sinking cities in indonesia alos palsar detects rapid subsidence due to groundwater and gas extraction abstract we use interferometric synthetic aperture radar insar time series analysis of alos l band sar data to resolve land subsidence in western indonesia with high spatial and temporal resolution the data reveal significant subsidence in nine areas including six major cities at rates up to 22 cm year land subsidence is detected near lhokseumawe in medan jakarta bandung blanakan pekalongan bungbulang semarang and in the sidoarjo regency the fastest subsidence occurs in highly populated coastal areas particularly vulnerable to flooding we correlate the observed subsidence with surface geology and land use despite the fact that subsidence is taking place in compressible deposits there is no clear correlation between subsidence and surface geology in urban areas we find a correlation between rapid patchy subsidence and industrial land use and elsewhere with agricultural land use this suggests that the subsidence is primarily caused by ground water extraction for industrial and agricultural use respectively we also observe subsidence associated with exploitation of gas fields near lhokseumawe and in the sidoarjo regency a continuation of these high rates of subsidence is likely to put much of the densely populated coastal areas below relative sea level within a few decades

rock weathering rates as functions of time the scarcity of documented numerical relations between rock weathering and time has led to a common assumption that rates of weathering are linear this assumption has been strengthened by studies that have calculated long term average rates however little theoretical or empirical evidence exists to support linear rates for most chemical weathering processes with the exception of congruent dissolution processes the few previous studies of rock weathering rates that contain quantitative documentation of the relation between chemical weathering and time suggest that the rates of most weathering processes decrease with time recent studies of weathering rinds on basaltic and andesitic stones in glacial deposits in the western united states also clearly demonstrate that rock weathering processes slow with time some weathering processes appear to conform to exponential functions of time such as the square root time function for hydration of volcanic glass which conforms to the theoretical predictions of diffusion kinetics however weathering of mineralogically heterogeneous rocks involves complex physical and chemical processes that generally can be expressed only empirically commonly by way of logarithmic time functions incongruent dissolution and other weathering processes produce residues which are commonly used as measures of weathering these residues appear to slow movement of water to unaltered material and impede chemical transport away from it if weathering residues impede weathering processes then rates of weathering and rates of residue production are inversely proportional to some function of the residue thickness this results in simple mathematical analogs for weathering that imply nonlinear time functions the rate of weathering becomes constant only when an equilibrium thickness of the residue is reached because weathering residues are relatively stable chemically and because physical removal of residues below the ground surface is slight many weathering features require considerable time to reach constant rates of change for weathering rinds on volcanic stones in the western united states this time is at least 0 5 my

engineering aspects and time effects of rapid deterioration of sandstone in the tropical environment of sabah malaysia cut slopes in rock masses start to deteriorate directly after excavation due to stress relief and weathering the deterioration is a time dependent process that depends on the local climate and the rock mass including its history and the environment the amount of deterioration per time unit the weathering intensity rate is not a constant over time but is for most rock masses larger when the mass is less weathered and becomes smaller with further progressing weathering a study has been carried out to establish the relationship between weathering intensity rate and exposure time for the intact rock strength irs of sandstone in humid tropical areas the data set for the study was collected in and near kota kinabalu sabah malaysia which has a humid tropical climate the geology in the area consists of thick sequences of sandstone and shale beds of the crocker formation results show that the best relationship between intact rock strength irs and exposure time t is by a logarithmic function irs t 105 34 log 1 t this relationship can likely be used for prediction of the intact rock strength development of similar sandstone over the engineering lifetime of man made slopes in tropical areas

climate logging with a new rapid optical technique at siple dome the dust logger design is based on a decade of experience in the use of light sources to measure optical properties of deep antarctic ice light is emitted at the top of the instrument by side directed leds scattered or absorbed by dust in the ice surrounding the borehole and collected in a downhole pointing photomultiplier tube pmt a meter below with this method the ice is sampled at ambient pressure in a much larger volume than is the case in a core study and the entire length can be logged in one day in ice in which scattering is dominated by bubbles the absorption from dust impurities is perceived as a drop in signal whereas in bubble free ice the scattering from dust increases the light collected we report on results obtained in siple dome hole a in december 2000 the instrument measured increases in dust concentration extending over many meters during glacial maxima as well as narrow spikes due to 1 cm thick ash and dust bands of volcanic origin monte carlo simulation is employed to clarify data analysis and predict the capabilities of future designs

inter hemispheric transport of volcanic ash from a 1259 a d volcanic eruption to the greenland and antarctic ice sheets a strong volcanic sulfuric acid signal corresponding to an age of 1259 a d has been reported in ice cores from greenland antarctica and arctic canada tiny 5 m volcanic glass shards were reported previously in samples from this layer in an ice core from the south pole here we report the discovery of volcanic glass shards from a contemporaneous layer in an ice core from summit greenland the major element composition of the glass shards in the greenland sample are identical to those from the south pole confirming the assumption that has been made previously that the sulfuric acid signal in the ice cores is an inter hemispheric time stratigraphic marker the composition of these glass shards is similar to those produced by a 550 700 yrs b p eruption of el chichon volcano in mexico suggesting that it may be the source of the widely dispersed material

seven years of postseismic deformation following the 1999 m 7 4 and m 7 2 izmit duzce turkey earthquake sequence 1 we report the results of nearly 7 years of postseismic deformation measurements using continuously recorded and survey mode gps observations for the 1999 izmit duzce earthquake sequence resolvable time dependent postseismic changes to the preearthquake interseismic velocity field extend at least as far as the continuous gps station in ankara 200 km southeast of the izmit rupture seven years after the earthquake sequence the relative postseismic velocity across the north anatolian fault naf reaches 10 12 mm a roughly 50 of the steady state interseismic rate with the highest postseismic velocities within 40 km of the coseismic ruptures we use a sequence of logarithmic time functions to fit gps site motions up to three logarithmic terms with decay constants of 1 150 and 3500 days are necessary to fit all the transient motion observed at the continuous gps stations the first term is required for the component of site motion parallel to the naf at near field sites strongly implicating rapid shallow afterslip the intermediate and longer term postseismic velocity components reflect more broadly distributed strain with a symmetric double couple pattern suggestive of either localized deep afterslip or viscoelastic relaxation of the upper mantle and or lower crust in two areas including the marmara sea this pattern is superimposed on north south extension centered on the naf we speculate that this extension may result from aseismic dip slip along coseismically weakened faults driven by the background tectonic stress

geodetic imaging of plate motions slip rates and partitioning of deformation in japan 1 interseismic deformation in japan results from the combined effects of tectonic processes including rotation of crustal blocks and the earthquake cycle process of elastic strain accumulation about upper plate faults and subduction zone interfaces we use spherical linear block theory constrained by geodetic observations from densely spaced global positioning system gps stations to estimate plate motions fault slip rates and spatially variable interplate coupling on the japan kuril sagami and nankai subduction zones the reference model developed in this paper consists of 20 blocks produces a mean residual velocity magnitude of 1 84 mm yr at 950 stations and accounts for 96 of the observed interseismic deformation signal we estimate fault slip rates in excess of 15 mm yr along the niigata kobe tectonic zone and itoigawa shizuoka tectonic line through central japan confirming their hypothesized roles as major tectonic boundaries oblique convergence across the nankai trough is partitioned with 3 4 of the 30 mm yr of trench parallel motion accommodated by strike slip motion on the subduction interface and the remaining 1 4 accommodated by right lateral slip on the median tectonic line in contrast our models suggest negligible slip partitioning in eastern hokkaido where oblique slip on the japan kuril subduction interface accommodates all of the trench parallel component of relative plate motion inferred spatial variations in the rake and magnitude of slip deficit on subduction zone interfaces reflect the influences of megathrust geometry and earthquake cycle processes such as enhanced elastic strain accumulation about seismic asperities and coseismic sense fault motion indicative of silent slip events or afterslip following large earthquakes

asymmetric dynamics at subduction zones derived from plate kinematic constraints abstract the lithospheric sinking along subduction zones is part of the mantle convection therefore computing the volume of lithosphere recycled within the mantle by subducting slabs quantifies the equivalent amount of mantle that should be displaced for the mass conservation criterion the rate of subduction is constrained by the convergence rate between upper and lower plates and the motion of the subduction hinge h that may either converge or diverge relative to the upper plate here starting from the analysis of the slab hinge kinematics we evaluate the subduction rate at 31 subduction zones worldwide useful to compute volumes of sinking lithosphere into the mantle our results show that 190 km3 yr and 88 km3 yr of lithospheric slabs are currently subducting below h divergent and h convergent subduction zones respectively we also propose supporting numerical models providing asymmetric volumes of the subducted lithosphere using the subduction rate instead of plate convergence as boundary condition furthermore h divergent subduction zones appear to be coincident with subductions having westward directed slabs whereas h convergent subduction zones are mostly compatible with those that have eastward to northeastward directed slabs on the basis of this geographical polarity our lithospheric volume estimation gives 214 km3 yr and 88 km3 yr of subducting lithosphere respectively this entails that w directed subduction zones contribute more than twice in lithospheric sinking into the mantle with respect to e to ne directed ones in accordance with the conservation of mass principle this volumetric asymmetry in the mantle suggests a displacement of 120 km3 yr of mantle material from west to east providing a constraint for global asymmetric mantle convection

block kinematics of the pacific north america plate boundary in the southwestern united states from inversion of gps seismological and geologic data 1 the active deformation of the southwestern united states 30 41 n is represented by a finite number of rotating elastic plastic spherical caps gps derived horizontal velocities geologic fault slip rates transform fault azimuths and earthquake derived fault slip vector azimuths are inverted for block angular velocities creep on block bounding faults permanent strain rates within the blocks and the rotations of 11 published gps velocity fields into to a common north american reference frame gps velocities are considered to be a combination of rigid block rotations recoverable elastic strain rates resulting from friction on block bounding faults and nonrecoverable strain rates resulting from slip on faults within the blocks the resulting pacific north america angular velocity is similar to some published estimates and satisfies transform azimuths and one spreading rate in the gulf of california earthquake slip vectors in the gulf of california and alaska and gps velocities along coastal california and within the pacific basin published fault slip rates are satisfied except in the southern mojave desert where the motion of the mohave block relative to north america is faster than can be explained by mapped faults the largest blocks the sierra nevada great valley and the eastern basin and range show permanent strain rates after removing elastic strain of only a few nanostrain per year demonstrating approximately rigid behavior observed horizontal strain rates correlate strongly with predicted strain rates from known faults suggesting that the short term strains evident in gps velocities are largely elastic in only about 20 of the region is distributed deformation needed to match the data indicating that a plate tectonic style description of the deformation of the western united states is plausible most blocks rotate about vertical axes at approximately the same rate as the pacific relative to north america suggesting that locally spin rates are communicated from block to block arguing against both floating block and ball bearing mechanisms of block rotation the similarities of the blocks spin rates to that of the pacific suggests that the pacific strongly influences their motions through edge tractions however it is shown that the blocks cannot rotate about the pacific north america pole without spinning counter to the sense of pacific north america shear unlike some other broad plate boundaries in the western united states vertical axis rotations take up very little of the slip rate budget across the region

