reliability of palaeozoic palaeomagnetic poles and apwp of gondwanaland abstract a review of reliable palaeomagnetic data from gondwana palaeozoic rocks supports the apparent polar wander path apwp initially proposed by morel and irving this path or versions of it has recently gained favour with a number of groups the apwp suggests that during the mid palaeozoic gondwanaland was very mobile no palaeomagnetic pole position s has been yet reported that confirms the contentious segment of apwp from the late ordovician to the early silurian the apwp implies that the south pole moved rapidly from north africa in the ordovician to a position off southern south america by the silurian back to central africa by the early carboniferous and across gondwanaland to australia by the late carboniferous the distribution of palaeozoic tillites independently supports such a mobilistic gondwanaland the palaeomagnetic and tectonic evidence are compatible with the lachlan fold belt of australia having been in place since the mid devonian

model for the evolution of the avalonian cadomian belt the inception and termination of the ca 670 550 ma avalonian cadomian orogenic cycle are interpreted in terms of the amalgamation and breakup of a late precambrian supercontinent synorogenic arc related volcano sedimentary and granitoid rocks are attributed to oblique southward directed subduction along the margin of the supercontinent after its amalgamation breakup of the supercontinent and inception of the iapetus cycle led to termination of subduction and its replacement by transform activity the resulting closure of late precambrian arc related basins and the development of early cambrian platform successions with acado baltic fauna accompanied the formation of iapetus but took place on the active margin of a preexisting ocean and do not record the evolution of its rifted european flank

impact of mesh and dem resolutions in sem simulation of 3d seismic response this study shows that the resolution of a digital elevation model dem and model mesh strongly influences 3d simulations of seismic response topographic heterogeneity scatters seismic waves and causes variation in seismic response am plification and deamplification of seismic amplitudes at the earth s surface dem resolution influences the accuracy and detail with which the earth s surface can be represented and hence affects seismic simulation studies apart from the spatial resolution of a dem the mesh resolution adopted in the creation of a 3d spectral element meshing also changes the detailedness of surface topography working with high resolution data is in most cases not possible on a regional scale because of its costliness in terms of time money and computation in this study we evaluate how low the resolution of dem and mesh can become before the results are significantly affected we simulated models with different combinations of dem and mesh resolutions the peak ground displacement pgd obtained from these simulations was compared with the pgd of the model with the finest mesh and dem resolution our results show that any mesh or dem resolution of 540 m or coarser will give unrealistic results these results are valid for similar terrains as studied here and might not be directly applicable to regions with significantly different topography

anatomy of strong ground motion near source records and three dimensional physics based numerical simulations of the mw 6 0 2012 may 29 po plain earthquake italy

strong ground motion and damage in the taipei basin from the moho reflected seismic waves during the march 31 2002 hualien taiwan earthquake 1 the march 31 2002 hualien offshore earthquake ml6 8 mw7 0 caused minor damage near its epicenter but significant damage in taipei about 110 km from the epicenter the recorded pga values around the taipei basin vary in a factor of 5 the high pga values in the southeastern part of the basin correspond to the most significant damage area during the earthquake strong ground motion recordings from this event recorded at stations around the taipei basin exhibit several distinct large amplitude seismic arrivals that can be interpreted as the pmp smp and sms phases the largest amplitude of the critically reflected s wave from the moho sms and the amplification of soft shallow sediments unique for each site are responsible for the maximum peak ground motion and the significant damage in the taipei basin during the hualien offshore earthquake

the assessment of the hydrocarbon potential and maturity of silurian intervals from eastern part of moesian platform romanian sector abstract the aim of this paper is the assessment of the hydrocarbon potential and maturity of silurian intervals from the c l rasi bordei verde biruin a perimeter east moesian platform all the information gathered from the wells drilled in the mentioned perimeter is used for the evaluation of the shale gas potential too this major sedimentary basin has all geological conditions for hydrocarbons generation migration and accumulation the main conclusions of the all geo analyses are the following the xrd analyses show that the samples consist of clay minerals with organic material the organic matter contained in the samples of the wells shows widely distributed type of organoclasts in absence of true vitrinite originating from higher plants in these lower paleozoic series the various encountered organic remains consist of tasmanites microporous or homogeneous fragments structured fragments of graptolites oxidized or naturally rich in oxygen organoclasts inherited from the continent phytoclasts fungal remains the maturity of the silurian at nd rei borehole is established taking into account the fluorescence of the tasmanites and the reflectance of graptolites the maturity increases with depth between 0 70 and 1 eq vro the organic matter of biruin a and c l rasi boreholes is overmature with maturity of around 1 40 1 55 at 400 m in biruin a and a maturity increase with depth between 1 85 and 2 05 eq vro in c l rasi borehole those values are mainly deduced from vitrinite graptolite correlation according to the maturity trend deduced of c l rasi and nd rei boreholes the high maturity of biruin a for such a low burial around 400 m indicates a possible erosion around 3400 m due to uplift the silurian studied samples consist of carbonated claystones with an organic matter of type ii with relatively low residual toc content less than 1 2 weight for the overmature boreholes biruin a and c l rasi and less than 1 6 weight in nd rei borehole

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

northern gondwanan affinity of the east moesian terrane based on chitinozoans abstract identification of palaeocontinental affinities is important to place moesia in the global context of palaeogeographical reconstructions in the absence of palaeomagnetic data and relevant macrofauna palynological data and especially chitinozoans represent an important tool recently used to unravel palaeogeographical affinities chitinozoans from three main boreholes c l rasi 2881 z voaia 2581 and nd rei 1052 located in east moesia have been studied they indicate a predominant palaeogeographical affinity with northern gondwana

near real time simulations of global cmt earthquakes summary we have developed a near real time system for the simulation of global earthquakes prompted by a trigger from the global centroid moment tensor cmt project the system automatically calculates normal mode synthetic seismograms for the preliminary reference earth model and spectral element synthetic seismograms for 3 d mantle model s362ani in combination with crustal model crust2 0 the 1 d and 3 d synthetics for more than 1800 seismographic stations operated by members of the international federation of digital seismograph networks are made available via the internet global shakemovie princeton edu and the incorporated research institutions for seismology data management center iris iris edu the record length of the synthetics is 100 min for cmt events with magnitudes less than 7 5 capturing r1 and g1 at all epicentral distances and 200 min for cmt events with magnitudes equal to or greater than 7 5 capturing r2 and g2 the mode simulations are accurate at periods of 8 s and longer whereas the spectral element simulations are accurate between periods from 17 to 500 s the spectral element software incorporates a number of recent improvements for example the mesh honours the moho as a first order discontinuity underneath the oceans and continents and the performance of the solver is enhanced by reducing processor cache misses and optimizing matrix matrix multiplication in addition to synthetic seismograms the system produces a number of earthquake animations as well as various record sections comparing simulated and observed seismograms

rheological properties of water ice applications to satellites of the outer planets 1 abstract the icy moons of the outer solar system have not been quiescent bodies in part because many have a substantial water component and have experienced significant internal heating we can begin to understand the thermal evolution of the moons and the rate of viscous relaxation of surface topography because we now have good constraints on how ice in several of its polymorphic forms flows under deviatoric stress at planetary conditions details of laboratory derived flow laws for pure polycrystalline ice are reviewed in detail one of the more important questions at hand is the role of ice grain size grain size may be a dynamic quantity within the icy moons and it may or may not significantly affect rheology one recent beneficiary of revelations about grain size sensitive flow is the calculation of the rheological structure of europa s outer ice shell which may be no thicker than 20 km

paleozoic laurentia gondwana interaction and the origin of the appalachian andean mountain system laurentia the rift bounded precambrian nucleus of north america may have broken out from a neoproterozoic supercontinent between east and west gondwana several lines of evidence suggest that the appalachian margin of laurentia subsequently collided with the proto andean margin of the amalgamated gondwana supercontinent in different relative positions during early and mid paleozoic time in route to final docking against northwest africa to complete the assembly of pangea hence the appalachian and andean orogens may have originated as a single mountain system the overall hypothesis retains the same paleomagnetic and paleobiogeographic controls as previous global reconstructions for the paleozoic era laurentia gondwana collisions may help to explain contemporaneous unconformities in the paleozoic sedimentary cover of the laurentian gondwanan and baltic cratons

tectonic evolution of nw iberia during the paleozoic inferred from the geochemical record of detrital rocks in the cantabrian zone the cantabrian zone of nw iberia preserves a voluminous almost continuous sedimentary sequence that ranges in age from ediacaran to early permian its tectonic setting is controversial and recent hypotheses include i passive margin deposition along the northern margin of gondwana ii an active continental margin or iii the margin of a drifting ribbon continent and iv a combination of the three aforementioned possibilities in this paper we present geochemical data from 21 samples taken in detrital rocks in the cantabrian zone from ediacaran to early permian age the results together with previously published detrital zircon ages from these strata allow a comprehensive analysis of changing tectonic scenarios and provenance through time collectively these data indicate that this portion of iberia was an active margin during the ediacaran that evolved to become part of the passive margin of gondwana at least from ordovician to late devonian times changes in geochemistry zircon age distribution and sm nd isotopes during the carboniferous are attributed to the far field effects of the onset of the collision between gondwana and laurussia and related processes such as recycling of older sedimentary sequences as well as the involvement of the rocks formed during the variscan orogeny and oroclinal buckling latest carboniferous and permian show a more juvenile sm nd and higher values of illite cristallinity that may support the hypothesis of lithospheric foundering after oroclinal buckling

provenance constraints from detrital zircon u pb ages in the nw iberian massif implications for palaeozoic plate configuration and variscan evolution detrital zircons from pre orogenic upper ordovician to devonian low grade metasedimentary rocks have been dated by laser ablation inductively coupled plasma mass spectrometry la icp ms to 1 constrain the variations of zircon age populations within the autochthonous sequences of nw iberia 2 compare u pb detrital zircon ages with previous data 3 test the hypothesis of the armorica microplate as a peri gondwanan terrane separated from gondwana the similarity in the ages of detrital zircons found in the palaeozoic samples studied here to those published for the upper proterozoic lower cambrian and lower ordovician sediments of nw iberia argues against the separation of armorica and points to a common source area for all of the palaeozoic detrital formations of nw iberia the west african craton and the surrounding pan african belts la icp ms u pb dating of zircons from a synorogenic flysch preserved in klippen in the core of a syncline establishes a maximum depositional age for this deposit as early namurian this age is also a maximum age limit for thrusting and refolding in this part of the iberian massif correlation of the zircon age populations with published ages confirms the link between the emplacement of the allochthonous complexes of nw iberia and synorogenic sedimentation

