mechanical properties of shale gas reservoir rocks part 2 ductile creep brittle strength and their relation to the elastic modulus we studied the elastic moduli ductile creep behavior and brittle strength of shale gas reservoir rocks from barnett haynesville eagle ford and fortst john shale in a series of triaxial laboratory experiments we found a strong correlation between the shale compositions in particular the volume of clay plus kerogen and intact rock strength frictional strength and viscoplastic creep viscoplastic creep strain was approximately linear with the applied differential stress the reduction in sample volume during creep suggested that the creep was accommodated by slight pore compaction in a manner similar to instantaneous strain there was more viscoplastic creep in samples deformed perpendicular to the bedding than parallel to the bedding the tendency to creep also correlated well with the static young s modulus we explained this apparent correlation between creep behavior and elastic modulus by appealing to the stress partitioning that occurs between the soft components of the shales clay and kerogen and the stiff components quartz feldspar pyrite and carbonates through a simple 1d analysis we found that a unique relation between the creep compliance and elastic modulus independent of composition and orientation can be established by considering the individual creep behavior of the soft and stiff components that arises from the stress partitioning within the rock this appears to provide a mechanical explanation for why long term ductile deformational properties can appear to correlate with short term elastic properties in shale gas reservoir rocks

mechanical properties of shale gas reservoir rocks part 1 static and dynamic elastic properties and anisotropy abstractunderstanding the controls on the elastic properties of reservoir rocks is crucial for exploration and successful production from hydrocarbon reservoirs we studied the static and dynamic elastic properties of shale gas reservoir rocks from barnett haynesville eagle ford and fort st john shales through laboratory experiments the elastic properties of these rocks vary significantly between reservoirs and within a reservoir due to the wide variety of material composition and microstructures exhibited by these organic rich shales the static young s modulus and dynamic p and s wave moduli elastic parameters generally decrease monotonically with the clay plus kerogen content the variation of the elastic moduli can be explained in terms of the voigt and reuss limits predicted by end member components however the elastic properties of the shales are strongly anisotropic and the degree of anisotropy was found to correlate with the amount of clay and organic content as well as the shale fab

plate boundary observatory and related networks gps data analysis methods and geodetic products the geodesy advancing geosciences and earthscope gage facility global positioning system gps data analysis centers produce position times series velocities and other parameters for approximately two thousand continuously operating gps receivers spanning a quadrant of earth s surface encompassing the high arctic north america and caribbean the purpose of this review is to document the methodology for generating station positions and their evolution over time and to describe the requisite tradeoffs involved with combination of results gage gps analysis involves formal merging within a kalman filter of two independent loosely constrained solutions one is based on precise point positioning produced with the gps inferred positioning system orbit analysis simulation gipsy oasis software at central washington university cwu and the other is a network solution based on phase and range double differencing produced with the gps at mit gamit software at new mexico institute of mining and technology nmt the primary products generated are the position time series that show motions relative to a north america reference frame and secular motions of the stations represented in the velocity field the position time series themselves contain a multitude of signals in addition to the secular motions co seismic and post seismic signals seasonal signals from hydrology and transient events some understood and other not yet fully explained are all evident in the time series and ready for further analysis and interpretation we explore the impact of analysis assumptions on the reference frame realization and on the final solutions and we compare within the gage solutions and with others

crystallographic controls on the frictional behavior of dry and water saturated sheet structure minerals 1 we compare the frictional strengths of 17 sheet structure mineral powders measured under dry and water saturated conditions to identify the factors that cause many of them to be relatively weak the dry coefficient of friction ranges upward from 0 2 for graphite leveling off at 0 8 for margarite clintonite gibbsite kaolinite and lizardite the values of dry correlate directly with calculated 001 interlayer bond strengths of the minerals this correlation occurs because shear becomes localized along boundary and riedel shears and the platy minerals in them rotate into alignment with the shear planes for those gouges with dry 0 8 shear occurs by breaking the interlayer bonds to form new cleavage surfaces where dry 0 8 consistent with byerlee s law the interlayer bonds are sufficiently strong that other frictional processes dominate the transition in dry friction mechanisms corresponds to calculated surface energies of 2 3 j m2 adding water causes to decrease for every mineral tested except graphite if the minerals are separated into groups with similar crystal structures wet increases with increasing interlayer bond strength within each group this relationship also holds for the swelling clay montmorillonite whose water saturated strength is consistent with the strengths of nonswelling clays of similar crystal structure water in the saturated gouges forms thin structured films between the plate surfaces the polar water molecules are bonded to the plate surfaces in proportion to the mineral s surface energy and wet reflects the stresses required to shear through the water films

anelasticity and dispersion in dry unconsolidated sands laboratory measurements reveal frame modulus dispersion and creeping behavior in room dry samples of unconsolidated quartzo feldspathic upper miocene turbidites from the wilmington field ca a single standard linear solid model predicts both the dispersion and the creep response similar behavior is observed in ottawa sand samples when mixed with wetted montmorillonite in this case the magnitude of dispersion and creep increase with increasing clay content we suggest that the anelastic behavior of the wilmington sands is due to the presence of micas and a small amount of clay the transition frequency of 2 10 4hz i e between high and low frequency behavior suggests that seismic sonic and ultrasonic measurements of rock moduli are quite similar in the absence of fluids the static frame modulus should be used to model tectonic processes and long term production related changes in oil field environments