major features and forcing of high latitude northern hemisphere atmospheric circulation using a 110 000 year long glaciochemical series the greenland ice sheet project 2 glaciochemical series sodium potassium ammonium calcium magnesium sulfate nitrate and chloride provides a unique view of the chemistry of the atmosphere and the history of atmospheric circulation over both the high latitudes and mid low latitudes of the northern hemisphere interpretation of this record reveals a diverse array of environmental signatures that include the documentation of anthropogenically derived pollutants volcanic and biomass burning events storminess over marine surfaces continental aridity and biogenic source strength plus information related to the controls on both high and low frequency climate events of the last 110 000 years climate forcings investigated include changes in insolation of the order of the major orbital cycles that control the long term behavior of atmospheric circulation patterns through changes in ice volume sea level events such as the heinrich events massive discharges of icebergs first identified in the marine record that are found to operate on a 6100 year cycle due largely to the lagged response of ice sheets to changes in insolation and consequent glacier dynamics and rapid climate change events massive reorganizations of atmospheric circulation that are demonstrated to operate on 1450 year cycles changes in insolation and associated positive feedbacks related to ice sheets may assist in explaining favorable time periods and controls on the amplitude of massive rapid climate change events explanation for the exact timing and global synchroneity of these events is however more complicated preliminary evidence points to possible solar variability climate associations for these events and perhaps others that are embedded in our ice core derived atmospheric circulation records

five year measurements of rock tablet weathering on a forested hillslope in a humid temperate region in order to elucidate the effects of rock type and geomorphic setting on weathering rates field experiments using microweight loss techniques were carried out rock tablets for eight kinds of rock types granite granodiorite gabbro limestone andesite rhyolite crystalline schist and tuff with a diameter of 3 5 cm and a thickness of about 1 cm were enclosed in a nylon mesh bag and placed in the four corners of a soil bedrock interface on a granodiorite hillslope of central japan for over 5 years the results show that 1 the saturated grus layer is the main locus of solutional denudation 2 the 18 and 11 weight losses of limestone and tuff under a saturated soil layer were clearly the largest of all the rock types examined and 3 the weight loss is smaller for granite gabbro crystalline schist and andesite while it is larger for tuff and rhyolite at every location these results suggest that weathering rates are influenced by both lithology and environmental conditions

interseismic coupling and asperity distribution along the kamchatka subduction zone 1 gps measurements of interseismic horizontal surface velocities reveal the degree of kinematic coupling of the plate boundary thrust along the kamchatka subduction zone from about 51 degrees to 57 degrees n latitude inversions for the distribution of aseismic slip rate along the similar to 15 degrees nw dipping underthrust suggest a nonslipping plate interface in southern kamchatka above similar to 50 km depth along the segment that ruptured in the m w 9 1952 earthquake north of similar to 53 degrees n the subduction interface experiences significant aseismic slip consistent with the lower seismic moment release in m 8 5 earthquakes along this portion of the subduction zone the gps velocities are consistent with a boundary element forward model in which historic earthquake rupture zones are represented as locked asperities surrounded by a zero shear stress subduction interface loaded by plate convergence models in which the complete rupture zones of historic earthquakes are considered locked greatly overpredict the degree of kinematic coupling reducing the area of the locked model asperities to the central 25 area of historic rupture zones fits the data well suggesting that large earthquakes involve small fully locked core asperities surrounded by conditionally stable portions of the plate interface areas of low aseismic slip rate appear to be roughly correlated with areas of low isostatic gravity anomalies over offshore forearc basins while less coupled portions of the kamchatka subduction zone coincide with high gravity anomalies offshore of two peninsulas possibly related to the subduction of the emperor meji seamount chain and the kruzenstern fracture zone

on the resolution of shallow mantle viscosity structure using postearthquake relaxation data application to the 1999 hector mine california earthquake 1 most models of lower crust mantle viscosity inferred from postearthquake relaxation assume one or two uniform viscosity layers a few existing models possess apparently significant radially variable viscosity structure in the shallow mantle e g the upper 200 km but the resolution of such variations is not clear we use a geophysical inverse procedure to address the resolving power of inferred shallow mantle viscosity structure using postearthquake relaxation data we apply this methodology to 9 years of gps constrained crustal motions after the 16 october 1999 m 7 1 hector mine earthquake after application of a differencing method to isolate the postearthquake signal from the background crustal velocity field we find that surface velocities diminish from 20 mm yr in the first few months to 2 mm yr after 2 years viscoelastic relaxation of the mantle with a time dependent effective viscosity prescribed by a burgers body provides a good explanation for the postseismic crustal deformation capturing both the spatial and temporal pattern in the context of the burgers body model which involves a transient viscosity and steady state viscosity a resolution analysis based on the singular value decomposition reveals that at most two constraints on depth dependent steady state mantle viscosity are provided by the present data set uppermost mantle viscosity depth 60 km is moderately resolved but deeper viscosity structure is poorly resolved the simplest model that explains the data better than that of uniform steady state mantle viscosity involves a linear gradient in logarithmic viscosity with depth with a small increase from the moho to 220 km depth however the viscosity increase is not statistically significant this suggests that the depth dependent steady state viscosity is not resolvably different from uniformity in the uppermost mantle

global variability in subduction thrust zone forearc systems deviations of slip vector azimuths of interplate thrust earthquakes from expected plate convergence directions at oblique subduction zones provide kinematic information about the deformation of forearcs and indirect evidence on the dynamics of the plate boundary a global survey of slip vectors at major trenches of the world reveals a large variability in the kinematic response of forearcs to shear produced by oblique convergence the variability in forearc deformation inferred from slip vector deflections is suggested to be caused by variations in forearc rheology rather than in the stresses acting on subduction zone thrust faults estimated apparent macroscopic rheologies range from elastic to perfectly plastic or viscous forearc rheologies inferred from slip vectors do not correlate with age of the subducting lithosphere but continental forearcs or old arcs appear to deform less than oceanic or young arcs the inferred absence of forearc deformation at continental arcs from this study is counter to inferences drawn from compiled geologic information on forearc faults correlations of the apparent forearc rheology with backarc spreading convergence rate slab dip arc curvature and downdip length of the thrust contact are poor however great subduction zone earthquakes occur where forearcs are apparently more elastic i e less deformed by oblique convergence which suggests that the mechanical properties of forearcs rather than stress magnitude on thrust faults control both the kinematic behavior of forearcs and where great subduction zone earthquakes occur

crustal thickness beneath central and east java indonesia inferred from p receiver functions abstract we compute receiver functions from teleseismic earthquake data recorded at the dense meramex network in central and east java indonesia in order to map the moho depths h and the bulk crustal vp vs ratio we apply the h stacking technique of zhu and kanamori 2000 though the interpretation of the results is hampered by the high complexity of the recorded waveforms in the context of a high noise level and of the heterogeneous assemblage of continental fragments and ophiolitic suture zones forming southeast asia we were able to derive an average crustal thickness of about 34 km support for the assumption of ophiolitic basement in the center of the island related to the meratus suture zone comes from shallowing of the moho to about 30 km beneath the kendeng zone north and west of the kendeng zone the moho is imaged at anomalous depths down to 39 km the observed anomalies line up along the hypothetical boundary between the continental sw borneo fragment and the meratus suture and are indicative of crustal thickening caused by overthrusting and compressional deformation in the context of a former collision zone resulting vp vs ratios cannot be inferred reliably due to the complexity of the waveforms our results do not corroborate the hypothesis of a major structural change along the southern coast at the division between central and east java likewise we do not find clear evidence for the existence of the postulated muria progo lineament

late quaternary tectonics and seismotectonics along the red river fault zone north vietnam abstract a study of active tectonic development in vietnam is of great importance right lateral strike slip offsets along the red river fault during the pliocene present are determined by analyzing tributaries quaternary alluvial fans river valley from landsat spot images detailed topographical maps and field observation along the sw fault of the red river right lateral offsets of stream channels range between 150 and 700 m mean offsets of 300 m drainage offsets 170 450 m are found on the eastern branch assuming the major phase of incision is visible in this area which is close to the red river delta due to the onset of riss glaciation using the average length of offset channels and a minimum rate of 100 150 mm yr for river propagation we estimate the horizontal slip rates of 2 9 1 7 mm yr for song chay fault 2 3 1 5 mm yr for red river left side fault and 2 1 1 5 mm yr for red river left side fault several active faults associated with it are observed in son la area the phong tho nam pia fault is clearly seen in the geomorphology which separates tu le and song da rift zones in normal fault segments striking nw se sw dipping is observed clearly from spot images in the field triangular facets indicate typical dip slip displacement based on different data vertical slip rate of phong tho nam pia fault is estimated to be 0 2 0 4 mm y for pliocene present 0 5 3 mm y for quaternary present and 0 6 1 7 for the present time based on various methods maximum credible earthquakes for different fault segments in vietnam were estimated

atmospheric effects and spurious signals in gps analyses improvements in the analyses of global positioning system gps obser vations yield resolvable mm to sub mm di erences in coordinate estimates thus provid ing su cient resolution to distinguish subtle di erences in analysis methodologies here we investigate the e ects on site coordinates of using di erent approaches to modelling atmospheric loading deformation atml and handling of tropospheric delays the rig orous approach of using the time varying vmf1 mapping function yields solutions with lower noise at a range of frequencies compared with solutions generated using empiri cal mapping functions this is particularly evident when atml is accounted for some improvement also arises from using improved a priori zenith hydrostatic delays zhd with the combined e ect being site speci c importantly inadequacies in both mapping functions and a priori zhds not only introduce time correlated noise but signi cant pe riodic terms at solar annual and semi annual periods we nd no signi cant di erence between solutions where non tidal atml is applied at the observation level rather than as a daily averaged value but failing to model diurnal and semi diurnal tidal atml at the observation level can introduce anomalous propagated signals with periods that closely match the gps draconitic annual 351 4 d and semi annual period 175 7 d ex acerbated by not xing ambiguities these signals are evident in both stacked and sin gle site power spectra with each tide contributing roughly equally to the dominant semi annual peak the amplitude of the propagated signal reaches a maximum of 0 8 mm with a clear latitudinal dependence that is not correlated directly with locations of maximum tidal amplitude this is the first evidence of aliased signals being produced from tidal atml deformations

