the 11 25 88 m 6 saguenay earthquake near chicoutimi quebec evidence for anisotropic wave propagation in northeastern north america on november 25 1988 a magnitude 6 earthquake occurred in the province of quebec canada this earthquake triggered nine digital strong motion instruments in new york and maine at epicentral distances of 200 to 820 km which were installed as part of an effort by the national center for earthquake engineering research nceer to study ground motions and wave propagation in eastern north america we calculate q f at discrete frequencies from 0 6 to 26 hz assuming that geometrical spreading causes a l r0 5 decay in spectral amplitudes of the nine stations four are in the adirondack mountains in new york and three are in eastern maine if we calculate q f for these two clusters of stations separately we obtain higher values for the adirondack stations the quebec adirondack path is along the strike of the predominant structural trends in northeastern north america in the grenville province crust while the quebec maine path is at high angle to the structural grain and crosses the boundary between the grenville and the appalachian provinces we thus have instrumental data in support of earlier observations based on contours of intensity from historic earthquakes seismic wave propagation in northeastern north america is more efficient along the predominantly ne sw striking geological trends we address possible biases due to site effects

micromorphlogy of recent and buried soils in a semi arid region of northwestern india abstract profiles of four recent soils and of eleven soils buried under archaeological sites of known ages were investigated in an area between the ghaggar valley and the northern piedmont of the arawalli hills in northwestern india the principal approach was through study of micromorphology data were also obtained on mineralogies of several size fractions characteristics shared by the recent and buried soils indicate that essentially the same processes operated in their formation the oldest soils are buried under protohistoric sites and thus were formed at least 5000 years ago they are developed on sediments rich in sand sized mica flakes which indicate an alluvial origin others are buried beneath historic sites with ages ranging from 500 b c to 1500 a d these soils and the recent ones have a silt fraction low in mice major features of both buried and recent soils are attributed to biological activity reflected in extensive channeling and additions of excrements throughout profiles local distribution of clay silt and carbonates indicates translocation of these components furthermore the forms of calcitic features indicate modifications of various kinds evidence of biological activity as expressed in characteristics of the soils becomes progressively weaker from older to younger profiles soil development seems to have weakened over that period as well these changes are correlated with the decline with time in the proportions of mica flakes in coarse fractions the decline is attributed to lack of alluvial sedimentation since the protohistoric period and to greater transport and winnowing of sediments by wind we believe this has reduced fertility of the soils formed during the last 4000 years

reply to comment on revisiting the 1872 owens valley california earthquake by susan e hough and kate hutton by william h bakun bakun 2009 argues that the conclusions of hough and hutton 2008 are wrong because the study failed to take into account the sierra nevada attenuation model of bakun 2006 in particular bakun 2009 argues that propagation effects can explain the relatively high intensities generated by the 1872 owens valley earthquake using an intensity attenuation model that attempts to account for attenuation through the sierra nevada bakun 2006 infers the magnitude estimate m w 7 4 7 5 that is currently accepted by national earthquake information center neic

the character and reactivation history of the southern extension of the seismically active clarendon linden fault system western new york state abstract integration of 11 types of data sets enabled us to determine the location character and fault history of the southern extension of the clarendon linden fault system clf in southwestern new york state the data sets utilized include detailed stratigraphic and fracture measurements at more than 1000 sites soil gas anomalies seismic reflection profiles well logs and lineaments on air photos topographic maps landsat and slar images the seismically active clf consists of as many as 10 parallel segmented faults across the fault system the fault segments are truncated by nw striking cross strike discontinuities csds the faults of the clf and intersecting csds form fault blocks that have semi independent subsidence and uplift histories east dipping reflectors in the precambrian basement indicate the southward continuation of thrusts of the intra grenvillian elzevir frontenac boundary zone these thrusts were reactivated during iapetan rifting as normal listric growth faults in ordovician black river to trenton time the southern clf segments experienced a second phase of growth fault activity with faults displaying a cumulative stratigraphic throw of as much as 170 m thrusting on the same east dipping precambrian reflectors typified the clf in taconic post trenton times detailed comparisons among the fault segments show that the fault activity in silurian and devonian times generally alternated between the western and central main faults in late devonian time the fault motion reversed from down on the east to down on the west about the time the appalachian basin axis passed across the clf in its westward migration the deep precambrian faults of the clf were thus reactivated as the appalachian basin developed in acadian times finally the clf thrust fault imaged on seismic line clf 1 offsets all bedrock devonian units thus significant motion occurred along this fault during late acadian or more likely alleghanian time

frequency dependent seismic attenuation in the eastern united states as observed from the 2011 central virginia earthquake and aftershock sequence abstract ground shaking due to earthquakes in the eastern united states eus is felt at significantly greater distances than in the western united states wus and for some earthquakes it has been shown to display a strong preferential direction shaking intensity variation can be due to propagation path effects source directivity and or site amplification in this paper we use s and lg waves recorded from the 2011 central virginia earthquake and aftershock sequence in the central virginia seismic zone to quantify attenuation as frequency dependent q f in support of observations based on shaking intensity we observe high q values in the eus relative to previous studies in the wus with especially efficient propagation along the structural trend of the appalachian mountains our analysis of q f quantifies the path effects of the northeast trending felt distribution previously inferred from the u s geological survey usgs did you feel it data historic intensity data and the asymmetrical distribution of rockfalls and landslides