seismic remote sensing for the earthquake source process and near source strong shaking a case study of the october 16 1999 hector mine earthquake a new methodology to automatically determine the earthquake source process and near source strong ground motions using regional and local distance data was used to study the october 16 1999 hector mine earthquake mw7 1 broadband displacement data were inverted for the seismic moment tensor and to resolve the fault plane ambiguity independent of aftershock location and surface faulting information the identified nnw striking fault plane was used to invert for the distribution of fault slip over a planar surface the slip model was used to predict near fault peak ground velocity which was found to agree well with the trinet shakemap and also with near fault observations that were not available at the time of the initial analysis our method if automated is capable of providing near source strong ground motion information within 30 minutes of the earthquake origin time even in cases where there are few near fault recording instruments

fluid flow in sedimentary basins abstract the pore waters in sedimentary basins are ultimately derived from sea water meteoric water mineral bound water or from the underlying basement geochemically these waters initially have different signatures however the pore water compositions are easily altered by reactions with minerals or by mixing with other fluids meteoric water is driven downwards into sedimentary basins by the gravitational potential which approximately corresponds to the elevation of the ground water table above the sea or lake level it is difficult to model such flow however because the permeability on a large scale is almost impossible to represent realistically the continuity of confined sandstone and limestone aquifers plays an important role in determining the flux of meteoric water received by rocks in different parts of the basin but this is again difficult to predict pore water flow driven by compaction typically has velocities several orders of magnitude lower than what is commonly found in meteoric water flow regimes the average rate of upwards flow is lower than the rate of subsidence and the difference is the rate of incorporation of sea water in the topmost layer at the sea floor the salinity of formation water provides important constraints on fluid flow in sedimentary basins in the north sea basin and the gulf coast basin these types of data indicate that vertical mixing by compaction driven flow and convection is limited compaction driven flow obeys darcy s law but there are complex interdependencies between pressure permeability and compaction given the low compressibility of water the flow which can result from pressure release alone is very limited except on a local scale along permeable faults and fractures the main flow of pore water during burial is driven by compaction which is a slow process even when overpressure is released abruptly with a resulting increase in the net effective stress in the case of high permeability faults the flow into the fault from low permeability sedimentary rocks at depth may be rate limiting the displacement of pore water in adjacent sediments near the top of the faults may also slow down fluid flow on fractures that do not reach the sea floor modelling of fluid flow in sedimentary basins should be based on permeability distributions which are mostly determined by primary facies diagenesis and the tectonic history of the basin extensional tectonics produce a predominantly vertical fracture network which may serve as conduits for pore water flowing deep into the crust upward flow of hot fluids in basement fractures must have a high velocity in order to produce large thermal anomalies concentrations of dissolved components precipitate at the surface and form deposits of quartz and ore minerals if basement fractures are overlain by a thick sequence of soft sediments the rate of flow on the fractures will be reduced because of the low permeability in the sedimentary cover and conductive heat transport will dominate flow of water at high enough velocities to bring hot water to the surface and produce hot springs is most likely to occur in fractured basements rocks or well cemented sedimentary rocks concentrated precipitation of dissolved components will occur near the surface where the rate of cooling is highest also sediment hosted ores precipitated from flow of hot water on fractures are therefore likely to form before accumulation of thick overlying sedimentary sequences

near field tsunami models with rapid earthquake source inversions from land and ocean based observations the potential for forecast and warning computation of tsunami models in the region adjacent to large earthquakes immediately after rupture initiation remains a challenging problem limitations of traditional seismological instrumentation in the near field and concern by tsunami modelers regarding the nonuniqueness of source inversions and the use of indirect observations have in the past been hurdles for such efforts employing near field data from the mw 9 0 2011 tohoku oki data we test source models obtained from newly developed algorithms and multisensor data we demonstrate the ability of such source models determined from land based coseismic data from the combination of gps and strong motion sensors to forecast near source tsunamis we also demonstrate that rapid ingestion of offshore shallow water 100 1000 m wave gauge data substantially improves the earthquake source and tsunami forecast to assess the success of such tsunami models we rely on detailed comparisons to 2000 tsunami survey measurements collected after the event we argue that deployments of shallow water wave gauges coupled with land based geophysical sensors can in the future provide enough information to issue timely and accurate forecasts of tsunami intensity immediately or shortly after rupture initiation of large earthquakes

coseismic and early postseismic deformation of the 5 january 2013 mw 7 5 craig earthquake from static and kinematic gps solutions static low rate 30 s and kinematic high rate 1 s global positioning system solutions are employed to investigate the near field coseismic and early postseismic deformation associated with the 5 january 2013 craig m w 7 5 earthquake based on the static solutions the coseismic slip distribution has an average slip of 6 m a geodetic moment m of 1 5 1020 n m and a magnitude m w of 7 4 a comparison of the static and kinematic results indicates that early first 4 days postseismic deformation was small compared to the coseismic deformation the postseismic transient can be characterized by a logarithmic decay function with an average decay time constant of about 56 days substantial postseismic deformation is observed over the first 1 6 yrs of the earthquake and can be explained by afterslip on an adjacent segment of the fault to the southeast of the main coseismic rupture additional study will be needed to confirm whether afterslip is indeed the dominant mechanism causing postseismic motions or if another mechanism is also active online material figures showing high rate global positioning system time series and model fits for selected sites