abrupt increase in greenland snow accumulation at the end of the younger dryas event the warming at the end of the last glaciation was characterized by a series of abrupt returns to glacial climate the best known of which is the younger dryas event1 despite much study of the causes of this event and the mechanisms by which it ended many questions remain unresolved1 oxygen isotope data from greenland ice cores2 4 suggest that the younger dryas ended abruptly over a period of about 50 years dust concentrations2 4 in these cores show an even more rapid transition 20 years this extremely short timescale places severe constraints on the mechanisms underlying the transition but dust concentrations can reflect subtle changes in atmospheric circulation which need not be associated with a large change in climate here we present results from a new greenland ice core gisp2 showing that snow accumulation doubled rapidly from the younger dryas event to the subsequent preboreal interval possibly in one to three years we also find that the accumulation rate change from the oldest dryas to the bo11ing allerod warm period was large and abrupt the extreme rapidity of these changes in a variable that directly represents regional climate implies that the events at the end of the last glaciation may have been responses to some kind of threshold or trigger in the north atlantic climate system

the south china block indochina collision where when and how this study uses new field observations and existing studies to shed new light on the origin and significance of two nw se striking orogens in nw and ne vietnam we conclude that the architecture of each belt is a stack of ne directed nappes formed either under deep ductile synmetamorphic conditions or under shallow depth in the sw and ne parts respectively the song ma zone and song chay ophiolitic melange represent two ophiolitic sutures however the late permian song da and babu mafic rocks are not ophiolites but intraplate basalts related to the emeishan plume a late triassic unconformity the 225 205 ma postorogenic plutonism and the 250 230 ma syntectonic metamorphism support an early to middle triassic age for these tectonic events both nw and ne belts are due to sw directed subduction with arc magmatism ocean closure and continental collision though two contemporary s dipping subduction zones might explain the structural evolution of the two belts a single convergent system offset by the tertiary red river fault is preferred as this s directed subduction better accounts for the late permian intraplate magmatism this scenario is discussed in the general geodynamic framework of se asia

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

global frequency of magnitude 9 earthquakes for decades seismologists have sought causal relationships between maximum earthquake sizes and other properties of subduction zones with the underlying notion that some subduction zones may never produce a magnitude 9 or larger event the 2004 andaman m w 9 2 earthquake called into question such ideas given multicentury return times of the greatest earthquakes ignorance of those return times and our very limited observation span i suggest that we cannot yet make such determinations present evidence cannot rule out that any subduction zone may produce a magnitude 9 or larger earthquake based on theoretical recurrence times i estimate that one to three m9 earthquakes should occur globally per century and the past half century with five m9 events reflects temporal clustering and not the long term average

tephrochronology of the siple dome ice core west antarctica correlations and sources abstract a total of 24 tephra bearing volcanic layers have been recognized between 550 and 987 m depth in the siple dome a sdm a ice core in addition to a number already recognized tephra in the upper 550 m dunbar et al 2003 kurbatov et al 2006 the uniform composition and distinctive morphological of the particles composing these tephra layers suggest deposition as a result of explosive volcanic eruptions and that the layers therefore represent time stratigraphic markers in the ice core despite the very fine grain size of these tephra mostly less than 20 microns robust geochemical compositions were determined by electron microprobe analysis the source volcanoes for these tephra layers are largely found within the antarctic plate statistical geochemical correlations tie nine of the tephra layers to known eruptions from mt berlin a west antarctic volcano that has been very active for the past 100 000 years previous correlations were made to an eruption of mt takahe another west antarctic volcano and one to mt hudson located in south america kurbatov et al 2006 the lowest tephra layer in the ice core located at 986 21 m depth is correlated to a source eruption with an age of 118 1 1 3 ka suggesting a chronological pinning point for the lower ice an episode of anomalously high volcanic activity in the ice in the sdm a core between 18 and 35 ka gow and meese 2007 appears to be related to eruptive activity of mt berlin volcano at least some of the tephra layers found in the sdm a core appear to be the result of very explosive eruptions that spread ash across large parts of west antarctica off the west antarctic coast as well as also being recognized in east antarctica basile et al 2001 narcisi et al 2005 narcisi et al 2006 some of these layers would be expected to should be found in other deep antarctic ice cores particularly ones drilled in west antarctica providing correlative markers between different cores the analysis of the tephra layers in the siple dome core along with other antarctic cores provides a timing framework for the relatively proximal antarctic and south american volcanic eruptive events allowing these to be distinguished from the tropical eruptions that may play a greater role in climate forcing

numerical modelling of combined erosion and weathering of slopes in weak rock due to various decay processes associated with weathering the stability of artificial slopes in weak rocks may be affected well within their envisaged engineering lifetime conceptually the decay following the initial stress release after excavation can be described as a process seeking equilibrium between weathering and erosion the extent to which such an equilibrium is actually reached influences the outcome of the weathering erosion decay process as well as the effects that the decay has on the geotechnical properties of the exposed rock mass and thus ultimately the stability of slopes affected by erosion and weathering this paper combines two conceptual models for erosion and weathering and derives a numerical model which predicts the resulting slope development this can help to predict the development of a slope profile excavated in a weak rock in time and can be extended with the addition of strength parameters to the weathering profile to enable prediction of slope stability as a function of time copyright 2011 john wiley sons ltd

the gisp2 δ18o climate record of the past 16 500 years and the role of the sun ocean and volcanoes measured 18o 16o ratios from the greenland ice sheet project 2 gisp2 ice core extending back to 16 500 cal yr b p provide a continuous record of climate change since the last glaciation high resolution annual 18o 16o results were obtained for most of the current millennium a d 818 1985 and record the medieval warm period the little ice age and a distinct 11 yr 18o 16o cycle volcanic aerosols depress central greenland annual temperature 1 5 c maximally and annual 18o 16o for about 4 yr after each major eruptive event on a bidecadal to millennial time scale the contribution of solar variability to holocene greenlandic temperature change is 0 4 c the role of thermohaline circulation change on climate problematic during the holocene is more distinct for the 16 500 10 000 cal yr b p interval analogous to 14c age calibration terminology we express time in calibrated cal yr b p a d 1950 0 cal yr b p the oldest dryas bolling older dryas allerod younger dryas sequence appears in great detail bidecadal variance in 18o 16o but not necessarily in temperature is enhanced during the last phase of lateglacial time and the younger dryas interval suggesting switches of air mass transport between jet stream branches the branched system is nearly instantaneously replaced at the beginning of the bolling and holocene at 14 670 and 11 650 cal yr b p respectively by an atmospheric circulation system in which 18o 16o and annual accumulation initially track each other closely thermodynamic considerations of the accumulation rate temperature relationship can be used to evaluate the 18 o 16o temperature relationship the gisp2 ice layer count years of major gisp2 climate transitions also support the use of coral 14c ages for age calibration

the distribution and timing of tephra deposition at siple dome antarctica possible climatic and rheologic implications approximately 300 volcanic ash and dust layers were observed in the siple dome antarctica ice core most of this tephra deposited between 700 and 800 m depth consisted primarily of glass shards with varying amounts of crystalline material and groundmass fragments the pattern of distribution of tephra fallout closely replicates that found in the byrd ice core indicative of contemporaneous deposition at both locations peak fallout occurred approximately 19 500 years ago based on methane tie points in the siple dome and greenland ice sheet project 2 gisp2 ice cores mount berlin was identified as a potential source of tephra although other volcanoes in west and east antarctica appear to have contributed ash and dust ice between 697 and 730 m in which fine grained tephra is concentrated has undergone enhanced thinning compared to ice with a similar concentration of tephra deposited contemporaneously between 1300 and 1540m at byrd it is speculated that this thinning has occurred in response to dynamic interaction between ice at siple dome and the two ice streams flanking it a dramatic change to a shear fabric appears to be directly related to the higher concentration of volcanic particles in the ice between 700 and 800 m

the 2012 mw 8 6 wharton basin sequence a cascade of great earthquakes generated by near orthogonal young oceanic mantle faults we improve constraints on the slip distribution and geometry of faults involved in the complex multisegment mw 8 6 april 2012 wharton basin earthquake sequence by joint inversion of high rate gps data from the sumatran gps array sugar teleseismic observations source time functions from broadband surface waves and far field static gps displacements this sequence occurred under the indian ocean 400 km offshore sumatra the events are extraordinary for their unprecedented rupture of multiple cross faults deep slip large strike slip magnitude and potential role in the formation of a discrete plate boundary between the indian and australian plates the sugar recorded static displacements of up to 22 cm along with time varying arrivals from the complex faulting which indicate that the majority of moment release was on young wnw trending right lateral faults counter to initial expectations that an old lithospheric nne trending fracture zone played the primary role the new faults are optimally oriented to accommodate the present day stress field not only was the greatest moment released on the younger faults but it was these that sustained very deep slip and high stress drop 20 mpa the rupture may have extended to depths of up to 60 km suggesting that the oceanic lithosphere in the northern wharton basin may be cold and strong enough to sustain brittle failure at such depths alternatively the rupture may have occurred with an alternative weakening mechanism such as thermal runaway

slip vectors and stretching of the sumatran fore arc slip vectors from thrust earthquakes at the java trench southwest of sumatra demonstrate that the sumatran fore arc is not a single rigid plate that is translated to the northwest by oblique plate convergence instead they indicate arc parallel stretching of the fore arc at a uniform strain rate of 3 4 x 10 8 yr the northwestward motion of the fore arc relative to the upper plate southeast asia increases from near zero at the sunda strait to 45 60 mm yr in northwest sumatra and should result in variable slip rates on the sumatran fault

wedge geometry frictional properties and interseismic coupling of the java megathrust abstract the mechanical interaction between rocks at fault zones is a key element for understanding how earthquakes nucleate and propagate therefore estimating frictional properties along fault planes allows us to infer the degree of elastic strain accumulation throughout the seismic cycle the java subduction zone is an active plate boundary where high seismic activity has long been documented however very little is known about the seismogenic processes of the megathrust especially its shallowest portion where onshore geodetic networks are insensitive to recover the pattern of elastic strain here we use the geometry of the offshore accretionary prism to infer frictional properties along the java subduction zone using coulomb critical taper theory we show that large portions of the inner wedge in the eastern part of the java subduction megathrust are in a critical state where the wedge is on the verge of failure everywhere we identify four clusters with an internal coefficient of friction int of 0 8 and hydrostatic pore pressure within the wedge the average effective coefficient of friction ranges between 0 3 and 0 4 reflecting a strong decollement our results also show that the aftershock sequence of the 1994 mw 7 9 earthquake halted adjacent to a critical segment of the wedge suggesting that critical taper wedge areas in the eastern java subduction interface may behave as a permanent barrier to large earthquake rupture in contrast in western java topographic slope and slab dip profiles suggest that the wedge is mechanically stable i e deformation is restricted to sliding along the decollement and likely to coincide with a seismogenic portion of the megathrust we discuss the seismic hazard implications and highlight the importance of considering the segmentation of the java subduction zone when assessing the seismic hazard of this region

