geophysical and geological evidence of neotectonic deformation along the hovey lake fault lower wabash valley fault system central united states high resolution seismic shear wave reflection profiles were collected over a segment of the hovey lake fault a known paleozoic fault within a system of faults in the southernmost wabash river valley of the central united states although the fault zone called the wabash valley fault system lies in an area of recognized prehistoric and contemporary seismicity the seismogenic potential of this system remains poorly defined consequently the objectives of this study are to assess the hovey lake fault one of the more prominent fault strands in the system for neotectonic reactivation and if present collect sediment samples for dateable material from the disrupted horizons to provide an age constraint for the movement the resultant stacked profiles show high angle deformation extending above the paleozoic bedrock and into upper quaternary sediment time displacement calculations from the data show approximately 10 5 m of offset on the top of bedrock horizon and 2 m of inverted displacement along the earliest arriving quaternary soil reflector preliminary correlative coring and carbon 14 age dating of a disrupted soil horizon located 7 7 m below ground surface suggest fault movement at this site as late as approximately 37 000 years before present

late quaternary chronostratigraphic framework of terraces and alluvium along the lower ohio river southwestern indiana and western kentucky usa abstract the lower ohio river valley is a terraced fluvial landscape that has been profoundly influenced by quaternary climate change and glaciation a modern quaternary chronostratigraphic framework was developed for the lower ohio river valley using optically stimulated luminescence osl dating and allostratigraphic mapping to gain insights into the nature of fluvial responses to glacial interglacial stadial interstadial transitions and holocene climate change river deposits t0 youngest to t7 oldest were mapped along a 75 km reach of the lower ohio river and were dated using 46 osl and 5 radiocarbon samples the examination of cores combined with osl and radiocarbon dating shows that fluvial sediments older than marine oxygen isotope stage mis 2 are present only in the subsurface aggradation during mis 6 illinoian glaciation filled the valley to within 7 m of the modern floodplain and by 114 ka mis 5e sangamon interglacial the ohio river had scoured the mis 6 sediments to 22 m below the modern floodplain surface there were no fluvial sediments in the valley with ages between mis 5e and the middle of mis 3 the mis 3 ages 39 ka and stratigraphic position of t5 deposits suggest the ohio river aggraded 8 14 m during mis 4 or mis 3 near the end of mis 3 the ohio river incised the mid last glacial mid wisconsinan deposits 10 m and began aggrading again by 30 ka aggradation continued into mis 2 with maximum mis 2 aggradation occurring before 21 ka which is coincident with the global last glacial maximum lgm as the ohio river adjusted to changing fluxes in sediment load and discharge following the lgm it formed a sequence of fill cut terraces in the mis 2 outwash that get progressively younger with decreasing elevation ranging in age from 21 ka to 13 ka from 14 ka to 13 ka the ohio river rapidly incised 3 m to form a new terrace and by 12 ka at the onset of the holocene the ohio river established a meandering channel pattern the river formed a broad floodplain surface from 12 ka to 6 ka and then incised 1 m and formed a fill cut terrace from 6 ka to 5 ka after 5 ka likely in response to mid holocene drought in north america the ohio river incised 5 m and by 4 ka the river began aggrading again the ohio river has aggraded 4 m since aggradation began at 4 ka the chronostratigraphic framework and reconstructed history developed here suggest that the lower ohio river is highly sensitive to glacial interglacial transitions and abrupt holocene climate change and responds rapidly to these allogenic forcings

high resolution surface and subsurface sequence stratigraphy of late middle to late ordovician late mohawkian cincinnatian foreland basin rocks kentucky and virginia the late middle to late ordovician late mohawkian to cincinnatian supersequence in kentucky and virginia was deposited in a tectonically active foreland basin during a transition from the ice free early ordovician to the glacial late ordovician this sequence was deposited in less than 12 m y is 250 500 m thick and is composed of four large third order sequences each 40 150 m thick that are regionally correlative in outcrops cores and gamma ray logs smaller scale third order parasequence sets up to 20 m thick and component parasequences 1 8 m thick make up the larger sequences and are only locally correlative subtidal dominated parasequences comprise the basal part of each sequence whereas shallower subtidal or peritidal dominated parasequences compose upper parts of sequences each large third order sequence is asymmetric and marked by lowstand transgressive and highstand systems tracts with unique lithologic and gamma ray log response characteristics ramp margin wedges rmw are poorly developed and consist of marine siltstone or grainstone packstone sheets extending into deep ramp settings these sheets have high gamma ray values in their base and lower blockier gamma ray responses in their tops transgressive systems tracts tst are thin composed of high energy locally phosphatic grainstone copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received february 7 1996 revised manuscript received may 27 1997 final acceptance june 16 1997 2department of geology virginia tech blacksburg virginia 24061 0420 present address department of earth atmospheric and planetary sciences massachusetts institute of technology cambridge massachusetts 02139 3department of geology virginia tech blacksburg virginia 24061 0420 this study was supported by nsf grant ear 9316057 to j f read a grant from mobil oil company and grants in aid of research from the geological society of america and appalachian basin industrial associates to mike pope we thank john haynes brian keith and rick major for thorough and insightful reviews of an earlier version of this manuscript

