ground motion modeling of the 1906 san francisco earthquake part ii ground motion estimates for the 1906 earthquake and scenario events abstract we estimate the ground motions produced by the 1906 san francisco earthquake making use of the recently developed song et al 2008 source model that combines the available geodetic and seismic observations and recently constructed 3d geologic and seismic velocity models our estimates of the ground motions for the 1906 earthquake are consistent across five ground motion modeling groups employing different wave propagation codes and simulation domains the simulations successfully reproduce the main features of the boatwright and bundock 2005 shakemap but tend to over predict the intensity of shaking by 0 1 0 5 modified mercalli intensity mmi units velocity waveforms at sites throughout the san francisco bay area exhibit characteristics consistent with rupture directivity local geologic conditions e g sedimentary basins and the large size of the event e g durations of strong shaking lasting tens of seconds we also compute ground motions for seven hypothetical scenarios rupturing the same extent of the northern san andreas fault considering three additional hypocenters and an additional random distribution of slip rupture directivity exerts the strongest influence on the variations in shaking although sedimentary basins do consistently contribute to the response in some locations such as santa rosa livermore and san jose these scenarios suggest that future large earthquakes on the northern san andreas fault may subject the current san francisco bay urban area to stronger shaking than a repeat of the 1906 earthquake ruptures propagating southward towards san francisco appear to expose more of the urban area to a given intensity level than do ruptures propagating northward

evidence of large scale deformation patterns from gps data in the italian subduction boundary abstract we present the velocity field in italy derived from over 300 continuous gps stations operated in the 1998 2009 time span the gps network maps the whole country with a mean inter site distance of about 50 km and provides a valuable source of data to study the ongoing deformation processes in the central mediterranean the estimated horizontal and vertical velocity fields show major significant features and also less known second order kinematic features a general uplift characterizes the whole apennines and alpine belts that follow the topographic ridge whereas the po plain shows a gradually increasing subsidence from west to east the apennines belt displays a distinctive extension 50 80 10 9 yr 1 while compressive tectonic regimes characterize northern sicily eastern alps and the northeast front of the northern apennines 25 50 10 9 yr 1 second order deformation patterns on large scale wavelength 100 km have been detected on the accretionary prism of central and southern apennines that are highly correlated with other geophysical data vp anomalies seismic anisotropy etc and related to deep rooted sections 70 100 km marked by different subduction regimes apparently at this scale length the observed deformations are governed by the lithosphere as a whole we interpret these deformations as a result of different subduction mechanisms such as variations of the subduction rollback velocity affecting different segments of the subduction zone and or to mantle flows in proximity of the slab edges further south in central southern sicily we detect a contraction of 1 1 0 2 mm yr that probably accommodates part of the africa eurasia convergence on the outer thrust front of the apennines maghrebides belt this hypothesis agrees with an independent analysis of the seismicity associated to the sicilian basal thrust thought to be still active the itrf2005 estimates of the new gps velocity field are available also in sinex format as supplementary file s1

shallow subduction beneath italy three dimensional images of the adriatic european tyrrhenian lithosphere system based on high quality p wave arrival times 1 this paper presents a velocity model of the italian central mediterranean lithosphere in unprecedented detail the model is derived by inverting a set of 166 000 pg and pn seismic wave arrival times restricted to the highest quality data available the tomographic images reveal the geometry of the subduction collision system between the european adriatic and tyrrhenian plates over a larger volume and with finer resolution than previous studies we find two arcs of low vp anomalies running along the alps and the apennines describing the collision zones of underthrusting continental lithospheres our results suggest that in the apennines a significant portion of the crust has been subducted below the mountain belt from the velocity model we can also infer thermal softening of the crustal wedge above the subducting adriatic plate in the tyrrhenian back arc region strong and extensive low vp anomalies depict upwelling asthenospheric material the tomographic images also allow us to trace the boundary between the adriatic and the tyrrhenian plates at moho depth revealing some tears in the adriatic ionian subducting lithosphere the complex lithospheric structure described by this study is the result of a long evolution the heterogeneities of continental margins lithospheric underthrusting and plate indentation have led to subduction variations slab tears and asthenospheric upwelling at the present day the high resolution model provided here greatly improves our understanding of the central mediterranean s structural puzzle the results of this study can also shed light on the evolution of other regions experiencing both oceanic and continental subduction

the palaeomagnetic record of the santiago volcanics republic of cape verde multiphase magnetization and age consideration abstract the palaeomagnetism of the older volcanic complex of santiago constitutes a multicomponent structure and magnetomineralogical evidence suggests that the various remanence vectors are carried principally by titanomaghaemites when viewed in the context of the african palaeomagnetic reference frame the predominant magnetization is consistent with an upper tertiary age but two older magnetizations of inferred lower tertiary age are also in evidence the demonstrable secondary nature of all three palaeomagnetic axes each of them represented by both polarities makes it likely that the actual emplacement of the older complex is of pre tertiary age being probably an integral component of the pronounced tectonomagmatic uplift phase that affected the entire northwest african margin in upper cretaceous time the older complex of santiago can probably be correlated with the igneous core of the neighbouring island of maio which apparently formed during turonian time 90 ma ago some younger lavas of upper miocene age the flamengos formation show a much simpler palaeomagnetic history than rocks of the older complex yielding only the upper tertiary palaeomagnetic field axis

site amplification in the los angeles basin from three dimensional modeling of ground motion it is well established that sedimentary basins can significantly amplify earthquake ground motion however the amplification at any given site can vary with earthquake location to account for basin response in probabilistic seismic hazard analysis therefore we need to know the average amplification and intrinsic variability standard deviation at each site given all earthquakes of concern in the region due to a dearth of empirical ground motion observations theoretical simu lations constitute our best hope of addressing this issue here 0 0 5 hz finite difference finite fault simulations are used to estimate the three dimensional 3d response of the los angeles basin to nine different earthquake scenarios amplifi cation is quantified as the peak velocity obtained from the 3d simulation divided by that predicted using a regional one dimensional 1d crustal model average ampli fication factors are up to a factor of 4 with the values from individual scenarios typically differing by as much as a factor of 2 5 the average amplification correlates with basin depth with values near unity at sites above sediments with thickness less than 2 km and up to factors near 6 above the deepest 9 km and steepest dipping parts of the basin there is also some indication that amplification factors are greater for events located farther from the basin edge if the 3d amplification factors are divided by the 1d vertical sh wave amplification below each site they are lowered by up to a factor of 1 7 the duration of shaking in the 3d model is found to be longer by up to more than 60 seconds relative to the 1d basin response the simu lation of the 1994 northridge earthquake reproduces recorded 0 0 5 hz particle velocities relatively well in particular at near source stations the synthetic and observed peak velocities agree within a factor of two and the log standard deviation of the residuals is 0 36 this is a reduction of 54 and 51 compared to the values obtained for the regional 1d model and a 1d model defined by the velocity and density profile below a site in the middle of the basin dow respectively this result suggests that long period ground motion estimation can be improved consid erably by including the 3d basin structure however there are uncertainties con cerning accuracy of the basin model model resolution the omission of material with shear velocities lower than 1 km s and the fact that only nine scenarios have been considered therefore the amplification factors reported here should be used with caution until they can be further tested against observations however the results do serve as a guide to what should be expected particularly with respect to increased amplification factors at sites located above the deeper parts of the basin