anti plane responses of acceleration by a shallow hill next to an alluvial valley abstract this study proposed a hybrid method combining finite element method fem and a wave function based on the lamb series in conjunction with modified transfinite interpolation for use in examining surface accelerations on a semi elliptical hill subjected to shear horizontal sh waves of various dimensionless frequencies at various incident angles the case topography included a semi elliptical hill of fixed height adjacent to a semi elliptical alluvial valley of variable depth ehav differences in site effects between ehav and a single semi elliptical hill or a semi elliptical alluvial valley were investigated as a function of the modified transmissibility tr variations in tr associated with clearly revealed the resonance frequencies rfs associated with an elevated probability of landslides our simulation results revealed a larger number of rfs form in hills adjacent to av than in isolated hill this study proposes a systematic approach for the analysis of site effects of ehav focusing on the identification of potential landslides due to seismic waves excitation

transitions in thermal convection with strongly variable viscosity one of the most important material properties influencing the style of convection in the mantles of terrestrial planets is the extreme temperature dependence of viscosity three dimensional numerical convection calculations in a wide 8 8 1 cartesian box and in a spherical shell ratio of inner to outer radius of 0 55 characteristic of terrestrial planets both display two fundamental transitions as the viscosity contrast is progressively increased from unity to a factor of 105 these transitions not only mark changes in the style of deformation in the upper boundary layer from mobile lid to sluggish lid to stagnant lid but also have dramatic effects on the style planform and horizontal length scales of convection in the entire domain vertical variations of viscosity are the most important for determining the horizontal length scales of the convective patterns while lateral viscosity variations play a role in shaping the relative structures of the upwelling and downwelling flows convection in venus appears to be represented most closely by the sluggish lid regime of convection whereas the earth with plate tectonics more closely resembles the mobile lid style of convection forcing plate like characteristics onto the convective flows in the form of imposed weak zones and prescribed surface velocities results in flow patterns dominated entirely by the form used to enforce the plate like behavior and tells us little about why the mantle exhibits long wavelength heterogeneity

effects of dispersed particulates on the rheology of water ice at planetary conditions we have investigated the effects of initial grain size and hard particulate impurities on the transient and steady state flow of water ice i at laboratory conditions selected to provide more quantitative constraints on the thermomechanical evolution of the giant icy moons of the outer solar system our samples were molded with particulate volume fractions of 0 001 to 0 56 and particle sizes of 1 to 150 m deformation experiments were conducted at constant shortening rates of 4 4 10 7 to 4 9 10 4 s 1 at pressures of 50 and 100 mpa and temperatures 77 to 223 k for the pure ice samples initial grain sizes were 0 2 0 6 mm 0 75 1 75 mm and 1 25 2 5 mm stress strain curves of pure ice i under these conditions display a strength maximum u at plastic strains e 0 01 after initial yield followed by strain softening and achievement of steady state levels of stress ss at e 0 1 to 0 2 finer starting grain size in pure ice generally raises the level of u petrography indicates that the initial transient flow behavior is associated with the nucleation and growth of recrystallized ice grains and the approach to ss evidently corresponds to the development of a steady state grain texture effects of particulate concentrations 0 1 are slight at these concentrations a small but significant reduction in u with respect to that for pure water ice occurs mixed phase ice with 0 1 is significantly stronger than pure ice the strength of samples with 0 56 approaches that of dry confined sand the magnitude of the strengthening effect is far greater than expected from homogeneous strain rate enhancement in the ice fraction or from pinning of dislocations orowan hardening this result suggests viscous drag occurs in the ice as it flows around the hard particulates mixed phase ice is also tougher than pure ice extending the range of bulk plastic deformation versus faulting to lower temperatures and higher strain rates the high pressure phase ice ii formed in 0 56 mixed phase ice during deformation at high stresses bulk planetary compositions of ice rock 0 4 0 5 are roughly 2 orders of magnitude more viscous than pure ice promoting the likelihood of thermal instability inside giant icy moons and possibly explaining the retention of crater topography on icy planetary surfaces

evolution into the stagnant lid convection regime with a non newtonian water ice rheology 1 we study and compare the evolution into the stagnant lid regime with a non newtonian water ice and a silicate rheology by solving the equations of thermal convection dislocation creep of water ice is characterized by a larger stress dependence n 4 than silicates n 3 and with this water ice rheology the stagnant lid regime is attained at a temperature determined viscosity contrast greater than 1010 and at an effective viscosity contrast of 105 we also determine a nusselt rayleigh number scaling law for the n 4 rheology

lower cretaceous provenance and sedimentary deposition in the eastern carpathians inferences for the evolution of the subducted oceanic domain and its european passive continental margin

earthquake induced chains of geologic hazards patterns mechanisms and impacts large earthquakes initiate chains of surface processes that last much longer than the brief moments of strong shaking most moderate and large magnitude earthquakes trigger landslides ranging from small failures in the soil cover to massive devastating rock avalanches some landslides dam rivers and impound lakes which can collapse days to centuries later and flood mountain valleys for hundreds of kilometers downstream landslide deposits on slopes can remobilize during heavy rainfall and evolve into debris flows cracks and fractures can form and widen on mountain crests and flanks promoting increased frequency of landslides that lasts for decades more gradual impacts involve the flushing of excess debris downstream by rivers which can generate bank erosion and floodplain accretion as well as channel avulsions that affect flooding frequency settlements ecosystems and infrastructure ultimately earthquake sequences and their geomorphic consequences alter mountain landscapes over both human and geologic time scales two recent events have attracted intense research into earthquake induced landslides and their consequences the magnitude m 7 6 chi chi taiwan earthquake of 1999 and the m 7 9 wenchuan china earthquake of 2008 using data and insights from these and several other earthquakes we analyze how such events initiate processes that change mountain landscapes highlight research gaps and suggest pathways toward a more complete understanding of the seismic effects on the earth s surface

simulation of topographic effects on seismic waves from shallow explosions near the north korean nuclear test site with emphasis on shear wave generation 1 we performed high resolution 8 hz three dimensional simulations of ground motions from shallow explosions in the presence of rough surface topography near the north korean nuclear test site to study elastic propagation effects with emphasis on theoretical aspects of shear wave generation interaction with rough topography causes significant p to rg scattering along the surface with amplification of high frequency 2 8 hz shear waves relative to the flat earth case shear waves of different polarizations are coupled by topographic scattering rg precursors composed of p to rg conversions traveling as surface waves have the spectral amplitudes comparable to the p wave while the rg phase has the low frequency 0 5 3 hz spectral shape of the rg from the flat case plus the high frequency 3 8 hz p wave spectra motions at near vertical takeoff angles corresponding to teleseismic propagation are increased or decreased indicating that waves are focused or defocused by topographic features above the source topographic roughness has a dramatic effect as short wavelength features 2 5 km are included higher frequencies are amplified by topography including frequencies corresponding to wavelengths shorter than the shortest topographic scale length overall topography enhances energy propagating along the surface near the source amplifies surface waves and tends to balance sv and sh polarized motions all of which impact shear wave observations used for nuclear explosion monitoring further simulation studies could elucidate how the wavefield emerging from a topographically rough area ultimately propagates to regional and or teleseismic distances

ground motion and intraevent variability from 3d deterministic broadband 0 7 5 hz simulations along a nonplanar strike slip faultground motion and intraevent variability from 3d deterministic broadband simulations

strong ground motion over a large area in northern taiwan caused by the northward rupture directivity of the 2019 hualien earthquake abstract an mw 6 2 earthquake struck hualien on the eastern coast of taiwan on april 18 2019 its focal mechanism was determined to be a thrust fault with a depth of 18 8 km a wide range of strong ground shaking with an intensity value from 4 25 80 gal to 7 greater than 400 gal occurred in northern taiwan which is unusual for earthquakes of this size here we show a source model as determined by local seismic waveform inversion two asperities were found the smaller one occurred at the hypocenter and the larger one was found 10 km north of the hypocenter with a depth of 18 25 km the initial rupture started from the hypocenter and then rapidly propagated all the way to the large asperity in the north a near supershear speed of close to 4 0 km s was found to have occurred during this northward rupture process the inverted source model was evaluated using forward three dimensional ground motion simulations the results show strong agreement with island wide observed displacement waveforms and peak ground acceleration for periods from 3 0 to 20 0 s the rapid northward rupture caused a strong directivity effect coupled with the specific source radiation pattern resulting in a large area of strong ground shaking in northern taiwan even though the hualien earthquake was a moderately sized event