quaternary grabens in southernmost illinois deformation near an active intraplate seismic zone abstract narrow grabens displace quaternary sediments near the northern edge of the mississippi embayment in extreme southern illinois east central united states grabens are part of the fluorspar area fault complex fafc which has been recurrently active throughout phanerozoic time the fafc strikes directly toward the new madrid seismic zone nmsz scene of some of the largest intra plate earthquakes in history the nmsz and fafc share origin in a failed cambrian rift reelfoot rift every major fault zone of the fafc in illinois exhibits quaternary displacement the structures appear to be strike slip pull apart grabens but the magnitude and direction of horizontal slip and their relationship to the current stress field are unknown upper tertiary strata are vertically displaced more than 100 m illinoian and older pleistocene strata 10 to 30 m and wisconsinan deposits 1 m or less no holocene deformation has been observed average vertical slip rates are estimated at 0 01 to 0 03 mm year and recurrence intervals for earthquakes of magnitude 6 to 7 are on the order of 10 000s of years for any given fault previous authors remarked that the small amount of surface deformation in the new madrid area implies that the nmsz is a young feature our findings show that tectonic activity has shifted around throughout the quaternary in the central mississippi valley in addition to the nmsz and southern illinois the wabash valley illinois indiana benton hills missouri crowley s ridge arkansas missouri and possibly other sites have experienced quaternary tectonism the nmsz may be only the latest manifestation of seismicity in an intensely fractured intra plate region

interstratal dewatering origin for polygonal patterns of sand filled cracks a case study from late proterozoic metasediments of islay scotland sand filled cracks from the lower fine grained quartzite of dalradian late proterozoic age on the island of islay western scotland may be divided into two main types both of which form orthogonal and non orthogonal closed patterns on bedding surfaces type 1 cracks are short and lenticular in cross section contain sand which had been injected downwards and are found on the bottoms of cross laminated sandstone beds type 2 cracks cut several beds and preserve evidence of upward flow of water saturated sand both types of crack developed through the interstratal intrusion of water saturated sand into shrinkage cracks in mud or muddy sand not as previously thought as a result of sub aerial desiccation or sub aqueous cracking of the sediment surface synaeresis these cracks likely resulted from layer parallel contraction caused by compaction of mudstone layers during burial seismic shock may have provided the trigger for the preferential development of polygonal crack patterns in these layers instead of the more usual small scale dewatering structures from a detailed comparison with published descriptions of filled cracks from a number of different geological environments it is concluded that interstratal cracking is a mechanism which rivals sub aerial desiccation in importance and is more common in the geological record than is currently realized

evidence of strong earthquake shaking in the lower wabash valley from prehistoric liquefaction features earthquake induced liquefaction features in holocene sediments provide evidence of strong prehistoric shaking magnitude m b 6 2 to 6 7 in the wabash valley bordering indiana and illinois the source of the one or more earthquakes responsible was almost certainly in or near the wabash valley the largest event is interpreted to have occurred between 7500 and 1500 years ago on the basis of archeological pedological and stratigraphic relations

