paleoseismology along the 1980 surface rupture of the irpinia fault implications for earthquake recurrence in the southern apennines italy the irpinia fault was the source of the ms 6 9 1980 irpinia earthquake and produced the first unequivocal historical surface faulting in italy trenching of the 1980 fault scarp at piano di pecore a flat intermontane basin about 5 km south of the 1980 instrumental epicenter provides the first data on earthquake recurrence intervals slip per event and slip rate on a major normal fault in the southern apennines fault zone the trenches exposed evidence of four pre 1980 paleoearthquakes that occurred during the past 8600 years a best estimate average recurrence interval is 2150 years although the time interval between individual events varies by as much as a factor of 2 each paleo earthquake is similar to the 1980 surface rupture in amount of slip and style of deformation which suggests that the 1980 event is characteristic for the irpinia fault slip per event values average 61 cm the net vertical displacement of 2 12 2 36 m since 8600 cal year b p observed in the trenches gives a vertical slip rate of 0 25 0 35 mm yr a dip slip rate of 0 29 0 40 mm yr and an extension rate of 0 14 0 20 mm yr although fault behavior data are only available for the irpinia fault they provide a starting point for evaluating earthquake recurrence and rates of deformation in southern apennines they suggest that 1 fault specific earthquake recurrence intervals based on the historical seismic record overestimates the occurrence of large magnitude m7 earthquakes and 2 the holocene rate of extension across the apennines is 1 mm yr the 1980 earthquake and the paleoseismologic observations show that repeated and localized surface faulting occurs in southern apennines and leaves subtle but distinct geomorphic evidence that can be detected with detailed and careful investigation

quaternary evolution of the intermontane val d agri basin southern apennines optically stimulated luminescence osl enables the chronology of the late pleistocene evolution for the val d agri intermontane basin of southern apennines to be defined in the frame of mediterranean geodynamic and climate changes quartz sand from braided floodplain and alluvial fan depositional systems was analyzed using the coarse grained single aliquot regenerative dose sar technique the obtained optical ages are mostly consistent with other assessments radiocarbon tephrochronology and stratigraphic constraints osl allows for the dating to 56 43 ka of an asymmetric subsidence stage that forced alluvial fan progradation filling of a former lacustrine area and development of an axial alluvial plain a short period of mediterranean type pedogenesis recorded at the top of the prograding aggrading fans osl age bracket 43 32 ka corresponds with mis 3 during the subsequent stage of decline of vegetation cover possibly corresponding to mis 2 the latest progradation of alluvial fans occurred the subsequent uplift and breakthrough of the basin threshold during the latest pleistocene and holocene induced entrenchment of the drainage network the results presented here provide an example of the usefulness of osl dating in intermontane continental settings where other geochronological constraints are scarce

seismic imaging of complex structures by non linear traveltime inversion of dense wide angle data application to a thrust belt summary we have used a dense wide angle data set to test a two step procedure for the separate inversion of first arrival and reflection traveltimes data were collected in a complex thrust belt environment southern italy along a 14 km line with closely spaced sources 60 m and receivers 90 m we have applied a fully non linear tomographic technique specially designed to image complex structures to over 6400 first arrival traveltimes in order to determine a detailed velocity model a bi cubic spline velocity model parametrization is used the inversion strategy follows a multiscale approach and employs a non linear velocity optimization scheme the tomographic velocity model is adopted as the background reference medium for a subsequent interface inversion aimed at imaging a target upper crust reflector the interface inversion method is also based on a multiscale approach and uses a non linear technique for model parameters interface position nodes optimization we have applied the interface inversion method to over 1600 reflection traveltimes of a target event picked both in the near and in the wide angle offset range the retrieved interface is well resolved in the central part of the model where ray coverage mainly includes clear post critical reflections and the background velocity model is accurate in depth thanks to large offset deep turning rays the velocity and interface models thus determined are consistent with vertical seismic profiling data and correlate well with the geometry of known geological structures this study shows that the used inversion approach is efficient for target orientated investigations in complex geological environments

active faulting and paleoseismology along the bree fault lower rhine graben belgium paleoseismic analysis of the 10 km long bree fault scarp in the lower rhine graben yields numerous lines of evidence of earthquake activity in the holocene and late pleistocene this active normal fault a part of the feldbiss fault system dips 70 ne and is expressed at the surface by a prominent nw se trending 7 to 20 m high scarp formed since the deposition of the maas river main terrace 700 kyr b p trenches and geophysical prospecting show that the fault which is known to have 100 m of vertical offset since the late pliocene breaks late pleistocene and holocene deposits ground penetrating radar seismic refraction and electric tomography suggest that at shallow depth the amount of displacement is larger than the youngest vertical offset visible in the trenches and corresponds to cumulative fault displacements the analysis of 36 leveling profiles across the scarp indicates that its height can be classified into three groups likely corresponding to different events a morphologic dating gives approximate ages of 2 1 5 kyr b p 14 5 kyr b p and 41 6 kyr b p for the past three surface faulting earthquakes analysis of faulted stratigraphy and earthquake induced deformation structures exposed in trenches suggests the occurrence of three large earthquakes during the past 45 l03 years and yields 0 07 mm yr of relative vertical deformation rate the most recent seismic event occurred between a d 610 and 890 the first identification of an active fault with surface ruptures in the lower rhine graben area emphasizes that large earthquake sources exist within intraplate europe and that at least some of these events are preserved in the geologic record

reconstruction of continental margin architecture deformed by the contraction of the lagonegro basin southern apennines italy thrust propagation through previously rifted continental margins may result in fold and thrust belts whose structure is strongly controlled by the inherited basin architecture as it occurs in southern italy the lagonegro units of the southern apennines comprise a deformed pelagic basin succession showing variable stratigraphic characteristics mainly lateral variations in both facies and thickness interpreted to be due to a complex basin topography related to a triassic rifting event in contrast to previous studies cross section balancing and restoration indicate that the lagonegro units exposed in the high agri valley area suffered relatively limited internal shortening 8 km i e 35 early deformation of these rocks later incorporated into a large displacement thrust sheet was dominated by folding around present day roughly north south trending axes the attainment of a regional decollement level was favoured by an early mild inversion of the basin producing a roughly similar structural elevation of both hanging wall and footwall successions to mesozoic faults most of the contractional deformation was accommodated by buckling of the mesozoic syn rift strata between synsedimentary faults which represented major mechanical interfaces early strain localization in the lagonegro basin ahead of the active thrust front was most probably mechanically controlled by a faulted crustal segment which originally lay within the continental margin between two massive carbonate platforms

