anisotropy and transverse isotropy a number of authors in the exploration literature have written about anisotropy but have restricted their discussions to wave propagation through rock having transverse isotropy with a vertical symmetry axis this note shows that there are fundamental differences between transverse isotropy when the symmetry axis is vertical normal to the free surface and more general anisotropy with an azimuthal variation of properties these differences are important now that effective azimuthal shear wave anisotropy resulting from aligned cracks and pores is becoming recognized as a significant property of crustal rocks

anisotropy of magnetic susceptibility and p wave velocity in core samples from the taiwan chelungpu fault drilling project tcdp the anisotropy of magnetic susceptibility ams and anisotropy of p wave velocity apv were characterized in core samples retrieved from the tcdp hole a at depths ranging from 600m to 1400m thus cutting across the thrust fault that ruptured during the 1999 chi chi earthquake our data show that the ams was similar for all the samples regardless of the lithologic contrasts with a magnetic fabric characteristic of weakly deformed sedimentary rocks that had undergone layer parallel shortening this robust observation applies to both the siltstones and sandstones at all depths investigated in contrast the apv data reflect fundamental differences between the elastic fabrics in the two facies while apv of the siltstone samples is controlled by a preferred orientation of the matrix minerals the apv of the sandstones is greatly influenced by microcrack porosity with a preferred orientation parallel to the maximum principal direction of paleostress and tectonic deformation these ams and apv data obtained in tcdp hole a at locations not directly impacted by the coseismic rupture provide a first order petrofabric framework for the characterization of hydromechanical anisotropy in the chelungpu fault system

central arctic surface ocean environment during the past 80 000 years stable oxygen and carbon isotope and sedimentological paleontological investigations supported by accelerator mass spectrometry 14 c datings were carried out on cores from north of 85 degrees n in the eastern central arctic ocean significant changes in accumulation rates provenance of ice rafted debris ird and planktic productivity over the past 80 000 years are documented during peak glacials i e oxygen isotope stages 4 and 2 the arctic ocean was covered by sea ice with decreased seasonal variation limiting planktic productivity and bulk sedimentation rates in early stage 3 and during termination i major deglaciations of the circum arctic regions caused lowered salinities and poor oxygenation of central arctic surface waters a meltwater spike and an associated ird peak dated to similar to 14 12 14 c ka can be traced over the southern eurasian basin of the arctic ocean this event was associated with the early and rapid deglaciation of the marine based barents sea ice sheet a separate termination ib meltwater event is most conspicuous in the central arctic and is associated with characteristic dolomitic carbonate ird this lithology suggests an origin of glacial ice from northern canada and northern greenland where lower paleozoic platform carbonates crop extensively out

new insights on 3 d plates interaction near taiwan from tomography and tectonic implications abstract recent tomographic results are used to trace the south china sea and philippine sea subducting slabs south and northeast of taiwan along the manila and ryukyu trenches respectively in particular the 3 d plates interaction beneath taiwan is discussed based on a close up view of the tomographic sections together with earthquake hypocenters distribution our study indicates that 1 the east dipping south china sea slab can be followed to the north up to the latitude of hualien 2 the eurasian plate subducts beneath most part of the taiwan island down to the 670 km depth discontinuity 3 the north dipping philippine sea slab can be followed slightly west of the longitude of hualien both plates thus interact beneath northern taiwan where the arc continent collision is paroxysmal 4 slab detachment is envisaged at the northern edge of the subducted eurasian plate beneath the coastal range of taiwan which may facilitate the northwestward motion of the philippine sea plate with respect to eurasia slabs geometries obtained from tomographic sections allow us to reconstruct the late neogene plate kinematics and dynamics in this region our main conclusions are 1 the size of the original south china sea was about twice its present size 2 the subducted part of the west philippine basin i e the largest oceanic basin of the philippine sea plate extends only 400 km north of the ryukyu trench 3 slab detachment might have occurred 3 5 my ago beneath the central and northern ryukyu arc along a weak zone that is aligned with the gagua ridge an ancient plate boundary 4 the ryukyu trench has propagated westward from 126 e of longitude southeast of miyako island to the locus of the present arc continent collision along a major lithospheric tear that cut through the continent ocean boundary first and then through the continental lithosphere as a consequence the southern ryukyu margin developed progressively from east to west as a subduction zone during the last 8 my it has been elaborated onto a passive margin which corresponded to the edge of the eurasian continental shelf bordering the south china sea prior to pliocene 5 the southern okinawa trough rifted during the last 2 1 ma following the propagation of the subduction zone 6 subduction of the eurasian margin probably stopped recently beneath northern taiwan and a flip of subduction from west to east is being initiated near hualien