evidence of possible induced seismicity in the wabash valley seismic zone from improved microearthquake locations to evaluate the spatial structure of seismicity in the wabash valley of southern indiana and illinois we analyzed data from a temporary seismic network that included 10 three component short period seismometers and a 10 component dense phased array we produced the first comprehensive catalog of local earth quakes recorded during the 211 day deployment from november 1995 through june 1996 the results are dominated by a cluster of 534 microearthquakes with magni tudes ranging from 0 6 to 1 8 near the town of new harmony indiana that were detected and recorded only by the phased array the remarkable similarity of the cluster events in terms of waveform magnitude and temporal distribution suggests a tightly spaced grouping from a single seismic source we relocated the earthquakes using improved relative arrival times of p and s waves computed by time domain cross correlation of the vertical beam traces and by complex cross correlation of the horizontal beam traces respectively additional constraints on absolute locations were applied using a graphical method of arrival time difference analysis for six earthquakes recorded by two network stations outside the phased array the resulting locations define a tight spatial grouping about a zone of post paleozoic faulting just west of the indiana illinois border in white county illinois average source depths from phased array location methods and waveform modeling with synthetic seis mograms indicate in contrast to larger events in the region that the earthquakes occurred at depths less than 4 km within the sedimentary section of the illinois basin we propose that these earthquakes are artificially induced events likely related to water injection for the purpose of secondary recovery of petroleum in the illinois basin the primary evidence for this includes 1 tight spatial clustering of earth quakes 2 unusually shallow earthquake depths 3 good spatial correlation of the relocated hypocenters to existing wells and oil fields and 4 highly repetitive events with only a small range in magnitude

known and suggested quaternary faulting in the midcontinent united states abstract the midcontinent united states between the appalachian and rocky mountains contains 40 known faults or other potentially tectonic features for which published geologic information shows or suggests quaternary tectonic faulting we report results of a systematic evaluation of published and other publicly available geologic evidence of quaternary faulting these results benefit seismic hazard assessments by 1 providing some constraints on the recurrence intervals and magnitudes of large prehistoric earthquakes and 2 identifying features that warrant additional study for some features suggested quaternary tectonic faulting has been disproved whereas for others the suggested faulting remains questionable of the 40 features nine have clear geologic evidence of quaternary tectonic faulting associated with prehistoric earthquakes and another six features have evidence of nontectonic origins an additional 12 faults uplifts or historical seismic zones lack reported paleoseismological evidence of large quaternary earthquakes the remaining 13 features require further paleoseismological study to determine if they have had quaternary earthquakes that were larger than any known from local historical records seven of these 13 features are in or near urbanized areas where their study could affect urban hazard estimates these seven are 1 the belt of normal faults that rings the gulf of mexico from florida to texas 2 the northeast ohio seismic zone 3 the valmont and 4 goodpasture faults of colorado 5 the champlain lowlands normal faults of new york state and vermont and 6 the lexington and 7 kentucky river fault systems of eastern kentucky

strong influence of water vapor source dynamics on stable isotopes in precipitation observed in southern meghalaya ne india to calibrate 18o time series from speleothems in the eastern indian summer monsoon ism region of india and to understand the moisture regime over the northern bay of bengal bob we analyze the 18o and d of rainwater collected in 2007 and 2008 near cherrapunji india d values range from 18 5 to 144 4 while 18o varies between 0 8 and 18 8 the local meteoric water line lmwl is found to be indistinguishable from the global meteoric water line gmwl late ism september october rainfall exhibits lowest 18o and d values with little relationship to the local precipitation amount there is a trend to lighter isotope values over the course of the ism but it does not correlate with the patterns of temperature and rainfall amount 18o and d time series have to be interpreted with caution in terms of the amount effect in this subtropical region we find that the temporal trend in 18o reflects increasing transport distance during the ism isotopic changes in the northern bob surface waters during late ism and vapor re equilibration with rain droplets using an isotope box model for surface ocean waters we quantify the potential influence of river runoff on the isotopic composition of the seasonal freshwater plume in the northern bob temporal variations in this source can contribute up to 25 of the observed changes in stable isotopes of precipitation in ne india to delineate other moisture sources we use backward trajectory computations and find a strong correlation between source region and isotopic composition palaeoclimatic stable isotope time series from northeast indian speleothems likely reflect changes in moisture source and transport pathway as well as the isotopic composition of the bob surface water all of which in turn reflect ism strength stalagmite records from the region can therefore be interpreted as integrated measures of the ism strength

soft sediment deformation structures in the lixian lacustrine sediments eastern tibetan plateau and implications for postglacial seismic activity abstract the eastern margin of the tibetan plateau is characterized by frequent earthquakes which are closely associated with tectonic activity to assess tectonic activity during the late pleistocene we studied a well exposed 23 m thick lacustrine sequence on the eastern margin of the plateau and found a variety of soft sediment deformation ssd structures distributed in 24 stratigraphic levels they comprise clastic dykes ball and pillow structures flame structures clastic gravels micro faults and slump folds most of the ssd structures indicate deformation mechanisms related to liquefaction and or fluidization processes most probably triggered by paleoseismic events given at least 4 historical earthquakes of m 7 in the study area most ssd structures in the lixian lacustrine sequence indicate seismic events with m 6 while simple flame structures point to some lower magnitude earthquakes osl dating indicates that the sequence accumulated between 15 8 and 6 0 ka giving a mean recurrence interval of 480 years for the 24 events and demonstrating that lacustrine sediments in eastern tibet have the potential to record a continuous seismic history on the centennial scale

