this paper introduces a gpr inversion technique that accounts for the effects of attenuation the inversion is formulated in the time domain with the synthetic gpr waveforms calculated by a finite element method fem the jacobian matrix can be computed efficiently with the same fem forward modeling procedure synthetic data tests show that the inversion can generate high resolution subsurface velocity profiles even with data containing strong random noise the inversion can resolve small objects not readily visible in the waveforms further the inversion yields a dielectric constant that can help to determine the types of material filling underground cavities

active tectonics west of new zealand s alpine fault south westland fault zone activity shows australian plate instability university of canterbury s mason trust fund universidad de chile fcfm start up fund chilean cega fondap conicyt 15090013

recognizing surface scattering in ground penetrating radar data ground penetrating radar gpr data may show strong noise events as a result of scattering by surface objects on the ground or above the survey line the relative strength of these events can be large in comparison to reflections from geologic features because radar signals in the ground attenuate exponentially whereas signals that travel in the air attenuate geometrically migration of gpr field data from clastic and carbonate sequences in central oklahoma distinguishes between scattered events and geologic events because the former are focused at the air wave velocity while the latter are focused at the ground wave velocity forward modeling using locations of scatterers derived from migration confirms the presence of scattered events and common midpoint cmp gathers are helpful in identifying surface scattering scattered events displayed at a horizontal vertical scale of 1 1 are easily mistaken for subhorizontal geologic reflections methods of recognizing scattered events and removing them if possible are therefore crucial to correct geological interpretation of gpr data

developing sub 5 m lidar dems for forested sections of the alpine and hope faults south island new zealand implications for structural interpretations abstract kilometre wide airborne light detection and ranging lidar surveys were collected along portions of the alpine and hope faults in new zealand to assess the potential for generating sub 5 m bare earth digital elevation models dems from ground return data in areas of dense rainforest bush cover as an aid to mapping these faults the 34 km long franz whataroa lidar survey was flown along the densely vegetated central most portion of the transpressive alpine fault six closely spaced flight lines 200 m apart yielded survey coverage with double overlap of swath collection which was considered necessary due to the low density of ground returns 0 16 m 2 or a point every 6 m2 under mature west coast podocarp broadleaf rainforest this average point spacing 2 5 m allowed for the generation of a robust high quality 3 m bare earth dem the dem confirmed the zigzagged form of the surface trace of the alpine fault in this area originally recognised by norris and cooper 1995 norris and cooper 1997 and highlights that the surface strike variations are more variant than previously mapped the 29 km long hurunui hope lidar survey was flown east of the main divide of the southern alps along the dextral slip hope fault where the terrain is characterised by lower rainfall and more open beech forest flight line spacings of 275 m were used to generate a dem from the ground return data the average ground return values under beech forest were 0 27 m 2 and yielded an estimated cell size suitable for a 2 m dem in both cases the lidar revealed unprecedented views of the surface geomorphology of these active faults lessons learned from our survey methodologies can be employed to plan cost effective high gain airborne surveys to yield bare earth dems underneath vegetated terrain and multi storeyed canopies from densely forested environments across new zealand and worldwide

source parameters of the 15 november 1995 border town nevada earthquake sequence abstract the november 1995 border town nevada earthquake sequence occurred near the california nevada border approximately 20 km northwest of reno nevada the largest earthquake of the sequence m w 4 5 was widely felt throughout the reno sparks truckee region this event occurred on a west dipping high angle fault at a depth of 14 km and shows dip slip motion on a preferred fault plane orientation of strike n10 e dip 70 w and rake 75 we have relocated 27 aftershocks and one foreshock of the event using records from the local network and two portable digital instruments the largest aftershocks also align along a n10 e trend and define the preferred fault plane all of the aftershocks occur within a small volume with a 2 by 2 km horizontal extent and between depths of 10 and 14 km simultaneous determination of m 0 f c and is made by fitting spectra using various starting models i e initial s and based on an f 2 spectral shape m 0 ranges from 10 18 to 10 23 dyne cm for 14 events and hypocentral distances were less than 15 km we fit s wave spectra with different starting models to test the stability of s the results show that s and converged to different values depending on the starting model and the magnitude because of an attenuation source dimension trade off for example a model starting with a stress drop of 10 bars produced an average s of 27 bars and an apparent scaling breakdown below m w 3 starting the search at 50 bars produced an average s of 69 bars and no magnitude dependence we cannot resolve any breakdown in self similarity because we find plausible spectral models for all magnitudes where s is nearly constant at 60 bars seismograms of the four largest aftershocks m w 3 0 to 3 4 were deconvolved using smaller aftershocks as empirical green9s functions event radii estimated from the pulse widths yield stress drop averaging 34 bars within the range of the frequency domain results

empirical green s function analysis of loma prieta aftershocks abstract following the 18 october 1989 loma prieta earthquake an array of 22 three component iris passcal instruments was deployed in the santa cruz mountains we use an empirical green9s function method to study source properties of aftershocks as well as attenuation in the epicentral area using pairs of closely spaced events we show that the largest aftershocks are well modelled by an 2 source spectrum and we obtain estimates of the p wave corner frequency for a total of 15 events brune stress drops are observed to have no systematic variation over the range of moments spanned by the data set down to 10 19 dyne cm there is a suggestion that aftershocks that occurred outside the mainshock rupture have higher stress drops than those that occurred within the mainshock rupture a m l 3 4 foreshock in the subsequence associated with the 18 april 1990 m l 5 4 watsonville earthquake yields a stress drop estimate of 820 bars this value is well outside the stress drops obtained for all other events 6 to 266 bars site specific attenuation parameters suggest large lateral and vertical heterogeneity in p wave q structure station holy in a valley near the surface trace of the san andreas fault is characterized by low q values while stations to the north of the aftershock zone are characterized by the highest q values

earthquake source scaling relationships from 1 to 5 ml using seismograms recorded at 2 5 km depth the scaling relationships of earthquake sources less than about magnitude 3 have been the subject of considerable controversy over the last two decades studies of such events have shown a tendency for the constant stress drop self similarity of larger earthquakes to breakdown at small magnitudes and an apparent minimum source dimension of about 100 m has been observed other studies showed that this apparent breakdown in scaling could be an artifact of severe near surface attenuation limiting the spatial resolution of surface data in this study source parameters are determined for over 100 nearby tectonic earthquakes from recordings at a depth of 2 5 km in granite in the cajon pass scientific drill hole southern california comparison of the seismograms recorded at this depth with those at the wellhead clearly demonstrates the effect of the severe attenuation in the upper kilometers of the earth s crust source parameters are calculated by spectral modeling of three component p and s waves assuming four source models based on the brune 2 n 2 model in model l n 2 is fixed and q of p and s waves is determined to be 912 581 1433 and 1078 879 1323 respectively the numbers in parentheses are 1 standard deviation in model 2 qp qs 1000 is assumed and n is allowed to vary the 2 model is a good average for the data set but there is some real scatter supported by the data in model 3 qp qs 1000 is also assumed and 2 is constrained and in model 4 attenuation is ignored and n is allowed to vary source dimensions of less than 10m are observed for all four models 10 times smaller than the proposed minimum no breakdown in constant stress drop scaling is seen in the downhole data approximately ml 1 to 5 5 m0 109 1016 nm the ratio between radiated seismic energy estimated by integrating the velocity squared spectra with adequate signal bandwidth and seismic moment appears to decrease gradually with decreasing moment in the magnitude range 1 to 7 this is not incompatible with a constant stress drop but could result from errors in calculating energy the ratio of the s wave energy to that radiated by the p waves is about 14 after correction for attenuation this low value is consistent with the corner frequency shift of about 1 3 this corner frequency shift is observed for all four source models and therefore is interpreted as being source controlled

