strong inland propagation of low frequency long waves in river estuaries tidal waves traveling into estuaries are modified by channel geometry and river flow the damping effect of river flow on incident astronomical tides is well documented whereas its impact on low frequency tides like msf and mm is poorly understood in this contribution we employ a numerical model to explore low frequency tidal behavior under varying river flow msf and mm are locally generated by frictional mechanisms inside an estuary and they are larger in amplitude far upstream in tidal rivers and persist landward of the point of tidal extinction increasing river flow nonlinearly modulates the longitudinal variations of msf and mm amplitudes this is dynamically explained by flow enhanced asymmetry in subtidal friction over the spring neap msf and perigee apogee mm cycles respectively estuaries act as frequency filters where low frequency waves decay at a smaller rate and propagate more inland than high frequency waves strong inland penetration of low frequency tides informs compound flood management

finite faults and inverse theory with applications to the 1979 imperial valley earthquake abstract using a representation theorem from elastodynamics subsurface slip on a known fault is formulated as the solution to an inverse problem in which recorded surface ground motion is the data two methods of solution are presented the least squares method which minimizes the squared differences between theory and data and the constrained least squares method which simultaneously maintains a set of linear inequalities instabilities in the solution are effectively eliminated in both methods and the sensitivity of the solution to small changes in the data is quantitatively stated the inversion methodology is applied to 77 components of near field ground acceleration recorded during the 15 october 1979 imperial valley earthquake the faulting is constrained to propagate bilaterally away from the epicenter at an average velocity of 90 per cent of the shear wave speed on a vertical fault plane extending from the surface to 10 km depth inequality constraints are used to keep the faulting sequence physically reasonable by maintaining right lateral motion and positive slip velocity the preferred solution is stable and provides a good fit to the data it is also realistic and consistent with observed surface offsets and independent estimates of seismic moment

early and persistent supershear rupture of the 2018 magnitude 7 5 palu earthquake the speed at which an earthquake rupture propagates affects its energy balance and ground shaking impact dynamic models of supershear earthquakes which are faster than the speed of shear waves often start at subshear speed and later run faster than eshelby s speed here we present robust evidence of an early and persistent supershear rupture at the sub eshelby speed of the 2018 magnitude 7 5 palu indonesia earthquake slowness enhanced back projection of teleseismic data provides a sharp image of the rupture process along a path consistent with the surface rupture trace inferred by subpixel correlation of synthetic aperture radar and satellite optical images the rupture propagated at a sustained velocity of 4 1 km s 1 from its initiation to its end despite large fault bends the persistent supershear speed is further validated by seismological evidence of far field rayleigh mach waves the unusual features of this earthquake probe the connections between the rupture dynamics and fault structure an early supershear transition could be promoted by fault roughness near the hypocentre steady rupture propagation at a speed unexpected in homogeneous media could result from the presence of a low velocity damaged fault zone

inversion of complex body waves we have developed a method that inverts seismic body waves to determine the mechanism and rupture pattern of earthquakes the rupture pattern is represented as a sequence of subevents distributed on the fault plane this method is an extension of our earlier method in which the subevent mechanisms were fixed in the new method the subevent mechanisms are determined from the data and are allowed to vary during the sequence when subevent mechanisms are allowed to vary however the inversion often becomes unstable because of the complex trade offs between the mechanism the timing and the location of the subevents many different subevent sequences can explain the same data equally well and it is important to determine the range of allowable solutions some constraints must be imposed on the solution to stabilize the inversion we have developed a procedure to explore the range of allowable solutions and appropriate constraints in this procedure a network of grid points is constructed on the i plane where and i are respectively the onset time and the distance from the epicenter of a subevent the best fit subevent is determined at all grid points then the correlation is computed between the synthetic waveform for each subevent and the observed waveform the correlation as a function of and i and the best fit mechanisms computed at each i grid point depict the character of allowable solutions and facilitate a decision on the appropriate constraints to be imposed on the solution the method is illustrated using the data for the 1976 guatemala earthquake

a supershear transition mechanism for cracks seismic data indicate that fault ruptures follow complicated paths with variable velocity because of inhomogeneities in initial stress or fracture energy we report a phenomenon unique to three dimensional cracks locally stronger fault sections rather than slowing ruptures drive them forward at velocities exceeding the shear wave speed this supershear mechanism differentiates barrier and asperity models of fault heterogeneity which previously have been regarded as indistinguishable high strength barriers concentrate energy producing potentially destructive pulses of strong ground motion

mathematical model for regional land subsidence due to pumping 1 integrated aquifer subsidence equations based on vertical displacement only a mathematical model for regional land subsidence has been developed by employing terzaghi s concept of effective stress and assuming vertical solid compressibility only first the groundwater mass conservation equation in a compressible aquifer is developed for a three dimensional space assuming that the problem justifies an assumption of a thin aquifer relative to horizontal lengths of interest this equation is then integrated over the aquifer s thickness taking into account the conditions on top and bottom surfaces bounding the aquifer the result is the commonly used aquifer flow equation in terms of averaged piezometric head by introducing a relationship between changes in averaged piezometric head and corresponding changes in aquifer thickness a single equation is obtained in terms of land subsidence the development is carried out for a single and a multi layered confined aquifer and for a phreatic one an example is given of the application of the equation in radial coordinates describing land subsidence in a hypothetical six layered aquifer