late quaternary lacustrine paleo seismic archives in north western alps examples of earthquake origin assessment of sedimentary disturbances abstract the late quaternary sedimentary fills of several lakes of the north western alps are revealed to be possible paleo seismological archives in a moderately active seismo tectonic region the strongest historically reported events can be correlated with specific layers whose textures result from different processes i mass failures of sub aqueous slope deposits especially delta foresets evolving into hyperpycnal currents influenced by seiche effects and or multiple reflections on lake basin slopes ii in situ liquefaction and flowage and iii micro fracturing based on identification of the sedimentary signature of a well documented historical earthquake the paleoseismic interpretation can be extrapolated back to 16 000 yrs bp with a reconstruction of a time series and textural identification of slope failure related turbidites the most frequent earthquake signature the obtained time series are compatible with historical seismicity in terms of recurrence interval

seismic reflection profiling studies of a buried precambrian rift beneath the wabash valley fault zone sixty eight kilometers of 12 fold seismic reflection data were collected in the wabash river valley of southwestern indiana and southeastern illinois to investigate the configuration of a basement structure inferred from regional gravity and magnetic anomaly data the seismic profiles were also positioned to cross faults of the wabash valley fault system in a number of locations interpretation of the seismic reflection profiles and detailed gravity and magnetic profile data provides evidence for a series of northeasterly trending grabens in the basement these grabens are filled with pre mt simon layered rocks and are overlain by paleozoic sedimentary rocks of the illinois basin beneath the wabash river near grayville illinois an interpreted graben the grayville graben is approximately 15 km wide and contains about 3 km of fill individual boundary faults for the graben cut prominent reflectors within pre mt simon rocks and display offsets of up to 500 m the interpreted configuration of basement

can deglaciation trigger earthquakes in n america a spherical self gravitating viscoelastic earth model is used to calculate the spatial and temporal evolution of the glacially induced lithospheric stress and fault stability in north america the predicted onset time of a pulse of earthquake activities the mode of failure and the magnitude of instability are investigated for three sites with different distance from the former ice margin it is found that glacial unloading is able to trigger paleo earthquakes within the ice margin near charlevoix 47 5 n 70 1 w and in wabash valley 38 5 n 87 w outside the ice margin however rebound stress decays away from the former ice margin thus glacial unloading is unlikely to have triggered the large m8 earthquakes in new madrid 36 6 n 89 5 w

source and site response study of the 2008 mount carmel illinois earthquake abstract two separate inversions are performed using the ground motion data from the 2008 mount carmel illinois earthquake one uses aftershocks as empirical green s functions to determine a finite fault slip distribution the second uses mainshock ground motion spectra to calculate source path and site response parameters the slip inversion reveals a prominent asperity at the hypocenter with an area of approximately 6 km 2 moment of m w 5 20 and stress drop of about 100 bars considering all major and minor slip the total moment is m w 5 45 the rupture velocity is not resolvable due to the small source area after fixing the geometric spreading the source path and site parameter inversion yields a similar moment of m w 5 26 and a corner frequency of 0 89 hz which also give a stress drop of approximately 100 bars our combined geometric and anelastic attenuation function q f r b 1137 f 0 12 r 0 94 fits the regional spectral amplitudes where the data is more plentiful as well as previously derived attenuation relationships site response spectra show prominent resonant frequencies that correlate with the thickness of mississippi river sediments and mississippi embayment deposits in addition higher frequency resonance peaks are observed that most likely represent higher mode resonances and resonances from shallower structure