tectono geomorphic study of the karewa basin of kashmir valley abstract the karewa basin nestled between the pir panjal range and the great himalayan range in northwest india has been studied to understand its tectono geomorphic evolution on the basis of geomorphic indices and morphotectonic parameters supported by the field evidences satellite data topographic maps and digital elevation model dem were used to extract various parameters at various spatial scales four watersheds representative of the entire karewa basin were chosen for detailed studies on the basis of the researchable evidence of the complete sequence of the stratigraphic record and the preservation of geomorphic landscapes the integrated analysis of the geomorphic and morphometric data provides evidence of the relative variations in the tectonic activity among the watersheds geomorphic indices suggest a relatively high degree of tectonic activity along the pir panjal side of the karewa basin this variation in the relative degree of tectonic activity is consistent with the field evidence fault lineament locations and the landscape geometry of the karewa basin based on the results from this study it is suggested that late quaternary climate changes tectonic uplift and erosion of the pir panjal range and changing geometry of the karewa lake have played a key role in the evolution of the geomorphic landscape of the kashmir valley

weathering and clay mineral formation in two holocene soils and in buried paleosols in tadjikistan towards a quaternary paleoclimatic record in central asia abstract the upper part of the karamaydan section tadjikistan shows the most detailed loess paleosol sequence yet known for the brunhes chron and the central and lower parts of the chashmanigar section provide similar detail for most of the matuyama chron to enable paleoclimates to be deduced the primary and secondary minerals in the silt and clay fractions must be determined separately to evaluate the type and intensity of mineral weathering and clay mineral formation to distinguish between inherited and pedogenetically formed clay minerals the original petrographic homogeneity of the parent material from which a soil developed must be established the main sources of pedogenic clay minerals are phyllosilicates in the silt fractions illites and vermiculites are the dominant pedogenetically formed clay minerals in the b or bt horizons of the holocene climaphytomorphic soils and in all paleosols s and pedocomplexes pk in karamaydan and chashmanigar except s xvii in which large amounts of smectites were formed there is little difference in the type and amount of pedogenic clay mineral formation between the holocene soils and the paleosols in the brunhes epoch at karamaydan as well as during most of the matuyama epoch at chashmanigar these results indicate that the climates of the interglacials represented by the b or bt horizons of the buried paleosols of young mid and old pleistocene age were similar to that of the holocene

the 2002 m5 au sable forks ny earthquake sequence source scaling relationships and energy budget 1 we find invariant high stress drops and radiated energies for a sequence of intraplate earthquakes we estimate source parameters of the au sable forks ny earthquake m5 2002 and aftershocks this intraplate earthquake was the largest to occur in eastern north america since 1988 and the largest to be recorded by regional broadband networks we use the empirical green s function egf method and define a set of qualitative and quantitative rules for the selection of egf earthquake pairs and for the quality verification of the obtained egf spectral ratio we use a multitaper code that performs the complex spectral division with minimum frequency leakage and allows transformation back to the time domain to check the validity of the egf event we estimate source parameters for 22 earthquakes m1 m5 in the sequence the median stress drop of 104 mpa using madariaga source model and 19 mpa for a brune model is significantly larger than estimates for interplate earthquakes the lower crustal strain rates and longer fault healing times in intraplate environments may be responsible for this high average value we find constant stress drop between m2 and m5 up to the bandwidth resolution limit 80 hz of the study and no evidence of stress drop breakdown for m2 to m1 earthquakes we find consistently high radiated seismic energy and apparent stress and a median radiated energy to seismic moment ratio of 9 10 5 this is significantly larger than estimates for interplate earthquakes 2 10 5 and consistent with higher stress drops and stronger faults

micromorphological evidence of paleoenvironmental changes in northern cilento south italy during the late quaternary abstract three representative soil profiles developed during the late quaternary in northern cilento south italy were studied by optical microscopy and sem eds observation of thin sections to examine soil features as evidence for past climatic fluctuations two of the profiles are polygenetic and the third monogenetic all these have a clear interglacial imprint whereas the polygenetic profiles also contain other features which can be related to periglacial conditions during the stadial glacial periods although in midlatitude coastal areas all the paleosols show a strong marine influence during development which probably resulted from windblown processes or submergence during past interglacial phases

micromorphological investigations of the late quaternary loess paleosol sequences of the kashmir valley india abstract the loess paleosol sequences of the karewa group preserve a valuable repository of the late quaternary climatic changes and the landscape evolution history of the karewa basin of kashmir valley in their lithological and pedogenic records three representative loess paleosol sections at shankerpora sp khan sahib ks and pattan pt localities were chosen for detailed lithostratigraphic fieldwork and micromorphological observations of thin sections lithostratigraphic analysis revealed lateral and vertical variation in thickness and number of paleosol profiles from south west to north west of the karewa basin suggesting the availability of land surface for periodic loess deposition the sp section is marked by 6 sp s6 s7 s8 s9 s10 s12 ks section by 3 ks s2 s4 s5 and pt section by 2 pt s1 s3 thick mature paleosol profiles theses paleosols have well developed ah and btk horizons representing prolonged land surface stability when pedogenic processes outpace loess deposition on the other hand comparatively thin to thick paleosol profiles represent weak to moderate pedogenic maturity indicating short stratigraphic breaks with rapid loess deposition micromorphological observations of thin sections suggested that clay illuviation and caco3 accumulation have operated within the paleosol profiles caco3 features are often associated with clay coatings suggesting decalcification of carbonates followed by clay illuviation pedogenic caco3 probably resulted from the precipitation of the soil solution near the average depth of wetting front the pedogenic caco3 illuvial clay mottles iron manganese features pedal microstructure and blocky aggregates reveal variation in the pedogenic maturity among and within the loess paleosol sections the morphological both micro and macro morphological attributes of loess paleosols suggest variation of climatic conditions during the late quaternary period in the karewa basin of kashmir valley india