reservoir monitoring and characterization using satellite geodetic data interferometric synthetic aperture radar observations from the krechba field algeria deformation in the material overlying an active reservoir is used to monitor pressure change at depth a sequence of 11 field estimates allows us to construct a measure of diffusive traveltime throughout a reservoir the dense distribution of traveltime values means that we can construct an exactly linear inverse problem for reservoir flow properties application to interferometric synthetic aperture radar insar data gathered over a carbon dioxide c o2 injection site in algeria reveals pressure propagation along two northwest trending corridors an inversion of the traveltimes indicates the existence of two northwest trending high permeability zones the high permeability features trend in the same direction as the regional fault and fracture zones model parameter resolution estimates indicate the features are well resolved

seismic anisotropy in the uppermost mantle back arc region of the northeast japan arc petrophysical analyses of ichinomegata peridotite xenoliths 1 a dense network of seismic stations has been deployed across the northeast japan arc to investigate mantle wedge structures to attain independent petrophysical constraints we determined the seismic properties of ichinomegata mantle xenoliths from the back arc region that were brought to the surface from the mantle lithosphere by volcanic eruptions we calculated the seismic properties of the xenoliths from olivine and pyroxene crystal preferred orientations and single crystal elastic constants the small magnitude of measured s wave splitting delay time of 0 22 s in the area where the xenoliths were entrained can be explained by the average seismic properties of mantle xenoliths for an approximately 20 km thick horizontal anisotropic layer indicating that the mantle lithosphere could be one of the dominant sources of seismic anisotropy this layer is possibly related to deformation in the uppermost mantle lithosphere due to back arc spreading along the northeast japan arc

bed ribbing instability explanation testing a numerical model of ribbed moraine formation arising from coupled flow of ice and subglacial sediment 1 ribbed moraines are large up to 16 km long ridges of sediment produced transverse to ice flow direction that formed widely beneath palaeo ice sheets since ice sheet stability is sensitive to conditions operating at the bed an understanding of ribbed moraine genesis will provide critical information on ice sheet dynamics currently there is no consensus on ribbed moraine formation and various competing hypotheses have been presented to account for their genesis only one of these theories has been developed into a physically based numerical model that quantitatively describes ribbed moraine formation this theory known as the bed ribbing instability explanation brie argues that ribbed moraines are produced by a naturally arising instability in the coupled flow of ice and till brie demonstrates that transverse subglacial ridges i e ribbed moraine spontaneously grow under certain parameter combinations and it predicts their wavelength spacing between ridges the model represents a significant advance because it is the first time a theory of subglacial bedform generation has been developed to make quantitative predictions which can be formally tested this paper discusses the types of tests that are currently possible and reports the results from the first testing of brie this analysis centers on the ability of brie to predict the primary characteristics of ribbed moraine which are patterning and wavelength results show that brie successfully predicts the correct ribbed moraine pattern and appropriate wavelengths the tests fail to falsify the model and it is concluded that brie remains a viable explanation of ribbed moraine formation

accounting for uncertain fault geometry in earthquake source inversions i theory and simplified application the ill posed nature of earthquake source estimation derives from several factors including the quality and quantity of available observations and the fidelity of our forward theory observational errors are usually accounted for in the inversion process epistemic errors which stem from our simplified description of the forward problem are rarely dealt with despite their potential to bias the estimate of a source model in this study we explore the impact of uncertainties related to the choice of a fault geometry in source inversion problems the geometry of a fault structure is generally reduced to a set of parameters such as position strike and dip for one or a few planar fault segments while some of these parameters can be solved for more often they are fixed to an uncertain value we propose a practical framework to address this limitation by following a previously implemented method exploring the impact of uncertainties on the elastic properties of our models we develop a sensitivity analysis to small perturbations of fault dip and position the uncertainties of our fixed fault geometry are included in the inverse problem under the formulation of the misfit covariance matrix that combines both prediction and observation uncertainties we validate this approach with the simplified case of a fault that extends infinitely along strike using both bayesian and optimization formulations of a static slip inversion if epistemic errors are ignored predictions are overconfident in the data and slip parameters are not reliably estimated in contrast inclusion of uncertainties in fault geometry allows us to infer a robust posterior slip model epistemic uncertainties can be many orders of magnitude larger than observational errors for great earthquakes mw 8 not accounting for uncertainties in fault geometry may partly explain observed shallow slip deficits for continental earthquakes similarly ignoring the impact of epistemic errors can also bias estimates of near surface slip and predictions of tsunamis induced by megathrust earthquakes