induced stresses and fault potential in eastern canada due to a realistic load a preliminary analysis summary in order to understand the causal relation between postglacial rebound and earthquakes a simple disc load model is used to 1 calculate stresses induced in the lithosphere and mantle by glacial loading melting and postglacial rebound and 2 evaluate the effect of glacial loading rebound on the failure potential for earthquakes in the upper crust the dependence of the failure potential and the actual mode of failure on the coefficient of friction the ambient tectonic stress magnitude direction the stress due to the overlying rocks and lithospheric thickness are investigated prominent features of this paper are the inclusion of 1 a viscoelastic mantle and thus the migration of stress and 2 the ambient tectonic stress and overburden stress contributions in the calculation of the total stress field it is assumed that throughout the earth there are optimally oriented pre existing virtual faults that are initially close to but not at failure thus a time dependent quantity called dfsm related to the coulomb mohr failure criterion can be defined such that a negative value of dfsm would advocate faulting or earthquake activities whereas a positive value of dfsm would promote stability the results indicate that under all combinations of tectonic stress magnitude and overburden stress crustal loading promotes fault stability directly underneath the load upon the removal of the load thrust faulting is predicted within the ice margin if the horizontal stress s induced by the overburden is greater than or equal to the vertical component s of the overburden stress 121 where sjs under this condition theory predicts that faulting or earthquake activity should have reached a maximum immediately after deglaciation if the horizontal stress induced by the overburden is less than the vertical component of the overburden stress 1 l then theory predicts fault stability within the ice margin the theory predicts fault instability both north and south of the ice margin the mode of failure however is completely determined by the value of i the trade off between the tectonic stress magnitude and the overburden stress parameter 1 is also investigated it is shown that a larger tectonic stress magnitude can be used to compensate a smaller value of 1 the results of this analysis show that variations in the coefficient of friction lithospheric thickness and a ductile zone below the upper crust do not significantly affect the above conclusions

will earthquake activity in eastern canada increase in the next few thousand years knowledge of whether earthquake activity will increase in the next few thousand years is important for the planning of nuclear waste repositories assuming that fault instability portends earthquak

patterns of seismic activity after three great earthquakes in the light of reid s elastic rebound theory abstract reid9s elastic rebound theory implies that regional stress should increase in the interval between characteristic earthquakes based on this it is postulated that the size of the largest annual earthquakes should also increase in this interval to test this the variability of seismic activity in the new madrid missouri and the san francisco and fort tejon california regions is examined using sequences of magnitudes of largest annual earthquakes the calculated probability of a magnitude 6 5 or 7 5 earthquake based on past occurrences varies significantly with time it is currently growing in the new madrid and san francisco areas and declining in the fort tejon area the calculated probability frequently increases in the five years before earthquakes 1 5 magnitudes or more greater than the regional average maximum annual magnitude the center of significant activity is moving northeastward in the new madrid area

a new opportunity to detect paleo earthquake events dating back to the past 10 millennia a record from lacustrine sediment bulk density and grain density profiles of the uppermost 90 cm portion of lacustrine sediment from lake suigetsu one of the five major lakes of lake mikatagoko located in central japan indicate the occurrence of at least 10 depositional events characterized by anomalously high density spikes two events are accompanied by turbidites the dates of the sedimentary events estimated here are correlated with the occurrence of destructive earthquakes since 1100 a d close examination of the sedimentological signatures recorded in the lake sediment and historical literature describing destructive earthquake phenomena provides a new opportunity to detect paleo earthquake events in a high seismic area having a long history

late quaternary co seismic sedimentation in the sea of marmara s deep basins the deep northern part of the sea of marmara northwestern turkey is composed of several aligned actively subsiding basins which are the direct structural and morphological expression of the north anatolian fault s northern branch the last 20 kyr of their sedimentary fill lacustrine before 12 kyr bp have been investigated through giant piston coring onboard r v marion dufresne marmacore cruise 2001 and chirp subbottom profiler onboard r v atalante during marmarascarps cruise 2002 especially during the lacustrine stage the infilling of the deep basins tekirda central kumburgaz and cinarcic basins up to 1250 m depth was dominated by turbidites with coarse mixed siliciclastic and bioclastic basal part intercalated in hemipelagic type finegrained calcareous and slightly siliceous clays often especially in the thickest ones the turbidites show strong segregation and a sharp boundary between coarse part and suspendedload part in the central basin 8 m of a unique sedimentary event include a 5 to 8m thick homogenite well imaged on seismic profiles the latter is interpreted as related to a major possibly triggered tsunami effect as described in the eastern mediterranean by kastens and cita 1981 in the marine holocene upper part of the sedimentary fill repeated to and from structures affecting silt or fine sand are evidencing seiche like effects and thus earthquake triggering detailed correlations between two deep coring sites 1250 and 1200 m indicate more than 100 overthickening in the deepest one this implies specific processes of distribution of terrigenous input by dense hyperpycnal currents high kinetic energy seiche effect complex reflections on steep slopes the peculiar sedimentary infilling of the sea of marmara s central basin and by extrapolation of the whole set is tentatively interpreted as a direct consequence of the strong seismic activity the imprint of the latter is more obvious prior to the base of the holocene as environmental conditions favoured marginal accumulation especially on the southern shelf of large amounts of erosion products available for mass wasting