time dependent brittle creep in darley dale sandstone 1 the characterization of time dependent brittle rock deformation is fundamental to understanding the long term evolution and dynamics of the earth s crust the chemical influence of pore water promotes time dependent deformation through stress corrosion cracking that allows rocks to deform at stresses far below their short term failure strength here we report results from a study of time dependent brittle creep in water saturated samples of darley dale sandstone initial porosity 13 under triaxial stress conditions results from conventional creep experiments show that axial strain rate is heavily dependent on the applied differential stress a reduction of only 10 in differential stress results in a decrease in strain rate of more than two orders of magnitude however natural sample variability means that multiple experiments must be performed to yield consistent results hence we also demonstrate that the use of stress stepping creep experiments can successfully overcome this issue we have used the stress stepping technique to investigate the influence of confining pressure at effective confining pressures of 10 30 and 50 mpa while maintaining a constant 20 mpa pore fluid pressure our results demonstrate that the stress corrosion process appears to be significantly inhibited at higher effective pressures with the creep strain rate reduced by multiple orders of magnitude the influence of doubling the pore fluid pressure however while maintaining a constant effective confining pressure is shown to influence the rate of stress corrosion within the range expected from sample variability we discuss these results in the context of microstructural analysis acoustic emission hypocenter locations and fits to proposed macroscopic creep laws

time dependent deformation of shale gas reservoir rocks and its long term effect on the in situ state of stress abstract laboratory testing of shale gas reservoir rocks reveal varying amounts of time dependent viscous deformation in response to applied differential stress the time dependent deformation is an inherent property of the dry rock as it occurs in the absence of pore fluid the contribution of the time dependent deformation is generally larger for rocks with more clay and organic content the time dependent behavior can be modeled as a power law function of time its magnitude is approximately linear with the magnitude of the applied differential stress and nearly insensitive to the confining pressure by applying linear viscoelastic theory and using laboratory constrained constitutive parameters we evaluated the effect of the time dependent deformation in modifying the in situ differential stress over time modeling suggests that a significant proportion of a differential stress change would be relaxed over time scales on the order of days because of this short time scale the composition of the rock as it influences the time dependent behavior may influence the in situ differential stress magnitudes stronger than the formation s geological loading history for these reservoirs

self contained local broadband seismogeodetic early warning system detection and location earthquake and local tsunami early warning is critical to mitigating adverse impacts of large magnitude earthquakes an optimal system must rely on near source data to maximize warning time to this end we have developed a self contained seismogeodetic early warning system employing an optimal combination of high frequency information from strong motion accelerometers and low frequency information from collocated global navigation satellite systems gnss instruments to estimate real time displacements and velocities like gnss and unlike broadband seismometers seismogeodetic stations record the full waveform including static offset without clipping in the near field or saturating for large magnitude earthquakes however gnss alone cannot provide a self contained system and requires an external seismic trigger seismogeodetic stations detect p wave arrivals with the same sensitivity as strong motion accelerometers and thus provide a stand alone system we demonstrate the utility of near source seismogeodesy for event detection and location with analysis of the 2010 mw7 2 el mayor cucapah baja california and 2014 mw6 0 napa california strike slip events and the 2014 mw8 2 iquique chile subduction zone earthquake using observatory grade accelerometers and gps data we present lessons from the 2014 mw4 0 piedmont california and 2016 mw5 2 borrego springs california earthquakes recorded by our seismogeodetic system with micro electro mechanical system mems accelerometers and gps data and reanalyzed retrospectively we conclude that our self contained seismogeodetic system is suitable for early warning for earthquakes of significance m5 using either observatory grade or mems accelerometers finally we discuss the effect of network design on hypocenter location and suggest the deployment of additional seismogeodetic stations for the western u s

a new seismogeodetic approach applied to gps and accelerometer observations of the 2012 brawley seismic swarm implications for earthquake early warning 1 the 26 august 2012 brawley seismic swarm of hundreds of events ranging from m1 4 to m5 5 in the salton trough california provides a unique data set to investigate a new seismogeodetic approach that combines global positioning system gps and accelerometer observations to estimate displacement and velocity waveforms first in simulated real time mode we analyzed 1 5 hz gps data collected by 17 stations fully encircling the swarm zone at near source distances up to about 40 km using precise point positioning with ambiguity resolution ppp ar we used a reference network of north american gps stations well outside the region of deformation to estimate fractional cycle biases and satellite clock parameters which were then combined with ultrarapid orbits from the international gnss service to estimate positions during the brawley seismic swarm next we estimated seismogeodetic displacements and velocities from gps phase and pseudorange observations and 100 200 hz accelerations collected at three pairs of gps and seismic stations in close proximity using a new tightly coupled kalman filter approach as an extension of the ppp ar process we can clearly discern body waves in the velocity waveforms including p wave arrivals not detectable with the gps only approach for earthquake magnitudes as low as mw 4 6 and significant static offsets for magnitudes as low as mw 5 4 our study shows that gps networks upgraded with strong motion accelerometers can provide new information for improved understanding of the earthquake rupture process and be of critical value in creating a robust early warning system for any earthquake of societal significance

a response function approach for rapid far field tsunami forecasting predicting tsunami impacts at remote coasts largely relies on tsunami en route measurements in an open ocean in this work these measurements are used to generate instant tsunami predictions in deep water and near the coast the predictions are generated as a response or a combination of responses to one or more tsunameters with each response obtained as a convolution of real time tsunameter measurements and a pre computed pulse response function prf practical implementation of this method requires tables of prfs in a 3d parameter space earthquake location tsunameter forecasted site examples of hindcasting the 2010 chilean and the 2011 tohoku oki tsunamis along the us west coast and beyond demonstrated high accuracy of the suggested technology in application to trans pacific seismically generated tsunamis