current stress state and principal stress rotations in the vicinity of the chelungpu fault induced by the 1999 chi chi taiwan earthquake 1 we carried out various stress measurements in boreholes penetrating the northern segment of the chelungpu fault drilled about 5 years after the 1999 chi chi taiwan earthquake in the possible depth range of the chelungpu fault three major fault zones were encountered clearly recognizable principal stress rotations in the vicinity of the shallowest major fault zone at 1133 m depth in hole b suggest that this fault zone ruptured during the 1999 earthquake moreover the fault s rupturing altered the stress state in the area surrounding this fault zone in this paper we constrain the possible magnitudes of the current principal horizontal stresses around the fault zone and show that the current stress state belongs to a normal or strike slip fault regime therefore the stress state was changed from that of a reverse fault regime by the rupturing

nondestructive continuous physical property measurements of core samples recovered from hole b taiwan chelungpu fault drilling project 1 the taiwan chelungpu fault drilling project was undertaken in 2002 to investigate the faulting mechanism of the 1999 mw 7 6 taiwan chi chi earthquake hole b penetrated the chelungpu fault and core samples were recovered from between 948 42 and 1352 60 m depth three major zones designated fzb1136 fault zone at 1136 m depth in hole b fzb1194 and fzb1243 were recognized in the core samples as active fault zones within the chelungpu fault nondestructive continuous physical property measurements conducted on all core samples revealed that the three major fault zones were characterized by low gamma ray attenuation gra densities and high magnetic susceptibilities extensive fracturing and cracks within the fault zones and or loss of atoms with high atomic number but not a measurement artifact might have caused the low gra densities whereas the high magnetic susceptibility values might have resulted from the formation of magnetic minerals from paramagnetic minerals by frictional heating minor fault zones were characterized by low gra densities and no change in magnetic susceptibility and the latter may indicate that these minor zones experienced relatively low frictional heating magnetic susceptibility in a fault zone may be key to the determination that frictional heating occurred during an earthquake on the fault

core log integration studies in hole a of taiwan chelungpu fault drilling project summary taiwan chelungpu fault drilling project tcdp was initiated to understand the physical mechanisms involved in the large displacements of the 1999 taiwan chi chi earthquake continuous measurements of cores including laboratory work and a suite of geophysical downhole logs including p and s wave sonic velocity gamma ray electrical resistivity density temperature electrical borehole images and dipole shear sonic imager were acquired in hole a over the depth of 500 2003 m integrated studies of cores and logs facilitate qualitative and quantitative comparison of subsurface structures and physical properties of rocks a total of 10 subunits were divided on the basis of geophysical characteristics generally formation velocity and temperature increase with depth as a result of the overburden and thermal gradient respectively gamma ray resistivity formation density shear velocity anisotropy and density derived porosity are primarily dependent on the lithology zones with changes of percentage of shear wave anisotropy and the fast shear polarization azimuth deduced from dipole shear imager dsi are associated with the appearance of fractures steep bedding and shear zones the fast shear wave azimuth is in good agreement with overall dip of the bedding approximately 30 towards se and maximum horizontal compressional direction particularly in the kueichulin formation showing strong shear wave velocity anisotropy bedding parallel fractures are prevalent within cores whereas minor sets of high angle nnw sse trending with n and s dipping fractures are sporadically distributed the fault zone at depth 1111 m fza1111 is the chi chi earthquake slip zone and could be a fluid conduit after the earthquake the drastic change in fast shear wave polarization direction across the underlying non active sanyi thrust at depth 1710 m reflects changes in stratigraphy physical properties and structural geometry

consistently large marine reservoir ages in the norwegian sea during the last deglaciation with the exception of the gs 1 younger dryas coldperiodmarine reservoir ages for the last deglaciation in the north atlantic norwegian sea are generally assumed to have been around 400 500 radiocarbon years in magnitude earth planet sci lett 126 1994 275 radiocarbon 37 1995 53 quat res 52 1999 104 nature 412 2001 724 by comparing the climate records obtained from the grip ice core nature 359 1992 311 j quat sci 13 4 1998 283 andfrom north atlantic norwegian sea cores quat res 52 1999 104 geology 23 12 1995 1059 nature 356 1991 757 nature 356 1992 757 paleoceanography 3 1 1988 1 nature 343 1990 612 earth planet sci lett 126 1994 275 with radiocarbon dated european continental records we show that marine reservoir ages in the norwegian sea were of the order of 1000 14 c yr including large uncertainties this approach rests on the reasonable assumption that climate changes throughout the ne atlantic andeurope were more or less synchronous at the centennial scale fairly large variations in reservoir ages over time may have been causedby changing atmospheric 14 c content the results indicate that detailed land sea correlations for the north atlantic during the last deglaciation are not feasible using radiocarbon dating alone r 2003 elsevier science ltd all rights reserved