three dimensional vp and vs structural models associated with the active subduction and collision tectonics in the taiwan region summary 3 d vp and vs models for the crust and upper mantle beneath the taiwan area have been determined using selected high resolution earthquake data from an island wide seismic network and two local seismic arrays lateral structural variations in the upper crust as also evident from surface geology are responsible for the observed large traveltime residuals or station corrections prior shallow velocity information inferred from traveltime residuals and joint hypocentral determination jhd station corrections for the uppermost crust is essential to facilitate a reliable tomographic inversion a finite difference method that is efficient and accurate for a highly heterogeneous velocity structure is applied to calculate p and s wave traveltimes from the source to receiving stations all earthquakes in the taiwan central weather bureau s catalogue are then relocated using the resultant 3 d vp and vs models the depth of the moho varies significantly especially along the east west direction in the western coastal plain and western foothills the depth of the moho is around 35 km which deepens gradually eastward reaches a maximum depth of 55 km beneath the eastern central mountain range shallows up rapidly beneath the longitudinal valley and coastal range and merges with the thin philippine sea plate offshore of eastern taiwan in central taiwan the central mountain range is bounded to the east and west by two steeply westward dipping active faults from the upper crust to a depth of about 30 km therefore the uplifted and thickened central mountain range serves as a backstop for the converging eurasian and philippine sea plates the crust beneath the central mountain range is characterized by a brittle high velocity and seismically active upper crust 15 km and a ductile low velocity and aseismic mid to lower crust below 15 km most probably due to the high geothermal activity from the excess heat supplied from the hot upper mantle beneath the thin oceanic crust to the east from the surrounding hotter upper mantle beneath the thickened continental crust and from shear heating during active collision the collision zone in eastern taiwan is characterized by an active and steeply eastward dipping seismic zone along a region of low vp and high vp vs ratio near the taitung region in southeastern taiwan it transforms into an active westward steeply dipping seismic zone along a transition zone between the high vp and vs oceanic crust and the low vp and vs continental crust near hualien region in central eastern taiwan there is no apparent seismicity within many sedimentary basins imaged from the tomographic inversion however af ew basins are either bounded on one side by an active fault or are characterized by blind faults beneath the geometry of the subduction zone in northeastern taiwan can be clearly imaged from the relocated earthquake locations behind the subduction a region of low vp and high vp vs ratio at depths of 5 to 10 km can be identified beneath the tatun chilung volcano group indicating a potential magma reservoir two steeply dipping linear seismic zones in the volcano region may mark the upward escape paths of the magmatic materials in the region

contributions of basin edge induced surface waves to site effect in the dinar basin southwestern turkey ground motion amplifications in the dinar basin and contributions of the surface waves generated from basin edges are investigated in frequency and time domains amplification functions are computed from the aftershock data of the october 1 1995 dinar earthquake mw 6 4 using the standard spectral ratio method which requires a pair of instruments one located at the site under investigation generally on alluvium and the other on a reference site preferably a nearby rock site first a time window covering the whole signal is used to compute the amplification function and successively the noise p wave s wave and the surface wave time windows are used in computation to observe their contributions to the amplification function it is seen that the maximum amplifications observed at about 2 0 hz on the amplification functions of the stations located in the basin are largely due to basin edge induced surface waves these waves have significantly increased the duration of signals recorded within the basin particularly on the vertical component records the amplitudes of surface waves are larger than the s wave amplitudes the periods of waves amplified maximally due to the basin structure coincide with the natural periods of 4 6 story buildings which were heavily damaged in dinar this indicates that the site effects may have been important regarding the damage which occurred during the dinar earthquake of october 1995

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

joint vp and vs tomography of taiwan implications for subduction collision orogeny abstract the taiwan orogen sitting at the pre rifted eurasian margin and bracketed by two sub orthogonal subduction systems is subject to complicated geotectonics motivating numerous seismic tomographic studies in local and regional scale most of them obtained p wave velocities vp or with vp vs ratio jointly but few were for s wave velocities vs with unprecedented amount of s wave data in this study a new set of well tuned vp vs and vp vs models were determined by an elaborate joint inversion scheme integrating the data of p and s wave travel times s p times and the borehole logging data for near surface correction into one system this allowed us to revisit the subduction collision process in detail by comparing vp vs and vp vs ratio simultaneously with enhanced slab imaging of philippine sea plate psp under northeast taiwan we are able to discriminate the plausible missing luzon forearc basement along the plate boundary and propose a skateboarding edge model in which the westernmost psp rides on the east subducted forearc basement and subducts northward underneath the eurasian lithosphere the underlain forearc basement along with the psp subduction then results in the anomalous shallow double seismic zone observed only near taiwan island meanwhile at around 121 e the north subducting psp seems dipping west to collide with the deep eurasian lithosphere shaping an irregular corner wedge structure in addition we evaluate our model with previous ones by waveform modeling approach and show the current performance of travel time tomography in taiwan region

the margins of laurussia in central and southeast europe and southwest asia the continuation of the laurussian margin into central and southeast europe and southwest asia is defined by the rheic suture which becomes harder to trace to the southeast because of complex post variscan strike slip displacements and tectonic stacking linked to the cimmerian and alpine cycles the uncertain extent of the neoproterozoic baikalian orogeny fringing baltica ambiguous early paleozoic paleobiogeographic data and strike slip activity complicate the distinction of the tornquist suture from the transeuropean suture zone there is growing evidence for the incorporation of the brunovistulian malopolska and west moesian terranes into the late neoproterozoic cambrian baltican margin the istanbul zonguldak terrane along with the bitesh and east moesia terranes may have been part of the avalonian terrane assemblage although an arabian nubian shield or baltica provenance cannot be excluded the terranes of the armorica terrane assemblage bordering the rheic suture include the outer carpathian tatra getic and balkan terranes in southeast europe and sakarya and the anatolide tauride terrane in turkey further east the rheic suture may be present in the caucasus in all probability between the greater caucasus and the scythian platform or alternatively between the greater caucasus and transcaucasia alborz in northern iran is interpreted as a distal part of transcaucasia the location of the rheic suture in the southeast part of the turan domain of central asia is poorly constrained

rheology of the upper mantle a synthesis rheological properties of the upper mantle of the earth play an important role in the dynamics of the lithosphere and asthenosphere however such fundamental issues as the dominant mechanisms of flow have not been well resolved a synthesis of laboratory studies and geophysical and geological observations shows that transitions between diffusion and dislocation creep likely occur in the earth s upper mantle the hot and shallow upper mantle flows by dislocation creep whereas cold and shallow or deep upper mantle may flow by diffusion creep when the stress increases grain size is reduced and the upper mantle near the transition between these two regimes is weakened consequently deformation is localized and the upper mantle is decoupled mechanically near these depths

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

assessment of tomography models of taiwan using first arrival times from the taiger active source experiment in 2008 the taiger project conducted an active source experiment in which seismic records from 10 explosions were collected at nearly 1400 locations on the island of taiwan in this study we manually pick the first arrival times from the explosion records to ensure reliable and accurate travel time observations and use them to examine the complex p wave structural variations in the crust beneath taiwan

toward real time regional earthquake simulation ii real time online earthquake simulation ros of taiwan earthquakes abstract we developed a real time online earthquake simulation system ros to simulate regional earthquakes in taiwan the ros uses a centroid moment tensor solution of seismic events from a real time moment tensor monitoring system rmt which provides all the point source parameters including the event origin time hypocentral location moment magnitude and focal mechanism within 2 min after the occurrence of an earthquake then all of the source parameters are automatically forwarded to the ros to perform an earthquake simulation which is based on a spectral element method sem a new island wide high resolution sem mesh model is developed for the whole taiwan in this study we have improved sem mesh quality by introducing a thin high resolution mesh layer near the surface to accommodate steep and rapidly varying topography the mesh for the shallow sedimentary basin is adjusted to reflect its complex geometry and sharp lateral velocity contrasts the grid resolution at the surface is about 545 m which is sufficient to resolve topography and tomography data for simulations accurate up to 1 0 hz the ros is also an infrastructural service making online earthquake simulation feasible users can conduct their own earthquake simulation by providing a set of source parameters through the ros webpage for visualization a shakemovie and shakemap are produced during the simulation the time needed for one event is roughly 3 min for a 70 s ground motion simulation the ros is operated online at the institute of earth sciences academia sinica http ros earth sinica edu tw our long term goal for the ros system is to contribute to public earth science outreach and to realize seismic ground motion prediction in real time

seismicity increase after the construction of the world s tallest building an active blind fault beneath the taipei 101 1 seismic activity began to slightly increase during the construction but rose sharply upon the completion of the tallest building in the world the taipei 101 which stands at 508 m in the taipei basin where local seismicity had historically very low besides an increase in both seismic energy and the number of micro earthquakes two felt earthquakes astonishingly occurred beneath the completed building the focal mechanism of the larger felt earthquake and its aftershocks are indicative of an active blind normal fault just beneath the building estimations of the vertical loading of the taipei 101 show that local stress on its foundation increased at least 4 7 bars making it seem likely that the increased seismicity was a direct product of the loading of the mega structure further investigations in unison with continuous seismic monitoring must be conducted because the safety of the high rise building in the taipei basin be comprehensively assessed

constraints on average taiwan reference moho discontinuity model receiver function analysis using bats data summary by analysing teleseismic waveform data we propose a large scale taiwan reference moho discontinuity model trmdm through coherent stacking and h analysis of receiver functions rfs tectonic structural features are determined from accurate crustal thickness h and reliable vp vs ratio consequently poisson s ratio estimations for taiwan the best estimated regional average moho depth is 33 5 2 9 km noted is a westward crustal thinning from 39 3 0 km in eastern taiwan to 30 1 5 km in southeastern china the averaged moho depth is 23 0 2 5 km in northern taiwan and increases to 33 5 2 0 km in the south the markedly thin crust and high vp vs ratio in northern taiwan are mainly associated with backarc opening and magmatic activities based on h estimations and associated seismicity patterns beneath suang long sslb and adjacent four stations we propose two moho reference models that exhibit distinctive crustal thickening in central taiwan the spatial variations of crustal thickness models show strong lateral change in the moho topography the thick crust in the south thin crust in the north and transition in central taiwan mark the different tectonic units between the subduction wedge and the collision prism onshore in view of the following list of constraints thicker crust in the south than in the north eastward crust thickening significant moho depth changes clear 9 11 s subcrustal boundaries from five stations the compelling thickening of crust and upper mantle beneath the central mountain belt seismicity patterns with the absence of mantle earthquake in the wadatibenioff zone regional geological features the occurrence of the inland chi chi earthquake the compelling low at yulb 1 58 0 13 that may extend to central taiwan at sslb 1 59 0 23 relatively thick crust at yulb 39 5 1 6 km and sslb 40 5 1 3 km or 52 5 1 5 km and finally the apparent horizontal offset between highest yu shan mountain and the deepest moho at sslb we are able to suggest that the initial subduction of the eurasian plate occurred in southern taiwan and most likely extended to the transition zone in central taiwan although the current rf study is limited by large interstation distance our analysis provides more notable constraints than previous studies to explicitly determine the characteristic features of moho discontinuity this detailed approach means that rather than treating the tectonic framework as a whole heterogeneous lithospheric feature clear moho boundary geometry variations indicate that active orogenic processes and differential tectonic stress loading create separate and complex crustal and subcrustal to upper mantle structural features caused by the arc continent collision