application of tracers to measure monitor and verify breakthrough of sequestered co2 at the co2crc otway project victoria australia abstract at the cooperative research centre for greenhouse gas technology s co2crc field site in the otway basin of victoria australia investigations into the storage of co2 rich gas in a depleted hydrocarbon gas field have been conducted in the waarre c reservoir the injected gas from the nearby buttress field contained 75 mol co2 21 mol ch4 with the remaining balance being a mixture of wet hydrocarbons condensate and nitrogen chemical tracers sulphur hexafluoride sf6 krypton kr perdeuterated methane cd4 were added on the basis of literature surveys and small volume trials at the frio ii brine experiment in texas the aim of the project was to measure monitor and verify the presence of injected co2 in a depleted gas field and that the arrival of tracers was a major component of demonstrating breakthrough of co2 at the monitoring well naylor 1 the paper focuses on methods developed for the injection recovery and analysis of samples collected at the naylor 1 well results of tracer analysis compare well with other data collected including ph and density measurements to demonstrate breakthrough a slip stream injection system was designed to deliver the tracers mixed with the co2 rich gas into the subsurface at the crc 1 well the tracers were added to the gas stream 17 days after the start of injection co2 injection commenced 18th march 2008 into the depleted natural gas field at naylor a u tube system was used to retrieve the samples from the naylor 1 monitoring well collected gas and formation water samples were analysed in detail for gas composition tracers isotopes 13c co2 mainly and inorganic geochemistry for the broader project the tracer results confirm that co2 breakthrough at the monitoring well occurred within the predicted times however the interval between samples taken from the u tubes was too coarse to resolve detailed differences in arrival times between the co2 and tracers of the three tracers used sf6 provided the clearest evidence of breakthrough at u tube 2 kr because of its abundance in air and its potential to be present in the subsurface was more prone to contamination and had higher background levels prior to breakthrough cd4 was expected to provide some more unique data based on the presence of abundant ch4 in the reservoir interval with hindsight larger volumes should have been injected to facilitate comparisons with the other tracers and add value to the data set the test of cd4 however acted as a suitable proof of concept that cd4 could be used in such a high background of ch4 further work is ongoing to generate data for partition coefficients between supercritical co2 ch4 and water under the injection conditions

buoyant dispersal of co2 during geological storage carbon capture and storage is currently the only technology that may allow significant reductions in co2 emissions from large point sources seismic images of geological co2 storage show the rise of co2 is influenced by horizontal shales the buoyant co2 spreads beneath impermeable barriers until a gap allows its upward migration the large number and small scale of these barriers makes the prediction of the co2 migration path and hence the magnitude of co2 trapping very challenging we show that steady buoyancy dominated flows in complex geometries can be modeled as a cascade of flux partitioning events this approach allows the analysis of two dimensional plume dispersal from a horizontal injection well we show that the plume spreads laterally with height y above the source according to y h 1 2 l where l is the width of the shales and h is their vertical separation the fluid volume below successive shale layers and therefore the magnitude of trapped co2 increase as y h 5 4 above the source so that every additional layer of barriers traps more co2 than the one below upscaling small scale flow barriers by reducing the vertical permeability common in numerical simulations of co2 storage does not capture the dispersion and trapping of the co2 plume by the flow barriers

the 2010 m w 7 2 el mayor cucapah earthquake sequence baja california mexico and southernmost california usa active seismotectonics along the mexican pacific margin the el mayor cucapah earthquake sequence started with a few foreshocks in march 2010 and a second sequence of 15 foreshocks of m 2 up to m4 4 that occurred during the 24 h preceding the mainshock the foreshocks occurred along a north south trend near the mainshock epicenter the mw 7 2 mainshock on april 4 exhibited complex faulting possibly starting with a m6 normal faulting event followed 15 s later by the main event which included simultaneous normal and right lateral strike slip faulting the aftershock zone extends for 120 km from the south end of the elsinore fault zone north of the us mexico border almost to the northern tip of the gulf of california the waveform relocated aftershocks form two abutting clusters each about 50 km long as well as a 10 km north south aftershock zone just north of the epicenter of the mainshock even though the baja california data are included the magnitude of completeness and the hypocentral errors increase gradually with distance south of the international border the spatial distribution of large aftershocks is asymmetric with five m5 aftershocks located to the south of the mainshock and only one m5 7 aftershock but numerous smaller aftershocks to the north further the northwest aftershock cluster exhibits complex faulting on both northwest and northeast planes thus the aftershocks also express a complex pattern of stress release along strike the overall rate of decay of the aftershocks is similar to the rate of decay of a generic california aftershock sequence in addition some triggered seismicity was recorded along the elsinore and san jacinto faults to the north but significant northward migration of aftershocks has not occurred the synthesis of the el mayor cucapah sequence reveals transtensional regional tectonics including the westward growth of the mexicali valley and the transfer of pacific north america plate motion from the gulf of california in the south into the southernmost san andreas fault system to the north we propose that the location of the 2010 el mayor cucapah as well as the 1992 landers and 1999 hector mine earthquakes may have been controlled by the bends in the plate boundary

the diversity of large earthquakes and its implications for hazard mitigation with the advent of broadband seismology and gps significant diversity in the source radiation spectra of large earthquakes has been clearly demonstrated this diversity requires different approaches to mitigate hazards in certain tectonic environments seismologists can forecast the future occurrence of large earthquakes within a solid scientific framework using the results from seismology and gps such forecasts are critically important for long term hazard mitigation practices but because stochastic fracture processes are complex the forecasts are inevitably subject to large uncertainty and unexpected events will continue to surprise seismologists recent developments in real time seismology will help seismologists to cope with and prepare for tsunamis and earthquakes combining a better understanding of earthquake diversity with modern technology is the key to effective and comprehensive hazard mitigation practices