rise and fall of a hypothesized seismic gap source complexity in the mw 7 0 16 december 1857 southern italy earthquake abstract on 16 december 1857 a strong earthquake m 7 struck a large portion of the southern apennines about 150 km southeast of naples the earthquake was thoroughly investigated by irish engineer robert mallet who wrote an extensive report that is still regarded as a landmark in observational seismology because of the concentration of damage in the high agri valley and contrary to mallet s own findings for many years the earthquake was referred to as the val d agri earthquake and was believed by most investigators to have ruptured the 20 25 km normal fault lying beneath this intermontane basin the magnitude of the earthquake however and evidence for earthquake complexity suggest that the true rupture length has been so far underestimated we contend that the 1857 earthquake ruptured in a cascade fashion two adjacent and relatively well known faults first the smaller melandro pergola fault commonly believed to represent a seismic gap between the causative faults of the 1857 and of the 1980 irpinia m w 6 9 earthquakes and then the larger agri valley fault proper contemporary chronicles reported a time lapse of 2 3 min between the two ruptures thus effectively making them two independent shocks the rupture must have proceeded unilaterally from the northwestern edge of the melandro pergola fault where mallet placed the earthquake epicenter thus explaining the concentration of damage and attention by rescue crews and subsequent investigators in the southeastern portion of the high agri valley

surface rupture associated with a 5 3 mb earthquake the 5 april 1986 cuzco earthquake and kinematics of the chincheros quoricocha faults of the high andes peru abstract the shallow mb 5 3 1986 earthquake that affected the cuzco region reactivated the 18 km long chincheros qoricocha faults in the central part of the cuzco fault system although the event has a moderate magnitude clear surface ruptures were observed to total 3 km in length with maximum 10 cm normal displacements fault kinematics related to the earthquake analyzed where the qoricocha fault had a maximum surface fault displacement is in agreement with roughly n s extension the normal fault mechanism proposed for this earthquake is compatible with the surface kinematic analysis seismic activity prior to the 1986 earthquake is deduced from analysis of holocene scarps trench exposures give evidence for at least three fault displacements suggesting an average recurrence interval of the order of a few thousand years for surface rupturing seismic events these fault reactivations with vertical displacement ranging from 0 6 to 2 m were related to seismic events of mw magnitude probably ranging from 5 8 to 6 9 structural analyses of holocene faults indicate that the chincheros qoricocha fault activity was related to roughly n s trending extension characterized by a horizontal n s trending 3 axis and a vertical 1 axis the n s extensional tectonics that controlled the holocene and 1986 chincheros qoricocha fault activity are the typical deformational pattern of the peruvian high andes and seem to be in agreement with compensated high topography

patterns and timing of late quaternary faulting in the great basin province and relation to some regional tectonic features large scale surface faulting events each tens of kilometers long and involving more than a meter of displacement of late quaternary age have not been uniformly distributed but have been concentrated in subprovincial and smaller belts and areas within the great basin province furthermore faulting apparently has not been uniformly distributed over time the average recurrence interval of large scale faulting events on individual faults in the province is measured in thousands or tens of thousands of years in contrast to such long recurrence intervals in the central nevada and eastern california seismic belts large scale faulting events have occurred during the last 111 years in an apparently coherent sequential belt filling pulse of activity in which events were separated by only a few years or a few decades the questions are where are other pulses of large scale faulting likely to occur and what controls the localization of such belts and areas characterized by higher rates of faulting two examples of tectonic subprovinces that may play a role in delimiting smaller zones of faulting are the black rock carson sink zone of extension and the central nevada downwarp the central nevada seismic belt lies along the dividing line between these two subprovinces and the northwest margin of the black rock carson sink zone of extension coincides with the margin of a fingerlike belt of dense faulting in northwestern nevada

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

high resolution seismic tomography across the 1980 ms 6 9 southern italy earthquake fault scarp 1 a high resolution multi fold wide angle seismic survey carried out across the irpinia fault southern italy yields new information about the shallow structure of this normal fault that was reactivated in 1980 the fault zone is imaged to a depth of about 60 m by using a non linear tomographic technique that is specially designed to image strongly heterogeneous media results confirm the location of the fault as previously inferred by a trench excavated in soft soils and clearly delineates a 30 35 m step in the bedrock this single step is indicative of a narrow fault zone which corresponds upward to warped soils exposed in the trench thus demonstrating that the near surface warping is directly related to a brittle faulting in the bedrock assuming that the vertical slip rate yielded by paleoseismic data 0 25 0 35 mm yr has been constant since the fault s inception the latter should date back to about 100 140 kys ago such a young age may explain why the irpinia fault is not associated with evident large scale geomorphic indicators of its activity

high resolution petrophysical and palaeomagnetic study of late holocene shelf sediments salerno gulf tyrrhenian sea records of geomagnetic secular variation have been obtained from three cores recovered from the salerno gulf southern italy high resolution petrophysical and palaeomagnetic measurements enabled the reconstruction of a composite curve of geomagnetic palaeosecular variation psv which is compared with the reconstructed psv curve from britain and with the french archaeomagnetic data of the last 2 1ka the good agreement of the salerno gulf record with the above data conforms that our psv record reaches back for some 9 0ka in addition to a thick pumice layer originated during the somma vesuvius eruption at 79 two other tephra layers were recognized at about 1 3 and 3 0ka bp that are probably also of vesuvian origin the comparison provides an initial chronological framework for assessing the increasing trend of sedimentation rate and its significant changes at about 2 7ka and 7 0ka bp this variation in the deposition rate suggests a link with climatic changes recognized in the mediterranean region

tomographic imaging of late quaternary faulting oquirrh mountains utah 1 seismic tomography can be used to image colluvial material in the subsurface by inverting first arrival travel times for velocity colluvial material deposited at the base of a fault scarp free face often appears as a low velocity zone lvz on a tomogram because it is generally less compacted and cemented than the surrounding alluvium a tomogram generated from a forward model of a synthetic velocity structure successfully images two lvzs stacked in the hanging wall of a normal fault the mercur fan oquirrh mountains utah provides an opportunity to look for stacked lvzs in a distributed fault zone three tomographic images across fault scarps on an intermediate age alluvial fan can be used to identify two stacked low velocity zones interpretation of a fourth tomogram is less conclusive these two low velocity zones are interpreted as colluvial packages separated by higher velocity alluvial material and suggest that tectonic activity is interspersed with pulses of fan building