effects of realistic surface topography on seismic ground motion in the yangminshan region of taiwan based upon the spectral element method and lidar dtm we combine light detection and ranging lidar digital terrain model dtm data and an improved mesh implementation to investigate the effects of high resolution surface topography on seismic ground motion based upon the spectral element method in general topography increases the amplitude of shaking at mountain tops and ridges whereas valleys usually have reduced ground motion as has been observed in both records from past earthquakes and numerical simulations however the effects of realistic topography on ground motion have not often been clearly characterized in numerical simulations especially the seismic response of the true ground surface here we use lidar dtm data which provide two meter reso lution at the free surface and a spectral element method to simulate three dimensional 3d seismic wave propagation in the yangminshan region in taiwan incorporating the effects of realistic topography a smoothed topographic map is employed beneath the model surface in order to decrease mesh distortions due to steep ground surfaces numerical simulations show that seismic shaking in mountainous areas is strongly affected by topography and source frequency content the amplification of ground motion mainly occurs at the tops of hills and ridges whilst the valleys and flat topped hills experience lower levels of ground shaking interaction between small scale to pographic features and high frequency surface waves can produce unusually strong shaking we demonstrate that topographic variations can change peak ground accel eration pga values by 50 in mountainous areas and the relative change in pga between a valley and a ridge can be as high as a factor of 2 compared to a flat surface response this suggests that high resolution realistic topographic features should be taken into account in seismic hazard analysis especially for densely populated moun tainous areas

effects of topography on seismic wave propagation an example from northern taiwan topography influences ground motion and in general increases the amplitude of shaking at mountain tops and ridges whereas valleys have reduced ground motions as is observed from data recorded during and after real earthquakes and from numerical simulations however recent publications have focused mainly on the implications for ground motion in the mountainous regions themselves whereas the impact on surrounding low lying areas has received less attention here we develop a new spectral element mesh implementation to accommodate realistic topography as well as the complex shape of the taipei sedimentary basin which is located close to the central mountain range in northern taiwan spectral element numerical simulations indicate that high resolution topography can change peak ground velocity pgv values in mountainous areas by 50 compared to a half space response we further demonstrate that large scale topography can affect the propagation of seismic waves in nearby areas for example if a shallow earthquake occurs in the i lan region of taiwan the central mountain range will significantly scatter the surface waves and will in turn reduce the amplitude of ground motion in the taipei basin however as the hypocenter moves deeper topography scatters body waves which subsequently propagate as surface waves into the basin these waves continue to interact with the basin and the surrounding mountains finally resulting in complex amplification patterns in taipei city with an overall pgv increase of more than 50 for realistic subduction zone earthquake scenarios off the northeast coast of taiwan the effects of topography on ground motion in both the mountains and the taipei basin vary and depend on the rupture process the complex interactions that can occur between mountains and surrounding areas especially sedimentary basins illustrate the fact that topography should be taken into account when assessing seismic hazard

oceans in the icy galilean satellites of jupiter abstract equilibrium models of heat transfer by heat conduction and thermal convection show that the three satellites of jupiter europa ganymede and callisto may have internal oceans underneath ice shells tens of kilometers to more than a hundred kilometers thick a wide range of rheology and heat transfer parameter values and present day heat production rates have been considered the rheology was cast in terms of a reference viscosity 0 calculated at the melting temperature and the rate of change a of viscosity with inverse homologous temperature the temperature dependence of the thermal conductivity k of ice i has been taken into account by calculating the average conductivity along the temperature profile heating rates are based on a chondritic radiogenic heating rate of 4 5 pw kg 1 but have been varied around this value over a wide range the phase diagrams of h2o ice i and h2o 5 wt nh3 ice have been considered the ice i models are worst case scenarios for the existence of a subsurface liquid water ocean because ice i has the highest possible melting temperature and the highest thermal conductivity of candidate ices and the assumption of equilibrium ignores the contribution to ice shell heating from deep interior cooling in the context of ice i models we find that europa is the satellite most likely to have a subsurface liquid ocean even with radiogenic heating alone the ocean is tens of kilometers thick in the nominal model if tidal heating is invoked the ocean will be much thicker and the ice shell will be a few tens of kilometers thick ganymede and callisto have frozen their oceans in the nominal ice i models but since these models represent the worst case scenario it is conceivable that these satellites also have oceans at the present time the most important factor working against the existence of subsurface oceans is contamination of the outer ice shell by rock rock increases the density and the pressure gradient and shifts the triple point of ice i to shallower depths where the temperature is likely to be lower then the triple point temperature according to present knowledge of ice phase diagrams ammonia produces one of the largest reductions of the melting temperature if we assume a bulk concentration of 5 wt ammonia we find that all the satellites have substantial oceans for a model of europa heated only by radiogenic decay the ice shell will be a few tens of kilometers thinner than in the ice i case the underlying rock mantle will limit the depth of the ocean to 80 100 km for ganymede and callisto the ice i shell on top of the h2o nh3 ocean will be around 60 to 80 km thick and the oceans may be 200 to 350 km deep previous models have suggested that efficient convection in the ice will freeze any existing ocean the present conclusions are different mainly because they are based on a parameterization of convective heat transport in fluids with strongly temperature dependent viscosity rather than a parameterization derived from constant viscosity convection models the present parameterization introduces a conductive stagnant lid at the expense of the thickness of the convecting sublayer if the latter exists at all the stagnant lid causes the temperature in the sublayer to be warmer than in a comparable constant viscosity convecting layer we have further modified the parameterization to account for the strong increase in homologous temperature and therefore decrease in viscosity with depth along an adiabat this modification causes even thicker stagnant lids and further elevated temperatures in the well mixed sublayer it is the stagnant lid and the comparatively large temperature in the sublayer that frustrates ocean freezing

three dimensional simulation of a magnitude 7 75 earthquake on the san andreas fault simulation of 2 minutes of long period ground motion in the los angeles area with the use of a three dimensional finite difference method on a parallel supercomputer provides an estimate of the seismic hazard from a magnitude 7 75 earthquake along the 170 kilometer section of the san andreas fault between tejon pass and san bernardino maximum ground velocities are predicted to occur near the fault 2 5 meters per second and in the los angeles basin 1 4 meters per second where large amplitude surface waves prolong shaking for more than 60 seconds simulated spectral amplitudes for some regions within the los angeles basin are up to 10 times larger than those at sites outside the basin at similar distances from the san andreas fault

three dimensional simulations of seismic wave propagation in the taipei basin with realistic topography based upon the spectral element method we use the spectral element method to simulate strong ground motion throughout the taipei metropolitan area mesh generation for the taipei basin poses two main challenges 1 the basin is surrounded by steep mountains and 2 the city is located on top of a shallow low wave speed sedimentary basin to accommodate the steep and rapidly varying topography we introduce a thin high resolution mesh layer near the surface the mesh for the shallow sedimentary basin is adjusted to honor its complex geometry and sharp lateral wave speed contrasts variations in moho thickness beneath northern taiwan are also incorporated in the mesh spectral element simulations show that ground motion in the taipei metropolitan region is strongly affected by the geometry of the basin and the surrounding mountains the amplification of ground motion is mainly controlled by basin depth and shallow shear wave speeds although surface topography also serves to amplify and prolong seismic shaking

paleomagnetic study of siluro devonian volcanic rocks from the central lachlan orogen implications for the apparent pole wander path of gondwana 1 the apparent pole wander apw path for gondwana is still not clearly established in particular for silurian devonian times a controversial debate places authors who argue for an x path running directly through africa on a reconstruction of gondwana against those who advocate a large loop passing by southern south america the y path most of the paleomagnetic data used to draw this loop come from the lachlan orogen australia a paleomagnetic study was carried out in the well dated ambone and ural volcanics in the central subprovince of lachlan orogen new south wales anisotropy of magnetic susceptibility measurements confirms detailed mapping of the region and shows that these massive dacitic sills and or lava flows are flat lying among the different localities studied only one yields interpretable paleomagnetic results two components of magnetization can be identified a midtemperature direction yielding a corresponding pole in australian coordinates 67 9 s 084 4 e b 5 n 21 dp 17 5 dm 23 1 and a high temperature direction with a corresponding vgp 24 4 s 060 6 e b 5 n 25 dp 1 4 dm 2 5 the first is interpreted as corresponding to an early carboniferous pole position and can be regarded as an overprint probably related to the early carboniferous kanimblan orogenic event the second does not correspond to any expected silurian devonian or younger pole position this magnetization is thought to be primary in origin however secular variation has apparently not been averaged out in the single lava flow sampled therefore the earliest devonian paleopole position probably lies in a 30 cone around the obtained vgp and this position can only match the x type apw path for gondwana it is in particular very different from coeval poles obtained in the eastern subprovince of the lachlan orogen and it is mostly used as key poles supporting the silurian devonian loop for the apw path of gondwana therefore some poles from the lachlan orogen must be affected by rotation to explain these results the lachlan orogen was hence not stable up to the mid paleozoic and data from this region should not be used as representative for gondwana

modelling basin effects on earthquake ground motion in the santiago de chile basin by a spectral element code summary simulations of strong ground motion within the santiago de chile metropolitan area were carried out by means of 3 d deterministic wave propagation tool based on the spectral element method the simulated events take into account the pronounced interface between the low velocity sedimentary basin and the bedrock as well as topography of the area to verify our model we simulated a regional earthquake recorded by a dense network installed in the city of santiago for recording aftershock activity after the 2010 february 27 maule main shock the results proof the alluvial basin amplification effects and show a strong dependence of spectral amplification in the basin on the local site conditions moreover we studied the seismic response due to a hypothetical mw 6 0 event occurring along the active san ramon fault which is crossing the eastern edge of the city the scenario earthquakes exhibit that an unfavourable interaction between fault rupture radiation mechanism and complex geological and topographic conditions in the near field region may give rise to large values of peak ground velocity in the basin finally 3 d numerical predictions of ground motion are compared with the one computed according to ground motion prediction equations selected among the next generation attenuation relationships in terms of ground motion peak values and spectral acceleration the comparison underlines that the 3 d scenario simulations predict a significantly higher level of ground motion in the santiago basin especially over deep alluvial deposits moreover also the location of the rupture nucleation largely influences the observed shaking pattern