advanced seismic imaging techniques characterize the alpine fault at whataroa new zealand the plate bounding alpine fault in new zealand is a 850 km long transpressive continental fault zone that is late in its earthquake cycle we have acquired and processed reflection seismic data to image the subsurface around the main drill site of the deep fault drilling project dfdp 2 the resulting velocity models and seismic images of the upper 5 km show complex subsurface structures around the alpine fault zone the most prominent feature is a strong reflector at depths of 1 5 2 2 km with an apparent dip of 48 to the southeast below the dfdp 2 borehole which we assume to be the main trace of the alpine fault above the main reflector parallel reflectors suggest the presence of a 600 m wide damage zone additionally subparallel reflectors are imaged that we interpret as secondary branches of the main fault zone conjugate faults imaged by the data show the complexity of the subsurface the derived p wave velocity model reveals a 300 600 m thick sedimentary layer with velocities of 2 3 km s above a schist basement with velocities of 4 5 5 5 km s a low velocity layer can be observed within the basement at 0 8 2 km depth a small scale low velocity anomaly appears at the top of the basement that can be correlated to the fault zone the results provide a reliable basis for a seismic characterization of the dfdp 2 drill site that can be used for further structural and geological investigations of the architecture of the alpine fault in this area

influence of focal mechanism on peak accelerations of strong motions of the whittier narrows california earthquake and an aftershock focal mechanisms affect the pattern of the peak accelerations of the october 1 1987 whittier narrows earthquake and its october 4 aftershock the peak accelerations observed on 21 strong motion instrumentation program and 22 u s geological survey accelerograms correlate well with the ratio of shear wave amplitude computed from the thrust mechanism of the main shock and the strike slip mechanism of the aftershock this correlation means that seismic energy is radiated from the fault with close to the standard double couple radiation pattern at the frequencies 3 6 hz corresponding to the peak accelerations

stress directions and shear wave anisotropy observations from local earthquakes in southeastern sicily italy the spatial distribution of 414 earthquakes 1 0 m l 4 6 recorded from 1994 to 2002 in southeastern sicily italy has been analyzed the seismicity generally coincides with mapped plio quaternary faults including the north north west south southeast striking offshore fault system which is the most important tectonic structure of the area for the best located events we computed 70 focal mechanisms by combining p wave polarities with s wave polarizations a predom inance of strike slip and normal faults was observed focal mechanisms were then inverted for stress tensor parameters by using the algorithm of gephart and forsyth the results highlighted a region governed mainly by a north northwest south south east to northwest southeast compressional stress regime moreover anisotropy anal ysis of shear waves showed a polarization of fast s waves coherently aligned with this stress direction a finer scale analysis of the stress tensor evidenced three regions characterized by slightly differing orientation of the greatest principal stress axis r1 the eastern sector displays a nearly horizontal r1 trending northwest southeast the central sector is affected by a low dip north northwest south southeast r1 whereas in the western sector a north northwest south southeast oriented r1 with a higher dip angle was detected finally the comparison of the spatial distribution of seismicity occurring during 1994 2002 with locations of previous instrumental earthquakes and larger m 5 0 historical events showed that the seismicity patterns are persistent

irregular earthquake cycle along the southern tianshan front aksu area china 1 a long deformation record 16 5 ka showing nonsteady earthquake recurrence is established for the aksu thrust tianshan china on the basis of cosmogenic 10be dating of faulted surfaces topographic leveling across the aksu fault scarp indicates up to 10 m uplift across a moraine abandoned 16 5 ka and similar uplift of 6 m across two inset surfaces yielding ages of 12 5 and 5 ka successively smaller uplifts of terraces younger than 5 ka indicate that three or more major earthquakes occurred during this period these data show that the aksu thrust fault was quiet for at least 7500 years and active in the last 5000 years and probably in the interval 16 5 12 5 ka the seismic cycle along the aksu thrust fault over the last 16 500 years was thus strongly irregular showing long quiescence and clustering which is a challenge for paleoseismology and hazard assessment this irregularity also makes it more difficult to estimate long term shortening rates nevertheless we are able to constrain a minimum total shortening rate 7 mm yr across the southern tianshan front for the last 12 500 years that is about a third of the total geodetic rate for the western tianshan 20 mm yr

site response for seattle and source parameters of earthquakes in the puget sound region we analyzed seismograms from 21 earthquakes ml 2 0 4 9 recorded by digital seismographs we deployed in urban seattle to determine site response and earthquake stress drops the seismometers were situated on a wide variety of geologic units including artificial fill e g kingdome harbor island pleistocene age soils glacial till and outwash deposits of seattle s hills modified land downtown seattle space needle and tertiary sedimentary rock two mainshock aftershock sequences were recorded the june 1997 bremerton sequence mainshock ml 4 9 and the february 1997 south seattle sequence mainshock ml 3 5 along with other events in the puget sound region we developed a new inversion procedure to estimate site response source corner frequencies and seismic moments from the s wave spectra this inversion uses corner frequencies determined from spectral ratios of mainshock aftershock pairs as constraints the site responses found from the inversion are not relative to the rock site but are relative to an idealized site with a flat frequency response the response of the rock site is also found from the inversion the inversion results show high response for the sites on artificial fill more moderate amplification for most sites on stiff pleistocene soils or modified land and low response for the rock site some sites display resonances such as a strong 2 hz resonance at our site near the kingdome which is caused by the surficial layers of fill and younger alluvium the sites in west seattle exhibit high amplification even though they are on relatively stiff soils of glacial outwash this may be partly caused by basin surface waves produced by conversion of incident s waves this high response in west seattle is consistent with damage reports from the 1949 mb 7 1 and 1965 mb 6 5 earthquakes stress drop estimates for the events we recorded were generally low between 0 4 and 25 bars although some of the events may have had higher stress drops that could not be resolved because of the limited passband we calculated a stress drop of 24 bars for the bremerton mainshock and 10 bars for the south seattle mainshock

the subsidence history of the northern hyblean plateau margin southeastern sicily abstract the southeastern corner of sicily is dominated by the hyblean plateau which is composed of carbonate rocks of triassic to miocene age the plateau forms part of the african foreland which collided during tertiary times with the calabrian arc giving rise to the maghrebian thrust belt the present study attempts to reconstruct the subsidence history of the northern hyblean plateau during the neogene climax of the plate collision this area has been a centre for widespread basaltic volcanic activity 8 1 ma and uplift at the close of the collisional events pliocene early pleistocene the area under consideration has been affected by subsidence and the progressive consumption of the northern margin of the hyblean plateau led to the development of the modern foredeep a quantitative analysis was done by one dimensional airy backstripping of seven deep wells located on this crucial part of the hyblean plateau the results of the analysis show that the subsidence history of the northern hyblean plateau area is characterized by four main phases similar to other domains in the central and eastern mediterranean basins these phases are a neotethyan rifting during late triassic early jurassic time b a slow thermal subsidence from early jurassic until late cretaceous time leading to the formation of a widespread mesozoic carbonate platform c compressional phase during late cretaceous palaeogene time which resulted in the formation of fold systems and d uplift and subsidence events during the middle tertiary which are probably the result of the continued collision of the european african plates after the early pleistocene unlike other terranes within the mediterranean an uplift occurred in the northern hyblean plateau following the upper miocene lower pleistocene massive volcanic activity this uplift is probably associated with the latest stages of thrusting along the frontal part of the maghrebian thrust belt