implications of deformation following the 2002 denali alaska earthquake for postseismic relaxation processes and lithospheric rheology 1 during the first 2 years following the 2002 mw 7 9 denali alaska strike slip earthquake a large array of global positioning system gps receivers recorded rapid postseismic surface motions extending at least 300 km from the rupture and at rates of more than 100 mm yr in the near field here we use three dimensional 3 d viscoelastic finite element models to infer the mechanisms responsible for these postseismic observations we consider afterslip both from an inversion of gps displacements and from stress driven forward models poroelastic rebound and viscoelastic flow in the lower crust and upper mantle several conclusions can be drawn 1 no single mechanism can explain the postseismic observations 2 significant postseismic flow below a depth of 60 km is required to explain observed far field motions best explained by a weak upper mantle with a depth dependent effective viscosity that ranges from 1019 pa s at the moho 50 km depth to 3 4 1018 pa s at 100 km depth 3 shallow afterslip within the upper crust occurs adjacent to and beneath the regions of largest coseismic slip 4 there is a contribution from deformation in the middle and lower crust from either lower crustal flow or stress driven slip afterslip is preferred over broad viscoelastic flow owing to the existence of seismic velocity discontinuities across the fault at depth though our modeling does not favor either mechanism if the process is viscoelastic relaxation the viscosity is a factor of 3 greater than the inferred mantle viscosity 5 poroelastic rebound probably contributed to the observed postseismic deformation in the immediate vicinity of the denali totschunda junction these conclusions lead us to infer an alaskan mechanical lithosphere that is about 60 km thick overlying a weak asthenosphere and a denali fault that cuts through the entire lithosphere with shear accommodated by faulting in the top 20 km and time dependent aseismic shear below

first evidence for archean continental crust in northern vietnam and its implications for crustal and tectonic evolution in southeast asia southeast asia or in a more strict sense the indochinese continent was previously considered to be composed entirely of proterozoic to phanerozoic rocks and reliable evidence for archean crust was lacking gneisses from the cavinh complex south of the red river shear zone northern vietnam however show archean nd model ages of 3 4 3 1 ga zircon separates from the rocks yielded u pb dates of 2 8 2 5 ga the first convincing evidence for the presence of a late archean complex in southeast asia given that the red river shear zone was propagating in the south china block with a left lateral offset of 600 km the cavinh complex can be correlated with the late archean kangding complex in the western margin of the yangtze craton southwestern china the cavinh complex therefore represents one of the oldest crustal nuclei of the south china block

oblique plate convergence slip vectors and forearc deformation slip vectors from thrust earthquakes at subduction zones where convergence is oblique to the trench often point between the directions of relative plate convergence and normal to the trench axis suggesting that oblique convergence is taken up by partial decoupling decoupling means that a component of arc parallel motion of the leading edge of the upper plate results in less oblique thrusting at the trench partial decoupling is modeled by partitioning of oblique convergence into slip on thrust and strike slip faults that are parallel to the trench and to each other and starting with a force equilibrium condition a relationship between the obliquity and the earthquake slip vector orientation is derived assuming that either fault slips when shear stress on it reaches a yield stress oblique slip parallel to the plate vector should occur on the thrust fault when obliquity is smaller than a critical angle for obliquity at or greater than this angle the stress on the strike slip fault is large enough to start it slipping and when both faults are active the arc parallel motion of the forearc deflects the slip vector back toward the trench normal if we assume that continued slip on either fault occurs at constant stress but the two faults can be at different stresses the slip vector will maintain a constant angle relative to the trench normal even when obliquity is larger than the critical angle this limiting angle of the slip vector called max measured relative to the trench normal is simply the arcsine of the ratio of the shear forces resisting slip on the strike slip and thrust faults a consequence is that when the obliquity exceeds max the slip vectors on the thrust fault are sensitive only to the thrust fault orientation and contain no information about the convergence direction between the plates slip vectors at the java trench southwest of sumatra show the relationship clearly with max 20 5 while slip vectors at the aleutian trench show the relationship less clearly with max 25 to 45 the greater angle at the aleutian trench suggests that the upper plate is stronger in the aleutian arc relative to the thrust fault than in the sumatran arc consistent with the sumatran arc being continental and having a well developed strike slip fault while the aleutian arc is oceanic and without a clear transcurrent fault slip vectors at the philippine trench which like sumatra has a large strike slip fault inboard of it tend to stay within 25 of the trench normal when obliquity is as large as 50 if obliquity exceeds max and continues to increase along a subduction zone the rate of motion of the forearc relative to the upper plate will vary with obliquity in which case the forearc sliver should extend or contract parallel to the arc from the geometry of modern island arcs arc parallel extension should be the more common and has been hypothesized for both sumatra and the aleutians on the basis of earthquake slip vectors and for these and other arcs from geological observations from estimates of max and the arc parallel gradients in obliquity arc parallel strain rates are estimated to be 1 to 3 10 8 yr for the sumatran forearc 2 to 6 10 8 yr for the aleutian forearc and 0 3 to 3 10 8 yr for the philippine forearc oblique convergence and subsequent arc parallel extension if accompanied by crustal thinning may provide an important yet little appreciated mechanism for bringing high grade metamorphic rocks to the surface of subduction complexes

gravitational viscoelastic postseismic relaxation on a layered spherical earth viscoelastic relaxation of a ductile asthenosphere underlying a purely elastic plate is a strong candidate process for explaining anomalous rates of crustal deformation observed following large earthquakes the nongravitational treatment of pollitz 1992 which is valid on a global scale and includes the effects of compressibility is here extended to permit the calculation of gravitational viscoelastic relaxation for a specified spherically layered viscoelastic rheology following an earthquake in an elastic layer the simple approximations we adopt make the resulting treatment particularly suitable for near field calculations for an asthenosphere with a maxwell rheology the effect of gravitational coupling is manifested only many relaxation times after the earthquake as obtained by previous investigators its effect is generally to speed up the long wavelength component of the relaxation process and attenuate the overall vertical displacement pattern several subtle features common to the relaxation behavior from several different fault types thrust rift and strike slip are identified the effect of gravitational coupling on horizontal displacements is consistent with flexure of the upper elastic plate driven by the corresponding effects on the vertical displacement stress diffusion away from the source region generally exhibits pulse like behavior which is dispersive in both space and time if the asthenosphere is confined to a relatively narrow channel then the dispersion branches governing relaxation are radically altered and stress diffusion effects far from the coseismic rupture zone exhibit a complicated time dependence reflecting the competing tendencies of toroidal and spheroidal mode relaxation

post seismic relaxation following the great 2004 sumatra andaman earthquake on a compressible self gravitating earth summary the mw 9 0 2004 december 26 sumatra andaman and mw 8 7 2005 march 28 nias earthquakes which collectively ruptured approximately 1800 km of the andaman and sunda subduction zones are expected to be followed by vigorous viscoelastic relaxation involving both the upper and lower mantle because of these large spatial dimensions it is desirable to fully account for gravitational coupling effects in the relaxation process we present a stable method of computing relaxation of a spherically stratified compressible and self gravitating viscoelastic earth following an impulsive moment release event the solution is cast in terms of a spherical harmonic expansion of viscoelastic normal modes for simple layered viscoelastic models which include a low viscosity oceanic asthenosphere we predict substantial post seismic effects over a region several 100s of km wide surrounding the eastern indian ocean we compare observed gps time series from ten regional sites mostly in thailand and indonesia beginning in 2004 december with synthetic time series that include the coseismic and post seismic effects of the 2004 december 26 and 2005 march 28 earthquakes a viscosity structure involving a biviscous burgers body rheology in the asthenosphere explains the pattern and amplitude of post seismic offsets remarkably well

the relationship of the unsaturated soil shear strength to the soil water characteristic curve the measurement of soil parameters such as the permeability and shear strength functions used to describe unsaturate soil behaviour can be expensive difficult and often impractical to obtain this paper proposes a model for predicting the shear strength versus matric suction function of unsaturated soils the prediction model uses the soil water characteristic curve and the shear strength parameters of the saturated soil i e effective cohesion and effective angle of internal friction once a reasonable estimate of the soil water characteristic curve is obtained satisfactory predictions of the shear strength function can be made for the unsaturated soil closed form solutions for the shear strength function of unsaturated soils are obtained for cases where a simple soil water characteristic equation is used in the prediction model key words soil suction soil water characteristic curve shear strength function unsaturated soil

characteristics of residual soils in singapore as formed by weathering residual soils are weathering products of rocks that are commonly found under unsaturated conditions the properties of residual soils are a function of the degree of weathering a series of index properties engineering properties mercury porosimetry tests and scanning electron microscope sem examinations were performed on residual soils from two major geological formations in singapore the results indicate that the variation in the index and engineering properties as well as microstructural characteristics of the residual soils with depth can be related to the degree of weathering an increase in the degree of weathering results in an increase in pore volume and produces a larger range of pore size distribution the variation in the pore volume and the pore size distribution through a profile of weathered rock can be used as an indicative measure of the variation in the degree of weathering with depth

magnetotelluric and geomagnetic modelling reveals zones of very high electrical conductivity in the upper crust of central java abstract we present results of two and three dimensional modelling of magnetotelluric and geomagnetic data from central java indonesia we adopt a hypothesis testing approach where we examine the influence of individual structural elements of competing models on the total model responses the models show that ocean anomalies do not overwhelm the signal due to strong electrical conductivity anomalies within java these highly conducting regions with resistivities of below 1 m are located in the central and northern parts of the island fitting of the geomagnetic data requires that the innermost parts of both regions consist of material with extremely low resistivity 0 2 m young sediments tephra and their alteration products can be responsible for some of the low resistivity regions at shallow depths the two zones of extremely high conductivity however are best explained as consequences of geothermal activity in the vicinity of active volcanism mt merapi in central java and by fluid or graphite enrichment along shear zones in northern java subduction zone related processes in a depth range of 70 400 km cannot be resolved because the highly conductive regions at shallow depths effectively screen deeper structures

influence of earthquakes on the stability of slopes earthquakes are a major trigger for instability of natural and man made slopes often the instability of slopes due to an earthquake causes more destruction and kills more people than the actual earthquake itself a comparison is made between different methodologies to analyze the potential stability of slopes during earthquakes theoretically it seems simple to calculate the stability of a slope during an earthquake in reality however the stability is influenced by so many parameters that are either not known or which influence is so poorly known that a decent estimation of stability cannot be made offshore the situation is worse because proper data required for stability calculations are even less available than onshore on and offshore erosion and weathering create continuously slopes that may become unstable during a future earthquake offshore also sedimentation creates continuously new slopes another fundamental problem in stability analysis is the complicated and largely unknown behavior of seismic waves in three dimensions in natural materials the lack of accurate data and the unknown behavior of seismic waves in three dimensions make estimations of slope stability during an earthquake unreliable