the plio pleistocene geologic and climatic record of the kashmir valley india a review and new data abstract the kashmir valley located in the northwestern himalayas provides an intermontane valley fill comprising unconsolidated fluvio lacustrine sediments of more than a km thickness datable at 4 myr these sediments have been investigated for the last 7 years under an interdisciplinary multi agency project using a variety of proxy climatic data techniques and other analyses to decipher climatic change as a result of this study a variety of proxy climatic data from a long continental record is available now from northernmost south asia in this paper we briefly review the lithostratigraphic and chronologic framework of the sediment profile and proxy climatic data based on flora fauna stable isotopes pedology mineral magnetics and sedimentology lastly the climatic events are put in an absolute time frame for comparison with the global climatic trends the chronology is based on 14c thermoluminescence tl palaeomagnetic and fission track techniques

using microtremors to assess potential earthquake site response a case study in flushing meadows new york city abstract we have used portable 5 sec period seismometers to record ambient noise across a glacially cut valley filled with unconsolidated holocene sediments the valley located in flushing meadows new york city is surrounded by a densely populated urban environment microtremors were recorded at several sites on and adjacent to the valley while some raw spectra of valley site microtremors exhibit no predominant peaks spectral ratios taken with respect to recordings made at a reference station outside the valley show a sharp peak near 0 8 hz a secondary peak near 2 4 hz is also visible in some of the spectral ratios the frequency of the predominant peak remains constant across the valley width while the relative amplitude decreases systematically from a maximum at the valley center to background levels near the valley edge resonant frequencies predicted by one dimensional modeling of the valley center site response show excellent agreement with observations the 0 8 hz spectral ratio peak is interpreted as the fundamental resonance mode and the 2 4 hz peak is interpreted as the first harmonic of the region above the base of an organic clay layer observed in borehole data the amplification factors implied by the observed spectral ratios are unrealistically high up to 100 which can be attributed to the close proximity of microtremor sources an experiment involving the use of a pile driver source located outside the valley was also performed signals obtained at valley sites during times when the pile driver was in operation show a two fold increase in the amplitude of a spectral peak when compared to signals obtained when the pile driver was turned off this observation gives additional evidence that observed spectral peaks represent soil layer resonances in the valley based on the results of this and other previous studies we conclude that easily obtained microtremor measurements can contribute valuable microzonation and site response information to a study of regional earthquake hazard

revised magnetostratigraphy and characteristics of the fluviolacustrine sedimentation of the kashmir basin india during pliocene pleistocene 1 the pliocene pleistocene karewa group sediments of the kashmir basin india provide an important continental archive for past climatic reconstruction the present study reevaluates the magnetic polarity stratigraphy and the nature of the depositional environment at a 440 m thick section along romushi river near pakharpur 33 48 50 n 74 45 54 e magnetic remanences are predominantly carried by ti rich titanomagnetite and magnetite we identified eight normal and eight reversed polarity magnetozones in this succession ranging between 4 40 and 0 77 ma the polarity sequence includes the new identification of the cochiti and the mammoth and their preceding and succeeding reversed normal as well as the jaramillo subchrons anisotropy of magnetic susceptibility data suggest the existence of northeast and northwest flowing fluvial system before 4 18 ma indicating the pir panjal range at the southwest as the sediment source area following this the valley was under the influence of fluviolacustrine environment between 4 18 and 0 77 ma our results suggest relatively strong flow velocity toward the northeast during the upper gilbert gauss and lower and middle matuyama chrons 4 18 1 07 ma in the upper matuyama chron 1 07 ma the prevailing paleocurrent direction in the basin changed toward the northwest with a reduced flow velocity indicating the emergence of the ancestral jhelum river on the basis of the magnetic polarity chronology the sediment accumulation rate indicates a very low value of 4 6 cm kyr 1 before 1 95 ma to 33 cm kyr 1 between 1 95 and 1 77 ma and 23 cm kyr 1 after 1 77 ma we attribute temporal changes in sedimentation rate to the interplay between climate predominantly westerlies and tectonics pulsating pir panjal uplift

a novel technique for measuring lg attenuation results from eastern canada between 1 to 10 hz spectral amplitudes of regionally recorded lg waves are studied in detail between 0 6 and 10 hz using vertical component velocity seismograms of the eastern canada telemetered network stations and a supplementary seismic research observatory type station at glen almond gac quebec we find that the site responses vary among these stations by more than a factor of 3 within the frequency range of interest furthermore they are found to be strongly frequency dependent consequently it is essential that they be taken into consideration in studies of lg wave attenuation and lg source spectra of regionally recorded seismic events we present a new method of measuring interstation surface wave attenuation which is closely related to the conventional two station method while retaining all the desirable features of the conventional two station method the new technique which we will call the reversed two station method allows simple direct one parameter determination of the lg wave attenuation from sparse spectral data in a manner unaffected by station site effects and associated instrument error the reversed two station method is successfully tested over weakly attenuating short 53 to 210 km interstation paths in eastern canada a difficult experimental condition by normal standards the lg attenuation coefficient 0 6 to 10 hz in eastern canada is found to be frequency dependent and of the form f 0 0008 f 0 81 km 1 at higher frequencies the lg attenuation appears to be essentially frequency independent this latter finding is preliminarily interpreted as evidence that regionally recorded lg waves in the canadian shield are as in the case of lg waves propagating through the structurally complex appalachian province contaminated by the high frequency coda of sn waves the lg contamination over the shield paths becomes severe starting at 14 hz twice the frequency above which the lg signal propagating over the appalachian province becomes completely dominated by non lg arrivals