scaling of ground motion parameters state of stress and focal depth the ground motion parametersrv and ra where r is hypocentral distance v is peak velocity is density and a is peak acceleration are found observationally to be strong functions of stress state and linearly related to focal depth z if the stress state and focal depth are properly taken into account then the ground motion parameters depend on the seismic moment m0 as expected from basic scaling principles that is rv m01 3 and ra is independent of earthquake size regression lines fitted to observations covering broad ranges in seismic moment and focal depth indicate that for extensional and compressional tectonic regimes corresponding to normal and thrust or reverse faulting earthquakes respectively peak acceleration is given by ra 1 08 mpa 3 06 mpa km z normal and ra 5 65 mpa 8 76 mpa km z thrust and for peak velocity rv m01 3 10 4 m2 s n m 1 3 3 00 0 69 km 1 z normal and rv m01 3 10 4 m2 s n m 1 3 4 63 1 82 km 1 z thrust for strike slip earthquakes the data currently are insufficient to define regression fits but such lines would definitely lie between those for the normal and thrust stress regimes these equations are appropriate for ground motion at small hypocentral distance as recorded in a whole space it follows that for comparable hypocentral depth peak acceleration in a compressional tectonic regime for example much of the eastern united states is a factor of about 3 greater than in an extensional regime such as nevada and for peak velocity a similar comparison yields a factor of 2 difference the similarity in behavior of the peak acceleration parameter to crustal strength estimated from byerlee s law of friction with respect to depth and stress state indicates that crustal strength is probably the factor governing the seismic source processes that give rise to the high frequency peak ground motion analysis of the peak acceleration data in the context of crustal strength suggests bounds on this ground motion parameter as recorded at a typical surface site that depend on stress state specifically a normal 0 5 g and a thrust 1 9 g thus the state of stress as well as the focal depth clearly is an important factor to be taken into account in the prediction of seismic ground motion

landslide impact on organic carbon cycling in a temperate montane forest in humid forested mountain belts bedrock landslides can harvest organic carbon from above ground biomass and soil ocmodern while acting to refresh the landscape surface and turnover forest ecosystems here the impact of landslides on organic carbon cycling in 13 river catchments spanning the length of the western southern alps new zealand is assessed over four decades spatial and temporal landslide maps are combined with the observed distribution and measured variability of hillslope ocmodern stocks on average it is estimated that landslides mobilized 7 6 2 9 tc km 2 yr 1 of ocmodern 30 of which was delivered to river channels comparison with published estimates of ocmodern export in river suspended load suggests additional erosion of ocmodern by small shallow landslides or overland flow in catchments the exported ocmodern may contribute to geological carbon sequestration if buried in sedimentary deposits landslides may have also contributed to carbon sequestration over shorter timescales 100 years 5 4 3 0 tc km 2 yr 1 of the eroded ocmodern was retained on hillslopes representing a net carbon sink following re vegetation of scar surfaces in addition it was found that landslides caused rapid turnover of the landscape with rates of 0 3 of the surface area per decade high rates of net ecosystem productivity were measured in this forest of 94 11 tc km 2 yr 1 which is consistent with rapid landscape turnover suppressing ecosystem retrogression landslide ocmodern yields and rates of turnover vary between river catchments and appear to be controlled by gradients in climate precipitation and geomorphology rock exhumation rate topographic slope copyright 2011 john wiley sons ltd

source parameters of the 1980 mammoth lakes california earthquake sequence from the more than 1500 mammoth lakes earthquakes recorded on three component digital seismographs spudich et al 1981 150 were used in an analysis of the locations mechanism and source parameters a composite fault plane solution of nine earthquakes 3 9 m 5 1 defines a right lateral strike slip mechanism on a steeply dipping nearly east west plane striking s75 e or left lateral strike slip on a nearly north south plane striking n10 e vertical cross sections of well located aftershocks indicate possibly three east west planes that coincide with the locations of the four largest earthquakes with ml 6 0 using the spectral analysis of s waves brune 1970 source parameters for 67 earthquakes were determined forty eight had magnitudes greater than or equal to 3 0 seismic moments ranged from 9 20 1018 dyn cm to 2 33 1024 dyn cm earthquakes with seismic moment greater than about 1 0 1021 dyn cm had nearly constant stress drops 50 bars earthquakes with seismic moment less than about 1 0 1021 dyn cm had stress drops that apparently decrease as seismic moment decreases

active fault kinematics and crustal stresses along the ionian margin of southeastern sicily since the late cretaceous onset of plate convergence between africa and europe the malta escarpment has been converted from a mesozoic passive margin into a mega hinge fault system with an additional sinistral strike slip component the modern tectonic stress regime with nw se directed maximum horizontal stresses has been established since late messinian times since the pleistocene sinistral strike slip deformation and contemporaneous normal faulting along the malta escarpment have induced the opening of oblique trending onshore grabens at the eastern margin of the hyblean plateau in this study we focus on the kinematics the controlling state of stress and the temporal variation of the neotectonic to active strike slip and normal fault structures the stress tensor calculations reveals that the widespread map scaled to meso scaled normal fault structures are governed by the long term extensional state of stress during the quaternary this long term stress tensor is predominantly controlled by gravitational induced stresses due to vertical load 1 sv and lateral extension due to the topographic gradient of the malta escarpment 3 sh ne sw in this case the average tectonic stresses 2 sh nw se transmitted by the regional to plate tectonic stress field are significantly smaller than the gravitational induced stresses in contrast the clear localization of conjugate sets of meso scaled strike slip fault structures and shear zones without accompanying normal fault structures give strong indications for episodic seismotectonic strike slip faulting under critical stress conditions in this state tectonically induced maximum horizontal stresses are successively increased by ongoing plate convergence from low level stress magnitudes 1 sv 2 sh nw se up to critical stress magnitudes 1 sh nw se 2 sv which are significantly larger than gravitational stresses at the critical state seismotectonic stress release occurs by active strike slip faulting as recently indicated in mid crustal levels by the moderate 1990 augusta earthquake and re establishes the long term extensional state of stress because the strike slip faults and shear zones in the study area were formed as surface ruptures they additionally give indications of episodic large earthquakes in this region with magnitudes greater than 6 0 as reported by several large earthquakes devastating e and se sicily in historical times