hypothetical real time gnss modeling of the 2016 mw 7 8 kaikōura earthquake perspectives from ground motion and tsunami inundation predictionhypothetical real time gnss modeling of the 2016 mw 7 8 kaikōura earthquake

seismogeodesy of the 2014 mw6 1 napa earthquake california rapid response and modeling of fast rupture on a dipping strike slip fault real time high rate geodetic data have been shown to be useful for rapid earthquake response systems during medium to large events the 2014 mw6 1 napa california earthquake is important because it provides an opportunity to study an event at the lower threshold of what can be detected with gps we show the results of gps only earthquake source products such as peak ground displacement magnitude scaling centroid moment tensor cmt solution and static slip inversion we also highlight the retrospective real time combination of gps and strong motion data to produce seismogeodetic waveforms that have higher precision and longer period information than gps only or seismic only measurements of ground motion we show their utility for rapid kinematic slip inversion and conclude that it would have been possible with current real time infrastructure to determine the basic features of the earthquake source we supplement the analysis with strong motion data collected close to the source to obtain an improved postevent image of the source process the model reveals unilateral fast propagation of slip to the north of the hypocenter with a delayed onset of shallow slip the source model suggests that the multiple strands of observed surface rupture are controlled by the shallow soft sediments of napa valley and do not necessarily represent the intersection of the main faulting surface and the free surface we conclude that the main dislocation plane is westward dipping and should intersect the surface to the east either where the easternmost strand of surface rupture is observed or at the location where the west napa fault has been mapped in the past

superficial simplicity of the 2010 el mayor cucapah earthquake of baja california in mexico the geometry of faults is usually thought to be more complicated at the surface than at depth and to control the initiation propagation and arrest of seismic ruptures the fault system that runs from southern california into mexico is a simple strike slip boundary the west side of california and mexico moves northwards with respect to the east however the m w 7 2 2010 el mayor cucapah earthquake on this fault system produced a pattern of seismic waves that indicates a far more complex source than slip on a planar strike slip fault here we use geodetic remote sensing and seismological data to reconstruct the fault geometry and history of slip during this earthquake we find that the earthquake produced a straight 120 km long fault trace that cut through the cucapah mountain range and across the colorado river delta however at depth the fault is made up of two different segments connected by a small extensional fault both segments strike n130 e but dip in opposite directions the earthquake was initiated on the connecting extensional fault and 15 s later ruptured the two main segments with dominantly strike slip motion we show that complexities in the fault geometry at depth explain well the complex pattern of radiated seismic waves we conclude that the location and detailed characteristics of the earthquake could not have been anticipated on the basis of observations of surface geology alone

kinematic earthquake source inversion and tsunami runup prediction with regional geophysical data rapid near source earthquake source modeling relying only on strong motion data is limited by instrumental offsets and magnitude saturation adversely affecting subsequent tsunami prediction seismogeodetic displacement and velocity waveforms estimated from an optimal combination of high rate gps and strong motion data overcome these limitations supplementing land based data with offshore wave measurements by seafloor pressure sensors and gps equipped buoys can further improve the image of the earthquake source and prediction of tsunami extent inundation and runup we present a kinematic source model obtained from a retrospective real time analysis of a heterogeneous data set for the 2011 mw9 0 tohoku oki japan earthquake our model is consistent with conceptual models of subduction zones exhibiting depth dependent behavior that is quantified through frequency domain analysis of slip rate functions the stress drop distribution is found to be significantly more correlated with aftershock locations and mechanism types when off shore data are included the kinematic model parameters are then used as initial conditions in a fully nonlinear tsunami propagation analysis notably we include the horizontal advection of steeply sloping bathymetric features comparison with post event on land survey measurements demonstrates that the tsunami s inundation and runup are predicted with considerable accuracy only limited in scale by the resolution of available topography and bathymetry we conclude that it is possible to produce credible and rapid kinematic source models and tsunami predictions within minutes of earthquake onset time for near source coastal regions most susceptible to loss of life and damage to critical infrastructure regardless of earthquake magnitude

instantaneous geodetic positioning with 10 50 hz gps measurements noise characteristics and implications for monitoring networks 1 recent earthquake recordings from high rate 1 hz continuous gps stations in california indicate that even higher temporal resolution provided by modern gps receivers is desirable we measured seven baselines during time intervals devoid of detectable transient signals at sampling rates of 1 50 hz with geodetic receivers from four manufacturers to investigate the noise characteristics of these data our tests over short distances meters to typical station spacing tens of kilometers of regional gps networks show no loss of spatial resolution compared to 1 hz samples measurement noise is red with the typical ramp profile of log log spectra below about 0 5 hz above this frequency noise is essentially white low pass filtering of high rate positions achieves improved spatial resolution compared to decimated raw samples averaging 20 hz measurements to 2 hz samples on a 40 km baseline for example yields about 0 5 mm horizontal and about 3 4 mm vertical accuracy at high frequencies these estimates are a factor of 2 2 5 better than for 2 hz raw samples the improvements in spatial resolution due to averaging at high frequencies are substantial and approach the theoretical square root of n expectation for independent samples however since noise spectral densities rise rapidly below about 0 5 hz low pass filtering is only effective above this frequency these results have important implications for the design of continuous gps networks for crustal deformation and structural monitoring and for positioning and attitude determination of dynamic platforms