the world stress map database release 2016 crustal stress pattern across scales abstract knowledge of the present day crustal in situ stress field is a key for the understanding of geodynamic processes such as global plate tectonics and earthquakes it is also essential for the management of geo reservoirs and underground storage sites for energy and waste since 1986 the world stress map wsm project has systematically compiled the orientation of maximum horizontal stress shmax for the 30th anniversary of the project the wsm database has been updated significantly with 42 870 data records which is double the amount of data in comparison to the database release in 2008 the update focuses on areas with previously sparse data coverage to resolve the stress pattern on different spatial scales in this paper we present details of the new wsm database release 2016 and an analysis of global and regional stress pattern with the higher data density we can now resolve stress pattern heterogeneities from plate wide to local scales in particular we show two examples of 40 60 shmax rotations within 70 km these rotations can be used as proxies to better understand the relative importance of plate boundary forces that control the long wave length pattern in comparison to regional and local controls of the crustal stress state in the new wsm project phase iv that started in 2017 we will continue to further refine the information on the shmax orientation and the stress regime however we will also focus on the compilation of stress magnitude data as this information is essential for the calibration of geomechanical numerical models this enables us to derive a 3 d continuous description of the stress tensor from point wise and incomplete stress tensor information provided with the wsm database such forward models are required for safety aspects of anthropogenic activities in the underground and for a better understanding of tectonic processes such as the earthquake cycle

fission track and fault kinematics analyses for new insight into the late cenozoic tectonic regime changes in west central sulawesi indonesia abstract the left lateral strike slip central sulawesi fault system csfs composed of the nnw palu koro pkf and the ese matano faults is located within the eastern indonesian triple junction between the pacific indo australian and eurasian plates fault kinematic and fission track analyses show that the late cenozoic central sulawesi deformation results from three successive tectonic regimes 1 a late miocene early pliocene 5 ma wnw trending shortening characterized by transpressional deformation along the pkf and compressional in the poso area this tectonics resulted from the collision between the banggai sula block with sulawesi it produced locally a transpressional regime as a consequence of the northward extrusion of the central sulawesi block limited by the pkf 2 a pliocene collapse tectonic regime associated with w trending extension coeval with these events regional cooling and exhumation took place 3 a quaternary transtensional regime resulting from the combined effects of the central sulawesi block northward motion and extension related to back arc spreading behind the north sulawesi subduction tomini gulf

gravity currents with residual trapping motivated by geological carbon dioxide co 2 storage we present a vertical equilibrium sharp interface model for the migration of immiscible gravity currents with constant residual trapping in a two dimensional confined aquifer the residual acts as a loss term that reduces the current volume continuously in the limit of a horizontal aquifer the interface shape is self similar at early and at late times the spreading of the current and the decay of its volume are governed by power laws at early times the exponent of the scaling law is independent of the residual but at late times it decreases with increasing loss owing to the self similar nature of the current the volume does not become zero and the current continues to spread in the hyperbolic limit the leading edge of the current is given by a rarefaction and the trailing edge by a shock in the presence of residual trapping the current volume is reduced to zero in finite time expressions for the up dip migration distance and the final migration time are obtained comparison with numerical results shows that the hyperbolic limit is a good approximation for currents with large mobility ratios even far from the hyperbolic limit in gently sloping aquifers the current evolution is divided into an initial near parabolic stage with power law decrease of volume and a later near hyperbolic stage characterized by a rapid decay of the plume volume our results suggest that the efficient residual trapping in dipping aquifers may allow co 2 storage in aquifers lacking structural closure if co 2 is injected far enough from the outcrop of the aquifer

spontaneous rupture processes on a bending fault 1 we simulated spontaneous rupture processes on a vertical bending strike slip fault in a three dimensional half space using a finite difference method rupture area and overall slip distribution on the fault vary with the initial stress field which depends on strike change at the bend rupture velocity and detailed slip distribution around the bend on the other hand are affected by time dependent normal stress change caused by rupture this dynamic stress change plays an important role in the rupture process ahead of the bend as well as in the resulting ground motion the numerical simulation method demonstrated here in a simplified geometry is equally applicable to modeling strong ground motion from geometrically complex ruptures in realistic earth models

pollen analysis and 14c age of moss remains in a permafrost core recovered from the active rock glacier murtel corvatsch swiss alps geomorphological and glaciological implications within the framework of core drilling through the permafrost of the active rock glacier murtel corvatsch in the swiss alps subfossil stem remains of seven different bryophyte species were found at a depth of 6 m below surface and about 3 m below the permafrost table in samples from massive ice the composition of the moss species points to the former growth of the recovered mosses in the nearest surroundings of the drill site a total of 127 pollen and spores captured by the mosses and representing 23 taxa were determined the local vegetation during deposition time must be characterized as a moss rich alpine grassland meadow rich in cyperaceae poaceae chenopodiaceae and asteraceae comparable to today s flora present around the study site for l4 c analysis accelerator mass spectrometry had to be used due to the small sample mass about 0 5 mg carbon content the mean conventional 14 c age of 2250 100 years 1 variability corresponds to ranges in the calibrated calendar age of 470 170 bc and 800 bc to ad 0 at statistical probabilities of 68 and 95 respectively this result is compared with the present day flow field as determined by high precision photogrammetry and with information about the thickness vertical structure and flow of the permafrost from borehole measurements total age of the rock glacier as a landform is on the order of 10 4 years the development of the rock glacier most probably started around the onset of the holocene when the area it now occupies became definitely deglaciated the bulk of the ice rock mixture within the creeping permafrost must be several thousand years old characteristic average values are estimated for 1 surface velocities through time cm a 1 2 long term ice and sediment accretion rates mm a 1 on the debris cone from which the rock glacier develops 3 retreat rates 1 2 mm a 1 of the cliff which supplies the debris to the debris cone and rock glacier and 4 ice content of the creeping ice rock mixture 50 90 by volume the pronounced supersaturation of the permafrost explains the steady state creep mode of the rock glacier