three regimes of mantle convection with non newtonian viscosity and stagnant lid convection on the terrestrial planets numerical simulations of convection with strongly temperature dependent viscosity suggest that non newtonian viscosity convection dislocation creep passes through three convective regimes similar to those observed for newtonian viscosity convection diffusion creep the small viscosity contrast regime the transitional regime and the stagnant lid regime for realistic viscosity contrasts mantle convection is in the stagnant lid regime characterized by formation of a very viscous slowly creeping lid on top of an actively convecting mantle this explains the tectonic style observed on the terrestrial planets and the moon on the other hand this eliminates the possibility that the plates on earth could be mobile due to non newtonian viscosity the nature of the mobility of lithospheric plates on earth has yet to be explained

a palaeomagnetic study of the builth wells llandrindod wells ordovician inlier wales palaeogeographic and structural implications summary discrepancies exist in the southern british ordovician palaeomagnetic data set with individual studies indicating either high southerly or temperate southerly palaeolatitudes although previous palaeomagnetic investigations from the builth inlier have delineated a three component remanence structure doubts have been raised concerning i the magnetization age of the supposed primary component p ii the structural setting of the sampling area llanelwedd quarry within a zone of strike slip deformation and iii whether detailed step wise demagnetization has fully separated the various magnetization components in addressing these problems we present new palaeomagnetic results as follows i a positive palaeomagnetic conglomerate test establishing a pre late llanvirn age for component p ii an enlarged geographic sampling embracing several tectonic domains indicating that relative rotations linked to strike slip tectonism are minor within the builth sampling area and iii evidence that component p is uncontaminated by overprints at some sites suggesting the resulting palaeolatitude of 35 s to be representative for the builth inlier we also present evidence for local syn volcanic deformation within llanvirn volcanics and for intrusion related deformation of llanvirn shales when the revised llanvirn pole from the inlier 3 s 4 e is combined with other data from southern britain in a statistical spline analysis a mean palaeolatitude of 44 5 s is calculated for builth in llanvirn times a palaeoreconstruction for 468 474 ma c mid llanvirn is presented utilizing this analysis

numerical modelling of ground motion in the taipei basin basin and source effects summary the taipei basin in northern taiwan is located in a high seismicity region and was affected by several earthquakes in the past ml 7 3 on 1909 april 15 ml 6 8 on 1986 november 15 the chi chi ml 7 3 earthquake on 1999 september 21 and ml 6 8 on 2002 march 31 the main characteristic of the taipei basin is its complex shape with a deep western and shallow eastern part the uppermost sungshan formation with its low shear wave velocities 90 200 m s 1 is also a distinct feature of the basin based on the large data base of earthquake records obtained from the taiwan strong motion instrumentation program network many studies on ground motion within the taipei basin exist however the influence of the various subsurface structures on the observed ground motions as well as the variability of ground motion with respect to earthquake location is not fully understood we apply a 3 d finite difference method to simulate wave propagation up to 1 hz for a small earthquake close to the basin in order to resolve these open questions by varying source and structural parameters we explore the variability of ground motion our study includes a subsurface model that is based on recent studies on the basin structure and on the crustal structure of taiwan from our simulations we find a good fit between simulated and observed waveforms and peak ground accelerations for the considered small earthquake near the basin we also explore the influence of fault plane orientation hypocentre location deep basin structure and soft soil surface layers of the sungshan formation by varying the subsurface structure and earthquake position our studies reveal that the basin structure produces an amplification factor of about 4 compared to hard rock conditions additionally the soft soil sungshan formation produce amplification of a factor of 2 this results in a maximum amplification of the basin structure of about 8 which is in good comparison with amplification values larger than 5 found from the analysis of observed earthquakes these values clearly exceed the amplification values of about 2 3 obtained when applying standard 1 d site effect analysis our simulations for different earthquake positions show that ground motion depends strongly on earthquake location and fault orientation therefore the application of average values of spectral amplification obtained from the analysis of recorded data from distant earthquakes with different azimuths and fault planes may significantly underestimate future ground motions of possible earthquakes on known faults close to the taipei basin the simulation of a small earthquake near the taipei basin presented in this study will help to set up adequate simulation parameters for a possible large earthquake close to the taipei basin such a simulation of a scenario earthquake close to the taipei basin would allow to significantly improve hazard assessment as no observations of strong earthquakes in the vicinity of the basin exist

seismic effects of a small sedimentary basin in the eastern tibetan plateau based on numerical simulation and ground motion records from aftershocks of the 2008 mw7 9 wenchuan china earthquake abstract in this study the ground motions that can be attributed to the aftershocks of the 2008 mw7 9 wenchuan china earthquake recorded in the wudu basin which is a small basin in the eastern tibetan plateau are analyzed to investigate the seismic effect of a small sedimentary basin in case of the wudu basin the site responses from the basin edge are stronger than those from the basin center the monitoring sites located near the wudu basin edge and the wudu basin center are sensitive to the low frequency 5 hz components of ground motion respectively it indicates that some different seismic phenomena occurred in a small sedimentary basin compared with a large sedimentary basin to further study the ground motion in a small sedimentary basin a simulation of the wudu basin was conducted using the finite element method with a viscous elastic artificial boundary the grid size of the surface layer of the basin is 2 5 2 5 m2 and high frequency up to 10 hz components of a synthetic waveform were obtained the simulation denoted that the surface wave initially appeared in the wudu basin edge and subsequently propagated into its interior the near surface soil layers exhibiting a relatively low wave velocity magnified the amplitude of the seismic wave in the wudu basin furthermore the numerical simulation results are basically consistent with the actual ground motion records especially with the same predominant frequencies of ground motions at the sites located near the wudu basin edge

stratigraphic and structural characteristics of the romanian black sea shelf abstract the western black sea basin opened during cretaceous times by back arc rifting in association with a north dipping subduction at the rear of the cretaceous early tertiary pontide volcanic arc the sedimentary wedge developed on the shelf of the romanian black sea sector reflects a complex interplay between large scale rifting uplift of the orogenic flanks large scale post rift subsidence and sea level changes we examine the detailed structural configuration of this sector for a regional correlation with the adjacent offshore in ukraine and bulgaria the evolution of the western black sea basin started in the albian cenomanian times when two extensional phases with significantly different directions n s and subsequently e w lead to the formation of a complex interplay between isolated blocks organised in horsts and grabens generally deepening eastwards superposition of normal faults footwall blocks from the two extensional episodes generated a deeply subsided area with enhanced accommodation space i e the histria depression and consequently recorded a larger thickness of paleogene sediments in the post rift stage re activation of faults and associated folding reflects repeated inversion during the late cretaceous oligocene times associated with subsequent periods of non deposition and or erosion during moments of basin fill exposure these periods of inversion recorded in the black sea are controlled by coeval orogenic deformations taking place in the balkans pontides and the crimean thrust belt sea level fluctuations during the neogene and late alpine tectonics in the neighbouring orogens caused massive sedimentation followed by sediment starvation and or significant erosion large thicknesses of sediments accumulated during the pontian presumably associated with an extensional episode deepening the distal parts of the basin and with differential compaction structures the interpretation of a high quality seismic dataset combined with published data allowed the correlation of major structural units and lineaments defined onshore towards the carpathians with the ones deeply buried below the western black sea basin sediments unit correlations are furthermore used to derive an integrated tectonic image of the western black sea area

a global chitinozoa biozonation for the silurian a global chitinozoan biozonation for the silurian period is proposed each biozone is an interval range defined by the first occurrence of an index species selected from well defined species with a relatively short biostratigraphic range to be included in the scheme index species must have been recorded from at least two major silurian palaeocontinents where usable chitinozoa assemblages have been studied that is avalonia baltica which had already undergone collision by the silurian laurentia gondwana and southern china seventeen biozones are identified with seven in the llandovery the fragilis postrobusta electa maennili alargada dolioliformis and longicollis biozones four in the wenlock the margaritana cingulata pachycephala and lycoperdoides biozones three in the ludlow the elongata philipi and barrandei biozones and three in the p idoli the kosovensis elegans and superba biozones chronostratigraphic calibration is partly provided by reference to the range of the appropriate chitinozoa index species in the global stratotype sections and points gssp of the silurian series e g in bohemia czech republic for the p idoli and the welsh borderland in england for the ludlow and part of the wenlock when this information was not available independent biostratigraphic control was provided by calibration with graptolite biozones or in a few cases conodont or trilobite biozonal schemes the index and most characteristic species of each biozone are illustrated and their total stratigraphie range provided

three dimensional full waveform inversion of short period teleseismic wavefields based upon the sem dsm hybrid method we present a method for high resolution imaging of lithospheric structures based on full waveform inversion of teleseismic waveforms we model the propagation of seismic waves using our recently developed direct solution method spectral element method hybrid technique which allows us to simulate the propagation of short period teleseismic waves through a regional 3 d model we implement an iterative quasi newton method based upon the l bfgs algorithm where the gradient of the misfit function is computed using the adjoint state method compared to gradient or conjugate gradient methods the l bfgs algorithm has a much faster convergence rate we illustrate the potential of this method on a synthetic test case that consists of a crustal model with a crustal discontinuity at 25 km depth and a sharp moho jump this model contains short and long wavelength heterogeneities along the lateral and vertical directions the iterative inversion starts from a smooth 1 d model derived from the iasp91 reference earth model we invert both radial and vertical component waveforms starting from long period signals filtered at 10 s and gradually decreasing the cut off period down to 1 25 s this multiscale algorithm quickly converges towards a model that is very close to the true model in contrast to inversions involving short period waveforms only which always get trapped into a local minimum of the cost function