facies and provenance analysis of upper carboniferous to lower permian fan sequences at a convergent plate margin using phyllosilicates heavy minerals and rock fragments erbendorf trough f r g the erbendorf trough is a narrow permo carboniferous graben in the northeast bavarian crystalline basement at the saxothuringian moldanubian plate edge its elastic and volcanic rocks reflect a complex story of alluvial fan progradation and retreat unit i precambrian gneissic bedrock is followed by units ii to v a wet mixed fan debris stream flows braided streams peat swamps organic lake units vi to x reflect a retrogradational dry fan braided streams calcretes flood plain deposition with tuffaceous interbeds units xi to xii are acid extrusive rocks the uppermost part hydrothermally altered and units xiii to xiv denote a progradational dry fan the wet fan at the base is characterized by a predominance of illite stable to intermediate heavy mineral associations zircon and garnet and a clast community pointing to medium pressure metamorphic rocks in the variscan nappe the following dry fan contains various 14 a phyllosilicates besides white mica its heavy mineral suite contains more labile constituents apatite and amphibole gneissic pebbles accompany those from acid volcanic and plutonic rocks the volcanogenic rocks contain expandable 14 a phyllosilicates formed by devitrification anatase and brookite dominate the heavy minerals tio2 associated with phosphate indicates hydrothermal alteration of host rock whereas detrital tio2 and a high ztr zircon tourmaline rutile index reflect paleosol formation as shown at the wet dry fan boundary fan progradation occurred under semi arid conditions with kaolinization and formation of illite partly detrital and a moderately stable heavy mineral association apatite dominated owing to the kaolinization only quartz bearing gneisses were preserved the facies succession reflect the evolution from a fault bordered basin with various fan sections proximal vs distal preserved into a caldera like volcanotectonic depression regionally the grain size intervals reflect a passage from recycled orogen into a transitional arc which accords with the late variscan horizontal gliding of the moldanubian plate over the saxothuringian plate and basement uplift proximal to this suture

high resolution seismic reflection profiling of the santa monica fault zone west los angeles california high resolution seismic reflection data obtained across the santa monica fault in west los angeles reveal the near surface geometry of this active oblique reverse left lateral fault although near surface fault dips as great as 55 cannot be ruled out we interpret the fault to dip northward at 30 to 35 in the upper few hundred meters steepening to 65 at 1 to 2 km depth a total of 180 m of near field thrust separation fault slip plus drag folding has occurred on the fault since the development of a prominent erosional surface atop 1 2 ma strata in the upper 20 to 40 m strain is partitioned between the north dipping main thrust strand and several closely spaced near vertical strike slip faults observed in paleoseismologic trenches the main thrust strand can be traced to within 20 m of the ground surface suggesting that it breaks through to the surface in large earthquakes uplift of a 50 000 year old alluvial fan surface indicates a short term dip slip rate of 0 5 mm yr similar to the 0 6 mm yr dip slip rate derived from vertical separation of the oxygen isotope stage 5e marine terrace 3 km west of the study site if the 0 6 mm yr minimum dip slip only rate characterizes the entire history of the fault then the currently active strand of the santa monica fault probably began moving within the past 300 000 years

high resolution imaging of the high agri valley basin southern italy with electrical resistivity tomography abstract the first high resolution images of the fault controlled high agri valley basin obtained with the electrical resistivity tomography are presented the agri valley is one of the more complex components of the quaternary fault network of the apennine chain the geometry of the pre quaternary bedrock the location and dip of the master fault and the tectonic evolution of the basin are still a subject of debate therefore deep electrical resistivity tomography integrated with stratigraphic analyses has been carried out to improve knowledge of the geological setting of the basin the high resolution electrical images allow us to reconstruct the complex geometry of the basin the electrical imaging highlights the irregular shape of the basin which is bordered by shallow faults and filled with pleistocene alluvial deposits in longitudinal cross section the basin appears as a mosaic of fault bounded blocks forming three different depocenters separated by intrabasinal highs in transverse cross section the basin is an irregular graben locally asymmetric to the northeast and with secondary grabens due to antithetic faults

high resolution seismic and resistivity profiling of a buried quaternary subglacial valley northern alberta canada high resolution seismic and resistivity profiles were acquired to assist in the delineation of a buried quaternary subglacial valley the existence of which was first discovered by drilling one aspect of this valley is the glacial sediments that host substantial methane at shallow depths 50 m or less geophysical well logs indicate that the glacial sediments in this area generally have lower compressional wave speeds v p 10 m than adjacent undisturbed cretaceous age rocks which have v p 2200 m s and r 300 m valley the reflection profile reveals a complex series of events consistent with heterogeneous deposition one major reflection dips eastward across the valley the reflection character changes abruptly on either side of this event with dipping clinoform reflections beneath and nearly horizontal reflections above these may be related to changes in deposition processes beneath a retreating ice sheet as has been suggested by earlier workers the buried valley s basal reflections are complex and possibly reflect glaciotectonic deformation or block plucking the near surface methane gas is within but at the edge of the valley the methane gas saturated zone displays anomalously high resistivities both in the well logs and in resistivity tomography

detecting young slow slipping active faults by geologic and multidisciplinary high resolution geophysical investigations a case study from the apennine seismic belt italy 1 the southern apennines range of italy presents significant challenges for active fault detection due to the complex structural setting inherited from previous contractional tectonics coupled to very recent middle pleistocene onset and slow slip rates of active normal faults as shown by the irpinia fault source of a m6 9 earthquake in 1980 major faults might have small cumulative deformation and subtle geomorphic expression a multidisciplinary study including morphological tectonic paleoseismological and geophysical investigations has been carried out across the extensional monte aquila fault a poorly known structure that similarly to the irpinia fault runs across a ridge and is weakly expressed at the surface by small scarps warps the joint application of shallow reflection profiling seismic and electrical resistivity tomography and physical logging of cored sediments has proved crucial for proper fault detection because performance of each technique was markedly different and very dependent on local geologic conditions geophysical data clearly 1 image a fault zone beneath suspected warps 2 constrain the cumulative vertical slip to only 25 30 m 3 delineate colluvial packages suggesting coseismic surface faulting episodes paleoseismological investigations document at least three deformation events during the very late pleistocene 20 ka and holocene the clue to surface rupturing episodes together with the fault dimension inferred by geological mapping and microseismicity distribution suggest a seismogenic potential of m6 3 our study provides the second documentation of a major active fault in southern italy that as the irpinia fault does not bound a large intermontane basin but it is nested within the mountain range weakly modifying the landscape this demonstrates that standard geomorphological approaches are insufficient to define a proper framework of active faults in this region more in general our applications have wide methodological implications for shallow imaging in complex terrains because they clearly illustrate the benefits of combining electrical resistivity and seismic techniques the proposed multidisciplinary methodology can be effective in regions characterized by young and or slow slipping active faults