how fast is rupture during an earthquake new insights from the 1999 turkey earthquakes we report that during the two devastating 1999 earthquakes in turkey rupture propagated over a large part of the nearly 200km long fault zone at supershear speed approaching 5km s we present observations and modeling which confirm the original inference of supershear rupture during the izmit earthquake and we show that supershear rupture also occurred during the duzce earthquake we show that the rupture velocity measured about 2 times the shear wave velocity is the value predicted by theoretical studies in fracture dynamics we look for clues to explain these observations

inchworm like source evolution through a geometrically complex fault fueled persistent supershear rupture during the 2018 palu indonesia earthquake abstract how does fault slip follow an earthquake rupture front propagating faster than the local shear wave velocity i e at supershear speed how does a supershear rupture front pass through a geometrically complex fault system resolving the evolution of such complex earthquake ruptures is fundamental to our understanding of earthquake source physics but these events have not been well captured by conventional waveform inversions of observational data we applied a new framework of finite fault inversion to globally observed teleseismic waveforms and resolved both the spatiotemporal evolution of slip and the fault geometry of the 2018 palu earthquake moment magnitude 7 6 in sulawesi indonesia we show that supershear rupture propagation for this event was sustained by transient slip stagnation and advancement as the rupture front passed through the geometrically complex fault system this peculiar inchworm like slip evolution was caused by the rupture front encountering fault bends with favorable and unfavorable orientations for rupture propagation our analysis also identified the possible existence of a fault junction beneath palu bay connecting an unmapped primary fault in northern sulawesi with the palu koro fault in the south

attenuation of radiated ground motion and stresses from three dimensional supershear ruptures 1 radiating shear and rayleigh waves from supershear ruptures form mach waves that transmit large amplitude ground motion and stresses to locations far from the fault we simulate bilateral ruptures on a finite width vertical strike slip fault of width w and half length l with l w breaking the surface of an elastic half space and focus on the wavefield out to distances comparable to l at distances much smaller than w two dimensional plane strain slip pulse models i e models in which the lateral extent of the slip zone is unbounded accurately predict the subsurface wavefield amplitudes in the shear mach wedge of those models are undiminished with distance from the fault when viewed from distances far greater than w rupture is accurately modeled as a moving point source that produces a shear mach cone and on the free surface rayleigh wave mach fronts geometrical spreading of the shear mach cone occurs radially and amplitudes there decrease with the inverse square root of distance the transition between these two asymptotic limits occurs at distances comparable to w similar considerations suggest that rayleigh mach waves suffer no attenuation in the ideally elastic medium studied here the rate at which fault strength weakens at the rupture front exerts a strong influence on the off fault fields only in the immediate vicinity of the fault for both sub rayleigh and supershear ruptures and at the mach fronts of supershear ruptures more rapid weakening generates larger amplitudes at the mach fronts

flow and internal structure of a rock glacier exposure of a full transverse cross section of the terminus of fireweed rock glacier wrangell mountains alaska revealed a thin layer of unconsolidated debris mantling a consolidated melange of ice and rock the main rock glacier is fed by three tributaties at the terminus contacts between the three are sharply defined ice content is 50 by volume bubble foliation and crystal morphologies of the ice matrix are similar to those reported from glacier ice folded ice rich strata and lenses foliation planes and the long intermediate axial planes of tabular shaped englacial clasts dip steeply toward the center line of the rock glacier the planar structures generally parallel the steep walls of the gorge containing the trunk stream these steeply dipping longitudinal structures appear to result from transverse compression where the tributaries converge and the trunk stream narrows down valley bergschrund like and moulin like features at the heads of the middle and west tributaries respectively exposed admixed ice and rock similar to that of the terminus but lacking the well developed flow texture talus from the unstable cirque headwall and polygeneticice both accumulate at the base of the headwall and nourrish the tributary rock glaciers