adjoint tomography of the southern california crust using an inversion strategy based on adjoint methods we developed a three dimensional seismological model of the southern california crust the resulting model involved 16 tomographic iterations which required 6800 wavefield simulations and a total of 0 8 million central processing unit hours the new crustal model reveals strong heterogeneity including local changes of 30 with respect to the initial three dimensional model provided by the southern california earthquake center the model illuminates shallow features such as sedimentary basins and compositional contrasts across faults it also reveals crustal features at depth that aid in the tectonic reconstruction of southern california such as subduction captured oceanic crustal fragments the new model enables more realistic and accurate assessments of seismic hazard

paleomagnetic results from a reconnaissance study of santiago cape verde islands identification of cryptochron c2r 2r 1 abstract new paleomagnetic data from three lava sequences on santiago cape verde islands are presented the paleomagnetic data are coupled with ar 40 ar 39 age determinations allowing detailed correlations between the three profiles and the geomagnetic polarity time scale gpts the younger of the profiles the ribeira da barca profile recorded flows of normal polarity that correlate with the brunhes chron whereas the porto formosa profile of reverse polarity correlates with the lower matuyama chron the sao goncalo profile consists of both reverse and normal polarity flows that belong to the matuyama and gauss chron respectively virtual geomagnetic poles vgps from a sequence of flow units in the sao goncalo profile classify as transitional and we interpret it as a geomagnetic event sg i well defined ar 40 ar 39 ages bound the occurrence of event sg i to the interval 2 37 2 43 ma 2 which is synchronous with the timing of cryptochron c2r 2r 1 in the marine magnetic anomaly record this study therefore confirms the existence of cryptochron c2r 2r 1 and indicates that it was a global scale phenomenon the vgps indicate that the field was in a meta stable transitional state during cryptochron c2r 2r 1 and that it spent some time in or around the paleomagnetic transitional vgp cluster patch close to australia

estimation of q for long period 2 sec waves in the los angeles basin we simulate 0 to 0 5 hz 3d wave propagation through the southern california earthquake center seismic velocity reference model version 2 for the 1994 northridge earthquake in order to examine the effects of anelastic attenuation and amplification within the near surface sediments we use a fourth order finite difference staggered grid method with the coarse grained frequency independent anelastic scheme of day and bradley 2001 and a variable slip distribution from kinematic inversion for the northridge earthquake we find that the near surface material with s wave velocity v s as low as 500 m sec significantly affects the long period peak ground velocities compared with simulations in which the s wave velocity is constrained to 1 km sec and greater anelastic attenuation also has a strong effect on ground motion amplitudes reducing the predicted peak velocity by a factor of up to 2 5 relative to lossless simulations our preferred q model is q s v s 0 02 v s in meters per second for v s less than 1 2 km sec and much larger q s v s 0 1 v s in meters per second for layers with higher velocities the simple model reduces the standard deviation of the residuals between synthetic and observed natural log of peak velocity from 1 13 to 0 26 relative to simulations for the lossless case the anelastic losses have their largest effect on short period surface waves propagating in the los angeles basin which are principally sensitive to q s in the low velocity near surface sediments of the basin the low frequency ground motion simulated here is relatively insensitive to q p as well as to the values of q s at depths greater than roughly that of the 2 km sec s wave velocity isosurface

far source long period displacement response spectra in the po and venetian plains italy from 3d wavefield simulations abstract design elastic displacement spectra for seismic codes and zoning studies of seismic hazard for long period structures are becoming of utmost importance in modern earthquake engineering the increase of displacement based design approaches together with the availability of good quality digital strong motion data allow the creation of reliable spectral shapes for seismic design of up to 10 s nevertheless to characterize the site amplification effects during large levels of shaking additional studies are needed especially in deep sedimentary basins and plains that can be strongly excited by large amplitude long period waves data within deep basins is rare because accelerometric seismic networks are normally deployed on rock or stiff soil and modeling of waveforms is hence necessary for bridging this gap focusing on the numerical modeling of the 3d wavefield in 1d flat layered and 3d structures in the po and venetian plains northern italy and on earthquakes with magnitudes m 6 6 and hypocentral distances greater than 50 km in this study we 1 estimate the displacement response spectra drs from 1 to 10 s in the po and venetian plains 2 compare the drs from numerical simulations using flat layered and heterogeneous 3d models against the currently available uniform hazard drs for italy and 3 evaluate the influence of deep sediments on drs shape and thus on seismic codes finally 1d and 3d simulated drs are compared with drs obtained from recordings in the kanto basin where similar long period displacement is observed

moho reflection effects in the po plain northern italy observed from instrumental and intensity data abstract recent moderate sized earthquakes m l 5 2 that occurred in northern italy demonstrate that the currently available ground motion prediction equations gmpes largely underestimate shaking in the po plain region at hypocentral distances greater than 70 km in order to investigate this phenomenon we collected a set of peak ground acceleration pga observations for weak and moderate earthquakes in the area nonparametric regression analysis of pga observations as a function of magnitude and hypocentral distance shows that pga is systematically enhanced for distances between 70 and 200 km an indirect estimation through the analysis of the attenuation of macroseismic intensities suggests that the effect also applies to strong earthquakes m l 5 5 we performed numerical modeling experiments to investigate the cause of the phenomenon the characteristics of the computed synthetic seismograms indicate that the enhancement of ground motion is mainly an effect of the reflection of s waves at the moho sms phase the analysis of both real and synthetic data shows that the moho reflection effect is maximized at hypocentral distances between 90 and 150 km where the pga increases by a factor larger than 2 4

simulations of ground motion in the los angeles basin based upon the spectral element method we use the spectral element method to simulate ground motion generated by two recent and well recorded small earthquakes in the los angeles basin simulations are performed using a new sedimentary basin model that is constrained by hundreds of petroleum industry well logs and more than 20 000 km of seismic reflection profiles the numerical simulations account for 3d variations of seismic wave speeds and density topography and bathymetry and attenuation simulations for the 9 september 2001 m w 4 2 hollywood earthquake and the 3 september 2002 m w 4 2 yorba linda earthquake demonstrate that the combination of a detailed sedimentary basin model and an accurate numerical technique facilitates the simulation of ground motion at periods of 2 sec and longer inside the basin model and 6 sec and longer in the regional model peak ground displacement velocity and acceleration maps illustrate that significant amplification occurs in the basin