the 2009 l aquila central italy mw6 3 earthquake main shock and aftershocks 1 a m w 6 3 earthquake struck on april 6 2009 the abruzzi region central italy producing vast damage in the l aquila town and surroundings in this paper we present the location and geometry of the fault system as obtained by the analysis of main shock and aftershocks recorded by permanent and temporary networks the distribution of aftershocks 712 selected events with m l 2 3 and 20 with m l 4 0 defines a complex 40 km long nw trending extensional structure the main shock fault segment extends for 15 18 km and dips at 45 to the sw between 10 and 2 km depth the extent of aftershocks coincides with the surface trace of the paganica fault a poorly known normal fault that after the event has been quoted to accommodate the extension of the area we observe a migration of seismicity to the north on an echelon fault that can rupture in future large earthquakes

physical and acoustic properties of shelf sediments the south sea of korea abstract laboratory determinations of compressional wave velocity porosity density and sediment texture have been conducted on samples collected from the inner shelf holocene mud sediment in the south sea and southern part of the east sea of korea thirty five piston core samples were used for the measurement mean grain size decreases seaward reflecting the distance from source velocity decreases with increasing water depth porosity and clay content increase gradually with deepening bathymetry on the inner shelf the study area can be divided into three different areas namhae pusan and ulsan by sediment source texture and physical properties velocity increases from west to east namhae pusan ulsan porosity has a pattern that is inverse to that of velocity sediment texture mean grain size and clay content is a very important factor to determine physical and acoustic properties of sediment the geoacoustic properties of the three study areas generally coincide well with that of hamilton s 1970 north pacific continental terrace sediment ulsan area is a little different from the hamilton s model which has a relatively higher velocity at the same textural range the difference is believed to be related to the lowest clay content in ulsan area

the italian cmt dataset from 1977 to the present abstract the ingv harvard european mediterranean regional centroid moment tensor rcmt catalog collects solutions routinely computed since 1997 for earthquakes with moderate magnitude 4 5 m 5 5 in the mediterranean region the database represents an extension to smaller magnitudes of the harvard global cmt catalog based on analysis of seismograms recorded at regional distance and modeling of intermediate period surface waves the catalog includes about 600 events 200 of which in the italian region this study extends the catalog back in time for the italian region as long as made possible by available digital data i e since 1977 with the same analysis and inversion method used for current seismicity as a result we present here 65 new moment tensors for years between 1977 and 1997 these solutions represent 45 of the total number of events analyzed the existing seismograms being often too scarce to allow a stable solution the new dataset includes events in many seismic zones where moderate seismicity had previously been scarcely documented e g the po plain the central to southern apennines and the adriatic sea the complete dataset including previously determined rcmts and cmts represents the seismic deformation in the italian area during the last 25 years

surface rupture of the 1857 southern italian earthquake in october 1862 robert mallet published an extensive study of a large earthquake that occurred on 16 december 1857 150 km south east of naples this event is one of the most destructive ever recorded in italy although continental earthquakes of similar size are almost invariably associated with surface faulting mallet did not identify any surface rupture and subsequent workers have also failed to find surface traces using satellite images and aerial photographs as a guide we examined two prominent quaternary normal fault systems in the field flanking the val d agri and the val di diano both trend nw se and dip to the sw the distribution of damage suggests that one or both moved in 1857 on one fault segment in val d agri we found a 2 5 m high scarp whose youthfulness and height suggest it is due to the 1857 earthquake comparison of the observed slip with rates derived from geomorphic evidence suggests a recurrence time for 1857 type events of about 3000 years while the new data we provide are consistent with the event having a magnitude of ms 7 0 there are also grounds for supposing it might have been bigger

the relationship between seismic deformation and deep seated gravitational movements during the 1997 umbria marche central italy earthquakes abstract this paper re evaluates the origin of some peculiar patterns of ground deformation in the central apennines observed by space geodetic techniques during the two earthquakes of the colfiorito seismic sequence on september 26th 1997 the surface displacement field due to the fault dislocation as modelled with the classic okada elastic formulations shows some areas with high residuals which cannot be attributed to non simulated model complexities the residuals were investigated using geomorphological analysis recognising the geologic evidence of deep seated gravitational slope deformations dsgsd of the block slide type the shape and direction of the co seismic ground displacement observed in these areas are correlated with the expected pattern of movement produced by the reactivation of the identified dsgsd at least a few centimetres of negative line of sight ground displacement was determined for the costa picchio mt pennino and mt prefoglio areas a considerable horizontal component of movement in the costa picchio dsgsd is evident from a qualitative analysis of ascending and descending interferograms the timing of the geodetic data indicates that the ground movement occurred during the seismic shaking and that it did not progress appreciably during the following months this work has verified the seismic triggering of dsgsd previously hypothesized by many researchers a further implication is that in the assessment of dsgsd hazard seismic input needs to be considered as an important cause of accelerated deformation