gps observed horizontal ground extension at the hutubi china underground gas storage facility and its application to geomechanical modeling for induced seismicity abstract induced earthquakes and ground displacements were seldom reported in relation to gas injection or extraction the hutubi underground gas storage hugs facility is the largest one in china and is also a unique case with both earthquakes and ground displacements detected during multiple cycles of injection and extraction since 9 june 2013 unlike previous studies with a primarily seismological focus here we conducted quantitative analysis on the geomechanics of seismicity induced by the hugs through developing a hydrogeologic framework which systematically integrated geodetic geophysical and geological data first we measured horizontal ground extension and shortening on the order of cm in response to gas injection and extraction of the hugs at depth using a local gps network which was not reported in other regions with induced seismicity second we synthesized a variety of data including seismic reflection profiles a newly acquired local velocity model rock physics measurements well drilling and logging data to build up a 2d geomechanical model for the hugs third based on fully coupled poroelasticity we proposed two methods to optimize the permeability of the upper aquifers as well as the reservoir porosity and permeability with constraints from well level gps and well pressure data numerical simulations using the calibrated 2d model revealed that the horizontal extension due to the reservoir dilation is larger than ground uplift the observed seismicity on faults without hydraulic connections to the gas repository was probably induced by the poroelastic effect of reservoir dilation our study provided a prototype scheme for detecting and characterizing the geomechanical behavior of cyclic fluid injection and extraction in a deep reservoir which would be applicable to other ugs facilities

does a damaged fault zone mitigate the near field impact of supershear earthquakes application to the 2018 7 5 palu indonesia earthquake the impact of earthquakes can be severely aggravated by cascading secondary hazards the 2018 m w 7 5 palu indonesia earthquake led to devastating tsunamis and landslides while triggered submarine landslides possibly contributed substantially to generate the tsunami the rupture was supershear over most of its length but its speed was unexpectedly slow for a supershear event between the wave velocity v s and eshelby s speed 2v s an unstable speed range in conventional theory here we investigate whether dynamic rupture models including a low velocity fault zone can reproduce such a steady supershear rupture with a relatively low speed we then examine numerically how this peculiar feature of the palu earthquake could have affected the near field ground motion and thus the secondary hazards our findings suggest that the presence of a low velocity fault zone can explain the unexpected rupture speed and may have mitigated the near field ground motion and the induced landslides in palu

long lasting epeirogenic uplift from mantle plumes and the origin of the southern african plateau 1 we investigate under what conditions the present day long wavelength anomalous elevation 500 m of the southern african plateau can be attributed to mesozoic plume events the anomalous long wavelength topography of the southern african plateau cannot be easily explained by recent heating of the upper mantle as opposed to other areas of the african superswell and geomorphological studies provide few hard constraints on the timing of the uplift a mesozoic origin for the plateau uplift is attractive in that southern africa experienced several large magmatic events in the mesozoic we formulate numerical and scaling models to investigate if plume material ponded beneath cratonic lithosphere in the mesozoic could produce 500 m of present day elevation we find that starting plume heads are ineffective at producing much long lasting uplift because the material spreads into a thin layer tens of km thick the ponded plume material also suppresses secondary convection by having a stable boundary at its base over time heat continues to flow out of the top of the lithosphere and a net imbalance of heat flow in the lithosphere develops resulting in subsidence even after the plume material has cooled to the temperature of the mantle adiabat secondary convection supplies less heat to the lithosphere than is lost upward by conduction the cratonic lithosphere returns to its original thermal structure on a timescale of less than 200 m y even two mantle starting plume heads one at the time of karoo volcanism ca 183 ma and the other at the time of kimberlite eruption ca 80 90 ma in our models cannot produce much 200 m of the present day anomalous elevation however significant uplift can be generated by plume tails provided they linger beneath the lithosphere for 25 30 m y and if the uplift effects of mesozoic plume heads and tails are considered together then it is possible to account for 500 m of present day elevation consequently a mesozoic plume model for plateau uplift in southern africa appears to be a viable model if plume tails delivered heat to the southern african lithosphere over a period of 25 m y or more

spatio temporal distribution of fault slip and high frequency radiation of the 2010 el mayor cucapah mexico earthquake 1 earthquake slip history and moment release are best resolved using long period seismic waves but details in the rupture process such as sharp changes in rupture velocity or direction can be imaged more clearly using higher frequency waves here we investigate the slip and the high frequency radiation histories of the 2010 el mayor cucapah baja california mexico earthquake mw 7 2 the slip distribution inferred from inversion of strong motion data between 0 02 and 0 25 hz indicates northwest propagating rupture followed by bilateral rupture for 40 s the sources of high frequency radiation between 0 3 and 2 hz inferred from back projection analysis using teleseismic data are adjacent to but not within the high slip patches from the finite slip model in time and space this implies relatively smooth rupture during the times and regions of maximum moment release as theoretical models have predicted high frequency radiation seems mostly associated with changes in rupture velocity or slip magnitude strong high frequency radiation is also found where the rupture propagated to a branch fault 50 km northwest of the hypocenter complementary constraints on both fault slip and high frequency radiation provide increased understanding of earthquake rupture mechanics and may help improve strong motion evaluation at high frequencies