recurrent liquefaction induced by the 1989 loma prieta earthquake and 1990 and 1991 aftershocks implications for paleoseismicity studies sandblows formed in man made lake deposits near watsonville california resulted from the october 1989 m 7 1 loma prieta earthquake and its april 1990 m 5 5 aftershock and a march 1991 m 4 6 aftershock excavations in the dry bed of soda lake expose the subsurface structure of sandblows induced by the october and april events we also made surface observations three days after the march 1991 event lateral spread fissures developed in the lake sediment during the mainshock and the host deposits were vertically offset 3 to 6 5 cm liquefied sand erupted through the fissures onto the dry lake bed and formed sandblow cone deposits these deposits range from low angle conical structures 30 to 50 cm thick and 2 to 5 m in diameter to elongate deposits up to 35 m long sandblows associated with the april 1990 aftershock commonly reoccupied preexisting fissures but also formed new solitary vents sandblows developed during the march 1991 aftershock erupted only through preexisting vents sandblow vents reactivated in april 1990 contain sediment clasts of sandblow deposits formed in the october 1989 mainshock clasts of host sediment were also present in the sand dikes lamination in the sandblow cones and sand dikes shows that they were not formed in a single episode surface cones and feeder dikes composed of multiple laminated subunits represent the three generations of sandblows the subunits suggest that the cone deposits were formed by pulses of water and sediment expelled from the vent the pulses result from cyclic phases of local excess pore pressure and its release in the liquefied bed at depth the three generations of structures at soda lake formed six months to a year apart have distinct tonal and textural differences that may mimic liquefaction structures formed decades or centuries apart this study provides modern analogs for comparison to and interpretation of prehistoric liquefaction structures that are frequently partly eroded or poorly exposed

the first surface faulting from a historical intraplate earthquake in north america although many fault ruptures are known from the boundaries of the earth s lithospheric plates the stable interiors of continents are much less active1 worldwide only ten historical intraplate earthquakes are known to have produced surface faulting2 and none of these was in eastern north america despite the confirmed prehistoric rupture of the meers fault3 some have wondered if intraplate earthquakes in the stable north american craton might somehow be different from plate boundary earthquakes and hence fail to rupture the surface4 this is an important consideration for seismic hazard assessments when the ungava earthquake with magnitude ms 6 3 and apparent shallow depth occurred on 25 december 1989 in northern canada we and independently a johnston of memphis state university concluded that it might have produced surface faulting here we report that there was indeed a surface rupture 8 5 km long with up to 1 8 m of reverse faulting on a steeply dipping arcuate fault plane the faulting confirms the seismological process and indicates that there is a hazard from ground rupturing earthquakes in eastern north america but the poor surface expression shows that finding prehistoric fault ruptures in order to constrain seismic hazard estimates will be difficult

late quaternary paleoseismicity of the xiadian fault in the north china plain with implications for earthquake potential abstract the xiadian fault is a crucial seismogenic structure in the north china plain because of the 1679 a d sanhe pinggu m8 earthquake however 12 km of the coseismic surface rupture does not match the worldwide statistical relationship between magnitudes and rupture lengths paleoseismicity research can assist in resolving this debate in this study the synthesized data from geologic investigations satellite image interpretations geomorphic mapping trench logging and sample dating show that the xiadian fault undergone strong deformation in the late quaternary with a characteristic assemblage of landforms including linear scarps troughs sag ponds small horsts and grabens and at least eight paleo earthquake events can be observed the coseismic displacements are not exactly the same but instead show a range of variation from 1 4 0 1 m to 0 9 0 1 m on average and the median interval between the strong earthquakes was estimated at 2820 561 years with an uncertainty value of 0 199 the quasi periodicity behavior of the xiadian fault is not as obvious as that of structures in the plate boundary the surface rupture traces of the m8 earthquake which is composed of 6 segments in an echelon pattern with a single length vary from 1 km to 5 km the asymmetric bell shaped displacement distribution tends to approach a maximum in the central part in pangezhuang village while gradually decreasing toward the tips in east liuhetun and dongxing villages this suggests that the surface rupture of this event is may be only 12 km long although underlying causes require further study