structural geology of a classic thrust belt earthquake the 1999 chi chi earthquake taiwan mw 7 6 abstract we document the structural context of the 1999 chi chi earthquake m w 7 6 in western taiwan which is one of the best instrumented thrust belt earthquakes the main surface break and large slip 3 10 m is on two segments of the shallow otherwise aseismic bedding parallel chelungpu sanyi thrust system which shows nearly classic ramp flat geometry with shallow detachments 1 6 km in the pliocene chinshui shale and mio pliocene kueichulin tungkeng formations however rupture is complex involving at least six faults including a previously unknown deeper thrust 8 10 km on which the rupture began we compare the coseismic displacements with a new 3d map of the chelungpu sanyi system the displacements are spatially and temporally heterogeneous and well correlated with discrete geometric segments of the 3d shape of the fault system geodetic displacement vectors are statistically parallel to the nearest adjacent fault segment and are parallel to large scale oblique fault corrugations the displacement magnitudes are heterogeneous at several scales which requires in the long term other non chi chi events or significant aseismic deformation the chelungpu thrust has a total displacement of 14 km but the area of largest chi chi slip 10 m is on a newly propagated north chelungpu chinshui detachment 0 3 km total slip which shows abnormally smooth rupture dynamics

an earthquake slip zone is a magnetic recorder during an earthquake the physical and the chemical transformations along a slip zone lead to an intense deformation within the gouge layer of a mature fault zone because the gouge contains ferromagnetic minerals it has the capacity to behave as a magnetic recorder during an earthquake this constitutes a conceivable way to identify earthquakes slip zones in this paper we investigate the magnetic record of the chelungpu fault gouge that hosts the principal slip zone of the chi chi earthquake mw 7 6 1999 taiwan using taiwan chelungpu fault drilling project core samples rock magnetic investigation pinpoints the location of the chi chi mm thick principal slip zone within the 16 cm thick gouge at 1 km depth a modern magnetic dipole of earth magnetic field is recovered throughout this gouge but not in the wall rocks nor in the two other adjacent fault zones this magnetic record resides essentially in two magnetic minerals magnetite in the principal slip zone and neoformed goethite elsewhere in the gouge we propose a model where magnetic record 1 is preserved during inter seismic time 2 is erased during co seismic time and 3 is imprinted during post seismic time when fluids cooled down we suggest that the identification of a stable magnetic record carried by neoformed goethite may be a signature of friction heating process in seismic slip zone

ultrafine spherical quartz formation during seismic fault slip natural and experimental evidence and its implications abstract in recent works on the determination of pseudotachylyte within the principal slip zone psz of the chelungpu fault taiwan we demonstrated that frictional melting occurred at shallow depths during the 1999 mw 7 6 chi chi earthquake thus the characteristics of melts are of paramount importance to investigate processes controlling dynamic fault mechanics during seismic slips we conducted rock friction experiments on siltstone recovered from the taiwan chelungpu fault drilling project tcdp at a slip rate of 1 3 m s and a normal stress of 1 mpa here we not only target to characterize experimental pseudotachylyte and evaluate the associated frictional behavior but also compare it with natural frictional melts of tcdp our results show that 1 initial shear stress drop was related to the generation of low viscosity melt patches 2 the evolution of shear stress in the postmelting regime was congruent with frictional melt rheology and 3 the slip strengthening presumably resulted from the extremely low content of water of the frictional melt in particular the state of art of in situ synchrotron analyses x ray diffraction and transmission x ray microscope determine the presence of ultrafine spherical quartz usq grains 10 nm to 50 nm in the glassy matrices presumably produced at high temperature our observations confirm that the usq grains formed in rock friction experiments do occur in natural faults we surmise the usq is the result of frictional melting on siltstone and represents the latest slip zones of the chelungpu fault and further infer that the viscous melts may terminate seismic slips at shallow crustal conditions

the chi chi earthquake sequence active out of sequence thrust faulting in taiwan we combined precise focal depths and fault plane solutions of more than 40 events from the 20 september 1999 chi chi earthquake sequence with a synthesis of subsurface geology to show that the dominant structure for generating earthquakes in central taiwan is a moderately dipping 20 to 30 thrust fault away from the deformation front a second subparallel seismic zone lies about 15 kilometers below the main thrust these seismic zones differ from previous models indicating that both the basal decollement and relic normal faults are aseismic

stress induced borehole elongation a comparison between the four arm dipmeter and the borehole televiewer in the auburn geothermal well the nature and origin of borehole elongation recorded by the four arm dipmeter calipers is studied utilizing information obtained from hydraulic fracturing stress measurements and borehole televiewer data taken in a well located in auburn new york a preferred orientation n10 w s10 e 10 and a less prominant e w orientation of borehole elongation was observed on two runs of the dipmeter comparisons of borehole geometry determined using the televiewer and the dipmeter show that both tools give the same orientation of borehole elongtion provided that the zone of elongation is longer than 30 cm comparisons of dipmeter caliper data with orientation of in situ stress and natural fractures obtained from hydrofracturing tests and televiewer data show that the n10 w s10 e borehole elongations 1 are axisymmetric 2 are aligned with the minimum horizontal stress sh and 3 are not associated with natural fractures intersecting the well these elongations are interpreted as stress induced well bore breakouts the e w elongation direction is characterized by an asymmetric borehole cross section in thinly bedded rocks and is not caused by breakouts this asymmetric geometry can be discriminated from breakouts using the oriented electric measurements provided by the dipmeter this study demonstrates that the dipmeter can be used to determine the orientation of sh by mapping breakouts confirming the results of earlier less detailed studies and provides a firm basis for mapping regional stress patterns using existing dipmeter data