tsunami forecast by joint inversion of real time tsunami waveforms and seismic or gps data application to the tohoku 2011 tsunami correctly characterizing tsunami source generation is the most critical component of modern tsunami forecasting although difficult to quantify directly a tsunami source can be modeled via different methods using a variety of measurements from deep ocean tsunameters seismometers gps and other advanced instruments some of which in or near real time here we assess the performance of different source models for the destructive 11 march 2011 japan tsunami using model data comparison for the generation propagation and inundation in the near field of japan this comparative study of tsunami source models addresses the advantages and limitations of different real time measurements with potential use in early tsunami warning in the near and far field the study highlights the critical role of deep ocean tsunami measurements and rapid validation of the approximate tsunami source for high quality forecasting we show that these tsunami measurements are compatible with other real time geodetic data and may provide more insightful understanding of tsunami generation from earthquakes as well as from nonseismic processes such as submarine landslide failures

high rate real time gps network at parkfield utility for detecting fault slip and seismic displacements 1 a network of 13 continuous gps stations near parkfield california has been converted from 30 second to 1 second sampling with positions of the stations estimated in real time relative to a master station most stations are near the trace of the san andreas fault which exhibits creep the noise spectra of the instantaneous 1 hz positions show flicker noise at high frequencies and change to frequency independence at low frequencies the change in character occurs between 6 to 8 hours our analysis indicates that 1 second sampled gps can estimate horizontal displacements of order 6 mm at the 99 confidence level from a few seconds to a few hours high frequency gps can augment existing measurements in capturing large creep events and postseismic slip that would exceed the range of existing creepmeters and can detect large seismic displacements

earthquake early warning shakealert in the pacific northwest we evaluate the performance of earthquake early warning algorithm elarms 2 earthquake alarm system v 2 in the pacific northwest real time and prerecorded seismic data from oregon california and washington in the united states and british columbia in canada are used the earthquakes tested range up to moment magnitude 7 2 the limit for which the elarms 2 magnitude method is accurate elarms 2 reliably detects catalog magnitude 3 and larger earthquakes within the network but the cut off magnitude for accurate event recognition is higher for events offshore and on the edges of the network we have made several adjustments that make the elarms 2 algorithm less likely to falsely report multiple alerts for earthquakes replaying of past earthquakes shows that the new settings improve the algorithm s behavior for edge cases while not degrading previously well constrained solutions within the dense part of the network we expect few false alerts none that would predict significant shaking anywhere in our region even though elarms 2 assumes a fixed earthquake depth the epicenter and magnitude estimates are accurate enough to provide good predictions of shaking intensities online material tables listing parameters of 31 calibration earthquakes elarms 2 real time detections and comparison of elarms 2 performance for calibration events before and after adjusting configuration

a rapid estimation of near field tsunami runup many efforts have been made to quickly estimate the maximum runup height of tsunamis associated with large earthquakes this is a difficult task because of the time it takes to construct an accurate tsunami model using real time data from the source it is possible to construct a database of potential seismic sources and their corresponding tsunami a priori however such models are generally based on uniform slip distributions and thus oversimplify the knowledge of the earthquake source here we show how to predict tsunami runup from any seismic source model using an analytic solution that is specifically designed for subduction zones with a well defined geometry i e chile japan nicaragua and alaska the main idea of this work is to provide a tool for emergency response trading off accuracy for speed the solutions we present for large earthquakes appear promising here runup models are computed for the following the 1992 mw 7 7 nicaragua earthquake the 2001 mw 8 4 peru earthquake the 2003 mw 8 3 hokkaido earthquake the 2007 mw 8 1 peru earthquake the 2010 mw 8 8 maule earthquake the 2011 mw 9 0 tohoku earthquake and the recent 2014 mw 8 2 iquique earthquake the maximum runup estimations are consistent with measurements made inland after each event with a peak of 9 m for nicaragua 8 m for peru 2001 32 m for maule 41 m for tohoku and 4 1 m for iquique considering recent advances made in the analysis of real time gps data and the ability to rapidly resolve the finiteness of a large earthquake close to existing gps networks it will be possible in the near future to perform these calculations within the first minutes after the occurrence of similar events thus such calculations will provide faster runup information than is available from existing uniform slip seismic source databases or past events of premodeled seismic sources

comparing source inversion techniques for gps based local tsunami forecasting a case study for the april 2014 m8 1 iquique chile earthquake

real time centroid moment tensor determination for large earthquakes from local and regional displacement records summary we present an algorithm to rapidly determine the moment tensor and centroid location for large earthquakes employing local and regional real time high rate displacement records from gps the algorithm extracts the coseismic offset from the displacement waveforms and uses the information to invert for the moment tensor the green s functions for a layered earth are obtained numerically from open source code edgrn to determine the centroid multiple inversions are simultaneously performed within a grid of inversion nodes and the node with the smallest misfit is then assigned the centroid location we show results for two large earthquakes replayed in simulated real time mode using recorded 1 hz gps displacements the 2003 mw 8 3 tokachi oki and the 2010 mw 7 2 el mayor cucapah earthquakes we demonstrate that it is feasible to obtain accurate cmt solutions within the first 2 3 min after rupture initiation without any prior assumptions on fault characteristics demonstrating an order of magnitude improvement in latency compared to existing seismic methods for the two earthquakes studied this methodology is useful for rapid earthquake response tsunami prediction and as a starting point for rapid finite fault modelling