pedosedimentary development and palaeoenvironmental significance of the s1 palaeosol on the northeastern margin of the qinghai xizang tibetan plateau the s1 pedocomplex correlated to oxygen isotope stage 5 of the ocean cores has been traced west of the loess plateau on to the extreme northeastern margin of the qinghai xizang tibetan plateau in china detailed micromorphological analysis of closely spaced thinsections from the pedocomplex at this site provides the basis for reconstruction of the sequence of pedosedimentary processes and associated palaeoenvironmental changes occurring during this time interval the six pedosedimentary stages identified are interpreted in terms of temporal variations in depositional rates size of particles transported and availability of moisture for pedogenic alteration as determined by changing balances in dominance of winter and summer monsoonal forces two main soil forming intervals are identified the more extensive of the two in terms of resultant pedological features reflects pedogenic alteration at a relatively stable land surface under a semi arid climate during the later part of pedosedimentary stage 2 the other main period corresponds to pedosedimentary stages 4 and 5 when leaching and bioturbation processes were active at aggrading surfaces leading to development of an accretionary unit without clear differentiation of horizons pedosedimentary stages 1 3 and 6 were characterised mainly by rapid rates of coarse loess accumulation with synsedimentary modification restricted to surface slaking and crust formation and minor localised redistribution of calcite

seismological constraints on source properties of the mb 4 0 1985 ardsley new york earthquake a characteristic rupture on october 19 1985 a magnitude 4 0 earthquake occurred in southern westchester county new york approximately 30 km north of central manhattan barstow et al 1988 concluded that this earthquake consisted of two sub events with the larger sub event occurring 0 6 s after the first one we present analysis of data for the main shock as well as aftershocks and foreshocks which were recorded on the new york state seismic network because this data set includes a range of source magnitudes from less than 2 to 4 recorded for virtually identical source receiver pairs an empirical green s function technique can be used to study the source characteristics of the larger events the corner frequency of the main shock and an attenuation parameter t are resolved from the initial portion of the seismogram at station pal in palisades new york 8 km northwest of the epicenter spectra of small foreshocks and aftershocks can then be corrected for attenuation using t following an iterative procedure it is then possible to make reliable determinations of seismic corner frequency for these events several conclusions are obtained 1 the spectrum of the first subevent in the main shock can be well modelled by a brune spectrum from 1 to 10 hz with a corner frequency of 7 1 hz at higher frequencies the source spectrum contains sharp peaks which do not fit an omega square model and may reflect complexities in the rupture process 2 the average stress drop of the sequence is 205 bars the stress drop of the main event is 540 bars but no stress drop dependency on moment is resolved over the magnitude range 1 8 4 0 3 attenuation parameters t are obtained for the 8 km northwestward path from ardsley to palisades and for a 52 km westward path to a station in the hudson highlands and their similarity suggests an increase of q with depth 4 assuming that the two main shock sub events did not rerupture the same area but were contiguous a maximum rupture dimension is 440 680 m the rupture diameter of the largest aftershock mb 3 is determined to be approximately 320 meters the combined rupture for the sequence inferred from spectral methods is consistent with the size of the rupture inferred from the area surrounded by the early aftershocks 700 m diameter the rupture dimension of the ardsley sequence may be characteristic of the dobbs ferry fault and other seismogenic faults in the manhattan prong which are segmented with characteristic dimensions of 0 5 2 km seeber and dawers 1989 assuming that the range of stress drops in the ardsley sequence is also characteristic of the manhattan prong this range of dimensions corresponds to a range of characteristic magnitudes between mb of 3 3 and 5 5 we note that this magnitude range encompasses the five largest known earthquakes in the new york city seismic zone the 1985 ardsley main shock and events in 1737 1783 1884 and 1895

source spectra for the 1988 saguenay quebec earthquakes abstract source spectra are obtained for the 1988 saguenay quebec earthquake m n 6 5 its foreshock m n 4 8 and largest aftershock m n 4 1 using recordings from analog and digital seismographs on rock sites at epicentral distances from 40 to 700 km the source spectra of the foreshock and the aftershock are well matched by a single corner frequency 2 model with seismic moments of 2 2 10 22 and 2 2 10 21 dyne cm respectively and a stress parameter of 65 bars for both events by contrast the spectrum of the mainshock differs dramatically from this simple shape a stress parameter of 500 bars is required to match the observed high frequency amplitudes using the seismic moment determined from teleseismic observations as a constraint this single corner frequency model however overestimates amplitudes at frequencies near 1 hz by a factor of about 2 the relative radiation of short and long period energy for the mainshock is inconsistent with that from other intraplate earthquakes the fore and aftershocks appear typical in this regard the extraction of source spectra from the regional data required a careful examination of attenuation azimuthal variations were observed with the attenuation being most severe to the southeast normal to the st lawrence valley and the dominant structural grain of the region the st lawrence river coincides in part with the boundary between the grenville and appalachian tectonic provinces and the difference in attenuation may be related to the difference in tectonic province the distribution of data however makes it difficult to obtain good estimates of the attenuation in each province lumping the data from both provinces and the three earthquakes together results in an anelastic attenuation factor given by q 755 f 0 5 for frequencies f from 0 6 to 18 hz using data at distances r beyond 100 km from the sources and assuming 1 r geometrical spreading this attenuation is similar to that obtained in a number of other studies in the general area three component recordings were available at a few stations and from these the following frequency dependent ratio of horizontal to vertical motion was obtained hiv 1 14 0 118 f 0 00638 f 2 for frequencies from 0 2 to 15 hz different methods of correcting observations for attenuation in order to derive source spectra were examined source spectra derived by simple regression analyses of observed data assuming a uniform medium are very similar to those based on a more complicated synthetic seismogram correction which accounts for wave propagation in a layered earth