measurement of the sortable silt current speed proxy using the sedigraph 5100 and coulter multisizer iie precision and accuracy the weight percentage and mean size of the 10 63 m terrigenous silt fraction termed sortable silt of fine grained marine sediments have recently been argued to be proxies for near bottom palaeocurrent intensity this paper details the accuracy and precision of the sedigraph 5100 and the coulter multisizer iie in determining the weight percentage and mean size of the sortable silt at abundances characteristic of deep ocean sediments three sortable silt standards and a fine silt clay diluent were generated from natural deep sea sediment of the iceland basin these were used to produce silty clays with standard additions of sortable silt ranging from 1 to 20 of the total by weight accuracy was measured relative to the size of the pure spike measured by each instrument at sortable silt abundance 5 the sedigraph and the coulter multisizer estimate both weight percentage and mean grain size precisely and accurately while below 5 instrumental noise degrades their performance on the basis of the sedigraph results a series of percentage errors is defined which may be applied to sortable silt mean size and weight percentage estimates used in palaeoceanographic near bottom current reconstruction it is suggested that ideally palaeocurrent reconstructions should be based on sedigraph determinations of the 0 63 m grain size distribution yielding both mean and abundance or on coulter multisizer determinations of the sortable silt grain size mean the coulter multisizer may prove especially useful in regions of very depleted 5 sortable silt component

velocity field of gps stations in the taiwan area abstract the 131 stations of the taiwan gps network were surveyed 4 6 times from 1990 to 1995 with dual frequency geodetic receivers the standard deviation of an observed baseline length with its linear trend removed is in the range of 6 10 mm for a 3 120 km long baseline the average rates of length change for all baselines of the network and those from nine continuously monitoring permanent stations are used in a least squares adjustment to estimate the velocities of the gps stations relative to paisha penghu situated at the chinese continental margin to the south of fengping in the northern coastal range the velocity vectors of stations in lanhsu lutao and the coastal range trend in the directions of 306 322 with rates of 56 82 mm yr in contrast there is a dramatic decrease in the rates to the north of fengping this may be caused by the motion along the ne sw trending thrusts which obliquely cut the northern coastal range a discontinuity of about 30 mm yr in the rates along with a remarkable change in the directions of station velocity is observed across the longitudinal valley then the moving directions gradually shift to the west for the stations in the western foothills in the kaohsiung pingtung coastal area the station velocities are even directed toward the southwest to the north of the peikang high the velocity vectors of the stations change direction from the west gradually to the north and finally to the east and southeast significant nw se extensional deformation is found in the ilan plain and northern taiwan in general the pattern of the velocity field for gps stations in the taiwan area is quite consistent with the directions of present day tectonic stress

determining the maximum overburden along thrust faults using a porosity versus effective confining pressure curve abstract this study aims to quantify the tectonically induced thrusting and erosion here we propose and evaluate a laboratory based method for determining the maximum effective stress ever sustained by a sedimentary rock formation the porosities of nineteen samples collected from two deep boreholes of the taiwan chelungpu fault drilling project were measured under different confining stresses the relation between measured porosity and confining pressure compaction curve is bilinear in log log scale the maximum effective stress of the tested rocks was determined from the intersection point of the two straight lines of the compaction curve the maximum effective stresses of the rocks below the sanyi fault reverse fault are close to the in situ vertical effective stress above the sanyi fault hanging wall where the rocks have been thrust the maximum effective stresses of the rocks are significantly greater than the in situ stress with an average value of 29 48 mpa that is the eroded thickness of the formation on the hanging wall of the sanyi fault is 2482 m a value close to that determined from the geological profile 2773 m it is inferred that the total displacements along the thrust sanyi fault is 11 5 km a value close to that determined from the geological profile 14 16 km these results indicate that the proposed laboratory based method is potentially useful for determining the thrusting and erosion in a fold thrust belt and the total displacements along a thrust fault

a vertical exposure of the 1999 surface rupture of the chelungpu fault at wufeng western taiwan structural and paleoseismic implications for an active thrust fault we mapped and analyzed two vertical exposures exposed on the walls of a 3 to 5 m deep 70 m long excavation and a smaller 3 m deep 10 m long excavation across the 1999 rupture of the chelungpu fault the primary exposure revealed a broad anticlinal fold with a 2 5 m high west facing principal thrust scarp contained in fluvial cobbly gravel beds and overlying fine grained overbank deposits sequential restoration of the principal rupture requires initial failure on the basal east dipping thrust plane followed by wedge thrusting and pop up of an overlying symmetrical anticline between two opposing secondary thrust faults net vertical offset is about 2 2 m across the principal fault zone from line length changes we estimate about 3 3 m of horizontal shortening normal to fault strike the ratio of these values yields a total slip of 4 0 m and an estimate of about 34 for the dip of the fault plane below the excavation this value is nearly the same as the 35 average dip of the fault plane from the surface to the hypocenter restoration of the exposed gravelly strata and adjacent overbank sediments deposited prior to the 1999 event around the principal rupture suggests the possible existence of a prior event a buried 30 m wide anticlinal warp beneath the uplifted crest of the 1999 event is associated with three buried reverse faults that we interpret as evidence for an earlier episode of folding and faulting in the site the prior event is also recorded in the smaller excavation which is located 40 m south and is oriented parallel to the larger excavation radiocarbon dating of samples within the exposed section did not place tight constraints on the date of the previous event available data are interpreted as indicating that the previous event occurred before the deposition of the less than 200 14 c yr b p overbank sands and after the deposition of the much older fluvial gravels we interpret the previous event as the penultimate event relative to the 1999 chi chi earthquake we estimated the long term slip rate of the chelungpu fault to be 10 15 mm yr during the last 1 ma based on previously published retrodeformable cross sections this rate is however significantly higher than geodetic rates of shortening across the chelungpu thrust where two pairs of permanent global positioning system stations suggest 7 10 mm yr of shortening across the fault given the 4 m of average slip the long term slip rate yields an interseismic interval of between 267 and 400 yr for the chelungpu fault