earthquake magnitude scaling using seismogeodetic data 1 the combination of gps and strong motion data to estimate seismogeodetic waveforms creates a data set that is sensitive to the entire spectrum of ground displacement and the full extent of coseismic slip in this study we derive earthquake magnitude scaling relationships using seismogeodetic observations of either p wave amplitude or peak ground displacements from five earthquakes in japan and california ranging in magnitude from 5 3 to 9 0 the addition of the low frequency component allows rapid distinction of earthquake size for large magnitude events with high precision unlike accelerometer data that saturate for earthquakes greater than m 7 to 8 and is available well before the coseismic displacements are emplaced these results though based on a limited seismogeodetic data set support earlier studies that propose it may be possible to estimate the final magnitude of an earthquake well before the rupture is complete

estimated seismic source parameters for 2019 magnitude 7 6 papua new guinea earthquake on 14 may 2019 a major mw 7 6 earthquake struck eastern papua new guinea causing a tsunami warning that was later canceled the last major rupture in the region was a 2000 mw 8 0 event which resulted in massive horizontal land movements of up to several meters and a series of aftershocks with primarily thrust mechanisms and caused a damaging tsunami seismic methods for characterizing the source process were applied vertical components of the long period p waves from 35 stations of the global seismic network with even azimuthal coverage were adopted in the inversions first the focal mechanism solution was retrieved after the earthquake from the inverted results as well as aftershock distribution the causative fault of the great png earthquake was confirmed to be a fault of strike 316 dip 84 and rake 0 indicating that the earthquake was a left lateral strike slip event then to clearly understand the spatiotemporal evolutionary process of the source rupture of the earthquake far field body wave data were collected and the source rupture process of this earthquake was studied using the finite fault inversion method a finite fault model was estabished with length and width of 152 and 32 km respectively and we set the initial seismic source parameters referring to the center of the focal mechanism solution this was estimated by the focal mechanism solutions of defferent studies referring to different focal mechanism solutions we found that the focal mechanism solution determined by global centroid moment tensor catalog was not appropriate inversion results indicated that the seismic moment was 3 63 1020 nm mw 7 6 and the source duration was 40 s the rupture propagated mainly toward the northwest in an asymmetrical bilateral mode with a maximum slip of 13 2 m and a large scale slip patch strongly ruptured to the surface the study of coulomb stress changes suggested that the png earthquake may trigger a thrust type rupture in the new britain trench which has the potential to trigger a tsunami

developing framework to constrain the geometry of the seismic rupture plane on subduction interfaces a priori a probabilistic approach summary a key step in many earthquake source inversions requires knowledge of the geometry of the fault surface on which the earthquake occurred our knowledge of this surface is often uncertain however and as a result fault geometry misinterpretation can map into significant error in the final temporal and spatial slip patterns of these inversions relying solely on an initial hypocentre and cmt mechanism can be problematic when establishing rupture characteristics needed for rapid tsunami and ground shaking estimates here we attempt to improve the quality of fast finite fault inversion results by combining several independent and complementary data sets to more accurately constrain the geometry of the seismic rupture plane of subducting slabs unlike previous analyses aimed at defining the general form of the plate interface we require mechanisms and locations of the seismicity considered in our inversions to be consistent with their occurrence on the plate interface by limiting events to those with well constrained depths and with cmt solutions indicative of shallow dip thrust faulting we construct probability density functions about each location based on formal assumptions of their depth uncertainty and use these constraints to solve for the most likely fault plane examples are shown for the trench in the source region of the mw 8 6 southern sumatra earthquake of march 2005 and for the northern chile trench in the source region of the november 2007 antofagasta earthquake we also show examples using only the historic catalogues in regions without recent great earthquakes such as the japan and kamchatka trenches in most cases this method produces a fault plane that is more consistent with all of the data available than is the plane implied by the initial hypocentre and cmt mechanism using the aggregated data sets we have developed an algorithm to rapidly determine more accurate initial fault plane geometries for source inversions of future earthquakes

geological carbon storage storage of the carbon dioxide that is produced by burning fossil fuels is one way to avoid the damaging consequences of climate change a range of observations suggests that geological carbon storage is much less risky than unabated carbon emissions to the atmosphere

the effect of vertically varying permeability on tracer dispersion we study the migration of a tracer within an injection driven flow in a horizontal aquifer in which the permeability varies with depth the permeability gradient produces a shear and this leads to lateral dispersion of the tracer in the high permeability regions the tracer moves substantially faster than the mean flow and eventually enters the nose region of the flow where the depth of the current is less than the depth of the aquifer depending on the influence of i the viscosity contrast between the injected fluid and the original fluid and ii the vertical permeability gradient the nose of the current may be of fixed shape or may gradually lengthen with time this leads to a variety of patterns of dispersal of the tracer which may either remain in the nose or cycle through the nose and be left behind our results illustrate the complexity of the migration of a tracer in a heterogeneous aquifer which has important implications for interpreting the results of tracer tests as may be proposed for monitoring text co 2 or gas injected into subsurface reservoirs

long period long duration seismic events during hydraulic fracture stimulation of a shale gas reservoir we report here a series of long period and long duration lpld seismic events observed during hydraulic fracturing in a shale gas reservoir these unusual events 10 100 s in duration are observed most clearly in the frequency band of 10 80 hz and are remarkably similar in appearance to tectonic tremor sequences first observed in subduction zones these complex but coherent wave trains have finite moveouts obtained from cross correlation the moveout direction of the events confirms that they originate in the reservoir from the area where the fracturing is going on clear p and s wave arrivals cannot be resolved within the lpld episodes but in some cases small micro earthquakes occur in the sequences whether these micro earthquakes are causal or coincidental is not known it has also been observed that in three contiguous frac stages all lpld events appear to come from two distinct places along one of two hypothetical fracture planes interestingly the stages which have the largest number of lpld