attenuation of short period seismic waves at mt vesuvius italy we analysed short period seismograms from about 250 very local events recorded by a network of high dynamic range short period seismic stations deployed on mt vesuvius to estimate the site corrected short period seismic attenuation we calculated qc 1 the inverse of the quality factor for coda waves for short lapse times 12 s and qp 1 and qs 1 the inverse of the direct body wave quality factors for p and s waves follow ing shallow ray paths we used the single scattering assumption to fit the amplitude envelopes of the coda at different frequency bands obtaining a qc 1 slowly varying with frequency similar to values measured for other volcanoes at the same lapse time site corrected qp 1 and qs 1 were estimated using the frequency decay method for both p and s waves in two frequency bands 1 6 hz and 15 24 hz results show that qp 1 is 0 028 in both frequency bands and qs 1 is 0 015 and 0 017 at low and high frequencies respectively almost independent of the frequency and that the value of qp 1 is about twice that of qs 1 as measured worldwide a check was made by measuring the broadening of the first p wave pulse with station source distance finding qp 1 0 024 using the independent estimates of qc 1 and qs 1 we separated the intrinsic from the scattering quality factor at mt vesuvius obtaining a high scattering and a low intrinsi c q 1 as already observed for other volcanoes this result confirms the hypothesis of the predominant role of the scattering phenomena with respect to the intrinsic dissipation in the seismogram formation for volcanic earthquakes

attenuation and source parameters of shallow microearthquakes at mt etna volcano italy we estimated the attenuation laws of high frequency seismic waves in the shallow crust depth 5 km and earthquake source parameters by using a se lected data set of 320 shallow events 2 6 md 4 2 recorded at mt etna volcano during the last two flank eruptions occurring in 2001 and 2002 2003 the quality factor q was estimated from spectra of p and s waves for 24 stations of the local permanent network by applying a spectral ratio technique the results show varia tions in both qp and qs as a function of frequency according to the power law q q0f n with n ranging between 0 3 and 1 3 for p waves and between 0 2 and 0 9 for s waves as typical of volcanic environments strong azimuthal variations of qp were also found suggesting the presence of local strong lateral heterogeneities and or of fluid filled cracked volumes after correction for attenuation we estimated the source parameters seismic moment source radius and stress drop of a subset of 66 shallow events under the assumption of a circular dislocation the estimated seismic moments m0 range from 10 13 to 10 15 n m the source radii r are confined between 100 and 1000 m and stress drop dr ranges between 0 2 mpa and about 4 mpa combining the source parameters obtained in this study with those calculated by pataneet al 1997 for an old data set of smaller microearthquakes 10 9 m0 10 14 n m recorded in the same area we re evaluated the scaling relationship between seismic moment m 0 and corner frequency f c for the earthquakes with m 0 ranging between 10 13 and 10 15 n m we confirm that microearthquakes at mt etna seem not to obey a

evidence for a landslide origin of new zealand s waiho loop moraine the waiho loop moraine has been interpreted as evidence for younger dryas cooling in southern new zealand but recent dating and climatological studies have questioned this idea a detailed analysis of the sedimentology of the moraine suggests it was formed after a large landslide onto the franz josef glacier triggered a glacial surge independent of climate forcing

continental transforms a view from the alpine fault abstract continental transform faults are dominantly highly localized strike slip shear zones hundreds of kilometers long that accumulate tens to hundreds of kilometers of displacement from work on the alpine fault we pose the questions what is the deep structure of a continental transform and how does the displacement become localized we review research on the alpine fault and propose a model in which the fault partitions at depth into a steep zone extending into the mantle with largely fault parallel motion and a flat ductile decollement in the lower crust the fault localizes around two thirds of the plate motion within a 100 km wide zone of distributed deformation a review of other active continental fault systems suggests that variation between them may reflect their tectonic origins the nature of the crust in which they develop the presence of a significant oblique component of motion and the displacement rate all however have evidence for the development of a single principal fault zone that carries 50 of the total displacement and extends as a localized zone of shear into the upper mantle we review mechanisms of strain weakening and suggest that localization of a principal fault may be initiated in the seismogenic crust and through a series of positive feedbacks eventually extend through the lower crust into the upper mantle

source parameters of the 23 april 1992 m 6 1 joshua tree california earthquake and its aftershocks empirical green s function analysis of geos and terrascope data source parameters of the m 6 1 23 april 1992 joshua tree mainshock and 86 m 1 8 to 4 9 aftershocks are determined using an empirical green s function methodology for the aftershocks deconvolved p and s wave spectra are calculated for 126 pairs of closely spaced events recorded on portable geos stations s wave spectra from the two horizontal components are averaged the deconvolved spectra are fit by a ratio of omega square source models yielding an optimal least squares corner frequency for both the large and the small event in each pair we find no resolved difference between the inferred p and s wave corner frequencies using the standard brune model for stress drop we also find no resolved nonconstant scaling of stress drop with moment although we also conclude that detailed scaling systematics would be difficult to resolve in particular a weak increase of stress drop with moment over a limited moment magnitude cannot be ruled out for magnitudes smaller than m 3 to 3 5 the inferred stress drop values will be limited by the maximum observable corner frequency value of 60 hz for the mainshock source time functions are obtained from mainshock recordings at three terrascope stations pfo pas and gsc using an m 4 3 foreshock as an empirical green s function the results indicate a fairly simple single pulse source time function with clear south to north directivity and an inferred rupture radius of 5 to 6 km the deconvolved source time functions are inverted to obtain a finite rupture model that gives a robust estimate of rupture dimension early aftershocks are found to lie along the perimeters of regions with high mainshock slip the inferred mainshock stress drop value 56 bars is within the range determined for the aftershocks our derived mainshock source spectra do not show resolvable deviation from the omega square model

seismic source parameters from the guerrero subduction zone abstract a method to systematically determine seismic moment and corner frequency from shear wave spectra has been applied to strong motion data recorded in guerrero mexico the method determines a model spectrum that minimizes the misfit from the observed spectrum after a correction for frequency dependent site response has been applied the calculated moments for larger events in guerrero are consistent with moments determined from teleseismic body waves adjusted for differences in focal depth and consequent assumed differences in the velocity and density structure in the source region the average stress drop for the 82 earthquakes with magnitudes from 3 to 7 is 150 bars the spatial distribution of the stress drops shows a distinctive pattern at the northwest end of the guerrero gap adjacent to the aftershock zones of large earthquakes in 1979 and 1985 there is a mix of low and high stress drop events at the southeast end of the guerrero gap where the most recent large earthquake occurred in 1957 there are predominantly high stress drop events this pattern might be caused by the different relative positions of these two active regions in the earthquake cycle although several other explanations cannot be ruled out

new evidence for the serpentinization of the palaeozoic basement of southeastern sicily from joint 3 d seismic velocity and attenuation tomography

determination of seismogenic structures in southeastern sicily italy by high precision relative relocation of microearthquakes abstract in december 1990 southeastern sicily was struck by a moderate earthquake m l 5 4 the event and the subsequent aftershocks represent renewed activity for the malta escarpment fault system mefs three centuries after the most recent of several large destructive historical earthquakes an 11 yr period of quiescence was interrupted with a minor swarm in 2002 m max 3 6 these sequences and regional seismicity were relocated through 3d tomography the resulting velocity model indicates a velocity contrast in the vicinity of mefs high precision relative relocations were derived by the cross spectral method for 18 events from the 1990 sequence and 10 earthquakes from the 2002 swarm these swarms were aligned along fault segments striking east northeast west southwest conjugate to the north northwest south southeast orientation of the mefs we conclude that the mefs is fragmented in segments with different seismic behaviors and that great stress accumulation along the main segment of the mefs is less likely