quaternary paleoceanography of the central arctic based on integrated ocean drilling program arctic coring expedition 302 foraminiferal assemblages the integrated ocean drilling program iodp arctic coring expedition acex hole 4c from the lomonosov ridge in the central arctic ocean recovered a continuous 18 m record of quaternary foraminifera yielding evidence for seasonally ice free interglacials during the matuyama progressive development of large glacials during the mid pleistocene transition mpt 1 2 0 9 ma and the onset of high amplitude 100 ka orbital cycles 500 ka foraminiferal preservation in sediments from the arctic is influenced by primary sea ice organic input and other environmental conditions and secondary factors syndepositional long term pore water dissolution taking these into account the acex 4c record shows distinct maxima in agglutinated foraminiferal abundance corresponding to several interglacials and deglacials between marine isotope stages mis 13 37 and although less precise dating is available for older sediments these trends appear to continue through the matuyama the mpt is characterized by nearly barren intervals during major glacials mis 12 16 and 22 24 and faunal turnover mis 12 24 abundant calcareous planktonic mainly neogloboquadrina pachyderma sin and benthic foraminifers occur mainly in interglacial intervals during the brunhes and very rarely in the matuyama a distinct faunal transition from calcareous to agglutinated foraminifers 200 300 ka in acex 4c is comparable to that found in arctic sediments from the lomonosov alpha and northwind ridges and the morris jesup rise down core disappearance of calcareous taxa is probably related to either reduced sea ice cover prior to the last few 100 ka cycles pore water dissolution or both

quaternary arctic ocean sea ice variations and radiocarbon reservoir age corrections a short sediment core from a local depression forming an intra basin on the lomonosov ridge was retrieved during the healy oden trans arctic expedition 2005 hotrax it contains a record of the marine isotope stages mis 1 3 showing exceptionally high abundances of calcareous microfossils during parts of mis 3 based on radiocarbon dating linear sedimentation rates of 7 9 cm ka persist during the last deglaciation the last glacial maximum lgm is partly characterized by a hiatus planktic foraminiferal abundance variations of neogloboquadrina pachyderma sinistral and calcareous nannofossils reflect changes in arctic ocean summer sea ice coverage and probably inflow of subpolar north atlantic water calibration of the radiocarbon ages using modeled reservoir corrections from previous studies and the microfossil abundance record of the studied core results in marine reservoir ages of 1400 years or more at least during the last deglaciation paired benthic planktic radiocarbon dated foraminiferal samples indicate a slow decrease in age difference between surface and bottom waters from the lateglacial to the holocene suggesting circulation and ventilation changes c 2010 elsevier ltd all rights reserved

distribution of planktic foraminifera at the ice margin in the arctic fram strait planktic foraminifera were collected in net tows 63 m along two east west transects at 78 and 80 n in the fram strait northern nordic seas at five concurrent depth intervals in the upper 200 m of the water column in the ice free zone absolute abundances in the upper 200 m of the water column up to 500 individuals m3 were obtained along the ice margin the absolute abundances reached up to 1250 ind m3 while in the ice covered areas not more than 50 ind m3 have been found surprisingly these strong variations in abundance are not accompanied by significant changes in faunal assemblages between the ice free and the ice covered regions neogloboquadrina pachyderma is the dominant species in most samples making up to 60 of the total faunal assemblage globigerina quinqueloba contributes 38 and all other species combined make up only 2 of the total fauna both absolute and relative abundances of the collected foraminifera are strongly dependent on the mesh size used using smaller mesh sizes provides a wider species spectrum which is of special interest for paleoceanographic reconstructions in the nordic seas where fossil assemblages 150 m often consist of only one species the specific hydrographic conditions in the fram strait with warm atlantic waters underlying cold polar surface waters result in a rather atypical depth distribution of the planktic foraminifera all species seem to prefer the temperate atlantic waters between 50 m and 200 m thus the species composition as well as geochemical tracers do not reflect the surface ocean conditions which again has potentially interesting implications for paleoceanographic reconstructions