strong ground motion from the michoacan mexico earthquake the network of strong motion accelerographs in mexico includes instruments that were installed under an international cooperative research program in sites selected for the high potenial of a large earthquake the 19 september 1985 earthquake magnitude 8 1 occurred in a seismic gap where an earthquake was expected as a result there is an excellent descripton of the ground motions that caused the disaster

an 40ar 39ar study of the cape verde hot spot temporal evolution in a semistationary plate environment the 40 ar 39 ar analyses of 28 groundmass separates from volcanic rocks from the islands of santiago sal and sao vicente cape verde archipelago are presented the new age data record the volcanic evolution for santiago from 4 6 to 0 7 ma for sal from around 15 to 1 1 ma and for sao vicente from 6 6 to 0 3 ma the major submarine constructional phase of santiago was erupted within a few hundred thousand years interval around 4 6 ma most of the subaerial santiago volcanic rocks were erupted in a second episode from 3 3 to 2 2 ma and late volcanism occurred at 1 1 0 7 ma volcanism on sal evolved in five stages 1 poorly constrained early miocene activity 2 16 14 ma 3 12 8 ma 4 around 5 4 ma and 5 1 1 0 6 ma sao vicente was constructed during three active periods 1 6 6 5 9 ma 2 4 7 4 5 ma and 3 0 3 ma sr isotope analyses of carbonates from maio confirm an early cretaceous age for limestones deposited on the seafloor and later uplifted the cape verde rise is indicated to have fully formed in the early miocene around 22 ma accompanied by the initial alkaline volcanism considerable volcanism on sal boa vista and maio took place in the miocene and pliocene and extended over much larger areas than the present islands whereas volcanism of the southwestern and northwestern island groups developed mainly during the pliocene and pleistocene and was mostly confined to the present island areas the periods of volcanic activity may be broadly correlated between the northwestern and southwestern groups of islands young volcanism 0 3 0 1 ma throughout the northwestern group extends along a 150 km long nw se trending lineament a relatively moderate average melting rate for the hot spot over the 22 ma period is estimated at 0 026 km 3 a corresponding to a total volume of 570 x 103 km 3 of magma emplaced in the crust and a mantle volume flux of 28 m 3 s much lower than iceland or hawaii the archipelago is situated to the south and sw of the center of the mantle plume anomaly and ahead of its relative movement the timing and location of volcanism suggest that mantle melting takes place in three channels an eastern one that has been active for 22 ma and in southwestern and northwestern channels since late miocene

near fault earthquake ground motion simulation in the grenoble valley by a high performance spectral element code near fault effects are known to produce specific features of earthquake ground motion such as long period velocity pulses and directivity that cannot be predicted by numerical approaches involving vertical plane wave propagation in one dimensional 1d soil models that are used as a standard in engineering applica tions coupling near fault conditions with site effects induced by complex geological structures such as deep alluvial basins or steep topographic irregularities further con tributes to the complexity of earthquake ground motion and to the difficulty to provide reliable predictions without making use of large size 3d numerical simulations in this article we present a parametric study of the seismic response of the grenoble valley france due to an mw 6 seismic source at some 10 km epicentral distance from the urban area that was carried out in the framework of an international benchmark for earthquake ground motion prediction the spectral element code geoelse for seismic wave propagation analyses in 3d heterogeneous media in the linear and non linear range was used for this purpose full advantage was taken of its implementation on parallel computer architectures after introducing geoelse and its parallel per formance and after introducing some of its validation benchmarks the spatial varia bility of the seismic response of the grenoble valley is quantitatively investigated taking into account two effects i the hypocenter location and ii the nonlinear soil behavior through a nonlinear viscoelastic soil model finally numerical results are compared with available data and attenuation relationships of peak values of ground motion in the near fault region based on the results of this work the unfavorable interaction between fault rupture radiation mechanism and complex geological con ditions may give rise to large values of peak ground velocity exceeding 1 m sec even in low to moderate seismicity areas it may therefore considerably increase the level of seismic risk especially in highly populated and industrially active regions such as the alpine valleys

the geological history of maio cape verde islands the oldest igneous rocks on maio are pillow lavas of mid ocean ridge pillow basalts character which have been tilted and uplifted about 4 km from the ocean floor to outcrop as a partial ring dipping steeply away from a central plutonic complex made up of pyroxenites essexites syenites and carbonatites the ocean floor volcanic rocks are overlain conformably by a stratigraphically continuous pelagic carbonate succession which demonstrates a shallowing depositional environment from the upper jurassic to upper cretaceous times when tuffaceous beds indicate renewed volcanism the tuffs are associated with rudites demonstrating the emergence of the island and amongst the clasts are plutonics indicating upper cretaceous magmatism and the unroofing of the volcano to a substantial depth deformation under compressive stress resulted in the folding and local repetition by thrusting of this sedimentary cover which together with the plutonic core had been intensively injected by major sills the mesozoic succession has been planed off and overlain with marked unconformity by a largely neogene sequence of volcanic and terrestrial sedimentary rocks there is a hiatus throughout the palaeogene and constructional activity appears to recommence with ankaramitic hyaloclastite and lava deltas and subaerial ankaramitic flows these are overlain by fluvial sediments and tuffs stratigraphically above these is an extensive plateau of silica undersaturated lavas olivine melilitites and nephelinites which rest on a planed and locally lateritized surface at topographically higher levels in the eastern part of the island there are thick ankaramitic lavas and pyroclasts which evidently flowed eastward through valleys cut down into the mesozoic strata and appear to be of pliocene age the subsequent history of the island appears to be non volcanic

long period seismic amplification in the kanto basin from the ambient seismic field tokyo like many seismically threatened cities is situated atop a sedimentary basin that has the potential to trap and amplify seismic waves from earthquakes we study amplification in the kanto basin by exploiting the information carried by the ambient seismic field we use 375 seismic stations from the high sensitivity seismograph network across central honshu as virtual sources and 296 seismic stations of the metropolitan seismic observation network shallow borehole seismometers within the basin as receivers to map the basin response we find a linear relationship between ground motion and basin depth at periods of 2 10 s that could be used to represent 3 d basin effects in ground motion prediction equations we also find that the strength of basin seismic amplification depends strongly on the direction of illumination by seismic waves