what we can and cannot learn about earthquake sources from the spectra of seismic waves earthquake sources are commonly viewed as shear dislocations this imposes distinct limitations on what source parameters can be realistically determined from radiated shear wave spectra first the slip velocity on the fault is the real parameter that controls the strength of the high frequency radiation it can be directly determined from acceleration spectra by fitting their high frequency level second the relationship between corner frequency of the spectrum and the radius of the source is fundamentally unclear as a result the source dimensions cannot be accurately determined from the spectra such an estimate would be as accurate as any other informed guess third the stress drop only serves as a proxy for the source radius in the relationship between the radius and the corner frequency it thus cannot be reliably determined from the spectra the quantity usually obtained from the spectra and referred to as the stress drop is a poorly defined parameter that may bear little relevance to the actual stresses acting on faults this parameter has little meaning unless converted to the maximum slip velocity which is the only quantity that can be accurately determined from the spectra the typical value of stress drop of 100 bars established from the spectra of california events may imply that the typical slip velocities have been on the order of 0 5 m sec although it is more accurate to determine slip velocities directly from the spectra

seismic source parameters for microearthquakes of the granada basin southern spain abstract ninety five microearthquakes of the granada basin southern spain with duration magnitudes ranging from 1 3 to 3 5 moment magnitude from 0 9 to 2 5 have been spectrally analyzed with digital recordings from ten stations of the andalusian seismic network the coda q quality factor qc assumed to be frequency dependent was used instead of q for the path correction and the q adopted was equal to 9 4 qc the k parameter for site attenuation correction had values in the range of 0 02 0 05 fourier displacement spectra were calculated for p and s waves and analyzed with respect to the source model of brune 1970 1971 spectral parameters were automatically determined by the method of snoke 1987 the seismic moment ranged from 1017 to 1020 dyne cm with average m0 p to m0 s ratio of 1 02 and the source radii spanned from 0 14 to 0 40 km with average r p to r s ratio of 1 3 the seismic energy values ranged from 1 103 to 9 107 j with p to s energy ratio from 1 to 10 for about 85 of the events whereas the static stress drop varied from 0 02 to 2 6 bar the scaling relation between the seismic moment and the stress drop indicates a decrease in stress drop with decreasing seismic moment apparent stress is linearly correlated with stress drop and have on average similar values and this points out to a partial stress drop

timing of late holocene paleoearthquakes on the hurunui segment of the hope fault implications for plate boundary strain release through south island new zealand the hurunui segment of the dextral slip hope fault extends for 42 km between the hope and hurunui river catchments and westward to harper pass at the main divide of south island we conducted paleoseismic soil and landscape dating studies in the upper hurunui valley to determine the timing of past earthquake ruptures along this geometric fault segment on a late holocene alluvial surface at matagouri flat a young channel system is displaced dextrally by 4 5 0 6 m which is attributed to the most recent faulting event a trench and soil pits excavated nearby yield evidence for the timing of the last two surface faulting events these events dated from a combination of radiocarbon dates relative soil tree and historical constraints modified within an oxcal analysis occurred at ca a d 1655 1835 and 1425 1625 the occurrence of two rupture events during the last 600 yr is consistent with previous estimates stating a short recurrence interval for the hurunui segment the most recent faulting event in our trenches predates the historic 1888 north canterbury amuri earthquake which ruptured the hope river segment to the east a comparison of the record from the hurunui segment with paleoseismic records from other segments along the hope fault zone indicates evidence for two or three rupture events within the last 700 900 yr within the age resolution of the current dates the data suggest that along strike rupture occurred along the majority of the hope fault zone between 120 and 360 yr ago i e a d 1650 1888 and may all postdate the most recent rupture of the alpine fault in ca a d 1717 in addition the timings of penultimate faulting events along the hurunui hope river and conway segments and the hanmer fault all fall in the range 400 700 yr ago these preliminary observations indicate that rupture of segments of the hope fault and indeed the alpine fault could occur as clusters that are years to decades apart rupture of the major plate boundary faults in the northern south island may therefore occur in sequences that are enhanced or even retarded by stress triggering and fault interactions

prehistoric dates of the most recent alpine fault earthquakes new zealand we use four methods to investigate the earthquake history over the past 600 yr of the central alpine fault new zealand trenches across the active fault trace at five locations identify two ruptures on the fault in the past 450 yr three other indirect indicators episodes of landsliding and aggradation dated either via 14 c or from forest establishment on the resulting surfaces and tree ring growth anomalies provide further evidence for these two earthquakes and a greater resolution in estimates of their timing and extent the most recent earthquake occurred in a d 1717 and the rupture extended over a section of fault between milford and the haupiri river a distance of 375 km about 1630 another earthquake occurred on the fault and this extended between at least the paringa and ahaura rivers 250 km regional episodes of landsliding and forest establishment provide evidence for a third earthquake at about 1460 over the same section of fault the pattern of earthquake recurrence is not regular but averages 200 yr and varies from 100 yr to at least 280 yr which is the lapsed time since the most recent rupture

a 2000 yr paleoearthquake record along the conway segment of the hope fault implications for patterns of earthquake occurrence in northern south island and southern north island new zealand paleoseismic trenches excavated at two sites reveal ages of late holocene earthquakes along the conway segment of the hope fault the fastest slipping fault within the marlborough fault system in northern south island new zealand at the green burn east gbe site a fault perpendicular trench exposed gravel colluvial wedges fissure fills and upward fault terminations associated with five paleo surface ruptures radiocarbon age constraints indicate that these five earthquakes occurred after 36 b c e with the four most recent surface ruptures occurring during a relatively brief period 550 yr between about 1290 c e and the beginning of the historical earthquake record about 1840 c e additional trenches at the green burn west gbw site 1 4 km west of gbe reveal four likely coseismically generated landslides that occurred at approximately the same times as the four most recent gbe paleoearthquakes independently overlapping with age ranges of events gb1 gb2 and gb3 from gbe combining age constraints from both trench sites indicates that the most recent event gb1 occurred between 1731 and 1840 c e the penultimate event gb2 occurred between 1657 and 1797 c e gb3 occurred between 1495 and 1611 c e gb4 occurred between 1290 and 1420 c e and gb5 occurred between 36 b c e and 1275 c e these new data facilitate comparisons with similar paleoearthquake records from other faults within the alpine hope jordan kekerengu needles wairarapa al hp jkn wr fault system of throughgoing fast slip rate 10 mm yr reverse dextral faults that accommodate a majority of pacific australia relative plate boundary motion these comparisons indicate that combinations of the faults of the al hp jkn wr system may commonly rupture within relatively brief 100 year long sequences but that full wall to wall rupture sequences involving all faults in the system are rare over the span of our paleoearthquake data rather the data suggest that the al hp jkn wr system may commonly rupture in subsequences that do not involve the entire system and potentially at least sometimes in isolated events