coseismic displacements of the footwall of the chelungpu fault caused by the 1999 taiwan chi chi earthquake from insar and gps data abstract the differential sar interferometry technique interferometric synthetic aperture radar insar is applied on the chelungpu fault surface rupture zone of the september 20 1999 taiwan chi chi earthquake using six ers 2 images covering the period from february 1999 to january 2000 as compared with available geodetic data insar measurements result in more extensive analysis because of high spatial sampling and centimetric accuracy however coseismic displacements can be evaluated only on the footwall of the fault the analysis of interferograms shows the existence of a linear trend in phase difference mainly caused by orbital errors which we removed from interferograms using gps data the corrected interferograms provide a precise map of the insar component of the coseismic displacement showing a continuous decrease over the footwall from a maximum of 36 7 cm at the fault east of taichung city to a value of about 5 cm at the coastline 30 km further west the map analysis reveals that the changhua fault whose surface trace is located about 20 km west of the chelungpu one and the tuntzuchio fault influence the displacement field we interpret this in terms of minor reactivation of these faults triggered by the earthquake a 1 7 cm uncertainty estimated from the gps data is proposed to quantify the precision of the map beyond this single value we highlight the interest of having several coseismic interferograms to evaluate the reliability of the map in a more comprehensive way comparisons with displacements inferred from models of slip distribution inverted without insar data highlight the advantage of carrying out a joint inversion including our results as new constraints

late interseismic state of a continental plate bounding fault petrophysical results from dfdp 1 wireline logging and core analysis alpine fault new zealand 1 we present a geophysical characterization at 0 1 100 m scales of a major plate bounding continental fault in a late interseismic state the alpine fault produces mw 8 earthquakes every 200 400 years and last ruptured in 1717 ad wireline geophysical logs and rock cores extending from one side of the alpine fault to the other were acquired in two boreholes drilled in 2011 at gaunt creek during the first phase of the deep fault drilling project dfdp 1 these data document ambient conditions under which the next alpine fault earthquake will occur principal component analysis of the wireline logging data reveals that 80 of the variance is accounted for by electrical acoustic and natural gamma properties and preliminary multivariate classification enables the lithologies of sections of missing core to be reconstructed from geophysical measurements the fault zone exhibits systematic variations in properties consistent with common processes of progressive alteration and comminution near the principal slip zone superimposed on different protolith compositions our observations imply that the fault zone has the opposite sense of elastic asymmetry at 0 1 100 m scales to that of the crustal scale orogen imaged by remote geophysical methods on the basis of the fault zone scale asymmetry the bimaterial interface model of preferred earthquake rupture directions implies a northeastward direction of preferred alpine fault rupture on going characterization of the structural and hydraulic architecture of the alpine fault will improve our understanding of the relationship between in situ conditions earthquake rupture processes and the hazards posed by future earthquakes

arctic ocean deep sea record of northern eurasian ice sheet history the sediment composition of deep sea cores from the central arctic ocean the fram strait and the yermak plateau was analyzed for several parameters to reconstruct the history of marine paleoenvironment and terrestrial glaciation in the last 200 000 years layers with high amounts of coarse terrigenous ice rafted debris ird and often high contents of smectite were deposited during extensive glaciations in northern eurasia when ice sheets reached the northern continental margins of the barents and kara seas and discharged icebergs into the arctic ocean intercalated layers with relatively low ird and smectite contents but abundant planktic foraminifers in the coarse fraction were deposited during periods of atlantic water inflow to the arctic ocean and seasonally open waters leads in a sea ice cover with only few icebergs in the arctic ocean high ird contents in the sediments reflect the presence of ice sheets on the kara and barents seas shelves and the hinterland during the entire oxygen isotope stage 6 ca 190 130 ka in substage 5b ca 90 80 ka at the stage boundary 5 4 around 75 ka and in late stage 4 early stage 3 ca 65 50 ka these results are in excellent correlation with those from recent field work in northern scandinavia european russia siberia and on the shelves relatively low amounts of ird in central arctic ocean sediments from the late weichselian glacial maximum ca 24 18 ka correlate well with the recent reconstruction of a very limited eastern ice sheet extension during this time oxygen and carbon isotope records of planktic foraminifers from the analyzed sediment cores show a number of prominent excursions which can be interpreted as evidence for freshwater events in the arctic ocean the synchroneity of freshwater events and ird input suggests a common source strongest events were associated with deglaciations of the barents and kara seas after the ice sheets had blocked the outflow of large rivers for several millennia the outflow of freshwater from large ice dammed lakes occurred at ca 130 80 75 and 52 ka freshwater events in the central arctic ocean during the last deglaciation ca 18 ka were relatively small compared to the previous events this indicates that during most of the late weichselian glacial maximum a river outflow from northern siberia to the arctic ocean was possible atlantic water inflow to the arctic ocean and seasonally open waters in the ice leads occurred during the interglacials ofoxygen isotope stage 1 and substage 5e during several interstadials stage 3 substages 5a and 5c and to a lesser degree within stadials and glacials stages 2 4 and 6 with the exception ofthe interglacials these periods were times ofstrong ice growth on the continents as revealed by terrestrial data the coincidence suggests that open waters in the arctic ocean and the nordic seas were an important moisture source in addition to more southerly sources which fostered the growth of ice sheets on northern eurasia