quaternary tectonics and large scale gravitational deformations with evidence of rock slide displacements in the central apennines central italy eight cases of large scale gravitational movements with evidence of rock slide type displacements evolving close to quaternary faults have been analysed in the central apennines geomorphological and structural surveys have defined the relationship between the gravitational displacements and the tectonically controlled modifications of the landscape the evolution of all the investigated cases has been conditioned by the presence of fault planes located along the mountain slopes in most cases mt cefalone cima della fossa villavallelonga casali d aschi gioia dei marsi the faults played or are playing a primary role in increasing the local relief and their activity represents the main geomorphic factor conditioning the gravitational movements this kind of relationship has been observed along mountain slopes bordering depressions which have not been drained for most of their geomorphic history or have been characterised by an evolution of the hydrographic network that has been conditioned only by the local tectonic subsidence in such cases the gravitational movements develop in the footwalls of the faults in other cases fiamignano pescasseroli the faults have played a passive role since they only bound the sliding masses and coincide with the surficial expressions of the sliding planes therefore the gravitational displacements develop in the hangingwall of the faults the evolution is conditioned by the incision of the hydrographic network in response to regional quaternary uplift the illustrated case studies provide a wide range of examples of the gravitational response of slopes to the modifications of the landscape due to linear and areal tectonics the identification of the geomorphic traces of the large scale gravitational movements along fault controlled mountain fronts has implications for hazard particularly for the evolution of the displacement the quantitative analysis of the vertical displacements and data on the characteristics of the surface breaking during historical earthquakes demonstrate that along fault offsets strongly increases where the unstable large scale rock masses are located therefore the large coseismic vertical offset may represent a major problem for the displacement of utilities and may represent a potential cause for the sudden and catastrophic evolution of the gravitational movement

controlled source nonlinear tomography a powerful tool to constrain tectonic models of the southern apennines orogenic wedge italy the anatomy of the southern apennines is a matter of compelling debate both thick and thin skinned tectonic models are proposed due to paucity of deep seismic constraints we present new and well defined information on the velocity structure of the mountain range by using an innovative nonlinear tomographic technique applied to refraction wide angle reflection data the velocity interface model shows a high velocity region with values exceeding 7 km s at 8 9 km depth such large velocities cannot be related to sedimentary rocks and imply the presence of shallow crystalline rocks i e the basement involvement in the thrust belt the integration of our results with other geophysical data local earthquake tomography bouguer and magnetic anomalies confirms this interpretation which strongly supports thick skinned tectonics and has significant implications for the seismotectonics and hydrocarbon potential of the southern apennines our inversion approach can be effective in other orogenic wedges when seismic reflection profiling fails to uniquely resolve deep complex structures

shallow seismic reflection survey across the meers fault oklahoma a high resolution seismic reflection survey over part of the meers fault scarp in comanche county oklahoma provides an improved understanding of the shallow structure associated with the fault zone the objective of this survey was to detect and identify shallow faulting near the meers fault and to appraise the resolving power of the shallow seismic reflection technique in a structurally complex area three reflection profiles were acquired using a downhole 50 caliber rifle energy source and two 100 hz geophones per channel connected in series field parameters were designed to optimize the recording of seismic reflections from geologic units in the 40 to 200 m depth range severe analog low cut filters helped to increase the dominant recorded reflection frequencies into the 100 to 250 hz range providing minimum bed resolution of about 6 m lines 1 and 2 straddle and cross the scarp orthogonally and line 3 was acquired approximately parallel to the scarp seismic data along line 2 show reverse faulting that extends from 250 m southwest to 200 m northeast of the scarp the cdp stacked seismic data are sufficiently good to interpret an up to the north vertical to high angle reverse displacement on the meers fault the amount of vertical displacement on the fault associated with the scarp cannot be determined with these seismic data maximum vertical displacement is less than 10 m on other secondary faults interpreted on seismic lines 1 and 2 normal faulting is common on line 3 the major structural feature on line 3 is a graben with net displacement of between 5 and 30 m the deformation on line 3 may be evidence of strike slip motion along the main fault the meers fault was in a transpressive tectonic setting during quaternary time as shown by strike slip motion in conjunction with high angle up to the north reverse faulting evidence for angular unconformities within the permian section exists on individual unprocessed field seismograms suggesting that some complex bedforms channel sands are present

local pattern of stress field and seismogenic sources in the pergola melandro basin and the agri valley southern italy summary our study area is a ca 50 km long section of the central southern apennines tectonic belt that includes the pergola melandro basin pm and the agri valley av this region is located between the areas affected by the 1980 ms 6 9 irpinia and the 1857 m 7 0 val d agri earthquakes and is characterized by rare historical events and very low and sparse background seismicity in this study we provide new seismological and geophysical information to identify the characteristics of the seismotectonics in the area as the prevailing faulting mechanism and the fit of local to regional stress field these data concern focal mechanisms from waveform modelling and p wave polarities analyses of borehole breakouts and detailed investigation of two seismic sequences all the data cover a significantly broad range of magnitudes and depths and suggest that no important local variation in stress orientation seems to affect this area which shows a ne sw direction of extension consistent with that regionally observed in southern italy such local homogeneity in the stress field pattern is peculiar to the study area the variations of orientation and or type of stress observed in the northern apennines or less than only 100 km toward the northwest within the same tectonic belt are absent here furthermore there is a suggestion for a northeastward sense of dip of the seismogenic faults in the region an interesting constraint to the characterization of seismic sources

insights on the kinematics of deep seated gravitational slope deformations along the 1915 avezzano earthquake fault central italy from time series dinsar abstract among the causes of deep seated gravitational slope deformations dgsd the most important is relief energy which is closely related to the intensity of the active tectonic deformations either at the regional scale or at the scale of a single active fault we analyzed some examples of dgsd from the eastern border of the fucino basin in the central apennines where extensional tectonics has been active since the late pliocene photogeological and field geomorphological analysis was performed to identify landforms typically associated with dgsd such as counterslope scarps double crests trenches and bulging slopes these features are located on a mountain range at less than 1 km from the causative fault of the 1915 avezzano earthquake we used the sbas differential sar interferometry technique to measure the slow movements of the surface and calculated differential vertical and horizontal ground velocities of 2 4 mm yr 1 during the period spanning from 1992 to 2001 the quantitative information on the kinematics of the deformation provided some inferences on the different processes responsible for the evolution of the observed dgsd the displacement time series shows non linear deformation trends at some locations possibly correlated with a strong meteorological event we speculate that dgsd in this area are normally subject to slow deformation and that sudden slip along sliding surfaces observed in excavations may sporadically be triggered off by extreme meteorological or seismic events evidence of catastrophic collapse of previous dgsd along the same mountain slope reinforce this hypothesis