evidence for ocean continent crust boundary beneath the abyssal plain of the east central atlantic abstract a survey of geophysical results and basalt characteristics of the east central atlantic suggests that such data are at present unable to define the seaward limit of the thinned continental crust the combined evidence from margin sedimentation deep sea diapirism salinity concentration in dsdp ipod cores and the distribution of deep sea barite and palygorskite sepiolite assemblages indicate that the central atlantic developed from a wide rift basin within a normal continental setting the notion of an extensive pre drift basin gains additional support from the occurrences of lower cretaceous black shales which are interpreted as resulting from a tectonomagmatic forerunner phase to the actual continental separation process seafloor spreading which appears to have commenced at around 90 ma b p cenomanian turonian following major phases of subsidence and crustal attenuation in jurassic and lower cretaceous is identified by an apparently sharp change over from reducing to oxygenated deep sea environment as well as by the onset of a major sedimentary hiatus the new development model of the east central atlantic is regarded as a representative example of a global pattern commencement of seafloor spreading in the upper cretaceous probably explains the world wide cenomanian transgression as well as the formation of extensive upper cretaceous sedimentary basins in the interior of the major continental blocks a consequence of this model is that vertical crustal dynamics seem to be as important as seafloor spreading in the development of the oceanic lithosphere thus in the central atlantic spreading is probably confined only to the region of the elevated mid atlantic ridge

electron probe microanalysis study on processes of low temperature oxidation of titanomagnetite abstract partially oxidized titanomagnetite grains in various kinds of volcanic rocks were investigated by electron probe microanalyzer epma in order to clarify the process of oxidation at low temperature the following results were obtained by the present investigation 1 primary composition of titanomagnetite is homogeneous in individual grains although variation in composition among different grains is observed on each thin section 2 migration of fe cations during low temperature oxidation is clearly seen in all oxidized grains some other constituent cations are also bleached and consequently the relative content of the remaining cations becomes large 3 the detailed internal structures of titanomagnetite grains are observed as backscattered electron images bei with an electronprobe microanalyzer and it seems likely that the structures depend upon the degree of low temperature oxidation 4 the chemical and physical properties of oxidized titanomagnetites imply that low temperature oxidation is not a simple process but a complex one such an oxidation process is correlatable to both the mobility of cation and the oxidation condition such as a circulation of some active hydrothermal materials at low temperature

finite difference p wave travel time seismic tomography of the crust and uppermost mantle in the italian region 1 we present a 3 d p wave velocity model of the crust and shallowest mantle under the italian region that includes a revised moho depth map obtained by regional seismic travel time tomography we invert 191 850 pn and pg wave arrival times from 6850 earthquakes that occurred within the region from 1988 to 2007 recorded by 264 permanent seismic stations we adopt a high resolution linear b spline model representation with 0 1 horizontal and 2 km vertical grid spacing and an accurate finite difference forward calculation scheme our nonlinear iterative inversion process uses the recent european reference 3 d crustal model epcrust as a priori information our resulting model shows two arcs of relatively low velocity in the crust running along both the alps and the apennines underlying the collision belts between plates beneath the western alps we detect the presence of the ivrea body denoted by a strong high p wave velocity anomaly we also map the moho discontinuity resulting from the inversion imaged as the relatively sharp transition between crust and mantle where p wave velocity steps up to values larger than 8 km s this simple condition yields an image quite in agreement with previous studies that use explicit representations for the discontinuity we find a complex lithospheric structure characterized by shallower moho close by the tyrrhenian sea intermediate depth along the adriatic coast and deepest moho under the two mountain belts

moho depth and vp vs ratio in peninsular italy from teleseismic receiver functions 1 we present a new data set of moho depth estimates for peninsular italy obtained from receiver functions analysis and a grid search approach teleseismic records from 174 broadband seismic stations were used to compute the receiver function data set in general our results agree well with previous knowledge adding original information in many regions where previous data were lacking or uncertain we find broad regions with consistent moho depth namely 1 the peri tyrrhenian areas bordering the homonymous sea have a 20 to 25 km deep moho 2 the foreland regions adriatic apulia iblean with 30 35 km deep moho 3 the apennines belt where we find westward deepening of the adriatic moho down to 50 km depth that well delineate the westward adria subduction overlayed by the shallow tyrrhenian moho 4 calabria shows a flat 40 km deep moho suddenly dipping at high angle from the tyrrhenian coast westward defining the ionian subduction and 5 a clear separation between northern and southern apennines is marked by a region of almost flat moho possible evidence of a detached slab in between we also find that in the northern apennines the shallow tyrrhenian moho is continuous for more than 200 km from the sea to under the northern apennines with a generally flat geometry and a few undulations suggesting either the boudinage or episodic pulses of extension of the tyrrhenian crust during its pliocene quaternary stretching the eastward extent of the tyrrhenian moho below the apenninic belt approximately corresponds to the eastward extent of the observed extension in the upper crust as mapped by the normal faulting earthquakes in this portion of the apennines we interpret an intracrustal discontinuity sw dipping below the belt parallel to the adria moho as the top of the lower crust being subducted beneath the apennines the subcrustal earthquakes of this region down to 80 km depth seem to be located within this subducted crustal layer the southern apennines show the same general geometry of subduction as the northern arc although the former have a less defined on land extended region and no earthquakes in the lower crust uppermost mantle in between the central apennines present a different moho geometry no clear doubling of the two plates but rather a constant bilateral deepening possibly associated to a crustal root with no evidence of a subduction setting this reinforces the hypothesis of a detached slab in this area we also present the first large scale mapping of average crustal vp vs ratios for peninsular italy the results although representing averages over the whole crust enhance some interesting features the most evident are belts of high vp vs in the thinned crust of the apennines where extension has long been active in the quaternary probably as an effect of highly fractured rocks with abundant fluid circulation strong correlation exists between areas of high vp vs and quaternary volcanoes suggesting the presence of fluids at depth

a crustal model for the eastern alps region and a new moho map in southeastern europe in the last two decades south central europe and the eastern alps have been widely explored by many seismic refraction experiments e g celebration 2000 alp 2002 sudetes 2003 although quite detailed images are available along linear profiles a comprehensive three dimensional crustal model of the region is still missing this limitation makes this region a weak spot in continental wide comprehensive representations of crustal structure to improve on this situation we select and collect 37 published active source seismic lines in this region after geo referencing each line we sample them along vertical profiles every 50 km or less along the line and derive p wave velocities in a stack of homogeneous layers separated by discontinuities depth of crystalline basement top of lower crust and moho we finally merge the information using geostatistical methods and infer s wave velocity and density using empirical scaling relations we present here the resulting crustal model for a region encompassing the eastern alps dinarides pannonian basin western carpathians and bohemian massif covering the region within 45 circ text 51 circ hbox n and 11 circ text 22 circ hbox e with a resolution of 0 2 circ times 0 2 circ we are also able to extend and update the map of moho depth in a wider region within 35 circ text 51 circ hbox n and 12 circ text 45 circ hbox e gathering moho values from the collected seismic lines other published dataset and using the european plate reference epcrust as a background all the digitized profiles and the resulting model are available online