stress estimated using microseismic clusters and its relationship to the fracture system of the hijiori hot dry rock reservoir a method for estimating the in situ stress state by analyzing microseismic clusters induced by hydraulic injections is proposed the method is based on focal mechanism analysis supplemented with microseismic doublet analysis the latter is used to discriminate between the fault plane and the auxiliary planes of the focal mechanism solution the method was applied to estimate the stress field within the hijiori hot dry rock geothermal reservoir and yielded results which were consistent with other estimates the mechanics of permeability creation within the reservoir during major hydraulic injections was then examined by evaluating the interaction of the inferred stress field with the natural fracture system the characteristics of the latter were determined by integrating information obtained from core samples acoustic borehole televiewer images and pressure temperature and spinner logs the results indicated that the observed microseismicity and orientation dependent permeability characteristics of the fracture population are well explained by shear failure inferred from coulomb s friction theory it is also shown that the growth direction of the reservoir is strongly controlled by the distribution of favorably oriented pre existing fractures and their interaction with the stress field

spatial slip distribution of the september 20 1999 chi chi taiwan earthquake mw7 6 inverted from teleseismic data the teleseismic waveforms of the mw7 6 september 20 1999 chi chi earthquake were examined to obtain the quick information on the fault rupture process the deconvolution results show the fault ruptured from south to the north and revealed the west movement of the hanging wall to the footwall on the eastern dipping plane the spatial slip distribution shows that the earthquake was mainly composed by a large asperity with a dimension of about 45km 15km the maximum slip was about 8 m located at about 45 km to the north of the epicenter the slip distributions obtained in this study have a good agreement with the observed surface breaks the comparable static and the dynamic stress drops of about 11 mpa in the large slip region indicate that the melting fluid pressurization might have taken place in this earthquake it reduces the dynamic friction and results in the large slip observed

preseismic deformation and coseismic displacements associated with the 1999 chi chi taiwan earthquake the destructive 1999 chi chi taiwan earthquake m w 7 5 produced an approximately 100 km long surface rupture mostly along the previously recognized north south trending chelungpu fault preseismic deformation in central taiwan is realized from annually repeated global positioning system gps data acquired during the 1992 1999 period the total wnw ese shortening rate in the vicinity of the epicentral region that is from the west coast to the western boundary of the central range is up to 25 mm yr the crustal deformation before the chi chi earthquake was essentially a uniaxial compressional strain of 0 36 strain yr in the direction of 114 the gps measurements taken 0 2 2 7 yr before and within 3 months after the mainshock were utilized to estimate the coseismic displacements horizontal movements of 1 1 9 1 m in the nw nnw directions are observed on the hanging wall eastern side of the fault there is a northward increasing trend in the magnitude of the displacement vectors and a dramatic change in the direction of about 50 toward the east along the fault strike in contrast much smaller se see movements of 0 1 1 5 m are found on the footwall western side of the fault the gps data show 2 4 10 1 m of total horizontal offsets across the chelungpu fault vertical offsets of 1 2 4 4 m with the eastern side up are also observed along the surface rupture the uplift on the hanging wall decreases rapidly toward the east it becomes subsidence at sun moon lake and in the puli wushe area the stations on the footwall show subsidence of 0 02 0 26 m the width of the uplift zone increases from about 10 km in the south to approximately 30 km in the north manuscript received 13 october 2000

heat signature on the chelungpu fault associated with the 1999 chi chi taiwan earthquake 1 we have made observations of a heat signature that is associated with the frictional heat generated at the time of faulting for a large earthquake temperature measurements in a borehole that intersects the chelungpu fault at a depth of about 1100 m show a small increase near the fault even six years after the earthquake the temperature signature has a symmetric shape with a width of about 40 m and is centered on the fault that slipped about 5 m during the 1999 chi chi taiwan earthquake the small amplitude of 0 06 c for the observed temperature anomaly indicates a very low level of friction that generated heat at the time of the earthquake

sortable silt and fine sediment size composition slicing parameters for palaeocurrent speed and palaeoceanography fine sediment size 63 ixm is best measured by a sedimentation technique which records the whole size distribution repeated size measurement with intermediate steps of removal of components by dissolution allows inference of the size distribution of the removed component as well as the residue in this way the size of the biogenic and lithogenic noncarbonate fractions can be determined observations of many size distributions suggest a minimum in grain size frequency curves at 8 to 10 ixm the dynamics of sediment erosion deposition and aggregate breakup suggest that fine sediment behavior is dominantly cohesive below 10 1xm grain size and noncohesive above that size thus silt coarser than 10 ixm displays size sorting in response to hydrodynamlc processes and its properties may be used to infer current speed silt that is f mer than 10 ixm behaves in the same way as clay 2 xm useful parameters of the distribution are the 10 63 ixm mean size and the percentage 10 63 ixm in the fine fraction we cannot use size distributions to distinguish the nature of the currents therefore to infer water mass advection speeds i e the mean kinetic energy of the flow ku regions of high eddy kinetic energy ke must be avoided at the present such abyssal regions lie under the high surface k e of major current systems gulf stream kuroshio agulhas antarctic circmpolar current and brazil falldand currents in the argenthe basin this is probably a satisfactory guide for the pleistocene with regard to the carbonate subfraction of the size spectrum size modes due to both cocco iths and foramlnlferal fragments can be recognized and analyzed with the boundary between them again at about 10 lm the flux of less than 10 lm carbonate at pelagic sites above the lysocline is another candidate for a productivity indicator