source properties of dynamic rupture pulses with off fault plasticity large dynamic stresses near earthquake rupture fronts may induce an inelastic response of the surrounding materials leading to increased energy absorption that may affect dynamic rupture we systematically investigate the effects of off fault plastic energy dissipation in 2 d in plane dynamic rupture simulations under velocity and state dependent friction with severe weakening at high slip velocity we find that plasticity does not alter the nature of the transitions between different rupture styles decaying versus growing pulse like versus crack like and subshear versus supershear ruptures but increases their required background stress and nucleation size we systematically quantify the effect of amplitude and orientation of background shear stresses on the asymptotic properties of self similar pulse like ruptures peak slip rate rupture speed healing front speed slip gradient and the relative contribution of plastic strain to seismic moment peak slip velocity and rupture speed remain bounded from fracture mechanics arguments we derive a nonlinear relation between their limiting values appropriate also for crack like and supershear ruptures at low background stress plasticity turns self similar pulses into steady state pulses for which plastic strain contributes significantly to the seismic moment we find that the closeness to failure of the background stress state is an adequate predictor of rupture speed for relatively slow events our proposed relations between state of stress and earthquake source properties in the presence of off fault plasticity may contribute to the improved interpretation of earthquake observations and to pseudodynamic source modeling for ground motion prediction

influence of plastic deformation on bimaterial fault rupture directivity 1 material juxtapositions across mature faults are a common occurrence previous work has found that this elastic mismatch results in a rupture that will preferentially propagate in the direction of slip displacement on the more compliant side of the fault with more off fault damage in the stiffer material this result has implications for inferring preferred rupture directions based on observations of damage zone asymmetry we perform a complete numerical investigation of the role of the stress state on the distribution of plastic deformation and the direction of preferred rupture propagation we show that there are important factors in addition to the elastic mismatch which control the preferred direction of propagation as well as the side of the fault in which damage predominately accumulates the orientation of the most compressive principal stress is the controlling factor in determining the location of plastic deformation for different orientations plastic deformation can accumulate in either the stiffer or the more compliant material for high angles of most compressive stress the aforementioned preferred rupture direction prediction holds true however the off fault plastic response can reverse that direction for low angles of most compressive stress so that rupture will preferentially propagate in the direction of slip displacement in the stiffer material

faulting characteristics of supershear earthquakes article i nfo recent observations of large continental strike slip earthquakes show that different fault segments may rupture at different speeds and that rupture may propagate faster than the shear wave velocity of surrounding rocks we report that all the documented occurrences of supershear rupture are associated with faults which have simple geometry the surface trace of these faults is described in the field or seen on satellite images as remarkably linear continuous and narrow segmentation features along these segments are small or absent and the deformation is highly localized as theoretically predicted supershear is clearly associated with mode ii rupture

status of co2 storage in deep saline aquifers with emphasis on modeling approaches and practical simulations carbon capture and storage ccs is the only viable technology to mitigate carbon emissions while allowing continued large scale use of fossil fuels the storage part of ccs involves injection of carbon dioxide captured from large stationary sources into deep geological formations deep saline aquifers have the largest identified storage potential with estimated storage capacity sufficient to store emissions from large stationary sources for at least a century this makes ccs a potentially important bridging technology in the transition to carbon free energy sources injection of co2 into deep saline aquifers leads to a multicomponent multiphase flow system in which geomechanics geochemistry and nonisothermal effects may be important while the general system can be highly complex and involve many coupled nonlinear partial differential equations the underlying physics can sometimes lead to important simplifications for example the large density difference between injected co2 and brine may lead to relatively fast buoyant segregation making an assumption of vertical equilibrium reasonable such simplifying assumptions lead to a range of simplified governing equations whose solutions have provided significant practical insights into system behavior including improved estimates of storage capacity easy to compute estimates of co2 spatial migration and pressure response and quantitative estimates of leakage risk when these modeling studies are coupled with observations from well characterized injection operations understanding of the overall system behavior is enhanced significantly this improved understanding shows that while economic and policy challenges remain co2 storage in deep saline aquifers appears to be a viable technology and can contribute substantially to climate change solutions

observation of far field mach waves generated by the 2001 kokoxili supershear earthquake regional surface wave observations offer a powerful tool for determining source properties of large earthquakes especially rupture velocity supershear ruptures being faster than surface wave phase velocities create far field surface wave mach cones along which waves from all sections of the fault arrive simultaneously and over a sufficiently narrow frequency band in phase we present the first observation of far field mach waves from the major kokoxili earthquake tibet 2001 11 14 mw7 9 and confirm that ground motion amplitudes are indeed enhanced on the mach cone theory predicts that on the mach cone bandpassed surface wave seismograms from a large supershear rupture will be identical to those from much smaller events with similar focal mechanisms with an amplitude ratio equal to the ratio of the seismic moments of the two events cross correlation of 15 25 s love waves from the kokoxili event with those from a much smaller mw5 foreshock indicates a high degree of similarity correlation coefficients ranging from 0 8 to 0 95 in waveforms recorded at stations near the far field mach cone this similarity vanishes away from the mach cone these observations provide further evidence for supershear propagation of the kokoxili rupture and demonstrate how this simple waveform correlation procedure can be used to identify supershear ruptures