paleomagnetic evidence from cape verde islands basalts for fully reversed excursions in the brunhes chron abstract in this study we present paleomagnetic data from two lava sequences on santo antao cape verde islands the tarrafal and agua nova profiles from which 63 and 43 lava flows were sampled respectively previous 40ar 39ar ages have constrained the two profiles to the brunhes chron which is in accordance with the normal polarity of the majority of the flows some individual lava flows as well as flow sequences with virtual geomagnetic poles deviating more than 45 from the geographic north pole are interpreted to represent geomagnetic excursions based on interpretation of the directional data three excursions are recorded in the tarrafal profile t i t ii and t iii and four in the agua nova profile ag i ag ii ag iii and ag iv both 40ar 39ar results and paleomagnetic directional data indicate that an excursion defined by eight flows in the tarrafal profile t i is the same as one recorded in six flows in the agua nova profile ag i this excursion which passes the reversal test with classification c is the first geomagnetic excursion in the brunhes chron to pass the reversal test the 40ar 39ar ages suggest that this excursion could represent chryptochron c1n 1 0 493 0 504 ma the only chryptochron or tiny wiggle identified in the marine magnetic anomaly record for the brunhes chron the remaining excursions may not yet be unambiguously correlated between the two profiles another excursion recorded by two flows in the top of the tarrafal profile t iii also displays completely reversed polarity

thick skinned tectonics in the external apennines italy new evidence from magnetic anomaly analysis 1 we discuss the tectonic implications of a new residual magnetic map of the apennine belt adriatic apulian foreland obtained by integrating ground and offshore data sets chiappini et al 2000a negative anomalies are documented over the adriatic apulian foreland areas whereas the external apennine belt is characterized by a ubiquitous low amplitude 30 nt long wavelength positive anomaly in the central northern apennines three 100 km wide more intense 100 200 nt round shaped anomalies are superimposed to the long wavelength feature finally in the tyrrhenian sea and margins high intensity short wavelength positive negative couplets coincide with magmatic outcrops or bodies at shallow depth the low amplitude anomaly pattern over italy suggests that the magnetic basement beneath the triassic evaporites is ubiquitously incorporated in the external belt compressive fronts implying a thick skinned tectonic style for the external apennines the new residual magnetic map resolves the inconsistency between previous aeromagnetic data agip spa italia 1981 which suggested a lack of basement involvement in the apennine belt and recent seismic data which imaged deep reflectors penetrating the basement two magnetic models along ne sw transects in the northern and southern apennines suggest consistent structural styles in the northern apennines positive anomalies roughly coincide with the external compressive fronts although there are local second order differences between the belt front and the edges of the anomaly here the magnetic data show that the basement rises southwestward along the thrust fronts from 6 7 km depth in the adriatic foreland to 2 3 km depth in the axial belt where some exploration wells have penetrated basement within the belt front basement exhumation is inferred to occur along high angle low displacement thrust faults inverting preexisting normal faults in the southern apennines a remarkable positive magnetic anomaly is parallel with and tens of kilometers southwest of the belt front seismic data and oil wells show that the basement surface cannot be shallower in the belt than in the foreland therefore the observed magnetic anomaly is produced by strongly magnetic basement beneath the belt likely an internal crustal wedge tectonically interposed between the apulian carbonate sequences and basement

aftershock patterns of ms 7 earthquakes in the india asia collision belt anomalous results from the muzaffarabad earthquake sequence kashmir 2005 the seismicity rate triggered by the muzaffarabad kashmir 2005 m w 7 6 m s 7 7 earthquake is above the average when analyzing the aftershock rate of the 18 m s 7 0 events in the india asia collision belt between 1973 and 2008 all 17 m s 7 0 events occurred within 10 latitude and 20 longitude distance from the 2005 muzaffarabad earthquake epicenter we determined the huge aftershock productivity for this earthquake is not driven by a specific omori law parameter this anomaly in aftershock rate value corresponds to a relatively higher rate decay as measured by the p value and a larger density value in a higher background seismicity rate setting prestress conditions than the other 17 sequences respectively after normalizing by the mainshock size and by the magnitude range of observation we resolved the anomalies with a 95 confidence level for five aftershock sequences for either the duration the productivity the density or the background seismicity rate when we did not include the local processes that drive these specific anomalies two other global results emerged for the averaged data from the 18 m s 7 0 aftershock sequences first for all sequences background seismicity and duration are anticorrelated graphic 1 within the framework of rate and state friction law this result supports the assertion that the observed background seismicity rate can be used as a proxy for the stressing rate dieterich 1994 second we robustly resolve the dependence of aftershock productivity on the mainshock faulting styles for example the aftershock productivity for strike slip mainshocks is on average four times smaller than the productivity of thrust faulting mainshocks 1 embed inline graphic 1 gif

spectral element simulations of seismic waves generated by the 2009 l aquila earthquake abstract we adopt a spectral element method sem to perform numerical simulations of the complex wavefield generated by the 6 april 2009 m w 6 3 l aquila earthquake in central italy the mainshock is represented by a finite fault solution obtained by inverting strong motion and global positioning system data testing both 1d and 3d wavespeed models for central italy surface topography attenuation and the moho discontinuity are also accommodated including these complexities is essential to accurately simulate seismic wave propagation three component synthetic waveforms are compared to corresponding velocimeter and strong motion recordings the results show a favorable match between data and synthetics up to 0 5 hz in a 200 km 200 km 60 km model volume capturing features mainly related to topography or low wavespeed basins we construct synthetic peak ground velocity maps that for the 3d model are in good agreement with observations thus providing valuable information for seismic hazard assessment exploiting the sem in combination with an adjoint method we calculate finite frequency kernels for specific seismic arrivals these kernels capture the volumetric sensitivity associated with the selected waveform and highlight prominent effects of topography on seismic wave propagation in central italy online material movie of wave propagation waveform fits and stable of station parameters

a geology based 3d velocity model of the los angeles basin sediments abstract seismic hazard studies of the los angeles basin area require a realistic seismic velocity model we use geologic information about depth to crystalline basement depths to sedimentary horizons uplift of sediments and surface geology in a velocity depth age function to construct a three dimensional velocity model in earthquake location tests the model predicts travel times satisfactorily and in earthquake ground motion simulations the model correctly determines the timing and amplitude of late arriving waves

empirical corrections for basin effects in stochastic ground motion prediction based on the los angeles basin analysis amplification corrections are presented for the finite fault stochastic ground motion simulation model these corrections represent the total effect of the los angeles basin on the ground motion spectra spectral amplification ratios were calculated by dividing the observed spectra for the 1994 northridge and 1987 whittier narrows earthquakes including shear and basin generated waves by the simulated spectra created assuming an average rock site condition smoothed amplification data were plotted above 3d images of the basin revealing a general correlation between the estimated basin depth and total basin amplification for both earthquakes over three frequency ranges low 0 2 2 hz intermediate 2 8 hz and high 8 12 5 hz the depth dependent corrections are derived from the regression of the combined data from both earthquakes in order to reduce an uncertainty caused by the azimuth of incoming waves ground motion duration is defined as the time for 95 of the acceleration spectral energy to pass after the s wave arrival due to ambiguity in defining a basin parameter controlling duration it was impossible to develop a generic equation that would relate the duration ratio observed synthetic to some characteristic of the basin users are cautioned though that the durations within the basin may be as much as four times longer than the simulated ones the procedure is outlined for potential users who wish to use the results of this study in synthesizing more accurate earthquake ground motions taking into account complicated basin geometry and near surface effects the results are directly applicable to engineering simulation of strong ground motions in a sedimentary basin environment manuscript received 21 may 2002