scattering of high frequency surface waves in scotland high frequency 5 hz coda waves for velocities of arrival less than 3 km s recorded on vertical component instruments and generated from a local earthquake in scotland are analyzed to ascertain their cause the adaption of existing velocity models and scattering from near surface irregularities in scotland such as mountains and lochs are considered as possible causes of the observed behavior the former mechanism is not feasible as it implies a significant alteration of the velocities in the upper 2 km crust contradicting previous seismic surveys in the area an analysis of the effects of scattering is performed using a formalism derived from the born approximation the scattered wave field is computed for interactions between first six rayleigh and love modes the general character of the synthetic seismograms for these scattered waves agrees with the observations on a qualitative basis the apparent absence of the fundamental mode energy from the records is also explained by the synthetic seismograms the calculations imply that scatterers with a scale length of less than 300 m are applicable to these data from the northernmost stations but around 2 km for the more southern areas it is thought that the scale length relates to the size of a region on the slopes of the mountains or lochs where there is a sharp gradient this study emphasises the effectiveness of linear scattering theory in accounting on a qualitative basis for many of the observed features of the apparently complex coda waves

the information content of high frequency seismograms and the near surface geologic structure of hard rock recording sites due to hardware developments in the last decade the high frequency end of the frequency band of seismic waves analyzed for source mechanisms has been extended into the audio frequency range 20 hz in principle the short wavelengths corresponding to these frequencies can provide information about the details of seismic sources but in fact much of the signal is the site response of the nearsurface several examples of waveform data recorded at hard rock sites which are generally assumed to have a flat transfer function are presented to demonstrate the severe signal distortions includingfmax produced by near surface structures analysis of the geology of a number of sites indicates that the overall attenuation of high frequency 1 hz seismic waves is controlled by the whole path q between source and receiver but the presence of distinctfmax site resonance peaks is controlled by the nature of the surface layer and the underlying near surface structure models of vertical decoupling of the surface and nearsurface and horizontal decoupling of adjacent sites on hard rock outcrops are proposed and their behaviour is compared to the observations of hard rock site response the upper bound to the frequency band of the seismic waves that contain significant source information which can be deconvolved from a site response or an array response is discussed in terms offmax and the correlation of waveform distortion with the outcrop scale geologic structure of hard rock sites it is concluded that although the velocity structures of hard rock sites unlike those of alluvium sites allow some audio frequency seismic energy to propagate to the surface the resulting signals are a highly distorted limited subset of the source spectra

an empirical study of earthquake source spectra for california earthquakes we generalize source path and site effects for california earthquakes as functions of magnitude and distance based on regression analysis of 1000 fourier acceleration spectra from 43 california earthquakes in the moment magnitude range from 4 4 to 7 4 recorded at rupture distances from 1 to 200 km empirically derived source spectra for california earthquakes are generally inconsistent with the spectral shape implied by a brune omega squared point source model this is manifested by magnitude and frequency dependence of the brune model parameters for ex ample the brune stress parameter that best matches the data at high frequencies decreases from a value of about 120 bars at m5 5 to a value near 50 bars at m7 5 at frequencies below 1 hz though source spectra have much lower spectral ampli tudes than predicted by the brune point source model for these values of stress this discrepancy grows with increasing magnitude finite fault simulations indicate that this is a consequence of the breakdown of the validity of the point source approxi mation for large ruptures a stochastic finite fault model in which the fault is dis cretized as a number of subfaults each of which is represented by a brune omega squared point source correctly matches the observed spectral shapes and amplitudes the spectral decay parameter kappa representing average near surface attenuation of high frequency motion at rock sites increases with increasing magnitude from values near 0 035 sec at m5 5 to 0 050 sec at m7 5 magnitude dependence of kappa may be interpreted as evidence of nonlinearity for typical california sites subjected to strong ground motion comparisons of our empirical source spectra for california to corresponding spec tra for eastern north america suggest that the spectral amplitudes are similar in the two regions for low frequency motions f 2 hz for m5 5 f 0 5 hz for m7 5 for equivalent crustal conditions the eastern events appear to have enhanced high frequency near source amplitudes relative to the california events this is particularly pronounced for large magnitude earthquakes