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

creep of water ices at planetary conditions a compilation many constitutive laws for the flow of ice have been published since the advent of the voyager explorations of the outer solar system conflicting data have occasionally come from different laboratories and refinement of experimental techniques has led to the publication of laws that supersede earlier ones in addition there are unpublished data from ongoing research that also amend the constitutive laws here we compile the most current laboratory derived flow laws for water ice phases i ii iii v and vi and ice i mixtures with hard particulates the rheology of interest is mainly that of steady state and the conditions reviewed are the pressures and temperatures applicable to the surfaces and interiors of icy moons of the outer solar system advances in grain size dependent creep in ices i and ii as well as in phase transformations and metastability under differential stress are also included in this compilation at laboratory strain rates the several ice polymorphs are rheologically distinct in terms of their stress temperature and pressure dependencies but with the exception of ice iii have fairly similar strengths hard particulates strengthen ice i significantly only at high particulate volume fractions ice iii has the potential for significantly affecting mantle dynamics because it is much weaker than the other polymorphs and its region of stability which may extend metastably well into what is nominally the ice ii field is located near likely geotherms of large icy moons

high resolution seismic array imaging based on an sem fk hybrid method we demonstrate the feasibility of high resolution seismic array imaging based on teleseismic recordings using full numerical wave simulations we develop a hybrid method that interfaces a frequency wavenumber fk calculation which provides analytical solutions to 1 d layered background models with a spectral element sem numerical solver to calculate synthetic responses of local media to plane wave incidence this hybrid method accurately deals with local heterogeneities and discontinuity undulations and represents an efficient tool for the forward modelling of teleseismic coda including converted and scattered waves we benchmark the accuracy of the sem fk hybrid method against fk solutions for 1 d media we then compute sensitivity kernels for teleseismic coda waves by interacting the forward teleseismic waves with an adjoint wavefield produced by injecting coda waves as adjoint sources based on adjoint techniques these sensitivity kernels provide the basis for mapping variations in subsurface discontinuities density and velocity structures through non linear conjugate gradient methods we illustrate various synthetic imaging experiments including discontinuity characterization volumetric structural inversion for the crust or subduction zones these tests show that using pre conditioners based upon the scaled product of sensitivity kernels for different phases combining finite frequency traveltime and waveform inversion and or adopting hierarchical inversions from longto short period waveforms could reduce the non linearity of the seismic inverse problem and speed up its convergence the encouraging results of these synthetic examples suggest that inversion of teleseismic coda phases based on the sem fk hybrid method and adjoint techniques is a promising tool for structural imaging beneath dense seismic arrays

the protomoesian microcontinent of the balkan peninsula a peri gondwanaland piece abstract based on differences in their pre palaeozoic and palaeozoic development the protomoesian microcontinent is divided into two terranes the balkan and the moesian a precambrian cambrian ophiolite island arc assemblage unconformably overlain by a palaeozoic sequence forms the first terrane the pre palaeozoic basement of the moesian terrane consists of proterozoic vendian metamorphics of continental origin the differences in the development of the palaeozoic rocks are also significant reason for dividing the balkan and the moesian terrane numerous features of the palaeozoic sediments palaeoclimatologic palaeobiogeographic palaeomagnetic from both terranes and the pan african affiliations of the ophiolite island arc assemblage identify the protomoesian microcontinent as a peri gondwanaland piece

storm effects on siliciclastic and carbonate shelf sediments in the medial silurian succession of pennsylvania abstract upper llandoverian through wenlockian strata in the pennsylvania part of the northern appalachian basin formed on a gentle epeiric ramp that extended from marginal tidal flats through coarser grained mid shelf shoals to a muddy basin center over approximately 10 million years the composition of the accumulating sediment evolved from siliciclastic to carbonate while the ramp maintained a relatively similar configuration and position below sea level and while storm generated processes continued as the major producers of sediment characteristics in both siliciclastic and carbonate parts of the succession sedimentary structures and their sequences are generally similar with only a small number of dissimilar features resulting from the differences in composition small scale coarsening and shallowing upward sequences are present in both mid shelf bar and basin transition deposits although specific sequence characteristics are different in siliciclastic and carbonate parts such sequences record cyclic fluctuations of relative sea level while the composition of the sediment evolved over this extended period the gentle ramp gradient was maintained largely by the processes generated by storms such processes were more effective because of the fluctuations of relative sea level

faunal evidence for oceanic separations in the palaeozoic of britain the faunal criteria for the recognition of the relative separation of old continents are 1 the contrast between shallow not deep water faunas off opposite shorelines 2 the recognition of deeper water facies surrounding the edges of continents and 3 the recognition of the disposition of ancient climatic belts these criteria are defined and used to assess the relative position of the various parts of what is now britain in the palaeozoic the iapetus ocean is well characterized by faunal differences from the cambrian until the lower ordovician but from caradoc times onwards these differences dwindle until by the latest silurian only the distribution of the ostracods separates the two sides of the ocean on faunal grounds in the early ordovician s british faunas are comparable with those from bohemia france and elsewhere to the s indicating connection with gondwanaland and these faunas differ from those in the baltic area a distribution which we attribute to a true ocean tornquist9s sea between n and s europe tornquist9s sea probably closed in the upper ordovician and from ashgill times onwards the s british and baltic faunas remained similar during the middle and late silurian there is evidence of increasing faunal distinction between britain the baltic area and north america on the one hand and southern europe and gondwanaland on the other indicating an opening rheic ocean which appears to have persisted until late carboniferous times

source complexity of the 4 march 2010 jiashian taiwan earthquake determined by joint inversion of teleseismic and near field data abstract the jiashian earthquake m l 6 4 occurred on 4 march 2010 it was the largest inland event in southern taiwan of 2010 the mainshock location was unexpected since it occurred in an area with relatively low background seismicity in addition reports of earthquake focal mechanisms do not fit with any known active fault geometry in order to understand the origin of this earthquake especially its rupture process we perform a joint source inversion by using teleseismic body wave gps coseismic displacements and near field ground motion data in this study we considered a northwest southeast trending fault with a northeast dip retrieved from gps coseismic data and aftershocks distribution to analyze the detailed slip distribution in space and time we used near field 3d green s functions provided by spectral element method and a full time space inversion technique we find a complex rupture process with several slip patches distributed inside two main asperities the slip map reveals a mean slip of 12 9 cm for a maximum slip of 27 3 cm leading to a m w 6 47 for this event the rupture initiates in the deepest portion of the fault at 20 km depth and propagated upward up to 2 km depth to form the two asperities the source time function of this event revealed two pulses corresponding to the two asperities for a total duration time of about 16 s most aftershocks occurred near the upper boundary of the deepest asperity while no aftershocks are located close to the shallowest one we infer that the locations of these slip patches are related to the surrounding fault systems that may have restricted the rupture propagation during the earthquake

the high cut parameter kappa for the near surface geology in and around the taipei basin taiwan abstract the decay parameter at the high frequency kappa value introduced by anderson and hough 1984 is measured from 54 stations situated in and around the taipei basin northern taiwan different frequency windows for the s wave amplitude spectra are used to measure the r value for each individual record the preferred r values are determined by the least squared fitting with the best correlation coefficient the site specific 0 values which are computed by removing the anelastic effect of regional geological structure by grouping r into the crustal and subduction events according to the focal depth and site classification i e class b c d and e sites are calculated to be in the range of 0 034 0 066 s we correlate the 0 values with the averaged shear wave velocity of the topmost 30 m layer v s 30 and find the independence of 0 on v s 30 in addition 28 stations lie on sediment in the taipei basin the gradient of 0 versus the sedimentary thickness to the tertiary base in the basin is calculated and then used to estimate the effective quality factor q ef of the layer q ef is 75 3 for the whole sedimentary layers above the tertiary base given one standard deviation q ef are in the 41 9 376 7 range q ef can provide an accurate referred parameter for the future ground motion simulation applications

large scale deformation in a locked collisional boundary interplay between subsidence and uplift intraplate stress and inherited lithospheric structure in the late stage of the se carpathians evolution 1 the interplay between slab dynamics and intraplate stresses in postcollisional times creates large near surface deformation particularly in highly bent orogens with significant lateral variations in mechanical properties this deformation is expressed through abnormal foredeep geometries and contrasting patterns of vertical movements intraplate folding is often the controlling mechanism particularly when the orogenic belt is locked the study of these tectonic processes in the se carpathians indicates a generalized subsidence period during latest miocene pliocene times driven by the slab pull and an intraplate folding due to an overall quaternary inversion the latter accommodates 5 km ese ward movement of this area with respect to the neighboring units which creates complicated three dimensional deformation patterns potentially driven at a larger scale by the interaction between the adriatic indentor and the entire carpathians system the lithospheric anisotropy inherited from the subduction times concentrates strain and induces large scale deformation far away from the active plate margins this anisotropy is dynamic because of deep mantle processes related to the subducted slab during postcollisional times such as thermal reequilibration or increase in slab dip

les bassins d avant pays de la chaine hercynienne au carbonifere inferieur the evolution of marine sedimentary basins deformed by the hercynian orogeny was studied in germany france iberia northwest africa and north america in the lower carboniferous these basins opened along strike slip faults and were filled with turbidites and shelf deposits until the main compressive phase at the end of visean and the namurian the infilling was interrupted with frequent volcanic episodes and gravity induced movements according to sedimentary vergence these basins were set into two festoons on both sides of an elongated and emergent swell structured during the devonian and corresponding to the internal zones of the orogen these basins were filled during a general tectonic compression phase they correspond to the foreland basins of the hercynian belt