weathering of submerged stressed calcarenites chemo mechanical coupling mechanisms long portions of the apulian coast are steep cliffs in carbonate soft rocks these especially the calcarenite are affected by weathering processes that markedly alter their mechanical properties with time potentially leading to instability of coastal geomorphological structures such alterations are mainly due to chemical reactions between the solid and fluid phases and are driven by chemical variables which are internal variables and hence uncontrollable in a search for the variables that drive the process of rock weakening recourse is made to the micro scale at which most of the chemical processes are observed and quantified observations using scanning electron microsope thin sections and x ray computed tomography analyses appear to be crucial for the understanding interpretation and definition of the degradation mechanisms of the material a chemo mechanical coupled model at the meso scale of the chemically reactive stressed porous system is presented and framed in the context of a multi sca

a low viscosity wedge in subduction zones geochemical petrologic and seismological observations indicate that there may be high concentrations of water in the region above a subducting slab the mantle wedge which could decrease the viscosity of the mantle locally by several orders of magnitude using numerical models we demonstrate that a low viscosity wedge has a dramatic influence on the force balance in a subduction zone and leads to an observable signal in the topography gravity and geoid a regional dynamic model of the tonga kermadec subduction zone shows that the viscosity of the wedge is at least a factor of 10 smaller than surrounding mantle lithosphere and asthenosphere consistent with estimates from seismic dissipation and deformation experiments

methanesulfonate in the greenland ice sheet project 2 ice core in this paper we present measurements of methanesulfonate in the greenland ice sheet project 2 gisp2 ice core methanesulfonate is an atmospheric oxidation product of dimethylsulfide the gisp2 methanesulfonate record contains information about the atmospheric loading of biogenic sulfur over the past 110 kyr and its relationship to climate change the gisp2 data set supports the inferences made from the renland ice core from greenland that the glacial atmosphere over greenland had reduced concentrations of biogenic sulfur compared with the present day hansson and saltzman 1993 we conclude that the flux of biogenic sulfur from the north atlantic ocean must have been lower during glacial times and speculate that this decrease may have been related to differences in phytoplankton speciation the data suggest that changes in direct radiative forcing from biogenic sulfur aerosols would act as negative feedback to the glacial interglacial climate cycles in this region

diverse slow slip behavior at the hikurangi subduction margin new zealand 1 the installation of a continuous gps cgps network in new zealand since 2002 has enabled the discovery of 15 slow slip events at the hikurangi subduction margin our analysis and interpretation of the cgps data reveal a marked diversity in characteristics of slow slip events sses in the north island with durations varying from 6 days to 1 5 years equivalent moment release between mw 6 3 7 2 and recurrence intervals of repeating sses on the order of 2 years to more than 5 years the duration and magnitude characteristics of hikurangi sses appear to be related to the depth where they occur the deepest longest duration and largest sses occur at the southern hikurangi margin near the downdip limit of deep down to 40 km depth strong interseismic coupling the shallowest shortest duration smallest and most frequent sses occur at the northern and central hikurangi margin near the downdip limit of unusually shallow 10 15 km depth interseismic coupling the direction of slip on the interface in the hikurangi sses is consistent with slip partitioning at the hikurangi subduction margin we also show that moment accumulation rates on the interface for the time periods between sses are 40 higher than for the period of more than a decade averaging through the sses indicating that sses compose a major portion of the overall moment release budget of the hikurangi subduction interface

a new gps velocity field for the pacific plate part 1 constraints on plate motion intraplate deformation and the viscosity of pacific basin asthenosphere

waves of destruction in the east indies the wichmann catalogue of earthquakes and tsunami in the indonesian region from 1538 to 1877

linking weathering and rock slope instability non linear perspectives weathering is linked complexly to the erosion and evolution of rock slopes weathering influences both the strength of rock slopes and the stresses that act upon them while weathering has often been portrayed in an over simplified way by those studying rock slope instability in reality it consists of multiple processes acting over different spatial and temporal scales with many complex inter linkages through a demonstration of the sources of non linearities in rock slope weathering systems and their implications for rock slope instability this paper proposes five key linkages worthy of further study copyright 2012 john wiley sons ltd

resistivity characterization of the arjuno welirang volcanic geothermal system indonesia through 3 d magnetotelluric inverse modeling abstract the arjuno welirang geothermal area is located in east java indonesia in the arjuno welirang geothermal area the arjuno welirang and anjasmoro volcanic complex is dominated by quaternary volcanic rocks and a complex geological structure several impressive surface thermal manifestations are found in the study area including a high temperature solfataric fumarole about 137 c on the top of mt welirang and also bicarbonate hot springs with a temperature range of 39 55 c in the northern and western parts of the study area the occurrences of the surface manifestations are probably controlled by the nw se and nne ssw fault structures the occurrence of the high temperature solfataric fumarole with high magmatic gas contents indicates that the arjuno welirang geothermal area can be classified as a volcanic geothermal system to investigate the subsurface condition of the geothermal system magnetotelluric mt survey was conducted within 34 mt stations distributed in the northern and western parts of the study area considering the complexity of the subsurface volcanic rocks and the geological structures of the study area one and two dimensional mt data inversion approaches could not be applied properly accordingly a 3 d inversion of the mt data will be the most representative approach in such conditions in order to investigate the reservoir structure of the volcanic geothermal system the 3 d inversion was then applied to all mt data with a frequency range of 100 0 01 hz generally the quality of the mt data varies from good to excellent a clear subsurface resistivity structure revealed by the 3 d inversion showed a good correlation with geological and geochemical evidences overall the resistivity structure consists of a conductive 1 10 ohm m altered rock at the upper part overlying a reservoir zone with a slightly higher resistivity range 20 60 ohm m the lower part of the resistivity structure showed the highest resistivity value 80 ohm m indicating a hot rock region the main upflow is represented by an updome structure of the base of the conductive layer boc beneath the mt welirang summit it is supported by the occurrence of solfataric fumaroles on the summit of mt welirang moreover the outflow zones of the arjuno welirang geothermal system are indicated by a thickening of the low resistivity layer toward the northern and western parts of mt welirang supported with the occurrence of bicarbonate hotsprings the existence of magmatic gas components i e h2s and so2 detected in the fumarole gives an early warning regarding the possible existence of acidic fluid further exploration drilling should consider this issue a conceptual model is then developed to visualize the geothermal system of the arjuno welirang prospect area by integrating the geological and geochemical data

tectonic features of the southern sumatra western java forearc of indonesia 1 multichannel reflection seismic profiles along the active sunda arc where the indo australian plate subducts under the overriding eurasian margin revealed two accretionary wedges the inner wedge i is of assumed paleogene age and the outer wedge ii is of neogene to recent age the inner wedge i is composed of tectonic flakes stretching from southeast sumatra across the sunda strait to northwest java implying a similar plate tectonic regime in these areas at the time of flake development during upper oligocene today wedge i forms the outer arc high and the backstop for the younger outer wedge ii the missing outer arc high of the southern sunda strait is explained by a combination of neogene transtension due to a clockwise rotation of sumatra with respect to java and by arc parallel strike slip movements the rotation created transtensional pull apart basins along the western sunda strait semangka graben as opposed to transpression and inversion on the eastern sunda strait within the new detected krakatau basin the arc parallel transpressional mentawai strike slip fault zone mfz was correlated from the sumatra forearc basin to the northwest java forearc basin off the sunda strait northward bending branches of the mfz are connected with the right lateral sumatra fault zone sfz along the volcanic arc segment on sumatra it is speculated that the sfz was attached to the cimandiri pelabuhan ratu strike slip fault of java prior to the presumed rotation of sumatra and that since the late lower miocene the main slip movement shifted from the volcanic arc position to the forearc basin area due to increasingly oblique plate convergence

weathering and deterioration of geotechnical properties in time of groundmasses in a tropical climate abstract weathering and degradation of slope materials govern erosion and stability of slopes over time weathering is often ignored or over simplified in engineering due to absence of time series of material properties and uncertainty on future environment the research in this paper investigates the rate of deterioration of geotechnical properties due to weathering over time after excavation of cut slopes in completely weathered material and residual soil in a tropical environment three cut slopes are studied with different excavation dates but with similar geological geotechnical and groundwater conditions identical slope aspect and land cover index and strength properties are determined by field and laboratory tests the results show that the hydro mechanical properties of completely weathered material in cut slopes evolve very rapidly to those of residual soil within time spans of 30 to 90 years in a tropical humid environment the properties reduce so much that instability of cut slopes is inevitable if this reduction is not taken into account during design and excavation of the slopes change of strength properties is around 1 1 to 1 3 pt per year from the original completely weathered material strength at the time of excavation this is based on simplified linear and logarithmic relationships the deterioration of geotechnical properties is likely the main reason for many slope failures in cut slopes after many years of stability in the research area of yen bai city in vietnam

a method for precise measurement of argon 40 36 and krypton argon ratios in trapped air in polar ice with applications to past firn thickness and abrupt climate change in greenland and at siple dome antarctica we describe a method for measuring the 40ar 36ar ratio and the 84kr 36ar ratio in air from bubbles trapped in ice cores these ratios can provide constraints on the past thickness of the firn layer at the ice core site and on the magnitude of past rapid temperature variations when combined with measured 15n 14n both variables contribute to paleoclimatic studies and ultimately to the understanding of the controls on earth s climate the overall precision of the 40ar 36ar method 1 standard error of the mean is 0 012 for a sample analyzed in duplicate corresponding to 0 6 m in reconstructed firn thickness we use conventional dynamic isotope ratio mass spectrometry with minor modifications and special gas handling techniques designed to avoid fractionation about 100 g of ice is used for a duplicate pair of analyses an example of the technique applied to the gisp2 ice core yields an estimate of 11 3k of abrupt warming at the end of the last glacial period 15 000 years ago the krypton argon ratio can provide a diagnostic of argon leakage out of the bubbles which may happen naturally during bubble close off or artifactually if samples are warmed near the freezing point during core retrieval or storage argon leakage may fractionate the remaining 40ar 36ar ratio by 0 007 per change in 84kr 36ar introducing a possible bias in reconstructed firn thickness of about 2 m if thermal diffusion is not accounted for or 6 m if thermal diffusion effects are quantified with measured 15n 14n reproducibility of 84kr 36ar measured in air is about 0 2 1 standard error of the mean but is about 1 for ice core samples ice core samples are systematically enriched in 84kr 36ar relative to atmosphere by 5 probably reflecting preferential size dependent exclusion of the smaller argon atom during bubble entrapment recent results from the siple dome ice core reveal two climate events during the last deglaciation including an 18 m reduction in firn thickness associated with an abrupt warming at sometime between 18 and 22 kyr bp and a partial or total removal of the firn during an ablation event at 15 3 kyr bp