an assessment of the impact of the 2003 epri ground motion prediction models on the usgs national seismic hazard maps ground motion attenuation relations have an important impact on seismic hazard analyses ground motion modeling is particularly sensitive to assumptions about wave propagation attenuation crustal q and geometrical spreading as well as source and site conditions studies of path attenuation from earthquakes in eastern north america ena provide insights into the appropriateness of specific attenuation relations an electric power research institute epri 2003 2004 study combines published ena ground motion attenuation relations into four model forms single corner double corner hybrid empirical and finite fault when substituted in the u s geological survey 2002 national seismic hazard maps for the five ena relations originally used in those hazard calculations the epri 2003 relations predict similar ground motions and hazard at short periods 0 5 sec relative to the 2002 national maps a major reason for this difference is due to the crustal seismic wave attenuation model assumed in a few of the ena relations combined into the epri 2003 2004 models although appropriate differences in geometrical spreading models among ena relations can also be significant a few ena relations have 1 hz q values q that are below the epri 1993 consensus range for q when coupled with a geometrical spreading of r 0 5 the epri 2003 2004 single corner relation is strongly influenced by the inclusion of ena relations with assumed q below the epri 1993 range which explains much of the discrepancy in predictions at longer periods

isotopic and micromorphological studies of late quaternary loess paleosol sequences of the karewa group inferences for palaeoclimate of kashmir valley abstract pedogenic carbonates widespread in paleosols throughout the geological ages have been widely used to infer climatic conditions and vegetation type during their formation they are ubiquitous and widespread in the late quaternary loess paleosol sequence of the kashmir valley mostly in the form of carbonate nodules in the present study pedogenic carbonates are studied to analyze trends in the stable isotopic composition of carbonate nodules across three well developed loess paleosol sections in the kashmir valley the stable carbon isotopic 13 c analysis reveals a gradual increase of the c 4 vegetation towards the top of the sections the development of c 4 plant biomass towards the top of sections possibly reflects water stress and or reduced atmospheric pco 2 and increasing aridity the oxygen 18 o isotopic analysis reveals little variation with the values ranging from 6 37 to 7 75 reflecting stable climatic conditions during the development of pedogenic carbonate nodules the use of geospatial data including digital elevation model dem and landsat tm remote sensing imagery have added morphological characterization of the topographic and landform features observed in the area the tectonic uplift of the pir panjal range variation in the geometry of karewa basin and the slope gradient have played a key role in the spatial variation of loess paleosol sequences in the valley the late quaternary climate changes deposition of loessic sediments formation of the interbedded paleosol profiles and the subsequent denudation processes have resulted in the present day typical geomorphic landscape of the kashmir valley the micromorphological analysis of loess paleosol horizons reveals cold arid to semi arid climatic conditions prevailed during the late quaternary in the valley

mafic gneissic complex batholithic root in the southernmost sierra nevada california a mafic complex of hornblende rich gneissic to granoblastic amphibolite to granulite grade metamorphic rocks and associated mafic to felsic magmatic rocks is exposed over an area of some 300 km2 in the southernmost sierra nevada the mafic complex probably reflects a deeper exposed crustal level than is represented by the dominantly granitic terrane of the sierra nevada batholith to the north and it may be the upper part of the root zone and metamorphic substrate of the sierra nevada batholith xenoliths of gneiss amphibolite and granulite from subbatholithic levels transported upward and preserved in volcanic rocks in the central sierra nevada are possible analogues of some of the rocks of the southernmost sierra nevada mafic complex

attenuation of high frequency shear waves in the crust measurements from new york state south africa and southern california we compare the attenuation of high frequency 3 30 hz shear waves for crustal paths in new york state south africa and southern california over source receiver distances of about 10 400 km the data consist of digital recordings of s waves 5 100 km and lg waves 100 400 km produced by earthquakes we use a coda normalization method to remove the effects of site amplification and source excitation from the amplitudes of the s and lg waves over the entire distance range studied 10 400 km the amplitude decay of 3 hz shear wave energy is considerably less for the tectonicaily stable areas of new york and south africa than for the tectonicaily active region of southern california high frequency 30 hz s wave attenuation is significantly less for new york and south africa than for southern california for distances between 15 and 90 km we parameterize the decay with distance r of coda normalized shear wave amplitudes with a frequency independent q and geometrical spreading exponent where geometrical spreading is proportional to r for new york state the s wave amplitude decay 3 30 hz is well described by a frequency independent q of 2100 330 490 and of 1 3 0 1 the decay of lg wave amplitudes from 3 to 15 hz in the new york state region is fit with a frequency independent q of 1600 280 330 of 0 70 0 2 the s wave amplitudes 3 30hz in south africa yield a q of 1500 190 380 and of 1 3 0 1 fixing the geometrical spreading at r 0 5 produces an lg wave q estimate at 3 hz in south africa of 360 50 80 this lg wave q is low considering that south africa is a cratonic tectonicaily stable area the s wave amplitudes from southern california are described with a frequency independent q of 800 150 240 and a large geometrical spreading exponent of of 1 9 0 2 we find an lg wave q at 3 hz of 260 30 for southern california after constraining the geometrical spreading at r 0 5

argillic horizon development in calcareous soils of arid and semiarid regions of southern iran abstract ten representative pedons with argillic horizons from southern iran were selected for micromorphological and mineralogical study they were classified as haploxeralfs haplustalfs argixerolls argiustolls and argigypsids with thermic hyperthermic and mesic temperature regimes some of the argillic horizons were probably formed in a less arid previous climate during which carbonate migrated through the profile thus allowing clay to illuviate into deeper horizons thin sections showed few to no clear clay coatings in argillic horizons with greater clay content where shrink swell has disrupted them clay coatings superimposed on carbonate coatings and in turn covered by calcite indicate recalcification calcite depletion pedofeatures were the most striking features in these soils sodium may have played an important role in the dispersion of clay and formation of argillic horizons within two of the pedons studied a micromorphological index of soil evolution in highly calcareous arid and semiarid conditions is proposed it correlates with the content of free fe2o3 fedcb in fine earth the colour index the clay illuviation index and the smectite chlorite illite ratio the index can be useful for correlation of soils with argillic horizons formed on highly calcareous parent material in different landscape units new subgroups of haploxeralfs and argiustolls are suggested for inclusion in soil taxonomy based on the properties of some of the studied profiles