ground penetrating radar survey of a prehistoric site in southern italy abstract in this paper we present and discuss the results of a ground penetrating radar gpr study carried out in an area of southern italy where a karst cave with prehistoric remains was found the aim of the study involved the imaging of the subsurface stratigraphy both inside and outside the cave in order to assist archaeologists in an excavation programme the survey grid comprised 18 intersecting gpr profiles problems associated with the use of the gpr within a cave environment are highlighted and the data processing sequence designed to extract useful geo archaeological signatures is described interpretation of the radar sections was controlled by the excavation of two trenches inside and outside the cave allowing detailed outlining the complex stratigraphy and the reconstruction of palaeolithic and neolithic subsurface horizons

modeling finite fault radiation from the ωn spectrum the high frequency seismic field near the epicenter of a large earth quake is modeled by subdividing the fault plane into subelements and summing their contributions at the observation point each element is treated as a point source with an o92 spectral shape where co is the angular frequency ground motion contributions from the subsources are calculated using a stochastic model attenuation is based on simple geometric spreading in a whole space coupled with regional anelastic atten uation q operator the form of the co n spectrum with natural n follows from point shear dislocation theory with an appropriately chosen slip time function the seismic moment and comer frequency are the two parameters defining the point source spectrum and must be linked to the subfanlt size to make the method complete two coefficients aa and k provide this link assigning a moment to a subfault of specified size introduces the stress parameter ao the relationship between comer frequency dislocation growth rate and fault size is established through the coefficient k which is inherently nonunique these two parameters control the number of subsources and the ampli tudes of high frequency radiation respectively derivation of the model from shear dislocation theory reveals the unavoidable uncertainty in assigning ogn spectrum to faults with finite size this uncertainty can only be reduced through empirical vali dation the method is verified by simulating data recorded on rock sites near epicenters of the m8 0 1985 michoacan mexico the m8 0 1985 valparaiso chile and the m5 8 1988 saguenay qurbec earthquakes each of these events is among the largest for which strong motion records are available in their respective tectonic environ ments the simulations for the first two earthquakes are compared to the more de tailed modeling of somerville et al 1991 which employs an empirical source function and represents the effects of crustal structure using the theoretical impulse response both methods predict the observations accurately on average the precision of the methods is also approximately equal the predicted acceleration amplitudes in our model are generally within 15 of observations an unexpected result of this study is that a single value of a parameter k provides a good fit to the data at high frequencies for all three earthquakes despite their different tectonic environments this suggests a simplicity in the modeling of source processes that was unanticipated

source parameters of microearthquakes in southeastern sicily italy we computed the source parameters of 135 local earthquakes that occurred in southeastern sicily italy between 1994 and 2001 magnitudes ranged from 0 6 to 2 5 the source parameters were determined from the spectral analysis of p waves after corrections for attenuation and site effects p wave quality qp and site s factors are known in the two frequency ranges 3 9 hz and 16 27 hz giampiccolo et al 2003 because the correction for qp and s over the whole spectrum could not be performed a new approach to estimate spectral parameters was applied we defined the new notion of holed spectrum to specify a spectrum lacking corrected spectral amplitude values within a certain frequency range whereas we referred to a whole spectrum to specify when the entire analyzed frequency band was used a detailed statistical analysis showed that dealing with the holed spectrum did not lead to significant differences in the estimate of spectral parameters displacement holed spectra corrected by the attenuation and site response were then used to estimate source parameters seismic moments ranged from 1017 to 1020 dyne cm and source dimensions from 150 to 500 m in general the stress drop values obtained analyzing p wave spectra were very low because they mainly span the range of 0 05 5 bars

new on fault evidence for a great earthquake in a d 1717 central alpine fault new zealand the dextral reverse alpine fault is the major onshore plate boundary structure between the australian and pacific plates in new zealand no previous study of the central portion of the 200 km long central segment has provided on fault evidence for the most recent event mre using lidar light detection and ranging data coupled with field mapping we recognized the main trace of the alpine fault north of gaunt creek south island as a north striking fault scarp we enhanced a natural exposure that revealed evidence for repeated late holocene thrust fault movement the north northwest striking fault zone is characterized by a distinct 5 50 cm thick clay fault gouge layer juxtaposing hanging wall bedrock mylonites and cataclasites over unconsolidated late holocene footwall colluvium the bedrock is cut by a strath terrace and overlain by mid holocene ca 5400 calibrated 14 c yr b p alluvial terrace which has been faulted repeatedly and is conformably overlain by undeformed late holocene colluvium and alluvium an unfaulted peat at the base of the scarp is buried by post mre alluvium and yields a calibrated 2 radiocarbon age of a d 1710 1930 which dates the mre as post 1709 our data are consistent with sparse on fault data and validate earlier off fault records that suggest an a d 1717 mre the 1717 event had a moment magnitude of m w 8 1 0 1 based on the 380 km long surface rupture because the fault has not ruptured for 300 yr it is likely approaching the end of its seismic cycle and poses a significant seismic hazard to new zealand

microseismicity in southern south island new zealand implications for the mechanism of crustal deformation adjacent to a major continental transform shallow 25km diffuse crustal seismicity occurs in a zone up to 150km wide adjacent to the southern alpine fault new zealand as a consequence of distributed shear and thickening in the obliquely convergent australian pacific plate boundary zone it has recently been proposed that continental convergence here is accommodated by oblique slip on a low angle detachment that underlies the region and as such forms a previously unrecognized mode of oblique continental convergence we test this model using microseismicity presenting a new 15 month high resolution microearthquake catalog for the southern lakes and northern fiordland regions adjacent to the alpine fault we determine the spatial distribution moment release and style of microearthquakes and show seismicity in the continental lithosphere is predominantly shallower than 20km in a zone up to 150km wide but less frequent deeper microseismicity extending into the mantle at depths of up to 100km is also observed the geometry of the subducted oceanic australian plate is well imaged with a well defined benioff zone to depths of 150km in detail the depth of continental microseismicity shows considerable variation with no clear link with major active surface faults but rather represents diffuse cracking in response to the ambient stress release the moment release rate is 0 1 of that required to accommodate relative plate convergence and the azimuth of the principal horizontal axis of contraction accommodated by microseismicity is 120 15 20 clockwise of the horizontal axis of contractional strain rate observed geodetically thus short term microseismicity independent of knowledge of intermittent large magnitude earthquakes may not be a good guide to the rate and orientation of long term deformation but is an indicator of the instantaneous state of stress and potential distribution of finite deformation thus we show that both the horizontal and vertical spatial distribution of microseismicity can be explained in terms of a low angle detachment model

coastal dunes in westland new zealand provide a record of paleoseismic activity on the alpine fault regional episodes of coastal progradation and dune formation in south westland new zealand have quickly followed all known alpine fault earthquakes since a d 1200 this reflects rapid transport of large postseismic sediment pulses from mountain catchments to the coast and accumulation of this material as a dune ridge this study provides the first demonstration of this link for multiple events over a region the dune sequences also provide evidence of another previously unrecognized regional aggradation event which may be earthquake related and which occurred just 50 yr after a large alpine fault earthquake coastal dunes have great potential for paleoseismic application because the spatial separation of earthquake induced sediment pulses on a prograding coast allows identification of events closely spaced in time coastal dune systems have the potential to improve paleoseismic understanding over the holocene for many plate boundary faults near coastal areas