modeling of 3d subsurface structure and numerical simulation of strong ground motion in the adapazari basin during the 1999 kocaeli earthquake turkey the 1999 kocaeli izmit earthquake seriously damaged the downtown area of adapazari turkey the wavefield of the strong ground motions is considered to have been affected by the deep ground structure a refraction and reflection seismic survey was made to obtain the velocity structure of the profile in the north south direction across the basin a 3d subsurface model is presented based on results of the refraction and reflection survey on data obtained from a gravity survey and on observations of microseisms and aftershocks the proposed model shows deep sediment with a steep slope beneath downtown adapazari strong ground motions in the frequency range of 0 1 1 0 hz propagating in the subsurface model during the kocaeli earthquake also were simulated numerically by the 3d finite difference method the simulated results show that ground motions in downtown adapazari were larger than those in the area between downtown and the source fault because the former were significantly amplified by the basin edge effect

ground motion simulation and validation of the 2008 chino hills california earthquake using different velocity models abstract we present a set of ground motion simulations of the 2008 m w 5 4 chino hills earthquake using different seismic velocity models available for southern california the simulations are tailored for a maximum frequency of 4 hz and a minimum shear wave velocity of 200 m s we use the community models developed by the southern california earthquake center cvm s and cvm h in the case of cvm h we use two available alternatives with and without considering the geotechnical layers gtl we compare the simulation results obtained with the models against each other and validate the synthetics with recordings obtained at more than 300 stations the comparisons are used to gain insight into the sensitivity of the results to differences in the models and to make conclusions about the strengths of each model s description of the crustal structure and the gtl in the region the validation is done using a goodness of fit gof criterion we find the gof values show a better match at frequencies below 1 hz within the basins and below 0 5 hz in general the models however do not converge at frequencies lower than 0 5 hz and the areas where each model leads to better results do not always coincide the synthetics start to deviate significantly from observations at frequencies above 1 and 2 hz although very good agreement with data can still be found at individual locations even at the higher frequencies cvm s yields the best results at frequencies up to 0 25 hz our results reveal significant sensitivity of the ground motion to the differences in the structural representation of basins and shallow layers in the models this indicates the models need to be cross referenced we close by offering suggestions on the type of improvements that could be adopted in the future

a new kinematic model for iberia further palaeomagnetic and isotopic age evidence abstract palaeomagnetic results and k ar age data from the algarve igneous province have uncovered three ancient relative field components it is inferred that the principal magnetization of the monchique complex with a mean direction of d 42 i 181 95 4 5 was acquired at around the time of the pluton s emplacement some 72 2 ma ago a second magmatic pulse affected the region at 68 2 ma leaving behind a relative field component of d 42 i 341 95 1 7 furthermore an overprinted magnetization characterized by shallow inclination and somewhat smeared northwesterly southeasterly declination most likely originates from the lower tertiary the new palaeomagnetic data are seen in conjunction with previously published upper cretaceous results from the sintra and sines intrusive complexes the resulting database gives entirely new perspectives for evaluating the plate tectonic history of the peninsula in upper cretaceous lower tertiary time a two phase rotation of the iberian micro plate an anticlockwise one of 40 followed by a clockwise one of 70 is clearly in evidence the net clockwise rotation provided a major impetus for the compressive deformation in the pyrenees and the bay of biscay and led to extensive remagnetization of older rock formations in the northern regions of iberia previous palaeomagnetic conclusions in favour of a single anticlockwise rotation of 35 supposed to be directly connected with the formation of the bay of biscay appear to be artefacts which stem from an incorrectly adopted palaeomagnetic reference frame

magnetization properties of intrusive extrusive rocks from east maio republic of cape verde and their geological implications summary the remanent magnetization of intrusive extrusive rocks of the basement complex of east maio constitutes four components that define two different axes of magnetization at around dec 328 inc 12 and dec 007 inc 14 respectively in general two or more components co exist in separate specimens or sites but both axes are present most frequently in the normal sense the nnw striking axis the b axis fits very well with the upper cretaceous polar wander path for africa it is consequently inferred that the major phase of sheet intrusions in maio dates from this time probably from the interval 90 70 myr bp comparisons of the directional dispersions in the folded and unfolded states suggest that this injection phase post dates the uplift of the central igneous complex of the island the second axis of magnetization the a axis agrees very well with late teritary quaternary palaeomagnetic data for africa and the canary islands the a axis is therefore regarded as of secondary origin being the consequence of a thermal chemical overprint during the miocene pliocene volcanism on the island the occurrence of a 50 70 myr long period of volcanic quiescence and erosion between the termination of the early igneous activity upper cretaceous and the rejuvenated magmatism in miocene pliocene time is compatible with similar observations in the canary islands in contrast to the palaeomagnetic conclusions the k ar data only give ages around 10 myr the unusually young isotope dates are regarded as being due to an almost complete age resetting and are seen in conjuction with the overprinted magnetization this explanation is further supported by the fact that k ar results of pillow lavas underlying upper jurassic limestones only give tertiary ages

palaeomagnetism and k ar ages of the south west african basalts and their bearing on the time of initial rifting of the south atlantic ocean summary palaeomagnetic and isotopic results from the kaoko lavas hoachanas basalts and dolerite sills of south west africa indicate that the upper triassic lower jurassic stormberg flows of south africa may have extended into sw africa and that younger igneous events of lower cretaceous age were simultaneous with the serra geral volcanism in brazil five analyses on three samples of the keetmanshoop sills gave k ar ages between 178 4 and 199 4 ma four analyses of two samples of the hoachanas basalts gave ages between 161 3 and 173 2 ma and eight analyses of five samples of kaoko basalt gave ages between 110 4 and 128 2 ma the components of remanent magnetization rm used to compute palaeomagnetic pole positions for the kaoko lavas 48 n 93 w a95 3 and for the hoachanas basalts 61 n 106 w a95 7 are stable to alternating field af and thermal demagnetization correlation on a pre drift map and on a map reconstructed for 112 ma bp before present between the palaeomagnetic poles from the kaoko and serra geral lavas suggests that the south atlantic had not opened appreciably by 112 ma bp cretaceous pole positions for s america and africa on a map reconstructed for 80 ma bp are also discussed

p wave seismic velocity structure derived from sonic logs and industry reflection data in the los angeles basin california 1 we present a new three dimensional seismic p wave velocity model of the los angeles basin that is based on more than 150 sonic logs and 7000 stacking velocities from industry reflection profiles the model was developed using kriging techniques implemented in gocad a commercial application specializing in the construction of surfaces the analysis of spatially distributed data and the modeling or simulation of properties and is characterized by a heterogeneous spatial varying velocity gradient with maximum velocities of 5000 m s in the sedimentary section variability of the observed p wave velocities increases with depth reflecting complex structural and sedimentological controls the model contains a new representation of the basin shape as defined by the sediment basement interface which was mapped using well control and seismic reflection profiles our model differs substantially in approach and outcome from previous representations of crustal velocity structure in southern california