palaeoclimatic changes deduced from 13c 12c and c n ratios of karewa lake sediments india most long palaeoclimatic records based on isotope studies have come from deep sea cores however in order to obtain information on regional climatic variations it is essential to study continental deposits the chief limitation has been the lack of well preserved datable geological records with the exception of cave formations we report here values for the stable carbon isotope ratio 13c 12c and the elemental carbon to nitrogen c n ratio of the organic fraction of the palaeomagnetically and radiometrically dated pleistocene karewa lake sediments from kashmir india together the two ratios which are anticorrelated provide an excellent marker of the source of organic matter in the lake the karewa sediments indicate at least three major episodes of shallower than normal levels these episodes of shallow lake levels and hence a cold dry climatic regime are broadly correctable with deep sea records

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

revisiting the 23 february 1892 laguna salada earthquake according to some compilations the laguna salada baja california earthquake of 23 february 1892 ranks among the largest earthquakes in california and baja california in historic times although surface rupture was not documented at the time of the earthquake recent geologic investigations have identified and mapped a rupture on the laguna salada fault that can be associated with high probability with the 1892 event mueller and rockwell 1995 the only intensity based magnitude estimate for the earthquake m 7 8 was made by strand 1980 based on an interpretation of macroseismic effects and a comparison of isoseismal areas with those from instrumentally recorded earthquakes in this study we reinterpret original accounts of the laguna salada earthquake we assign modified mercalli intensity mmi values in keeping with current practice focusing on objective descriptions of damage rather than subjective human response and not assigning mmi values to effects that are now known to be poor indicators of shaking level such as liquefaction and rockfalls the reinterpreted isoseismal contours and the estimated magnitude are both significantly smaller than those obtained earlier using the method of bakun and wentworth 1997 we obtain a magnitude estimate of m 7 2 and an optimal epicenter less than 15 km from the center of the mapped laguna salada rupture the isoseismal contours are elongated toward the northwest which is qualitatively consistent with a directivity effect assuming that the fault ruptured from southeast to northwest we suggest that the elongation may also thus reflect wave propagation effects with more efficient propagation of crustal surface lg waves in the direction of the overall regional tectonic fabric

regionalization of crustal coda q in the continental united states a contour map of crustal q sub 0 values for the entire united states is presented based on a scattering model to explain the coda waves of local and near regional earthquakes these coda q sub 0 values are in good agreement with q of lg waves data are obtained from over 250 local earthquakes with most magnitudes between 3 0 and 5 0 recorded by 25 wwssn and 27 lrsm stations throughout the continental united states these two sets of data provide a range of frequencies from 0 5 to 3 5 hz a frequency dependence of q is observed in the range of frequencies considered a power law dependence of the form q q sub 0 f f sub 0 sup eta is assumed the value of frequency dependence eta is found to be maximum in the tectonically active western united states and least in the stable regions of the central and south central united states the lowest q sub 0 values are obtained in the western united states with values ranging from 140 to 200 in the coastal plains average crustal q sub 0 values for the basin and range province vary from 200 to 300 increasing gradually to 400 in the colorado plateau region q sub 0 valuesmore in the columbia plateau vary from 200 to 400 q sub 0 values increase very rapidly along the central and southern rocky mountains from 400 to 800 east of the rocky mountains q sub 0 values increase gradually in the interior plains to a maximum value of around 1300 in the mississippi embayment region farther east q sub 0 values decrease gradually to an almost constant value of 1000 along the appalachian mountains coastal regions of eastern and northeastern united states have a crustal q sub 0 value between 900 to 700 regions of north central and gulf coastal plains show low q sub 0 values ranging from 600 to 400 and less the source factor b f sub p a measure of the intensity of scattering was obtained for several different regions of the continental united states regions of high q sub 0 values exhibit low intensity of scattering less

revisiting the 1872 owens valley california earthquake the 26 march 1872 owens valley earthquake is among the largest historical earthquakes in california the felt area and maximum fault displacements have long been regarded as comparable to if not greater than those of the great san andreas fault earthquakes of 1857 and 1906 but mapped surface ruptures of the latter two events were 2 3 times longer than that inferred for the 1872 rupture the preferred magnitude estimate of the owens valley earthquake has thus been 7 4 based largely on the geological evidence reinterpreting macroseismic accounts of the owens valley earthquake we infer generally lower intensity values than those estimated in earlier studies nonetheless as recognized in the early twentieth century the effects of this earthquake were still generally more dramatic at regional distances than the macroseismic effects from the 1906 earthquake with light damage to masonry buildings at nearest fault distances as large as 400 km macroseismic observations thus suggest a magnitude greater than that of the 1906 san francisco earthquake which appears to be at odds with geological observations however while the mapped rupture length of the owens valley earthquake is relatively low the average slip was high the surface rupture was also complex and extended over multiple fault segments it was first mapped in detail over a century after the earthquake occurred and recent evidence suggests it might have been longer than earlier studies indicated our preferred magnitude estimate is mw 7 8 7 9 values that we show are consistent with the geological observations the results of our study suggest that either the owens valley earthquake was larger than the 1906 san francisco earthquake or that by virtue of source properties and or propagation effects it produced systematically higher ground motions at regional distances the latter possibility implies that some large earthquakes in california will generate significantly larger ground motions than san andreas fault events of comparable magnitude