normal faulting along the southern margin of the puna plateau northwest argentina 1 though orogen parallel shortening and vertical extension have dominated the tectonic evolution of the central andes a significant kinematic shift from horizontal contraction to extension appears to have occurred within the high puna altiplano plateau with the establishment of extension oblique to the orogen since late miocene time we present data from the southern margin of the puna plateau nw argentina where new normal faults have been documented in the fiambala punta negra and la quebrada areas the unifying characteristics of these areas are that young normal faults reactivate or crosscut older thrust and reverse faults the relationship between the faults and the late miocene pliocene punaschotter conglomerate suggests that the extensional faulting must be younger than 3 5 to 7 ma existing data are incomplete but indicate that similar horizontal extension has occurred in many regions throughout the puna altiplano plateau while shortening continues along the plateau margins given the spatial and temporal distribution of this late miocene to pliocene kinematic shift both lithospheric loss in the puna plateau and plateau wide gravitational extensional spreading enhanced by slowing of plate convergence rate could be responsible the young disorganized horizontal extension in the andes today may be the precursor to more pronounced extension such as observed on the tibetan plateau since mid miocene time

stress aligned cracks in the upper crust of the val d agri region as revealed by shear wave splitting summary shear wave splitting is measured at 19 seismic stations of a temporary network deployed in the val d agri area to record low magnitude seismic activity the splitting results suggest the presence of an anisotropic layer between the surface and 15 km depth i e above the hypocentres the dominant fast polarization direction strikes nw se parallel to the apennines orogen and is approximately parallel to the maximum horizontal stress in the region as well as to major normal faults bordering the val d agri basin the size of the normalized delay times in the study region is about 0 01 s km 1 suggesting 4 5 per cent shear wave velocity anisotropy swva on the south western flank of the basin where most of the seismicity occurs we found larger values of normalized delay times between 0 017 and 0 02 s km 1 these high values suggest a 10 per cent of swva these parameters agree with an interpretation of seismic anisotropy in terms of the extensive dilatancy anisotropy eda model that considers the rock volume pervaded by fluid saturated microcracks aligned by the active stress field anisotropic parameters are consistent with borehole image logs from deep exploration wells in the val d agri oil field that detect pervasive fluid saturated microcracks striking nw se parallel to the maximum horizontal stress in the carbonatic reservoir however we cannot rule out the contribution of aligned macroscopic fractures because the main quaternary normal faults are parallel to the maximum horizontal stress the strong anisotropy and the seismicity concentration testify for active deformation along the sw flank of the basin

crustal velocity and strain rate fields in italy and surrounding regions new results from the analysis of permanent and non permanent gps networks summary we present a new geodetic velocity solution for italy and the surrounding areas obtained from an analysis of continuous and survey mode global positioning system observations collected between 1991 and 2002 we have combined local regional and global networks into a common reference frame velocity solution providing a new detailed picture of the regional scale deformation field in the central mediterranean our velocity estimates are computed with respect to a new stable eurasian reference frame constraining the kinematics of the greater african eurasian plate boundary system in the study area we provide strain rate values for the main seismotectonic districts which are in good agreement with the seismic deformation inferred from earthquake focal mechanisms the southern tyrrhenian area calabria the apennines the southeastern alps the southern dinarides and the albanides display deformation rates at the order of 20 30 nanostrain yr 1 the corsica sardinia block moves according to eurasian plate motions and there is no indication that the opening of the tyrrhenian is still active the pelagian and sicilian domains are separated by a northwest southeast discontinuity the sicily channel rifted area and marginally significant relative motion between the pelagian plateau and the african plate is also observed the southern tyrrhenian is affected by north south compression and accommodates up to 50 per cent of the africa eurasia relative plate motion whereas the calabrian arc exhibits 2 mm yr 1 northwest southeast extension the observed deformation pattern suggests the presence of a major approximately north south tectonic discontinuity separating the sicilian and calabrian domains an extensional boundary observed along peninsular italy coincides with the distribution of seismogenic faults along the axis of the apennines this boundary separates a tyrrhenian and an adriatic domain with diverging velocities orientated north nnw ward and northeastward respectively the apennines are extending perpendicularly to the chain axis at rates of less than 3 mm yr 1 and only in the outer northern apennines indications of active shortening are observed insignificant deformation is observed in the western po plain and the western alps while the central and eastern alps display north south shortening the eastern adriatic domain is shortening perpendicular to the dinaric front with strain rates increasing from north to south the locus of collision between the aegean balkan system and the adriatic and ionian domains is marked by the kephalonia fault system which accommodates up to 20 1 mm yr 1 of right lateral motion the deformation pattern observed in the peri adriatic domain is well described by a counter clockwise rotation of the adriatic microplate around a pole located in the western alps

late quaternary faulting within the southern apennines seismic belt new data from mt marzano area southern italy abstract an integrated geomorphological and geophysical investigation was performed in order to reconstruct the pliocene quaternary geomorphologic evolution and recent tectonics of mt marzano massif southern apennines italy the study area belongs to a region of high seismic energy release the last event being the strong ms 6 9 1980 irpinia earthquake most of the main faults of the area ceased their activity before development of the late pliocene age palaeosurfaces widely spread over the massif beginning in the lower part of the middle pleistocene strong extensional tectonics took place in the southern portion of the massif wnw trending faults created the buccino and s gregorio magno depressions which underwent subsidence until the holocene according to abundant morphostructural evidence during the late quaternary the n150 trending mt valva mt carpineta fault and the n110 100 trending mt ogna fault previously sealed by pliocene palaeosurfaces also were re activated morphostructural data were integrated with a high resolution seismic survey across the piano di pecore basin which is dammed by a fault that slipped 70 cm during the 1980 earthquake this fault produced no more than 50 60 m of throw during quaternary times most probably starting from 100 to 150 kyr bp

avoiding pitfalls in shallow seismic reflection surveys acquiring shallow reflection data requires the use of high frequencies preferably accompanied by broad bandwidths problems that sometimes arise with this type of seismic information include spatial aliasing of ground roll erroneous interpretation of processed airwaves and air coupled waves as reflected seismic waves misinterpretation of refractions as reflections on stacked common midpoint cmp sections and emergence of processing artifacts processing and interpreting near surface reflection data correctly often requires more than a simple scaling down of the methods used in oil and gas exploration or crustal studies for example even under favorable conditions separating shallow reflections from shallow refractions during processing may prove difficult if not impossible artifacts emanating from inadequate velocity analysis and inaccurate static corrections during processing are at least as troublesome when they emerge on shallow reflection sections as they are on sections typical of petroleum