a decade of horizontal deformation from great earthquakes 1 the 21st century has seen the occurrence of 17 great earthquakes mw 8 including some of the largest earthquakes ever recorded numerical modeling of the earthquakes shows that nearly half of the earth s surface has undergone horizontal coseismic deformation 1 mm with the 2004 sumatra andaman earthquake dominating the global deformation field this has important implications for both the realization of a terrestrial reference frame and in the interpretation of regional tectonic studies based on gps velocities we show that far field coseismic deformations from great earthquakes will if unaccounted for introduce errors in estimates of linear site velocities of at least 0 1 0 3 mm yr across most of the surface of the earth the accumulated global deformation field shows that two regions australia and the north atlantic arctic ocean have been largely undeformed by these great earthquakes with accumulated deformations generally 0 5 mm using gps estimates of surface deformation we show that the majority of the australian continent is deforming at 0 2 mm yr the northern part of new zealand is rotating clockwise relative to the australian plate with relative horizontal velocities of 2 mm yr while the southeastern coast of australia is undergoing post seismic relaxation caused by the 2004 mw 8 1 macquarie ridge earthquake the presence of ongoing post seismic relaxation thousands of kilometers from plate margins violates the secular linear assumption made in current terrestrial reference frame definitions these effects have significant ramifications for regional tectonic interpretations and global studies such as sea level rise that require reference frame accuracy greater than this level

slab1 0 a three dimensional model of global subduction zone geometries 1 we describe and present a new model of global subduction zone geometries called slab1 0 an extension of previous efforts to constrain the two dimensional non planar geometry of subduction zones around the focus of large earthquakes slab1 0 describes the detailed non planar three dimensional geometry of approximately 85 of subduction zones worldwide while the model focuses on the detailed form of each slab from their trenches through the seismogenic zone where it combines data sets from active source and passive seismology it also continues to the limits of their seismic extent in the upper mid mantle providing a uniform approach to the definition of the entire seismically active slab geometry examples are shown for two well constrained global locations models for many other regions are available and can be freely downloaded in several formats from our new slab1 0 website http on doi gov d9arbs we describe improvements in our two dimensional geometry constraint inversion including the use of average active source seismic data profiles in the shallow trench regions where data are otherwise lacking derived from the interpolation between other active source seismic data along strike in the same subduction zone we include several analyses of the uncertainty and robustness of our three dimensional interpolation methods in addition we use the filtered subduction related earthquake data sets compiled to build slab1 0 in a reassessment of previous analyses of the deep limit of the thrust interface seismogenic zone for all subduction zones included in our global model thus far concluding that the width of these seismogenic zones is on average 30 larger than previous studies have suggested

a 10 century comparison of prominent bipolar volcanic events in ice cores measurements of key chemical and physical parameters made along continuous and selected long sections of polar ice cores provide reliable past snow accumulation rates and other environmental records the prime accumulation indicators include variations found in the stable isotopes ionic constituents and acidity concentration levels and physical changes in the strata and structure cross correlations of the time series curves resulting from multiparameter analyses of ice cores from antarctica nby89 sp78 bs68 and greenland cr74 d3 81 d3 18c have been made the results permit construction of a bipolar chemical stratigraphy chronology of volcanic events that is coherent with the 18 o and electrical conductivity method data sets and consistent back in time with historically recorded volcanic activity a bihemispheric comparison of high non sea salt so 4 2 peaks shows strong correlation at 1885 1836 1816 1810 1459 1346 1287 1278 1259 1228 and 1168 a d at time of snow deposit the prominent 1259 a d volcanic signal appears to be a significant bipolar ice core index horizon

the kinematics of crustal deformation in java from gps observations implications for fault slip partitioning abstract our understanding of seismic risk in java has been focused primarily on the subduction zone where the seismic records during the last century have shown the occurrence of a number of tsunami earthquakes however the potential of the existence of active crustal structures within the island of java itself is less well known historical archives show the occurrence of several devastating earthquake ruptures north of the volcanic arc in west java during the 18th and the 19th centuries suggesting the existence of active faults that need to be identified in order to guide seismic hazard assessment here we use geodetic constraints from the global positioning system gps to quantify the present day crustal deformation in java the gps velocities reveal a homogeneous counterclockwise rotation of the java block independent of sunda block consistent with a ne sw convergence between the australian plate and southeast asia continuous gps observations show a time dependent change in the linear rate of surface motion in west java which we interpret as an ongoing long term post seismic deformation following the 2006 m w 7 7 java earthquake we use an elastic block model in combination with a viscoelastic model to correct for this post seismic transient and derive the long term inter seismic velocity which we interpret as a combination of tectonic block motions and crustal faults strain related deformation there is a north south gradient in the resulting velocity field with a decrease in the magnitude towards the north across the kendeng thrust in the east and the baribis thrust in the west we suggest that the baribis thrust is active and accommodating a slow relative motion between java and the sunda block at about 5 0 2 mm yr we propose a kinematic model of convergence of the australian plate and the sunda block involving a slip partitioning between the java trench and a left lateral structure extending e w along java with most of the convergence being accommodated by the java megathrust and a much smaller parallel motion accommodated along the baribis 5 0 2 mm yr and kendeng 2 3 0 7 mm yr thrusts our study highlights a correlation between the geodetically inferred active faults and historical seismic catalogs emphasizing the importance of considering crustal fault activity within java in future seismic assessments

long wavelength optical logging for high resolution detection of ash layers in glacier ice a new instrument for high resolution optical logging has been built and tested in antarctica its purpose is to obtain records of volcanic products and other scattering features such as bubbles and impurities preserved in polar ice sheets and it achieves this by using long wavelength near infrared light that is absorbed by the ice before many scattering events occur longer wavelengths ensure that the return signal is composed primarily of a single or few backscattering event s that limit its spatial spread the compact optical logger features no components on its body that draw power which minimizes its size and weight a prototype of the logger was built and tested at siple dome a borehole and the results were correlated with prior optical logging profiles and records of volcanic products from collected ice core samples

south pole glacial climate reconstruction from multi borehole laser particulate stratigraphy the icecube neutrino observatory and its prototype amanda were built in south pole ice using powerful hot water drills to cleanly bore 100 holes to depths up to 2500 m the construction of these particle physics detectors provided a unique opportunity to examine the deep ice sheet using a variety of novel techniques we made high resolution particulate profiles with a laser dust logger in eight of the boreholes during detector commissioning between 2004 and 2010 the south pole laser logs are among the most clearly resolved measurements of antarctic dust strata during the last glacial period and can be used to reconstruct paleoclimate records in exceptional detail here we use manual and algorithmic matching to synthesize our south pole measurements with ice core and logging data from dome c east antarctica we derive impurity concentration precision chronology annual layer thickness local spatial variability and identify several widespread volcanic ash depositions useful for dating we also examine the interval around similar to 74 ka recently isolated with radiometric dating to bracket the toba sumatra supereruption

rupture characterization and aftershock relocations for the 1994 and 2006 tsunami earthquakes in the java subduction zone 1 two tsunami earthquakes occurred in the java subduction zone within the last 12 years providing multiple well recorded tsunami events for analysis the june 2 1994 mw 7 8 and july 17 2006 mw 7 7 reverse mechanism earthquakes produced tsunami with locally large 8 m runups were deficient in high frequency energy relative to long period radiation had primarily normal faulting aftershocks and occurred near subducting seamounts previous models of the 1994 event and aftershocks suggested extension in the outer rise due to slip at depth at a subducted seamount here we relocate aftershocks for the 1994 and 2006 events and compare to slip distributions and bathymetry most 1994 aftershocks occurred within the slab updip of the mainshock consistent with the extensional hypothesis but the 2006 aftershocks have a more complex pattern regional subducting features as asperities and barriers may influence both events but in different ways

rates of weathering and temporal changes in strength of bedrock of marine terraces in boso peninsula japan the weathering rates of bedrock of the dated erosional marine terraces were examined for two definitions 1 the rates at which the thicknesses of weathered zones with different strengths increase with weathering time and 2 the rates at which the strength of weathered materials at an arbitrary depth decrease with time the bedrock of terraces in the study area consists mainly of tertiary sandstone and mudstone the weathering profiles were observed from drill cores on three levels of terrace surfaces i e 2850 290 and 70 years b p in the emergence age of terraces which is regarded as the weathering time of bedrock the degree of weathering grade was described by the residual strength ratio which is defined as the ratio of the needle penetration hardness of weathered part to that of fresh part of bedrock the weathering rates of the first definition do not decrease monotonically but decelerate logarithmically with time zones with lower weathering grades have faster weathering rates than those with higher weathering grades with respect to the weathering rates of the second definition mudstone starts to weather earlier than sandstone but is exceeded by the latter after a certain time has elapsed because mudstone has a higher slaking susceptibility

seismic and aseismic slip on the central peru megathrust slip on a subduction megathrust can be seismic or aseismic with the two modes of slip complementing each other in time and space to accommodate the long term plate motions although slip is almost purely aseismic at depths greater than about 40 km heterogeneous surface strain suggests that both modes of slip occur at shallower depths with aseismic slip resulting from steady or transient creep in the interseismic and postseismic periods thus active faults seem to comprise areas that slip mostly during earthquakes and areas that mostly slip aseismically the size location and frequency of earthquakes that a megathrust can generate thus depend on where and when aseismic creep is taking place and what fraction of the long term slip rate it accounts for here we address this issue by focusing on the central peru megathrust we show that the pisco earthquake with moment magnitude m w 8 0 ruptured two asperities within a patch that had remained locked in the interseismic period and triggered aseismic frictional afterslip on two adjacent patches the most prominent patch of afterslip coincides with the subducting nazca ridge an area also characterized by low interseismic coupling which seems to have repeatedly acted as a barrier to seismic rupture propagation in the past the seismogenic portion of the megathrust thus appears to be composed of interfingering rate weakening and rate strengthening patches the rate strengthening patches contribute to a high proportion of aseismic slip and determine the extent and frequency of large interplate earthquakes aseismic slip accounts for as much as 50 70 of the slip budget on the seismogenic portion of the megathrust in central peru and the return period of earthquakes with m w 8 0 in the pisco area is estimated to be 250 years