moment energy stress drop and source spectra of western united states earthquakes from regional coda envelopes we present a new method to estimate stable seismic source parameters such as energy moment and orowan stress drop using regional coda envelopes from as few as one broadband station we use the method to compute path and site corrected seismic moment rate spectra for 117 recent western united states earthquakes empirical green s function corrections were applied to our surface and body wave coda envelope measurements to generate s wave source spectra these source spectra provide stable single station estimates of radiated seismic energy es and seismic moment mo that for common events are in excellent agreement with network averaged estimates obtained using local and regional data teleseismic moment estimates are compatible with our regional results but teleseismic energy estimates appear to be nearly an order of magnitude low we estimated the seismic moment of events ranging between mw 2 2 and 7 3 and energy estimates for which we had measured at least 70 of the total energy generally events above mw 3 3 we use these estimates to examine the behavior of derived parameters such as the orowan stress drop 2 es mo while the earthquakes we studied have a small range in orowan stress drop generally between 0 1 and 20 mpa they show a strong tendency for orowan stress drop to increase with moment approximately as mo0 25 we believe this is a source effect and is not due to inadequate bandwidth or attenuation correction and note that this trend appears to continue for microearthquakes as described in a recent deep borehole study in southern california many of the large high stress drop earthquakes show complexity in their moment rate spectra near the corner frequency and cannot be fit by a simple square model instead above the first corner frequency the spectral decay ranges between f 1 0 and f 1 5 this leads to larger estimates of radiated energy than predicted with a simple square model and has implications for seismic hazard estimation coda envelopes have three main advantages over direct arrivals for estimating seismic moment and energy 1 coda amplitudes vary little with geology and source radiation anisotropy and allow accurate single station applications 2 path corrected coda amplitude measurements can be applied to very large regions allowing a comparison of source parameters throughout the western united states using a common methodology and stations 3 because long period coda can last for hours for large local and regional events it allows the analysis of seismograms with clipped early arrivals

spatial mapping of the b value at mount etna italy using earthquake data recorded from 1999 to 2005 1 the spatial pattern of the b value of the frequency magnitude relation has been analyzed using gridding techniques beneath mount etna italy a regional data set of 2900 events with md duration magnitude 1 5 up to 15 km depth occurring between august 1999 and december 2005 has been used two regions with an abnormally high b value have been found one centered beneath the southern part of the valle del bove above the 6 km below sea level bsl deep basement and the other beneath the summit region 2 km bsl east of the central craters we can infer that these high b value anomalies are regions of increased crack density and or high pore pressure related to the presence of nearby magma storage this interpretation is supported by all the available geophysical evidence such as tomographic studies and geodetic deformation measurements the data set has also been subdivided into five periods corresponding to different phases of volcanic activity 2001 preeruption 2001 eruptive 2002 2003 preeruption 2002 2003 eruptive and 2002 2003 posteruption the minimum magnitude of completeness mc and the b value were computed for each period a volume of anomalously high b values can be observed in each of these periods except for the 2002 2003 preeruption interval this approach has allowed the detection of the transient presence of magmatic intrusions during the various periods evaluated

revealing stratigraphy in ground penetrating radar data using domain filtering a common offset ground penetrating radar profile was collected from a mid continent fluvial environment characterized by sand with discontinuous clay layers signal was separated from coherent noise by a domain filter that exploits local differences in dip between signal and noise this filter proved effective in separating reflections from the direct air wave and from system ringing the processed section locates the base of a pleistocene river channel incised into bedrock and shows a change in a recent position of the river on the basis of radar character the water table which lies at a depth of approximately 2 m is characterized by a continuous reflection an earlier reflection is interpreted as a perched lens of water near the ground surface the predominant frequency of both reflections varies greatly with position along the profile shallow cores taken along the profile provide evidence that grain size in the transition zone from saturated to unsaturated sediments may determine the predominant frequency of the associated radar reflection the domain filter is also successful in separating transition zone reflections from saturated layer boundary reflections that are coincident in arrival time it is possible therefore to determine both grain size in the transition zone and the dip of sediments immediately beneath it even if the reflections from the two are superimposed

potential earthquake triggering in a complex fault network the northern south island new zealand summary a synthetic seismicity computer model of multiple interacting faults has been used to investigate potential earthquake triggering in the alpine marlborough buller fault network northern south island new zealand of particular interest is whether large characteristic earthquakes on the central 300 km long segment of the alpine fault average recurrence time of 240 yr might trigger events to the north and northeast possible temporal clustering of other large events and stress shadows the synthetic seismicity model generates long homogeneous catalogues that sample a wide range of possible stress interactions and stress states allowing statistical analysis the catalogues used here include 1500 central alpine fault events of m 7 8 and approximately 2 000 000 other events of magnitudes down to 4 8 these other events occur on four additional segments of the alpine fault on 30 segments of the major marlborough and buller faults and on 4650 randomly distributed smaller faults the synthetic seismicity model is of the quasi static type governed by the coulomb failure criterion with extensions to better account for rupture propagation and fault healing true rate and state friction and viscoelastic relaxation are not yet included mechanical properties are adjusted so that most events rupture an entire fault segment i e the faults behave characteristically the regional b value of 1 thus arises mainly from the fault size distribution the driving mechanism and fault properties are iteratively adjusted so that the resulting long term slip rates single event displacements and recurrence times match the observed real world values the major results are as follows i large alpine fault earthquakes m 7 8 on the central segment have recurrence times with a broad distribution from 81 to 601 yr average 234 yr ii the regional moment release rate is constant over periods of 1000 yr but is quite variable on scales of a few hundred years iii large events on the central alpine fault will usually propagate at least part way along strike to the northeast past the junctures with the marlborough faults that splay off to the east iv thirty seven per cent of such large alpine fault events lafes will also instantaneously trigger significant activity m 6 5 on one or another of the other major faults here instantaneous means with a 0 to approximately 3 yr delay v characteristic events initiating on other major faults also have a high chance of triggering activity elsewhere vi following the short period of increased risk of triggered events a stress shadow effect predominates probably reflecting the mutually inhibitory nature of parallel strike slip faults and the need for a constant long term moment release rate

source parameters of microearthquakes at mount st helens usa summary we estimate the source parameters for a selection of microearthquakes that occurred at mount st helens in the period 1995 1998 excluding the activity of 2004 september this time period includes the most intense episode of earthquake activity since the last dome building eruption in 1986 october 200 seismograms were processed to obtain seismic moments source radii stress drops and average fault slip the source parameters were determined from the spectral analysis of p waves after correction for attenuation and site effects in particular p wave quality qp and site s factors have been previously calculated in the frequency ranges 2 7 hz and 18 30 hz because it was impossible to perform corrections for qp and s over the whole spectrum we applied a new approach based on the notion of holed spectrum to estimate spectral parameters the term holed spectrum indicates a spectrum lacking corrected spectral amplitude values at certain frequencies we carried out a statistical study to verify that dealing with the holed spectrum does not lead to significant differences in the estimates of spectral parameters we also investigated the dependence of spectral parameters low frequency level corner frequency and high frequency decay on the bandwidth of spectral hole and defined the threshold values for three different spectral models displacement holed spectra corrected by attenuation and site response are then used to determine spectral parameters in order to calculate seismic source parameters seismic moments range from 1017 to 1019 dyne cm source dimensions from 100 to 350 m and average fault slip from 0 003 to 0 1 cm self similarity seems to break down in that stress drops are very low 0 1 1 bars we postulate that seismicity is associated with a brittle shear failure mechanism occurring in a highly heterogeneous material under a relatively low stress regime