40ar 39ar geochronology of santo antao cape verde islands santo antao the northernmost island of the cape verde archipelago consists entirely of silica undersaturated volcanic products and minor intrusions 40ar 39ar incremental heating experiments have been carried out on 24 samples that cover the entire exposed chronological sequence the oldest lavas 7 57 0 56 ma representing an older volcanic basement are exposed about 620 m above mean sea level after an interval of quiescence of up to 4 3 ma the volcanic activity resumed and continued at low eruption rates the older basement is unconformably overlain by a ca 810 m thick lava sequence that spans an age range from 2 93 0 03 to 1 18 0 01 ma this sequence is cut by many dykes and sills simultaneous volcanic activity occurred in the northeastern central and eastern part of the island a phonolitic pumice deposit that forms a noteworthy feature over most of the island has an estimated age of 0 20 ma this predates volcanic activity that formed the highest point of the island tope de coroa which has an age of 0 17 0 02 ma the most recent eruption on the island formed nephelinitic lavas in the porto novo region at 0 09 0 03 ma the oldest volcanism exposed on santo antao which took place about 7 6 ma ago was simultaneous with waning activity on maio at the eastern end of the cape verde archipelago

the tethys sea and the alpine himalayan orogenic belt mega elements in a new global tectonic system abstract analysis of meso cainozoic palaeomagnetic data for africa india and eurasia has led to the development of a new mobilistic alpine plate tectonic model characterized by a hierarchical system of plates in relative rotation the new model which discounts seafloor spreading implies that there have been no significant palaeogeographic changes in the overall distribution of continental and oceanic regions the mid oceanic ridges are interpreted as transpressive tectonic features caused by rotation of megaplates containing both continental and oceanic crust the isostatic uplift due to crustal lithospheric thickening giving rise to the general ridge topography as well as to the ridge parallel structural grain the new plate tectonic theory gains strong support from a variety of geophysical geological and palaeoclimatological evidence and several observations that have remained enigmatic or awkward within the context of the orthodox model can be readily accounted for in the new tectonic framework the model maintains the tethys as a relatively narrow epicontinental sea which during its maximum extent stretched latitudinally from the caribbean across the central atlantic to se asia the alpine himalayan orogenic belt developed along the boundary of two megaplates in relative rotation which provided a transpressive tectonic regime the location of the plate boundary to the north of the mediterranean has important implications for discussion of mediterranean microplates for example it now seems that italy has been subjected to 10 15 of clockwise microplate rotation previous conclusions in favour of 30 40 of anticlockwise rotation are regarded as artefacts which arise from incorrectly linking the mediterranean region to the european palaeomagnetic frame instead of to the african one the model suggests further that the indo pakistani plate was closely tied to eurasia this challenges the conventional view that the peninsula was part of an alleged gondwanaland the new pre drift configuration implies that the indo pakistani plate rotated 135 clockwise at around the cretaceous tertiary boundary before redocking with asia in approximately its present relative orientation

the scec southern california reference three dimensional seismic velocity model version 2 we describe version 2 of the three dimensional 3d seismic velocity model of southern california developed by the southern california earthquake center and designed to serve as a reference model for multidisciplinary research activities in the area the model consists of detailed rule based representations of the major southern california basins los angeles basin ventura basin san gabriel valley san fernando valley chino basin san bernardino valley and the salton trough embedded in a 3d crust over a variable depth moho outside of the basins the model crust is based on regional tomographic results the model moho is represented by a surface with the depths determined by the receiver function technique shallow basin sediment velocities are constrained by geotechnical data the model is implemented in a computer code that generates any specified 3d mesh of seismic velocity and density values this parameterization is convenient to store transfer and update as new information and verification results become available

tectonostratigraphic evolution of the jurassic extensional basins of the eastern southern alps and adriatic foreland based on an integrated study of surface and subsurface data successions that characterize the eastern southern alps have been compared with coeval units drilled in the alpine foreland po and veneto plains northern adriatic sea the eastern southern alps are composed of a carbonate platform plateau drowned in the early jurassic trento platform and plateau a basin formed in the early jurassic belluno basin and a carbonate platform that lasted from the jurassic to the cretaceous friuli platform integration of stratigraphic and geophysical data illustrates the extensional architecture of the alpine foreland subsurface at the beginning of the jurassic peritidal successions were widespread everywhere except for the belluno basin a reorganization of the early jurassic paleogeography affected the southern alps around the sinemurian pliensbachian boundary the pliensbachian successions were deposited in the central western areas of the trento platform whereas elsewhere in the same platform and in the northern friuli platform pliensbachian units are missing replaced by an unconformity surface covered by crinoidal sands that have also been found in the subsurface the belluno basin is recognizable in seismic profiles under the veneto plain southward northern adriatic sea and po plain the basin between the trento and the friuli platforms here called the northern adriatic basin possesses a stratigraphy different from that of the belluno basin the northern adriatic basin drowned later and seismic profiles indicate that it was wider and bounded by groups of small synsedimentary faults instead of the major faults displacing the belluno basin the northern adriatic basin can be interpreted as the northeastern extension of the umbro marchean basin of central italy

basin structure beneath the santa rosa plain northern california implications for damage caused by the 1969 santa rosa and 1906 san francisco earthquakes regional gravity data in the northern san francisco bay region reflect a complex basin configuration beneath the santa rosa plain that likely contributed to the significant damage to the city of santa rosa caused by the 1969 m 5 6 5 7 santa rosa earthquakes and the 1906 m 7 9 san francisco earthquake inversion of these data indicates that the santa rosa plain is underlain by two sedimentary basins about 2 km deep separated by the trenton ridge a shallow west northwest striking bedrock ridge west of santa rosa the city of santa rosa is situated above the 2 km wide protruding northeast corner of the southern basin where damage from both the 1969 and 1906 earthquakes was concentrated ground motion simulations of the 1969 and 1906 earthquakes two events with opposing azimuths using the gravity defined basin surface show enhanced ground motions along the northeastern edge of this corner suggesting that basin edge effects contributed to the concentration of shaking damage in this area in the past and may also contribute to strong shaking during future earthquakes