active tectonic studies in the united states 1987 1990 the techniques and instrumentation used in active tectonic studies are discussed and recent results are reviewed it is suggested that a critical mass of data on several particular regions has been accumulated making possible critical debates and attempts to assess earthquake hazards particular attention is given to studies of the pacific northwest region basin and range deformation studies and distributed deformation and hidden earthquake sources also included is a comprehensive bibliography for the period

regional spectral analysis of three moderate earthquakes in northeastern north america abstract we analyze fourier spectra obtained from the horizontal components of broadband and accelerogram data from the 1997 cap rouge the 2002 ausable forks and the 2005 riviere du loup earthquakes recorded by canadian and american stations sited on rock at hypocentral distances from 23 to 602 km we check the recorded spectra closely for anomalies that might result from site resonance or source effects we use beresnev and atkinson s 1997 near surface velocity structures and boore and joyner s 1997 quarter wave method to estimate site response at hard and soft rock sites we revise the street et al 1975 model for geometrical spreading adopting a crossover distance of r o 50 km instead of 100 km we obtain an average attenuation of q 410 25 f 0 50 0 03 for s l g surface waves with ray paths in the appalachian and southeastern grenville provinces we correct the recorded spectra for attenuation and site response to estimate source spectral shape and radiated energy for these three earthquakes and the 1988 m 5 8 saguenay earthquake the brune stress drops range from 130 to 419 bars and the apparent stresses range from 39 to 63 bars the corrected source spectral shapes of these earthquakes are somewhat variable for frequencies from 0 2 to 2 hz falling slightly below the fitted brune spectra

the 25 november 1988 saguenay quebec earthquake source parameters and the attenuation of strong ground motion the saguenay earthquake of 25 november 1988 occurred close to the southern margin of the saguenay graben in southern quebec it was caused by almost purely dip slip faulting centered at a depth of 26 km with a p axis oriented northeast southwest this faulting mechanism is similar to those of the larger historical earthquakes in eastern north america but the focal depth is substantially greater than all but one of these events the seismic moment estimated from regional pni waves and teleseismic long period body waves is 5 10 24 dyne cm corresponding to a moment magnitude of 5 8 the source duration of the earthquake is estimated to be 1 8 sec corresponding to a stress drop of 160 bars which is not significantly higher than the average stress drop of 120 bars estimated from previous large earthquakes in eastern north america in order to simultaneously match the recorded ground motion amplitudes of strong motion acceleration strong motion velocity and teleseismic short period and long period body waves it is necessary to use a source function having a complex shape that implies the presence of asperities and larger local stress drops the large set of strong motion recordings of the saguenay earthquake has been used to validate a procedure for estimating strong ground motion attenuation based on a simple wave propagation model the most important feature of the recorded strong motions is that their peak amplitudes do not decay significantly with distance inside 120 km but then decay abruptly beyond 120 km profiles of recorded accelerograms with absolute times indicate that at distances beyond 64 km the peak ground motions are due to strong postcritical reflections from velocity gradients in the lower crust the principal shear wave arrivals and the variation of their peak amplitudes with distance were reproduced in synthetic seismograms generated using a regional crustal structure model the critical distances for the postcritical reflections were short because of the deep focal depth of the event causing the elevation of ground motion amplitudes out to 120 km similar studies of earthquakes in other regions of eastern north america indicate that the strength of the postcritical reflections and the distance ranges over which they are dominant are controlled by the focal depth and crustal structure regional variations in crustal structure thus give rise to predictable regional variations in strong ground motion attenuation

micromorphology and genesis of paleosols in the luochuan loess section china pedostratigraphic and environmental implications the loess paleosol sequence in the well known potou section near luochuan covers the entire pleistocene back to 2 5 ma in a much more complete sequence than any known from europe or north america to deduce a record of the pleistocene climatic history an understanding of the genesis of the paleosols is important main diagnostic features normally observable in surface soils have disappeared in the case of fossil soils therefore micromorphology is of outstanding importance because it enables the reconstruction of original properties and polygenetic soil development especially in pedocomplexes the upper part of the loess paleosol sequence can well be compared with the 18o record shown in the specmap curve of the brunhes epoch although the sequence of paleosols shows partly an even more detailed record of cold and warm stages and allows more specific informations regarding the paleoclimate of the interglacial periods cf fig 2 the last four paleosols represented by the s1 pedocomplex the upper part of the s2 and the s3 are genetically well comparable with the natural holocene soil indicating a similar climate with a tall grass steppe vegetation the s6 is a steppe soil also whereas the five soils of the s4 the s5 complex and the s7 are forest soils indicating more moist and partly warmer interglaciations than the holocene the loess paleosol sequence of the matuyama epoch seems to give more paleoclimatic informations than the deep sea cores known so far the lishi loess below the b m boundary down to 84 m in the section contains two more soils s11 and s13 which are developed under steppe vegetation in interglaciations similar to the present one and four forest soils the s8 complex the upper soil of the s9 and the s10 indicating again more moist interglaciations than the holocene most of the numerous soils in the wusheng loess are probably formed synsedimentarily as alternation of soil formation and addition of loess the red clay at the basis consists of four intensively developed but truncated paleosols the parent material of at least the lower part must be regarded as pliocene loess