investigation of the active celano l aquila fault system abruzzi central apennines italy with combined ground penetrating radar and palaeoseismic trenching summary we studied fault scarps along the northern sector of the celano l aquila fault system in the abruzzi region central apennines up to 9 5 km long 3 m high fault scarp traces mark the slope foot of ridgetop valleys at mt ocre range in order to provide direct evidence of the deformation history of these scarps we initiated geomorphic ground penetrating radar gpr and trenching investigations gpr investigations yielded subsurface stratigraphic features of the scarp zones and determined the locations for trenching sites a total of five trenches were excavated at two different sites structural and stratigraphic analysis of the trench exposures combined with historical considerations showed three faulting events between 5620 bc and 1300 ad the most recent of them occurred after 1690 bc each of these events produced an estimated minimum vertical displacement ranging between 0 3 and 0 5 m our interpretation is that the mt ocre fault branch represents the northernmost surface expression of a single 35 km long seismogenic structure associated with m 7 earthquakes any attempt to estimate the seismic hazard in the area must consider the presence of this important source

density distribution functions and correlations of earthquake parameters abstract the statistical analysis of the source parameters of 9 earthquake sets of different types aftershocks scattered events swarms and of different seismic regions shows that the density distribution function ddf of the linear dimension l of a fault is represented by a negative power law as well as the ddf of the static stress drop and of the scalar seismic moment mo it is then suggested and tentatively verified that also the ddf of the root mean square ground acceleration defined as a function of l and may be represented by a negative power law and that at least in the cases examined it scales like the ddf of it is seen that the variability of the static stress drop is significant from one region to another as is well known but it seems remarkable also in the same seismic region in particular in california varies by several orders of magnitude and in the different sets of events of a given region as observed again for california it is hypothesized that a correlation although weak between the stress drop and the linear dimension of a fault exists and the analyses seem not to contradict that may be a decreasing function of l finally it is suggested that the seismicity of a region may be represented two dimensionally as a function of the ddf of the stress drop and of the linear dimension of a fault instead of the classic b and bo values

the role of earthquakes and climate in the formation of diamictic sediments in a new zealand mountain lake we used itrax xrf magnetic susceptibility grain size and micro ct scanning to provide a facies classification for a late holocene sediment sequence from lake chappa ai in the southern alps new zealand the record contained multiple diamictic layers and our objective was to determine the environmental significance of these deposits clast fabric analysis indicated that the diamicts comprise dropstones transported to the centre of the lake by ice rafting diamicts belonging to facies 1 represent rock falls onto lake ice triggered by earthquakes that produced mmi modified mercalli intensity 8 shaking in the catchment mmi 8 earthquakes may need to occur when the lake has ice cover to produce facies 1 diamicts mmi 8 earthquakes in the ice free season or mmi 7 8 earthquakes may also result in an increased flux of large 1 mm clasts to the centre of the lake but may not produce a facies 1 diamict more work is required to establish the role of climate related processes on the formation of non facies 1 diamicts in lake chappa ai climate change may directly lead to diamict formation by changing lake ice cover and facilitating transport of large clasts by anchor ice or increasing the likelihood of rain on snow events in the spring changing ice cover conditions will also affect how mountain lakes record past earthquake events lakes that are ice free will not produce earthquake diamicts and lakes that have perennial ice cover may produce a single diamict representing multiple earthquakes if the lake becomes ice free a reduction in the duration of winter ice cover will also decrease the probability of capturing primary rockfall deposits from earthquakes additional data such as a diatom or chironomid record from lake chappa ai may help to resolve the contribution of climate processes to diamict formation we should consider the lake chappa ai record as an indicator of minimum earthquake activity until we can disentangle the effects of climate change on non facies 1 diamict formation this study highlights the multiple mechanisms that can lead to diamict formation in mountain lake sediments these processes should always be considered before attributing the presence of diamict deposits to ice rafted debris in a pro glacial lake this is particularly true in seismically active settings where earthquake triggered rockfalls may lead to diamict formation

the significance of heat transport by shallow fluid flow at an active plate boundary the southern alps new zealand fluid flow can influence fault behavior here we quantify the role of groundwater heat advection in establishing the thermal structure of the alpine fault a major tectonic boundary in southern new zealand that accommodates most of the motion between the australian and pacific plates convergence on the alpine fault has rapidly uplifted the southern alps resulting in high geothermal gradients and a thin seismogenic zone a new equilibrium temperature profile from the 818 m deep deep fault drilling project 2b dfdp 2b borehole has been interrogated using one dimensional analytical models of fluid and rock advection models indicate a total heat flux of 720 mw m 2 results from groundwater flow with darcy velocities approximating to 7 8 10 10 m s 1 groundwaters advect significantly more heat than rock advection in the shallow orogen 6 km depth and are the major control on the subsurface temperature field

source attenuation and site parameters of the 1997 umbria marche seismic sequence from the inversion of p wave spectra a comparison between constant qp and frequency dependent qp models 1 the attenuation of p waves the site responses and the source parameters seismic moment corner frequency source dimension of 490 seismic events that occurred during the 1997 colfiorito umbria marche seismic sequence have been inferred from the inversion of p wave velocity spectra the boatwright source model has been assumed to model the source spectra a global nonlinear inversion scheme was developed to avoid any a priori selection of the initial qp and the corner frequency to establish if a frequency dependent qp model fits the data better than a constant qp model two inversion results have been compared application of the akaike information criterion indicates that the constant qp model represents the best compromise between model simplicity and data misfit the station qp values are small in the range of 50 to 200 a one dimensional qp model is obtained by back projecting the inverted t our results indicate both well defined near site attenuation effects at some sites and heterogeneity in the inelastic properties of the crust with the exception of the amplification response at five seismic stations most of the recording sites did not show amplification peaks at particular frequencies the stress drop clearly increases as a function of the seismic moment which indicates a deviation from self similarity whereas it does not show an increase with depth probably owing to the effects of fluid pressurization in the crust a stress drop of about 39 mpa is inferred the relationship between the seismic moment and the local magnitude for p waves has been calibrated

side looking underground radar slur physical modeling and case history a modification of conventional surface ground penetrating radar gpr was conceived tested and successfully applied in the field at brookhaven national laboratory bnl to investigate waste pits the modified gpr method consists of making measurements along a traverse line in a sloping trench with the radar s antenna oriented at an angle of up to 45 from the horizontal the direction of propagation of the electromagnetic field for this configuration is not vertical and the amount of energy scattered from objects that are oriented vertically relative to the energy scattered from horizontal layers is increased this fundamental feature of side looking underground radar slur measurements is illustrated by physical modeling measurements made along parallel trenches that are offset at different distances from a vertically oriented object provides gpr cross sections with a primary plane of investigation that intersects the vertical feature at different depths slur was used at bnl in conjunction with con