compressional and shear wave velocity versus depth relations for common rock types in northern california abstract this article presents new empirical compressional and shear wave velocity vp and vs versus depth relationships for the most common rock types in northern california vp versus depth relations were developed from borehole laboratory seismic refraction and tomography and density measurements and were converted to vs versus depth relations using new empirical relations between vp and vs the relations proposed here account for increasing overburden pressure but not for variations in other factors that can influence velocity over short distance scales such as lithology consolidation induration porosity and stratigraphic age standard deviations of the misfits predicted by these relations thus provide a measure of the importance of the variability in vp and vs caused by these other factors because gabbros greenstones basalts and other mafic rocks have a different vp and vs relationship than sedimentary and granitic rocks the differences in vs between these rock types at depths below 6 or 7 km are generally small the new relations were used to derive the 2005 u s geological survey seismic velocity model for northern california employed in the broadband strong motion simulations of the 1989 loma prieta and 1906 san francisco earthquakes initial tests of the model indicate that the vp model generally compares favorably to regional seismic tomography models but that the vp and vs values proposed for the franciscan complex may be about 5 too high

validating nevada shakezoning predictions of las vegas basin response against 1992 little skull mountain earthquake records over the last two years the nevada seismological laboratory has devel oped and refined nevada shakezoning nsz procedures to characterize earthquake hazards in the intermountain west simulating the ml 5 6 5 8 little skull mountain lsm earthquake validates the results of the nsz process and the ground shaking it predicts for las vegas valley lvv the nsz process employs a physics based finite difference code from lawrence livermore laboratory to compute wave propagation through complex 3d earth models computing limitations restrict the results to low frequencies of shaking for this lsm regional model the limitation is to frequencies of 0 12 hz and below the clark county parcel map completed in 2011 is a critical and unique geotechnical data set included in nsz predictions for lvv replacing default geotechnical velocities with the parcel map velocities in a sensitivity test produced peak ground velocity amplifications of 5 11 in places even at low frequencies of 0 1 hz a detailed model of lvv basin floor depth and regional basin thickness mod els derived from gravity surveys by the u s geological survey are also important components of nsz velocity model building in the nsz predicted seismograms at 0 1 hz rayleigh wave minus p wave r p differential arrival times and the pulse shapes of rayleigh waves correlate well with the low pass filtered lsm recordings importantly peak ground velocities predicted by nsz matched what was recorded to be closer than a factor of two observed seismograms within lvv show longer du rations of shaking than the synthetics appearing as horizontally reverberating 0 2 hz longitudinal waves beyond 60 s after rayleigh wave arrival within the basins the current velocity models are laterally homogeneous below 300 m depth leading the 0 1 hz nsz synthetics to show insufficient shaking durations of only 30 40 s

modeling of 3d basin structures for seismic wave simulations based on available information on the target area case study of the osaka basin japan practical procedures for modeling basin structure are proposed one is to construct a smooth 3d basin structure model under and around the target site for low frequency strong motion simulation the other is to make a 1d velocity structure model just under the target site for high frequencies these procedures were applied to the osaka basin japan in which numerous exploration studies were conducted before and after the 1995 hyogoken nanbu kobe earthquake the published results of those explorations in addition to those from our several investigations were compiled to construct the model a two dimensional third order b spline function was used to establish a smooth structure model from available depth data microtremor array observations were used to model the velocities and densities of the sedimentary layer structures a four layer model well explains the dispersion characteristics of rayleigh waves that make up the microtremors by adding a detailed shallow velocity structure to the top of the deeper four layer model adequate site responses for a wide frequency range of ground motions can be obtained this proposed procedure can be used to determine the basement geometry of other sedimentary basins

development and testing of a 3d seismic velocity model of the po plain sedimentary basin italy abstract we built a 3d seismic model of the po plain and neighboring regions of northern italy covering altogether an area about 600 km by 300 km with an approximately 1 km spaced grid we started by collecting an extensive and diverse set of geological and geophysical data including seismic reflection and refraction profiles borehole logs and available geological information major geological boundaries and discontinuities have thus been identified and mapped into the model we used kriging to interpolate the geographically sparse information into continuous surfaces delimiting geological bodies with laterally varying thickness seismic wave properties have been assigned to each unit using a rule based system and v p v s and derived from other studies sedimentary strata although with varying levels of compaction and hence material properties may locally reach a thickness of 15 km and give rise to significant effects in seismic wave propagation we have used our new model to compute the seismic response for two recent earthquakes to test its performance results show that the 3d model reproduces the large amplitude and the long duration of shaking seen in the observed waveforms recorded on sediments whereas paths outside the basin may be well fit by more homogeneous 1d hard rock structure we conclude that the new model is suited for simulation of wave propagation mostly for t 3 s and may serve well as a constraint for earthquake location and further improvements via body or surface wave inversion

tomography of the alpine region from observations of seismic ambient noise we use correlations of the ambient seismic noise to study the crust in western europe cross correlation of 1 year of noise recorded at 150 three components broadband stations yields more than 3 000 rayleigh wave group velocity measurements these measurements are used to construct rayleigh group velocity maps of the alpine region and surrounding area in the 5 80 s period band in the 5 10 s period band the seismic noise recorded in europe is dominated by surface waves originating from the northern atlantic ocean this anisotropy of the noise and the uneven station distribution affect the azimuthal distribution of the paths where we obtain reliable group velocity measurements as a consequence our group velocity models have better resolution in the northeast direction than in the southwest direction finally we invert the resulting rayleigh wave group velocity maps to determine the moho depth our results are in good agreement with the result of the numerous active experiments in the alps and provide a continuous image of the alpine structure

review on soil water isotope based groundwater recharge estimations groundwater recharge estimations are necessary for sustainable management of groundwater resources among various hydraulic hydrogeological and hydrological approaches tracer methods are proposed to improve groundwater recharge estimations soil water isotope based estimates of groundwater recharge rates were developed in the 1960s and have been applied in more than 40 studies reviewed within this manuscript this comprehensive review research distinguishes three fundamental research approaches 1 labelling method with tritium or deuterium which can be used to trace unsaturated zone water movement 2 tracing soil water movement using a seasonal signal of stable isotopes in precipitation mainly applied in humid zones and 3 interpretation of an evaporation signal that impacts soil water stable isotope composition mainly applicable in arid and semiarid regions more recently advances in soil water extraction and analytical methods allow a higher sampling resolution and in situ measurements of soil water stable isotopes analytical advances may strengthen and improve the applicability of stable isotope methods for quantitative recharge we present compare and discuss studies of unsaturated zone isotope profiles with an emphasis on necessary prerequisites such as a substantial thick porous sedimentary layer or negative influences through high clay and silt contents or dry soil conditions copyright 2015 john wiley sons ltd