basal ice sequences in antarctic ice stream exposure of past hydrologic conditions and a principal mode of sediment transfer 1 the brightness distribution of sequentially extracted borehole camera imagery shows two distinct sequences of basal ice in kamb ice stream the upper sequence 7 3 m comprises clear ice and layers with dispersed and stratified debris the lower sequence 8 2 m consists of accretion ice with alternating layers of stratified and solid debris the two sequences have volumetric debris contents of about 5 and 20 respectively we infer that the upper sequence formed in a tributary where subglacial meltwater was abundant and that the lower sequence formed on the siple coast plain where basal freezing currently dominates the basal thermal regime the basal ice layer contains the equivalent of 2 1 0 4 m of frozen sediment the high volume of sediment is a result of debris rich layers interpreted to have formed by accretion in the stagnant phase of ice stream on off cycles fast ice streaming punctuated by entrainment of debris during stagnation episodes is consistent with inferred past flow of adjacent ice streams and geologic features in the ross sea our results show that sediment wedges near grounding lines may form by melt out of basal ice debris this is different from previous studies where it was assumed that sediment transfer occurs through sediment deformation within layers of subglacial till cumulative freezing in recurring ice stream cycles shows that entrainment of sediment by basal freeze on is an important erosion mechanism and that high sediment fluxes can occur when ice streams override coulomb plastic substrates

the java margin revisited evidence for subduction erosion off java the eastern sunda margin off indonesia from central java to sumba island remains a little investigated subduction zone contrary to its well studied northwestern segment whereas large portions of the sunda margin are considered a classical accretionary zone subduction characteristics along the central java sector indicate erosive processes as the dominant mode of mass transfer the tectonic framework of the central java margin with a convergence rate of 6 7 cm yr insignificant sediment input and a pronounced seafloor roughness where the oceanic roo rise is subducting underneath java facilitates subduction erosion evidence for erosion comes from newly acquired geophysical data off central java local erosive processes in the wake of seamount subduction are documented by a high resolution bathymetric survey and result in an irregular trend of the deformation front sculpted by seamount collision scars subduction of oceanic basement relief leads to large scale uplift of the forearc as recorded on a reflection seismic profile and to a dismemberment of the previous outer forearc high giving way to isolated topographic elevations the broad retreat of the java trench and deformation front above the leading edge of the roo rise has exposed an area of approximately 25 000 km2 of deeper seafloor formerly covered by the previous frontal prism frontal erosion coincides with a steepening of the lower slope angle in the central java sector compared to the neighbouring segments in global compilations the key geological parameters of the central java margin lie in the erosive regime reflecting the interplay of basement relief subduction negligible sediment supply and a high convergence rate on the evolution of the margin

use of paleo records in determining variability within the volcanism climate system abstract volcanic eruptions that inject large quantities of sulfur rich gases into the stratosphere have the capability of cooling global climate by 0 2 0 3 c for several years after the eruption equatorial eruptions will impact global climate whereas mid latitude eruptions can cool climate in the hemisphere of origin magnitude of cooling varies by latitude and it is possible for warming to occur in certain regions primarily during the winter although instrumental records have been used to quantify the volcanic impact on climate they are limited in their temporal and spatial coverage and the style and magnitude of eruptions occurring over the two centuries of instrumental records is limited a thorough evaluation of the range of variability in the volcanism climate system requires a multidisciplinary approach that includes the analysis of ice core records geological data atmospheric measurements and visual phenomena tree ring records and other proxy data evaluation of these longer time series indicates that multiple volcanic eruptions have the potential to force climate over decadal to multi decadal time frames especially when these eruptions enhance or extend pre existing cool conditions on the other hand a lack of climatically significant eruptions may result in warmer average temperatures over decadal time frames because the volcanic cooling component within the climate system is absent mega eruptions like the toba eruption of 71 000 73 000 yr ago may impact climate on centennial time frames through positive feedback mechanisms evidence exists which indicates that environmental changes associated with rapid climatic fluctuations such as crustal loading unloading with glaciation deglaciation and variability in glacial meltwater loading on ocean basins may cause an increase in volcanic activity

breaking a subduction termination from top to bottom the large 2016 kaikōura earthquake new zealand abstract subduction systems globally terminate allowing plate motion to be transferred from the oceanic megathrust onto continental and or oceanic transform faults the mechanism of this kinematic transition over earthquake timescales is however poorly understood due to a lack of relevant data here we study the 2016 mw 7 8 kaik ura earthquake in new zealand the first large instrumentally recorded earthquake across a subduction termination to investigate this transfer mechanism in detail we find that the kaik ura earthquake unlike standard subduction earthquakes globally involved a predominance 80 of coseismic slip on upper plate faults and minor triggered slip on the underlying oceanic subduction thrust in the months following the earthquake the subduction thrust accommodated most of the earthquake s afterslip down dip of its co seismic rupture zone this top down strain release mechanism is in accord with local geological geodetic and historical seismicity data which suggest that the bulk of plate convergence 75 is accommodated in the upper plate we suggest therefore that this alternative strain release mechanism which is distinct from standard plate boundary earthquakes is characteristic of subduction terminations and results in the majority of seismic tsunami hazard being on steep near surface faults

crustal strain partitioning and the associated earthquake hazard in the eastern sunda banda arc we use global positioning system gps measurements of surface deformation to show that the convergence between the australian plate and sunda block in eastern indonesia is partitioned between the megathrust and a continuous zone of back arc thrusting extending 2000 km from east java to north of timor although deformation in this back arc region has been reported previously its extent and the mechanism of convergence partitioning have hitherto been conjectural gps observations establish that partitioning occurs via a combination of anticlockwise rotation of an arc segment called the sumba block and left lateral movement along a major ne sw strike slip fault west of timor we also identify a westward extension of the back arc thrust for 300 km onshore into east java accommodating slip of 6 mm yr these results highlight a major new seismic threat for east java and draw attention to the pronounced seismic and tsunami threat to bali lombok nusa tenggara and other coasts along the flores sea

the 1994 java tsunami earthquake slip over a subducting seamount on june 2 1994 a large subduction thrust earthquake ms 7 2 produced a devastating tsunami on the island of java this earthquake had a number of unusual characteristics it was the first recorded large thrust earthquake on the java subduction zone all of the aftershock mechanisms exhibit normal faulting no mechanisms are similar to the main shock also the large tsunami and the relatively low energy radiated by the main shock have led to suggestions that this earthquake might have involved slow shallow rupture near the trench similar to the 1992 nicaragua earthquake we first relocate the main shock and the aftershocks we then invert long period surface waves and broadband body waves to determine the depth and spatial distribution of the main shock slip a dip of 12 hypocenter depth of 16 km and moment of 3 5 l020 n m mw 7 6 give the best fit to the combined seismic data and are consistent with the plate interface geometry the source spectrum obtained from both body and surface waves has a single corner frequency between 10 and 20 mhz implying a stress drop of 0 3 mpa the main energy release was preceded by a small subevent lasting 12 s the main slip occurred at 20 km depth downdip and to the nw of the hypocenter this area of slip is collocated with a prominent high in the bathymetry that has been identified as a subducting seamount we interpret the java earthquake as slip over this subducting seamount which is a locked patch in an otherwise decoupled subduction zone we find no evidence for slow shallow rupture no thrust aftershocks are expected if the entire locked zone slipped during the main shock but extension of the subducting plate behind the seamount would promote normal faulting as observed it seems probable that such a source model could also explain the size and timing of the observed tsunami

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

seismic history and seismotectonics of the sunda arc historic records of the last 300 years reveal two great interplate earthquakes 1833 mw 8 1861 mw 8 8 which ruptured major segments of the sumatra fore arc in western indonesia a significant percentage of interplate slip along this portion of the plate boundary appears to occur seismically the ends of these rupture zones are coincident with clusters of large ms 7 and moderate 6 ms 7 shocks and with heterogeneities in the plate interface as inferred from geologic and geophysical data the northern extent of the 1833 rupture zone is coincident with a group of moderate and large earthquakes a structural arch in the fore arc and a fracture zone on the subducted plate the southern portion is coincident with a very prominent cluster and the along strike extension of a sediment filled trough on the subducted plate prior to this study sumatra was characterized as relatively aseismic as inferred from the lack of great earthquakes in the instrumental record of this century java and the lesser sunda islands had major ms 6 earthquakes in the historic record but none are of the same magnitude as the great events near sumatra there is no clear evidence that shocks in the java fore arc were interplate events yet geophysical data indicate recent uplift of the trench slope break and a change in strike of the trench axis where the northernmost flank of the roo rise a prominent bathymetrie high appears to be interacting with the fore arc this feature was formed at a ridge crest and is more buoyant and thus more difficult to subduct than the surrounding seafloor there is no increase in seismicity associated with this tectonism however that may indicate a lack of contact between the crystalline portions of the plates at this time we infer that a majority of slip on the plate interface near java occurs aseismically the variation in occurrence of great interplate earthquakes along the sunda arc may be interpreted in terms of a model that attributes variation in interplate coupling to the age of the subducted lithosphere great interplate earthquakes occur near sumatra where the age of the youngest crust is 46 ma the characteristics of the sunda arc and analogies with pacific arcs imply that the entire length of sumatra has the potential to produce great thrust earthquakes its seismic potential should be considered high as there has been no recurrence of the great events of 1833 and 1861 in contrast no such events have been reported off java and the lesser sunda islands where the oldest crust is 152 ma the plate interface near java and the lesser sunda islands should be considered to have low seismic potential

anatomy of the western java plate interface from depth migrated seismic images newly pre stack depth migrated seismic images resolve the structural details of the western java forearc and plate interface the structural segmentation of the forearc into discrete mechanical domains correlates with distinct deformation styles approximately 2 3 of the trench sediment fill is detached and incorporated into frontal prism imbricates while the floor sequence is underthrust beneath the decollement western java however differs markedly from margins such as nankai or barbados where a uniform continuous decollement reflector has been imaged in our study area the plate interface reveals a spatially irregular nonlinear pattern characterized by the morphological relief of subducted seamounts and thicker than average patches of underthrust sediment the underthrust sediment is associated with a low velocity zone as determined from wide angle data active underplating is not resolved but likely contributes to the uplift of the large bivergent wedge that constitutes the forearc high our profile is located 100 km west of the 2006 java tsunami earthquake the heterogeneous decollement zone regulates the friction behavior of the shallow subduction environment where the earthquake occurred the alternating pattern of enhanced frictional contact zones associated with oceanic basement relief and weak material patches of underthrust sediment influences seismic coupling and possibly contributed to the heterogeneous slip distribution our seismic images resolve a steeply dipping splay fault which originates at the decollement and terminates at the sea floor and which potentially contributes to tsunami generation during co seismic activity