geometry and spatial distribution of lenticulae on europa the surface of europa contains several types of roughly elliptical features collectively called lenticulae lenticulae may have positive relief domes or negative relief pits may disrupt the crust chaos or discolor the surface spots some lenticulae have attributes of both domes and chaos dome chaos we map the location dimensions and shapes of all lenticulae and their interactions with other lenticulae and lineaments we find that 1 pits and domes have similar sizes 2 chaos are larger than the other lenticulae 3 pits are clustered within the trailing antijovian quadrant and the leading subjovian quadrant whereas domes dome chaos and chaos terrains are more uniformly distributed 4 the areal density for all lenticulae is not uniform 5 lenticulae do not divert the path of younger lineaments such as ridges taken together these observations are consistent with conceptual models in which lenticulae are created by intrusion of liquid water bodies or convection within the ice shell additionally the observations are consistent with the notion that each type of lenticula is a surface expression of dynamics within the ice shell at a different stage of lenticulae evolution the similar size and shape of pits and domes suggests that one may evolve into the other because domes are more numerous and more uniformly distributed than pits they are more likely to represent the end stage of this evolution assuming the end stage leaves a longer lasting surface expression models also predict that larger features are more likely to disrupt the crust which is consistent with dome chaos and chaos being larger than pits and domes we find no examples of lineaments offsetting pits but lineaments do cross some chaos pits also have a preferred northwest southeast elongation whereas domes dome chaos and chaos do not have a preferred orientation if lenticulae orientation is influenced by crustal stress then pits may have formed during a shorter time interval than the other features as a result pits may sample a shorter more recent time period than domes dome chaos and chaos consistent with pits being the earliest stage in the evolution of lenticulae we find no strong evidence that lineaments are deflected by lenticulae implying either that the stresses created by lenticulae are too small to influence lineaments or that the complete evolution of lenticulae occurs on a time scale that is short compared to the time between the formation of lineaments at a given location

the seismic response of the los angeles basin california using strong motion data recorded in the los angeles region from the 1992 mw 7 3 landers earthquake we have tested the accuracy of existing three dimensional 3d velocity models on the simulation of long period 2 sec ground motions in the los angeles basin and surrounding san fernando and san gabriel valleys first the overall pattern and degree of long period excitation of the basins were identified in the observations within the los angeles basin the recorded amplitudes are about three to four times larger than at sites outside the basins amplitudes within the san fernando and san gabriel valleys are nearly a factor of 3 greater than surrounding bedrock sites then using a 3d finite difference numerical modeling approach we analyzed how variations in 3d earth structure affect simulated waveforms amplitudes and the fit to the observed patterns of amplification significant differences exist in the 3d velocity models of southern california that we tested magistrale et al 1996 graves 1996a hauksson and haase 1997 major differences in the models include the velocity of the assumed background models the depth of the los angeles basin and the depth location and geometry of smaller basins the largest disparities in the response of the models are seen for the san fernando valley and the deepest portion of the los angeles basin these arise in large part from variations in the structure of the basins particularly the effective depth extent which is mainly due to alternative assumptions about the nature of the basin sediment fill the general ground motion characteristics are matched by the 3d model simulations validating the use of 3d modeling with geologically based velocity structure models however significant shortcomings exist in the overall patterns of amplification and the duration of the long period response the successes and limitations of the models for reproducing the recorded ground motions as discussed provide the basis and direction for necessary improvements to earth structure models whether geologically or tomographically derived the differences in the response of the earth models tested also translate to variable success in the ability to successfully model the data and add uncertainty to estimates of the basin response given input scenario earthquake source models

wave propagation modelling of induced earthquakes at the groningen gas production site gas extraction from the groningen natural gas field situated in the netherlands frequently induces earthquakes in the reservoir that cause damage to buildings and pose a safety hazard and a nuisance to the local population due to the dependence of the national heating infrastructure on groningen gas the short term mitigation measures are mostly limited to a combination of spatiotemporal redistribution of gas production and strengthening measures for buildings all options become more effective with a better understanding of both source processes and seismic wave propagation detailed wave propagation simulations improve both the inference of source processes from observed ground motions and the forecast of ground motions as input for hazard studies and seismic network design the velocity structure at the groningen site is relatively complex including both deep high velocity and shallow low velocity deposits showing significant thickness variations over relatively small spatial extents we performed a detailed 3 d wave propagation modelling study for an induced earthquake in the groningen natural gas field using the spectral element method we considered an earthquake that nucleated along a normal fault with local magnitude of ml 3 we created a dense mesh with element size varying from 12 to 96 m such that with a dominant source frequency of 7 hz waveforms with a frequency content up to 10 hz could be accurately modelled the velocity density model is constructed using a 3 d geological model of the area including both deep high velocity salt deposits overlying the source region and shallow low velocity sediments present in a deep and narrow tunnel valley the results show that the 3 d density velocity model in the groningen area clearly plays a large role in the wave propagation and resulting surface ground motions and causes significant lateral variations in site response the highvelocity salt deposits have a dispersive effect on the radiated wavefield reducing the seismic energy reaching the surface near the epicentre in turn the presence of low velocity tunnel valley deposits can locally cause a significant increase in peak ground acceleration here we study induced seismicity on a local scale and use specfem3d to conduct full waveform simulations and show how local velocity variations can affect seismic records the author s 2018

shallow basin structure and attenuation are key to predicting long shaking duration in los angeles basin ground motions in the los angeles basin during large earthquakes are modulated by earthquake ruptures path effects into the basin basin effects and local site response we analyzed the direct effect of shallow basin structures on shaking duration at a period of 2 10 s in the los angeles region through modeling small magnitude shallow and deep earthquake pairs the source depth modulates the basin response particularly the shaking duration and these features are a function of path effect and not site condition three dimensional simulations using the cvm s4 26 m01 velocity model show good fitting to the initial portion of the waveforms at periods of 5 s and longer but fail to predict the long shaking duration during shallow events especially at periods less than 5 s simulations using cvm h do not match the timing of the initial arrivals as well as cvm s4 26 m01 and the strong late arrivals in the cvm h simulation travel with an apparent velocity slower than observed a higher quality factor than traditionally assumed may produce synthetics with longer durations but is unable to accurately match the amplitude and phase beamforming analysis using dense array data further reveals the long duration surface waves have the same back azimuth as the direct arrivals and are generated at the basin edges while the later coda waves are scattered from off azimuth directions potentially due to strong sharp boundaries offshore improving the description of these shallow basin structures and attenuation model will enhance our capability to predict long period ground motions in basins

new approach for coupling k 2 and empirical green s functions application to the blind prediction of broad band ground motion in the grenoble basin summary we present a new approach for performing broad band ground motion time histories 0 1 30 hz of a future earthquake in a sedimentary basin synthetics are computed with an hybrid scheme combining reciprocity based 3 d spectral element method simulations at low frequencies and empirical green s functions egf at high frequencies the combination between both deterministic and empirical parts results in a set of hybrid green s functions summed according to a new k 2 kinematic model algorithm the summation technique enables to remove the high frequency artefacts that appear above the egf corner frequency the ground motion variability is assessed by generating a variety of source parameter sets selected from ap rioriprobability density functions this leads to a population of response spectra from which the median spectral acceleration and standard deviation values are derived the method is applied to simulate a m w 5 5 event in the deep grenoble basin french alps the comparison with ec8 regulations suggests the need of specific design spectra in the grenoble valley

tidally heated convection constraints on europa s ice shell thickness 1 the thickness of europa s ice shell is constrained with numerical experiments of thermal convection including heterogeneous tidal heating thermal convection occurs in the stagnant lid regime with most of the tidal heating located in the bottom half of the layer the addition of tidal heating mainly results in the increase of the temperature of the well mixed interior and in the decrease of the heat flux at the base of the ice layer in many simulations the ice in hot plumes is heated up to its melting point this induces episodic upwellings 0 5 ma of partially molten ice up to the base of the conductive lid with possible implications for the formation of lenticulae and chaos regions the thickness of the convective ice shell in equilibrium with the heat flow from the silicate core is estimated to be about 20 25 km tidal dissipation and surface temperature variations create lateral variations of the ice shell thickness of about 5 km with maxima near the equator at the jovian and anti jovian points and minima at midlatitudes surface heat flux is about 35 40 mw m 2 it is almost constant all over europa s surface even though the tidal dissipation rate is four times larger at the poles than at the equator

numerical earthquake model of the 31 october 2013 ruisui taiwan earthquake source rupture process and seismic wave propagation abstract we build a numerical earthquake model including numerical source and wave propagation models to understand the rupture process and the ground motion time history of the 2013 ml 6 4 ruisui earthquake in taiwan this moderately large event was located in the longitudinal valley a suture zone of the philippine sea plate and the eurasia plate a joint source inversion analysis by using teleseismic body wave gps coseismic displacement and near field ground motion data was performed first the inversion results derived from a western dipping fault plane indicate that the slip occurred in depths between 10 and 20 km the rupture propagated from south to north and two asperities were resolved the largest one was located approximately 15 km north of the epicenter with a maximum slip about 1 m a 3d seismic wave propagation simulation based on the spectral element method was then carried out by using the inverted source model a strong rupture directivity effect in the northern area of the longitudinal valley was found which was due to the northward rupture process forward synthetic waveforms could explain most of the near field ground motion data for frequencies between 0 05 and 0 2 hz this numerical earthquake model not only helps us confirm the detailed rupture processes on the central range fault but also gives contribution to regional seismic hazard mitigation for future large earthquakes

global plate motion frames toward a unified model 1 plate tectonics constitutes our primary framework for understanding how the earth works over geological timescales high resolution mapping of relative plate motions based on marine geophysical data has followed the discovery of geomagnetic reversals mid ocean ridges transform faults and seafloor spreading cementing the plate tectonic paradigm however so called absolute plate motions describing how the fragments of the outer shell of the earth have moved relative to a reference system such as the earth s mantle are still poorly understood accurate absolute plate motion models are essential surface boundary conditions for mantle convection models as well as for understanding past ocean circulation and climate as continent ocean distributions change with time a fundamental problem with deciphering absolute plate motions is that the earth s rotation axis and the averaged magnetic dipole axis are not necessarily fixed to the mantle reference system absolute plate motion models based on volcanic hot spot tracks are largely confined to the last 130 ma and ideally would require knowledge about the motions within the convecting mantle in contrast models based on paleomagnetic data reflect plate motion relative to the magnetic dipole axis for most of earth s history but cannot provide paleolongitudes because of the axial symmetry of the earth s magnetic dipole field we analyze four different reference frames paleomagnetic african fixed hot spot african moving hot spot and global moving hot spot discuss their uncertainties and develop a unifying approach for connecting a hot spot track system and a paleomagnetic absolute plate reference system into a hybrid model for the time period from the assembly of pangea 320 ma to the present for the last 100 ma we use a moving hot spot reference frame that takes mantle convection into account and we connect this to a pre 100 ma global paleomagnetic frame adjusted 5 in longitude to smooth the reference frame transition using plate driving force arguments and the mapping of reconstructed large igneous provinces to core mantle boundary topography we argue that continental paleolongitudes can be constrained with reasonable confidence