twenty years of paleoseismology in italy abstract italy has one of the most complete and historically extensive seismic catalogues in the world due to a unique and uninterrupted flow of written sources that have narrated its seismic history since about the end of the iron age seismic hazard studies have therefore always been mainly based upon this huge mass of data nevertheless the italian catalogue probably lacks many m 6 5 events the seismogenetic structures responsible for which are characterized by recurrence times that are longer than the time span covered by our historical sources for these reasons and as in other countries earthquake data that in italy have been derived from paleoseismological studies should finally become a necessary ingredient in seismic risk assessment indeed over the past 20 years some hundred trenches have been excavated supplying reliable and conclusive data on the recent activities of many faults through to many robust datings of surface fault events these studies have provided the ages of several unknown or poorly known m 6 5 earthquakes here we summarize the state of the art of paleoseismology in italy and present a first catalogue of 56 paleoearthquakes pci that occurred mainly in the past 6 kyr the pci integrates the historical instrumental seismic catalogue and extends it beyond the recurrence time of the seismogenetic faults 2000 1000 yr we feel confident that the use of the pci will enhance future probabilistic seismic hazard assessment and thus contribute to more reliable seismic risk mitigation programs

fault behavior and characteristic earthquakes examples from the wasatch and san andreas fault zones paleoseismological data for the wasatch and san andreas fault zones have led to the formulation of the characteristic earthquake model which postulates that individual faults and fault segments tend to generate essentially same size or characteristic earthquakes having a relatively narrow range of magnitudes near the maximum analysis of scarp derived colluvium in trench exposures across the wasatch fault provides estimates of the timing and displacement associated with individual surface faulting earthquakes at all of the sites studied the displacement per event has been consistently large measured values range from 1 6 to 2 6 m and the average is about 2 m on the basis of variability in the timing of individual events as well as changes in scarp morphology and fault geometry six major segments are recognized along the wasatch fault on the basis of the most likely number of surface faulting events 18 that have occurred on segments of the wasatch fault zone during the past 8000 years an average recurrence interval of 400 666 years with a preferred average of 444 years is calculated for the entire zone geologic data on the distribution of slip associated with prehistoric earthquakes and slip rates along the south central segment of the san andreas fault suggest that the m 8 1857 earthquake is a characteristic earthquake for this segment comparisons of earthquake recurrence relationships on both the wasatch and san andreas faults based on historical seismicity data and geologic data show that a linear constant b value extrapolation of the cumulative recurrence curve from the smaller magnitudes leads to gross underestimates of the frequency of occurrence of the large or characteristic earthquakes only by assuming a low b value in the moderate magnitude range can the seismicity data on small earthquakes be reconciled with geologic data on large earthquakes the characteristic earthquake appears to be a fundamental aspect of the behavior of the wasatch and san andreas faults and may apply to many other faults as well

active faults and induced seismicity in the val d agri area southern apennines italy summary the nw se trending val d agri extensional basin is one of the regions in italy with the highest seismogenic potential field data do not univocally define which of the fault systems bordering the basin on the two opposite sides is accommodating the active deformation in this study we detect and locate by using an automatic picking procedure almost 2000 low magnitude earthquakes 0 2 ml 2 7 recorded by a dense network during a 13 months long seismic experiment events are mostly located along the southwestern flank of the basin to the south intense swarm type microseismicity defines a major cluster 5 km wide from 1 to 5 km depth to the west a clear alignment of events characterized by normal faulting kinematics defines a ne dipping normal fault between 1 and 6 km depth the upward continuation of this structure 5 km long matches a mapped active normal fault recognized by field and palaeoseismological surveys a temporal correlation found between the intense swarm type microseismicity and the water level changes in the nearby artificial pertusillo lake suggests that this seismicity is reservoir induced

palaeoseismicity of the oquirrh fault utah from shallow seismic tomography the magnitude and frequency of normal fault palaeoearthquakes are usually determined by trenching studies that ascertain the size and number of colluvial wedges along the fault such information can be invaluable in predicting the seismic hazard and potential for a future earthquake in that region digging trenches across normal faults however is environmentally intrusive expensive and limited in the penetration depth to overcome these problems we propose the use of 3 d seismic tomography as a means to identify the shapes and sizes of colluvial wedges along normal faults as an example 2 d and 3 d seismic surveys were conducted across the oquirrh fault utah with the purpose of imaging the normal fault structure to a depth of about 10 m results show that the 3 d tomogram clearly delineates the fault zone and a colluvial wedge both of which correlate extremely well with the geological cross section interpreted from an adjacent trench the thickness of the colluvial wedge image is used in conjunction with a seismic section to compute an estimate of a 6 8 moment magnitude earthquake for the most recent event on this fault which is in close agreement with the 7 0 estimate based on a nearby trenching study these tomographic results demonstrate for the first time that seismic imaging methods can be used in some cases to estimate unambiguously the shapes of colluvial wedges and the sizes of prehistoric earthquakes thus seismic tomography has the possibility of providing cheaper deeper and wider but less resolved images of fault systems than the intrusive excavation of trenches across faults

case studies of electrical and electromagnetic methods applied to mapping active faults beneath the thick quaternary it is of considerable importance to explore the geological structure around active faults especially near surface unconsolidated layers to estimate the faults activity there are numerous case studies to investigate active faults using geophysical exploration methods however only a few cases have been verified in detail by comparison with other geological information we have applied electric and electromagnetic methods which can be effective for exploring to several hundred meters depth to reveal geological structures covered by thick quaternary formations at four active fault sites in japan in this paper we used the controlled source audio frequency magnetotelluric csamt method the direct current dc resistivity method and the resistivity tomography method the resistivity profiles were analyzed by two dimensional inversion techniques and the resulting models were verified by comparison with geological evidence obtained by drilling or trenching our results are as follows 1 csamt is an effective method for defining an outline of geological structures around a fault to several hundred meters deep it enables us to define a resistivity boundary between different kinds of bedrock with a fault contact 2 the dc resistivity method distinguishes each sedimentary unit as a different resistivity zone and detects the vertical displacement in the quaternary formations 3 the resistivity tomography method is useful to determine in more detail the flexure structure produced by faulting using these latter two methods we can select drilling positions and trenching locations in addition it is verified from the data measured along trench walls and electrical logging that the resistivity of soft sedimentary layers and clayey cataclastic bedrock conforms to the relationship established between the resistivity and the clay content these resistivity methods have the advantages of detecting clayey layers as very low resistivity zones the overall conclusion is that the combination of these resistivity methods provides us with more detailed and accurate information for estimating fault activity