a mathematical model for regional land subsidence due to pumping 3 integrated equations for a phreatic aquifer a mathematical model is developed for the areal distribution of drawdown land subsidence and horizontal displacements due to groundwater pumping from a deformable phreatic aquifer this paper is a continuation of earlier works published by the authors bear and corapcioglu 1981a b on the subject of regional land subsidence due to pumping in confined and leaky aquifers all the basic assumptions underlying these previous works are also valid here however in this case the same methodology is extended to the case of a phreatic aquifer the main additional feature in the present paper is that due to the decline of the water table the total stress at points within the flow domain changes continuously following the development of a three dimensional mathematical model consisting of a mass conservation equation quasi static equilibrium equations and stress strain relations for an assumed perfectly elastic solid matrix a regional horizontal two dimensional model is derived by averaging the three dimensional model over the vertical thickness of the aquifer taking into account the continuous variation in total stress as a result of water table fluctuations the separation of an initially coinciding phreatic surface which serves as the upper boundary of the aquifer and a surface consisting of a set of solid particles during the lowering of the water table and the compaction of the aquifer has been incorporated into the averaging procedure an analytical solution is given for the case of a single pumping well the solution which is expressed in terms of the classical well function for a confined aquifer but with a modified storativity provides estimates of drawdown vertical subsidence and horizontal displacement the displacements for a sample problem are compared with those of a confined aquifer under similar conditions the results indicate that under the conditions of the studied case of radial flow vertical and horizontal displacements due to pumping from a phreatic aquifer with the same discharge rate would be less than those of a confined one furthermore the same averaging procedure is extended for a system of phreatic and leaky confined aquifers and for the unsaturated zone above the water table an additional change in total stress is obtained in terms of moisture content of the zone above the phreatic surface

the transition of dynamic rupture styles in elastic media under velocity weakening friction although kinematic earthquake source inversions show dominantly pulse like subshear rupture behavior seismological observations laboratory experiments and theoretical models indicate that earthquakes can operate with different rupture styles either as pulses or cracks that propagate at subshear or supershear speeds the determination of rupture style and speed has important implications for ground motions and may inform about the state of stress and strength of active fault zones we conduct 2d in plane dynamic rupture simulations with a spectral element method to investigate the diversity of rupture styles on faults governed by velocity and state dependent friction with dramatic velocity weakening at high slip rate our rupture models are governed by uniform initial stresses and are artificially initiated we identify the conditions that lead to different rupture styles by investigating the transitions between decaying steady state and growing pulses cracks sub shear and super shear ruptures as a function of background stress nucleation size and characteristic velocity at the onset of severe weakening our models show that small changes of background stress or nucleation size may lead to dramatic changes of rupture style we characterize the asymptotic properties of steady state and self similar pulses as a function of background stress we show that an earthquake may not be restricted to a single rupture style but that complex rupture patterns may emerge that consist of multiple rupture fronts possibly involving different styles and back propagating fronts we also demonstrate the possibility of a super shear transition for pulse like ruptures finally we draw connections between our findings and recent seismological observations

high slip rate for a low seismicity along the palu koro active fault in central sulawesi indonesia accurate chronological records are critical for understanding the landformsevolution and in particular of alluvial fan sequences emplaced during glocal global climatic changes toward this end we measured in situ produced 10be in quartz boulders exposed on top surfaces of sulawesian late quaternary alluvial fans combined geomorphic study spot image and field analyses indicate that this site is composed of twoalluvial fan units in situ produced 10be concentrations suggest that they were emplaced during two successive major climatic events the calculated minimum exposure ages date the younger unit abandonment at 11 000 2 000 years and seem consistent with a late interglacial abandonment age 120 000years for the older unit this study demonstrates that using both the neutron and muon components implicated in the production of in situ10be surficial erosion rates can be estimated 6 m ma in sulawesi and alluvial fan surfaces dated in particular it shows that10be may be used to date fan surface emplacement during the last 120 ka under humid tropical conditions significantly helping to constrain continental paleo climatology in these regions

inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 imperial valley california earthquake a least squares point by point inversion of strong ground motion and teleseismic body waves is used to infer the fault rupture history of the 1979 imperial valley california earthquake the imperial fault is represented by a plane embedded in a half space where the elastic properties vary with depth the inversion yields both the spatial and temporal variations in dislocation on the fault plane for both right lateral strike slip and normal dip slip components of motion inversions are run for different fault dips and for both constant and variable rupture velocity models effects of different data sets are also investigated inversions are compared which use the strong ground motions alone the teleseismic body waves alone and simultaneously the strong ground motion and teleseismic records the inversions are stabilized by adding both smoothing and positivity constraints the moment is estimated to be 5 0 10 25 dyne cm and the fault dip 90 5 dislocation in the hypocentral region south of the united states mexican border is relatively small and almost dies out near the border dislocation then increases sharply north of the border to a maximum of about 2 m under interstate 8 dipslip motion is minor compared to strike slip motion and is concentrated in the sediments the best fitting constant rupture velocity is 80 per cent of the local shear wave velocity however there is a suggestion that the rupture front accelerated from the hypocenter northward the 1979 imperial valley earthquake can be characterized as a magnitude 5 earthquake at the hypocenter which then grew into or triggered a magnitude 6 earthquake north of the border