crustal motion in indonesia from global positioning system measurements terrestrial reference frame 2000 we compute poles of rotation for the australia eurasia and pacific plates based on our analysis of the global gps data we find that regional tectonics is dominated by the interaction of four discrete rotating blocks spanning significant areas of the sunda shelf the south banda arc the bird s head region of new guinea and east sulawesi the largest the sunda shelf block ssh is estimated to be moving 6 3 mm yr se relative to eurasia the south banda block sbb rotates clockwise relative to both the ssh and australia plate resulting in 15 8 mm yr of motion across the timor trough and 60 3 mm yr of shortening across the flores sea southern new guinea forms part of the australia plate from which the bird s head block bhb moves rapidly wsw subducting beneath the seram trough the east sulawesi block rotates clockwise about a nearby axis with respect to the sunda shelf thereby transferring east west shortening between the pacific and eurasia plates into north south shortening across the north sulawesi trench except for the sunda shelf the crustal blocks are all experiencing significant internal deformation in this respect crustal motion in those regions does not fit the microplate tectonics model index terms 1206 geodesy and gravity crustal movements interplate 8155 1243 geodesy and gravity space geodetic surveys 8150 tectonophysics plate boundary general 3040 8158 tectonophysics plate motions present and recent 3040 9320 information related to geographic region asia keywords crustal motion indonesia tectonics gps current plate motions southeast asia

gps constraints on continental deformation in the africa arabia eurasia continental collision zone and implications for the dynamics of plate interactions 1 the gps derived velocity field 1988 2005 for the zone of interaction of the arabian african nubian somalian and eurasian plates indicates counterclockwise rotation of a broad area of the earth s surface including the arabian plate adjacent parts of the zagros and central iran turkey and the aegean peloponnesus relative to eurasia at rates in the range of 20 30 mm yr this relatively rapid motion occurs within the framework of the slow moving 5 mm yr relative motions eurasian nubian and somalian plates the circulatory pattern of motion increases in rate toward the hellenic trench system we develop an elastic block model to constrain present day plate motions relative euler vectors regional deformation within the interplate zone and slip rates for major faults substantial areas of continental lithosphere within the region of plate interaction show coherent motion with internal deformations below 1 2 mm yr including central and eastern anatolia turkey the southwestern aegean peloponnesus the lesser caucasus and central iran geodetic slip rates for major block bounding structures are mostly comparable to geologic rates estimated for the most recent geological period 3 5 myr we find that the convergence of arabia with eurasia is accommodated in large part by lateral transport within the interior part of the collision zone and lithospheric shortening along the caucasus and zagros mountain belts around the periphery of the collision zone in addition we find that the principal boundary between the westerly moving anatolian plate and arabia east anatolian fault is presently characterized by pure left lateral strike slip with no fault normal convergence this implies that extrusion is not presently inducing westward motion of anatolia on the basis of the observed kinematics we hypothesize that deformation in the africa arabia eurasia collision zone is driven in large part by rollback of the subducting african lithosphere beneath the hellenic and cyprus trenches aided by slab pull on the southeastern side of the subducting arabian plate along the makran subduction zone we further suggest that the separation of arabia from africa is a response to plate motions induced by active subduction

signal variability in replicate ice cores replicate ice cores have been drilled about 10 m apart for the top 790 m of the ice sheet at dome c antarctica this provides an opportunity to examine inter core variation of the signal for identical events based on dielectric profile dep comparisons comparison of the signal from the same core a section 48 m long measured 1 year apart showed good reproducibility with peak heights varying by around 10 between the two measurements for the two replicate cores identical peaks were matched and showed variability between cores of typically a factor 1 5 this can be explained based on the likelihood of significant time periods of missing accumulation in any single core at sites with such low snow accumulation rate to synchronize core depths by matching peaks it is essential to use the pattern of peaks rather than just widely spaced individual strong peaks to derive a quantitative volcanic index from these low accumulation rate sites it will be necessary to combine or average the results from several closely spaced parallel cores

structure and shearing conditions in the day nui con voi massif implications for the evolution of the red river shear zone in northern vietnam 1 the day nui con voi massif bears a record of the red river shear zone rrsz activity in north vietnam it forms a large scale antiformal core complex type structure bounded by the song hong and song chay faults the kinematics of both faults are identical and reflect transtensional shear initiated under upper amphibolite facies conditions and propagated into greenschist facies microfabric analysis establishes that both extensional and strike slip shearing initiated between 700 and 500 c the rrsz evolved from a single subvertical fault which due to strike perpendicular extension underwent progressive dilation the created space was intruded by already metamorphosed and deformed ductile middle crust in the form of a gneissic dome both strike slip and extensional shearing were accommodated in the limbs of the antiform while its core was uplifted from midcrustal level bearing only a minor record of sinistral shear

trench parallel stretching and folding of forearc basins and lateral migration of the accretionary wedge in the southern ryukyus a case of strain partition caused by oblique convergence detailed seafloor mapping in the area east of taiwan revealed trench parallel stretching and folding of the ryukyu forearc and lateral motion of the accretionary wedge under oblique convergence east of 122 40 e a steep accretionary wedge is elongated in an e w direction a major transcurrent right lateral strike slip fault accommodates the strain partitioning caused by an oblique convergence of 40 a spectacular out of sequence thrust may be related to the subduction of a structural high lying in the axis of the n s trending gagua ridge this asperity is likely responsible for the uplift of the accretionary wedge and forearc basement and may have augmented strain partitioning by increasing the coupling between the two plates west of 122 40 e the low taper accretionary wedge is sheared in a direction subparallel to the convergence vector with respect to the ryukyu arc the bayonet shape of the southern ryukyu arc slope partly results from the recent re opening of the southern okinawa trough at a rate of about 2 to 4 cm yr right lateral shearing of the sedimentary forearc with respect to the nonlinear ryukyu backstop generates trench parallel extension in the forearc sediment sequence at dilational jogs and trench parallel folding at compressive jogs the hoping basin lies above a diffuse trench trench fault ttf or tff unstable triple junction moving toward the south along a n s transform zone which accommodates the southward drift of the ryukyu arc with respect to eurasia

earthquake geology of the lembang fault west java indonesia abstract the lembang fault is a major fault in western java that skirts the northern edge of bandung one of indonesia s largest cities just south of the active tangkuban perahu volcano although it has no recorded or historical large earthquakes the lembang fault shows obvious geomorphic evidence of recent activity and has long been thought to be active in this study we use geomorphic analysis to unequivocally establish that the fault has a dominantly sinistral sense of movement with a slip rate of 1 95 3 45 mm yr this proves that the fault is accommodating trench parallel slip resulted from a slight obliquity in plate convergence at the javatrench with a length of 29 km this suggests that the lembang fault could produce a mw 6 5 7 0 earthquake with a recurrence time of 170 670 years we also conducted paleoseismological trenching of the lembang fault and found evidence for at least 3 earthquakes in the 15th century 2300 60 bce and 19 620 19 140 bp the 2300 60 bce earthquake had a measurable vertical displacement of 40 cm which is consistence with a mw 6 5 earthquake this is the first mapping of a source of crustal earthquakes in java indonesia the world s most densely populated island in one of its most tectonically active areas the lembang fault and other faults in java are likely to pose substantial risk to not only bandung but many of java s major urban agglomerations

light propagation in firn application to borehole video borehole optical stratigraphy bos is a borehole video system and processing routine for investigating polar firn bos records brightness variations in the firn and is effective at identifying stratigraphic markers bos brightness logs have been used to count annual layers and measure vertical strain even though a specific cause of the brightness variations has not been determined here we combine two models of light transport to examine potential errors with bos and identify improvements which will allow the system to estimate optical grain size we use a monte carlo radiative transfer model to estimate the influence of firn microstructure variations on borehole reflectance we then use a ray tracing algorithm to model the multiple reflections within the borehole that cause measured brightness variations multiple reflections cause the brightness measured at a point on the borehole wall to not necessarily be equal to the local wall reflectance the ray tracing further shows that wall imperfections or variations in the camera position can produce brightness variations that are unrelated to changes in firn properties smooth walls and good stabilization of the camera help ensure that brightness variations result from variations in firn properties and thus are a measure of firn stratigraphy rather than artifacts

interplate coupling model off the southwestern coast of java indonesia based on continuous gps data in 2008 2010 abstract we present an interplate coupling model of the australia java plate interface off the southwestern coast of java indonesia based on data from the indonesian permanent gps station network from 2008 to 2010 the majority of vertical data indicate uplift while the baseline change rate indicates coastal contraction in the middle of the network and coastal extension in the eastern part of the network using the rate of baseline length changes and the absolute rate of vertical displacements we apply a geodetic inversion method by yabuki and matsu ura 1992 from the inversion result we interpret the main source of the observed velocity in west java as resulting from contributions of 1 interplate coupling off ujung kulon pelabuhan ratu at 20 to 40 km depth with a slip rate range from 48 to 56 mm yr 2 interplate coupling off pangandaran at 37 to 45 km depth with a slip rate of 48 to 55 mm yr 3 afterslip off pangandaran within the rupture area of the 2006 m7 8 java earthquake in the depth range of 15 20 km with a slip excess rate of 57 61 mm yr the absence of a megathrust earthquake for at least 300 years in this region implies seismic moment accumulation during this time period of 1 6 10 21 nm mw 8 7 off ujung kulon pelabuhan ratu and 3 9 10 21 nm mw 8 3 off pangandaran unless episodic slow slips release tectonic stress

izmit earthquake postseismic deformation and dynamics of the north anatolian fault zone 1 we have modeled postseismic deformation from 1999 to 2003 in the region surrounding the 1999 izmit and duzce earthquake ruptures using a three dimensional viscoelastic finite element method our models confirm earlier findings that surface deformation within the first few months of the izmit earthquake is principally due to stable frictional afterslip on and below the izmit earthquake rupture a second deformation process is required however to fit the surface deformation after several months viscoelastic relaxation of lower crust and or upper mantle with a viscosity of the order of 2 to 5 1019 pa s improves the models fit to later gps site velocities however for a linear viscous rheology this range of values is inconsistent with highly localized interseismic deformation around the north anatolian fault zone nafz that was well observed prior to the earthquake sequence the simplest solution to this problem is to assume that the effective viscosity of the relaxing material increases with time after large earthquakes that is that it has a power law or burger s body transient rheology a burger s body rheology with two characteristic viscosities 2 to 5 1019 pa s and at least 2 1020 pa s in the mantle is consistent with deformation around the nafz throughout the earthquake cycle

global fire at the cretaceous tertiary boundary cretaceous tertiary k t boundary clays from five sites in europe and new zealand are 102 104 fold enriched in elemental c mainly soot which is isotopically uniform and apparently comes from a single global fire the soot layer coincides with the ir layer suggesting that the fire was triggered by meteorite impact and began before the ejecta had settled