the portland hills fault uncovering a hidden fault in portland oregon using high resolution geophysical methods abstract the portland metropolitan area historically is the most seismically active region in oregon at least three potentially active faults are located in the immediate vicinity of downtown portland with the portland hills fault phf extending directly beneath downtown portland the faults are poorly understood and the surface geologic record does not provide the information required to assess the seismic hazards associated with them the limited geologic information stems from a surface topography that has not maintained a cumulative geologic record of faulting in part due to rapid erosion and deposition from late pleistocene catastrophic flood events and a possible strike slip component of the faults we integrated multiple high resolution geophysical techniques including seismic reflection ground penetrating radar gpr and magnetic methods with regional geological and geophysical surveys to determine that the portland hills fault is presently active with a zone of deformation that extends at least 400 m the style of deformation is consistent with at least two major earthquakes in the last 12 15 ka as confirmed by a sidehill excavation trench high resolution geophysical methods provide detailed images of the upper 100 m across the active fault zone the geophysical images are critical to characterizing the structural style within the zone of deformation and when integrated with a paleoseismic trench can accurately record the seismic history of a region with little surface geologic exposure

active extension in val d agri area southern apennines italy implications for the geometry of the seismogenic belt summary integration of geologic geomorphologic and seismologic data sets is used to reconstruct the recent tectonic evolution and active deformation pattern in the val d agri area located in the seismically active axial sector of the southern apennines italy the western portion of the apennines thrust belt has been affected by pliocene quaternary extension during easterly roll back and crustal delamination of the adriatic slab the bulk of quaternary extension has been accommodated by sw dipping oblique and normal faults which have attained mature morphologic and structural features and nowadays separate mountain ranges from intermontane basins however in the present seismogenic belt coseismic faulting locally occurs on ne dipping structures which might cut the inherited pleistocene landscape in the val d agri basin in spite of the large early middle pleistocene displacement occurred on sw dipping faults bordering its eastern flank our investigations show that the recent basin evolution has been controlled by a ne dipping fault system monti della maddalena fault system mmfs this fault system cuts across the monti della maddalena range west of the agri valley and has not yet created an evident tectonic landscape notwithstanding fault motion since the middle pleistocene might explain geomorphologic and hydrographic anomalies of the agri river and its valley where fault controlled subsidence has captured the river course and produced an aggrading plain within a regional uplift context recent and ongoing motion is documented by fault scarplets in loose deposits 14c ages of palaeosols and the spatial relation with low to moderate instrumental seismicity results from fault kinematic analysis are compatible with fault plane solutions of local and regional seismic events and indicate ne sw oriented extension recognition of the mmfs as a potential seismogenic fault increases the longitudinal extent of the ne dipping morphologically immature seismic sources in the southern apennines and argues against the range bounding fault model for active extension in the region the regional size of the ne dipping seismogenic belt may result from impingement of a mantle wedge beneath the apenninic chain and possibly track the external front of crustal delamination

isobath variation and trapping of continental shelf waves since trosch proceedings of the 4th international conference on applied numerical modeling tainan taiwan 1984 ed h m hsia y l chou s y wang s j hsieh science and technology series vol 63 1986 pp 307 311 american astronautical society found trapped sub inertial oscillations in computations of low frequency variability in the lake of lugano models of trapping have generally considered evenly spaced isobaths parallel to shorelines with approximate boundary conditions at any shelf ocean boundary here an asymptotic analysis for slowly varying topography and accurate spectral computations demonstrate trapping on non rectilinear shelves it is shown that changes in any of three factors isobath curvature distance from the coast and the shelf break and the slope at the shelf break are sufficient on their own to give trapping continental shelves that abut smoothly onto the open ocean are considered thus avoiding the shelf ocean boundary condition approximation and allowing the accuracy of previous approximations to be assessed

2 d seismic trenching of colluvial wedges and faults abstract images of the depth and shape of colluvial wedges by 3 d travel time tomography can be valuable in estimating the past history of ancient earthquakes and assessing the earthquake hazard of a fault unfortunately 3 d seismic surveys can be both costly and time consuming in this paper we report our first successful results of detecting the shapes and depths of colluvial wedges with 2 d travel time tomography the locations of the colluvial wedges are along the oquirrh fault and the salt lake city segment of the wasatch fault we also report that the tomogram from one of our 2 d surveys suggests the possibility of detecting multiple colluvial wedges at depth using both reflection and tomographic images at another site clearly reveals the presence of a known shallow fault and the contact between native soil and recent fill our results suggest the synergistic use of both seismic tomography and reflection imaging we denote as seismic trenching as a means of detecting shallow colluvial wedges and faults seismic trenching has the potential to significantly expand the lateral extent and depth of investigation of paleoseismology

an engineering site investigation using non invasive geophysical approach subsurface geological formation is essential to validate design assumptions for the construction of deep engineering structures especially in the weathered terrains the geological formation can be delineated using resistivity values through an electrical survey however the subsurface resistivity alone is ambiguous to interpret the subsurface geological units as part of an ongoing investigation to select the key methods towards this end an integrated geophysical survey through a combination of electrical resistivity tomography ert induced polarization ip magnetic method and joint profile method jpm was carried out in a weathered terrain of south huizhou china resistivity ip and magnetic data were obtained using a variety of survey parameters subsurface resistivity was calibrated with upfront boreholes lithology to constrain geological formation into four discrete layers such as topsoil cover with resistivity 2 3257 m highly weathered layer having resistivity 2 636 m partly weathered layer with resistivity range 448 1204 m and unweathered bedrock having resistivity 791 116 497 m the integration of ert with ip magnetic and jpm delineated four faults namely f1 f2 f3 and f4 and several localized fractures the weathered layer fractures and faults were marked as the weakest zones for engineering projects whereas the unweathered fresh bedrocks were identified as the most appropriate locations for the construction of deep structures in the study area the weakest zones unsuitable for engineering structures were delineated as the most appropriate places of groundwater occurrence in the studied area revealed by low resistivity ranging from 2 to 1204 m and overlapped by low chargeability less than 14 8 ms this non invasive geophysical approach suggests the most suitable locations highly significant not only for the future construction of engineering structures but also the exploitation of groundwater resources in the investigated area