abrupt onset of the little ice age triggered by volcanism and sustained by sea ice ocean feedbacks 1 northern hemisphere summer temperatures over the past 8000 years have been paced by the slow decrease in summer insolation resulting from the precession of the equinoxes however the causes of superposed century scale cold summer anomalies of which the little ice age lia is the most extreme remain debated largely because the natural forcings are either weak or in the case of volcanism short lived here we present precisely dated records of ice cap growth from arctic canada and iceland showing that lia summer cold and ice growth began abruptly between 1275 and 1300 ad followed by a substantial intensification 1430 1455 ad intervals of sudden ice growth coincide with two of the most volcanically perturbed half centuries of the past millennium a transient climate model simulation shows that explosive volcanism produces abrupt summer cooling at these times and that cold summers can be maintained by sea ice ocean feedbacks long after volcanic aerosols are removed our results suggest that the onset of the lia can be linked to an unusual 50 year long episode with four large sulfur rich explosive eruptions each with global sulfate loading 60 tg the persistence of cold summers is best explained by consequent sea ice ocean feedbacks during a hemispheric summer insolation minimum large changes in solar irradiance are not required

evidence of supershear during the 2018 magnitude 7 5 palu earthquake from space geodesy a magnitude 7 5 earthquake hit the city of palu in sulawesi indonesia on 28 september 2018 at 10 02 43 coordinated universal time it was followed a few minutes later by a 4 7 m high tsunami palu is situated in a narrow pull apart basin surrounded by high mountains of up to 2 000 m altitude this morphology has been created by a releasing bend in the palu koro fault a rapidly moving left lateral strike slip fault here we present observations derived from optical and radar satellite imagery that constrain the ground surface displacements associated with the earthquake in great detail mapping of the main rupture and associated secondary structures shows that the slip initiated on a structurally complex and previously unknown fault to the north extended southwards over 180 km and passed through two major releasing bends the 30 km section of the rupture south of palu city is extremely linear and slightly offset from the mapped geological fault at the surface this part of the rupture accommodates a large and smooth surface slip of 4 7 m with no shallow slip deficit almost no aftershock seismicity was recorded from this section of the fault as these characteristics are similar to those from known supershear segments we conclude that the palu earthquake probably ruptured this segment at supershear velocities the devastating 2018 magnitude 7 5 earthquake in palu indonesia ruptured at supershear speeds according to evidence from space geodesy

mathematical model for regional land subsidence due to pumping 2 integrated aquifer subsidence equations for vertical and horizontal displacements a mathematical model for regional subsidence due to pumping from an aquifer is developed on the basis of biot s work on coupled three dimensional consolidation following biot s work on threedimensional consolidation with coupling between mass conservation and equilibrium equations a mathematical model for regional subsidence due to pumping from an aquifer is developed by averaging the three dimensional model over the thickness of the aquifer and assuming conditions of plane stress both vertical land subsidence and horizontal displacements as functions of plane coordinates and time can be estimated by solving the model equations for a given confined or leaky confined aquifer an analytical solution is presented for the special case of a single well pumping from an infinite homogeneous isotropic aquifer the solution provides estimates of changes in averaged over the vertical values of piezometric head vertical subsidence and horizontal displacement the results indicate that under the conditions of the studied case of radial flow the solution for piezometric head is identical to the one obtained by noncoupled models furthermore half the volume strain is produced by vertical subsidence while the other half by the horizontal displacement hence the vertical subsidence is only approximately half the value obtained in noncoupled models which neglect horizontal displacement a numerical example demonstrates these conclusions

microblock rotations and fault coupling in se asia triple junction sulawesi indonesia from gps and earthquake slip vector data the island of sulawesi eastern indonesia is located within the triple junction of the australian philippine and sunda plates and accommodates the convergence of continental fragments with the sunda margin we quantify the kinematics of sulawesi by modeling gps velocities and earthquake slip vectors as a combination of rigid block rotations and elastic deformation around faults we find that the deformation can be reasonably described by a small number of rapidly rotating crustal blocks relative to the sunda plate the southwestern part of sulawesi makassar block rotates anticlockwise at 1 4 myr the northeastern part of sulawesi the bangai sula domain comprises three blocks the central north sula block moves toward the nnw and rotates clockwise at 2 5 myr the northeastern manado block rotates clockwise at 3 myr about a nearby axis and east sulawesi is pinched between the north sula and makassar blocks along the boundary between the makassar block and the sunda plate gps measurements suggest that the trench accommodates 15 mm yr of slip within the makassar strait with current elastic strain accumulation the tectonic boundary between north sula and manado blocks is the gorontalo fault moving right laterally at about 11 mm yr and accumulating elastic strain the 42 mm yr relative motion between north sula and makassar blocks is accommodated on the palu koro left lateral strike slip fault zone the data also indicate a pull apart structure in palu area where the fault shows a transtensive motion and may have a complex geometry involving several active strands sulawesi provides a primary example of how collision can be accommodated by crustal block rotation instead of mountain building