structural and physical property characterization in the wenchuan earthquake fault scientific drilling project hole 1 wfsd 1 abstract the wenchuan earthquake fault scientific drilling project wfsd started right after the 2008 mw 7 9 wenchuan earthquake to investigate its faulting mechanism hole 1 wfsd 1 reached the yingxiu beichuan fault ybf and core samples were recovered from 32 to 1201 15 m depth core investigation and a suite of geophysical downhole logs including p wave velocity natural gamma ray self potential resistivity density porosity temperature magnetic susceptibility and ultrasound borehole images were acquired in wfsd 1 integrated studies of cores and logs facilitate qualitative and quantitative comparison of the structures and physical properties of rocks logging data revealed that the geothermal gradient of the volcanic pengguan complex above 585 75 m is 1 85 c 100 m while that of the sedimentary xujiahe formation below 585 75 m is 2 15 c 100 m in general natural gamma ray resistivity density porosity p wave velocity and magnetic susceptibility primarily depend on the rock lithology all major fault zones are characterized by high magnetic susceptibility low density and high porosity with mostly low resistivity high natural gamma ray and sound wave velocity the high magnetic susceptibility values most likely result from the transformation of magnetic minerals by frictional heating due to the earthquake the ybf exposed in wfsd 1 can be subdivided into five different parts based on different logging responses each of them corresponding to certain fault rocks the high gamma radiation porosity and p wave velocity as well as low resistivity and temperature anomalies indicate that the wenchuan earthquake fault zone is located at 585 75 594 5 m depth with an average inclination and dip angle of n305 and 71 respectively the fact that the fracture directions in the hanging wall and footwall are different suggests that their stress field direction is completely different implying that the upper pengguan complex may not be local

arctic ocean during the last glacial maximum atlantic and polar domains of surface water mass distribution and ice cover on the basis of 52 sediment cores analyzed and dated at high resolution the paleoceanography and climate of the last glacial maximum lgm were reconstructed in detail for the fram strait and the eastern and central arctic ocean sediment composition and stable isotope data suggest three distinct paleoenvironments 1 a productive region in the eastern to central fram strait and along the northern barents sea continental margin characterized by atlantic water advection frequent open water conditions and occasional local meltwater supply and iceberg calving from the barents sea ice sheet 2 an intermediate region in the southwestern eurasian basin up to 84 85 n and the western fram strait characterized by subsurface atlantic water advection and recirculation a moderately high planktic productivity and a perennial ice cover that breaks up only occasionally and 3 a central arctic region north of 85 n in the eurasian basin characterized by a low salinity surface water layer and a thick ice cover that strongly reduces bioproduction and bulk sedimentation rates although the total inflow of atlantic water into the arctic ocean may have been reduced during the lgm its impact on ice coverage and halocline structure in the fram strait and southwestern eurasian basin was strong

mapping the northern portion of the chelungpu fault taiwan by shallow reflection seismics 1 the chelungpu fault was activated by the 1999 chi chi earthquake mw 7 6 taiwan this fault exhibited extraordinarily large surface ruptures up to 9 8 m as well as underground fault slippages up to 12 m during the earthquake these large displacements were concentrated along the northern portion of the fault 40 km north of the epicenter to prepare data for the future drilling of deep wells in this area many shallow seismic reflection surveys were conducted to investigate the sites an approximate 3d structure of the fault surface can be deduced by this cost effective approach although the depth penetration may be limited e g 3 km the method still provides reliable information to study large ruptures and to better plan future deep wells

a new correlation of the glacial moraines in the southern apennines italy abstract analysis of late pleistocene moraines in the southern apennines in southern italy suggests a possible correlation with the sequence in other italian regions but correlations with other parts of europe remain uncertain the lowest moraines consisting of complex loops recognized on the highest peaks in the southern apennines are attributable to the maximum of the last main glaciation with the subsequent rise in the snow line the glaciers retreated to new limits marked by two further stadial moraines the oldest and older dryas respectively which according to federici 1979 can be referred to the first and second apenninic stages the highest moraine loop which is present only on the pollino group may date from the lisens stage of the younger dryas

biochronology and paleoceanography of late pleistocene and holocene calcareous nannofossil abundances across the arctic basin biochronology and paleoceanography of late pleistocene and holocene calcareous nannofossils across the arctic basin