spatial variation of seismogenic depths of crustal earthquakes in the taiwan region implications for seismic hazard assessment abstract this paper presents the first whole taiwan scale spatial variation of the seismogenic zone using a high quality crustal seismicity catalog the seismicity onset and cutoff depths i e seismogenic depths are determined by the earthquake depth moment distribution and used to define the upper and lower boundaries of the seismogenic zone respectively together with the published fault geometries and fault area moment magnitude relations the depth difference in the onset and cutoff depths i e seismogenic thickness is used as the fault width to determine the moment magnitudes of potential earthquakes for the major seismogenic faults results show that the largest mw7 9 8 0 potential earthquake may occur along the changhua fault in western taiwan where the seismic risk is relatively high and seismic hazard mitigation should be a matter of urgent concern in addition the first motion focal mechanism catalog is used to examine the relation between the seismogenic depths and earthquake source parameters for crustal earthquakes 50 km the shallowest onset and cutoff depths are observed for normal and strike slip events respectively this observation is different from the prediction of the conventional continental rheology model which states that thrust events have the shallowest cutoff depth thus a more sophisticated rheology model is necessary to explain our observed dependence of the seismogenic depths on faulting types meanwhile for intermediate to large crustal mw 4 depth 50 km earthquakes thrust events tend to occur at the bottom region of the seismogenic zone but normal and strike slip events distribute at a large depth range

europa s differentiated internal structure inferences from four galileo encounters radio doppler data from four encounters of the galileo spacecraft with the jovian moon europa have been used to refine models of europa s interior europa is most likely differentiated into a metallic core surrounded by a rock mantle and a water ice liquid outer shell but the data cannot eliminate the possibility of a uniform mixture of dense silicate and metal beneath the water ice liquid shell the size of a metallic core is uncertain because of its unknown composition but it could be as large as about 50 percent of europa s radius the thickness of europa s outer shell of water ice liquid must lie in the range of about 80 to 170 kilometers

the first record of cooksonia from south america in silurian rocks of bolivia plant megafossils resembling cooksonia caledonica lang aredescribed from the kirusillas formation in southern bolivia faunal and lithological evidence together with field relation ships advocate a late silurian ludlow age palaeocontinentalreconstructions suggest that the plants grew on the western edgeof gondwana at 50 60 s and indicate that cooksonia hadspread to higher latitudes soon after its appearance in the wenlock

australian palaeozoic palaeomagnetism and tectonics ii a revised apparent polar wander path and palaeogeography abstract new palaeomagnetic data from mid to late palaeozoic rocks in australia have enabled us to revise the palaeozoic apparent polar wander path apwp this modified australian apwp is supported by data from other parts of gondwanaland the palaeomagnetic poles indicate that during the early and mid palaeozoic australia underwent rapid rotation first clockwise during the mid ordovician to the early silurian then counterclockwise from the mid silurian until the end of the devonian while it remained at low to equatorial latitudes this was succeeded by a rapid southward movement during mid carboniferous times the implications of the palaeomagnetic data for the tectonic relationship between the lachlan fold belt lfb and cratonic australia are consistent with the tectonic evidence that the lfb has been in place since the mid devonian

an analysis of simulated and observed blast records in the salt lake basin we have simulated 0 2 to 1 2 hz 3d elastic wave propagation in the salt lake basin from a blast at a nearby open pit mine a fourth order staggered grid finite difference method was used to simulate the blast in a two layer basin model 58 43 9 km consisting of semiconsolidated sediments up to 1 3 km thick surrounded by bedrock data from four blasts in the mine pit recorded by a network of 10 digital three component instruments were compared to the results of the simulation the simulation reproduces the overall pattern of ground motion amplification at basin sites relative to a rock site as measured by ratios of peak particle velocities cumulative kinetic energies and spectral magnitudes considering the simple two layer basin model used in the 3d simulation this finding suggests that the deep 3d basin structure significantly contributes to low frequency ground motion amplification in the salt lake basin 1 1 effects of a near surface layer of low velocity unconsolidated sediments p and s wave velocities of 1 65 and 0 41 km sec respectively that at soil sites along the profile increase the peak particle velocities by up to a factor of 3 and significantly increase the ground motion durations 2 2 attenuation in the sediments which greatly diminishes the ground motion durations on the synthetic seismograms when parameterized by realistic values of the quality factor q 20 for soil sites and 35 for bedrock sites 3 3 2d topographic scattering which increases the peak particle velocities by up to a factor of 2 and increases the signal durations for sites along the profile compared to the records from the simple two layer 3d simulation the records from a 2d p sv wave simulation that includes processes 1 through 3 provide a better match to the blast data especially the observed durations of shaking at five of the six stations along the profile the 2d simulation reproduces the normalized radial and vertical peak particle velocities to within a factor of 2 and the normalized cumulative kinetic energies and spectral amplitudes on these components to within generally a factor of 3 our results suggest that deep basin resonance reverberations in the near surface low velocity layer attenuation and topographic scattering significantly influence site amplification in the salt lake basin future studies of site amplification in the salt lake basin should include the effects of all of these mechanisms

chitinozoan implications in the palaeogeography of the east moesia romania abstract palaeomagnetic data from moesia are absent and previous palynological and macrofaunal studies could not show clearly the palaeogeographical position of moesia between the larger palaeocontinents gondwana baltica or avalonia cutting samples from three boreholes on east moesia se romania have been investigated in this study using s e m technique chitinozoan assemblages prove the presence of wenlock ludlow possibly homerian and gorstian p idoli and lochkovian those of the last have a pronounced distribution in north gondwanan localities one of them cingulochitina plusquelleci is illustrative only in north gondwanan regions these chitinozoans argue that east moesia and probably west moesia were in good communication with the ibarmaghian domain of the northern gondwana palaeocontinent

site correction of a high frequency strong ground motion simulation based on an empirical transfer function abstract in this study an empirical transfer function etf which is the spectrum difference in fourier amplitude spectra between observed strong ground motion and synthetic motion obtained by a stochastic point source simulation technique is constructed for the taipei basin taiwan the basis stochastic point source simulations can be treated as reference rock site conditions in order to consider site effects the parameters of the stochastic point source approach related to source and path effects are collected from previous well verified studies a database of shallow small magnitude earthquakes is selected to construct the etfs so that the point source approach for synthetic motions might be more widely applicable the high frequency synthetic motion obtained from the etf procedure is site corrected in the strong site response area of the taipei basin the site response characteristics of the etf show similar responses as in previous studies which indicates that the base synthetic model is suitable for the reference rock conditions in the taipei basin the dominant frequency contour corresponds to the shape of the bottom of the geological basement the top of the tertiary period which is the sungshan formation two clear high amplification areas are identified in the deepest region of the sungshan formation as shown by an amplification contour of 0 5 hz meanwhile a high amplification area was shifted to the basin s edge as shown by an amplification contour of 2 0 hz three target earthquakes with different kinds of source conditions including shallow small magnitude events shallow and relatively large magnitude events and deep small magnitude events relative to the etf database are tested to verify site correction the results indicate that etf based site correction is effective for shallow earthquakes even those with higher magnitudes but is not suitable for deep earthquakes finally one of the most significant shallow large magnitude earthquakes the 1999 chi chi earthquake in taiwan is verified in this study a finite fault stochastic simulation technique is applied owing to the complexity of the fault rupture process for the chi chi earthquake and the etf based site correction function is multiplied to obtain a precise simulation of high frequency up to 10 hz strong motions the high frequency prediction has good agreement in both time and frequency domain in this study and the prediction level is the same as that predicted by the site corrected ground motion prediction equation

paleozoic paleogeography of north america gondwana and intervening displaced terranes comparisons of paleomagnetism with paleoclimatology and biogeographical patterns new paleomagnetic data have become available in the past 5 yr that require modifications in previously published paleogeographic reconstructions for the silurian and devonian in this paper the new paleopoles are compared to published paleogeographic models based on paleoclimatologic and biogeographic data the data from the three fields of paleomagnetism paleoclimatology and biogeography are generally in excellent agreement and an internally consistent paleogeographic evolutionary picture of the interactions between north america gondwana and intervening displaced terranes is emerging during the interval of the ordovician silurian and devonian north america stayed in equatorial paleoposition while rotating counter clockwise the northwest african part of gondwana was in high southerly latitudes during the late ordovician and was fringed by peri gondwanide terranes such as southern europe armorica and avalonian basement blocks now found in eastern newfoundland nova scotia the boston basin the appalachian piedmont and northern florida subsequently gondwana and the peri gondwanide terranes displayed rapid drift with respect to the pole this drift translates into the following pattern of movement for northwest africa during the latest ordovician early silurian this area moved rapidly northward from polar to subtropical latitudes followed by equally rapid southward motion from subtropical to intermediate about 50 s paleolatitudes during the late silurian middle devonian it is likely that significant east to west motion accompanied the latter shift in paleolatitudes with the caledonian acadian orogeny the result of silurian to early devonian convergence and collision between gondwana and north america this collision sandwiched several of the intervening displaced terranes between gondwana and north america subsequent to this collision gondwana was separated in the late devonian by a medium width ocean from north america and the avalonian and southern european blocks which were left behind adjacent to north america this new ocean closed during the carboniferous and the resulting convergence and collision were the cause of the hercynian alleghanian orogenic belt problems remaining for future research besides the further gathering of reliable paleopoles involve the uncertain pre devonian position of the southern british isles in this scenario and the very rapid velocity with respect to the pole that results from the rapid late ordovician silurian apparent polar wander for gondwana