advancing techniques to constrain the geometry of the seismic rupture plane on subduction interfaces a priori higher order functional fits 1 ongoing developments in earthquake source inversions incorporate nonplanar fault geometries as inputs to the inversion process improving previous approaches that relied solely on planar fault surfaces this evolution motivates advancing the existing framework for constraining fault geometry particularly in subduction zones where plate boundary surfaces that host highly hazardous earthquakes are clearly nonplanar here we improve upon the existing framework for the constraint of the seismic rupture plane of subduction interfaces by incorporating active seismic and seafloor sediment thickness data with existing independent data sets and inverting for the most probable nonplanar subduction geometry constraining the rupture interface a priori with independent geological and seismological information reduces the uncertainty in the derived earthquake source inversion parameters over models that rely on simpler assumptions such as the moment tensor inferred fault plane examples are shown for a number of wellconstrained global locations we expand the coverage of previous analyses to a more uniform global data set and show that even in areas of sparse data this approach is able to accurately constrain the approximate subduction geometry particularly when aided with the addition of data from local active seismic surveys in addition we show an example of the integration of many two dimensional profiles into a threedimensional surface for the sunda subduction zone and introduce the development of a new global threedimensional subduction interface model slab1 0 components 8122 words 8 figures 1 table

regard a new gnss based real time finite fault modeling system for geonet the short period seismometer based magnitude saturation problem especially for events with magnitude 8 can be improved by a real time global navigation satellite system gnss positioning technique which has enabled rapid estimation of a finite fault model for a large earthquake without any saturation a new real time fault modeling system based on the gnss earth observation network geonet is developed and is under experimental operation in japan in this paper we present the newly developed system regard the real time geonet analysis system for rapid deformation monitoring which consists of real time gnss positioning automatic detection of coseismic displacement by the event and quasi real time finite fault model inversion routines the performance of the automatic event detection system is tested through experimental real time operation based on geonet data for two months furthermore we also test the reliability of the finite fault model inversion routines using real raw gnss data observed for past large earthquakes the 2003 tokachi oki earthquake moment magnitude mw 8 3 the 2011 tohoku earthquake mw 9 0 and the 2011 off ibaraki earthquake mw 7 7 a simulated 1707 hoei type nankai trough earthquake mw 8 7 is also tested the real time experimental operation shows that real time gnss positioning is precise enough to detect all the tested earthquakes and the inversion results demonstrate that the regard can reliably estimate the earthquake size and its extent within 3 min after the origin time these results suggest that the regard system will complement the seismometer based magnitude determination system

real time gnss seismology using a single receiver summary high rate gnss has attracted increasing attention and numerous applications in geohazard monitoring and early warning in this paper we investigate three current existing singlereceiver approaches for real time gnss seismology comparing their observation models for equivalence andassessingtheimpactofmainerrorcomponents weproposesomerefinements to the variometric approach and especially consider compensating the geometry error component by using the accurate initial coordinates before the earthquake to eliminate the drift trend in the integrated coseismic displacements after careful corrections of satellite ephemeris ionospheric delay tropospheric delay and geometry errors the refined variometric approach andthetemporalpointpositioning tpp methodhaveequivalentmathematicalmodelwiththe converged precise point positioning ppp we evaluated the precision of the variometric and tpp approaches with various error correction schemes and duration time using numerous data sets and demonstrated that few centimetres accuracy of coseismic displacements is achievable even for 20 min interval we applied these single receiver approaches to process 1 hz gps data collected from the tohoku oki earthquake mw 9 0 2011 march 11 in japan to capture coseismic displacement and further inverted the obtained displacement fields for fault slip distribution and moment magnitude comparisons of the results obtained using the refined variometric approach and tpp as well as the converged ppp displayed very good consistence both in coseismic displacements within few centimetres and in the slip distribution patterns and moment magnitudes

application of real time gps to earthquake early warning in subduction and strike slip environments 1 we explore the application of gps data to earthquake early warning and investigate whether the coseismic ground deformation can be used to provide fast and reliable magnitude estimations and ground shaking predictions we use an algorithm to extract the permanent static offset fromgps displacement time series and invert for theslip distribution on the fault plane which is discretized into a small number of rectangular patches we developed a completely self adapting strategy in which the initial fault plane model is built based on a quick approximate magnitude estimation and is then allowed to increase in size based on the evolutionary magnitude estimation resulting from the slip inversion two main early warning outputs are delivered in real time magnitude and the along strike extent of the rupture area these are finally used to predict the expected ground shaking due to the finite source we tested the proposed strategy by simulating real time environments for three earthquakes for themw9 0 2011 tohoku oki earthquake our algorithm provides the first magnitude estimate of 8 2 at 39 s after the origin time and then gradually increases to 8 9 at 120 s the estimated rupture length remains constant from the outset at 360 km for the mw 8 3 2003 tokachi oki earthquake the initial magnitude estimate is 8 5 at 24 s and drops to 8 2 at 40 s with a rupture length of 290 km finally for the mw 7 2 2010 el mayor cucapah earthquake the magnitude estimate is 7 0 from the outset with a rupture length of 140 km the accuracy of the ground shaking prediction using the gps based magnitude and finite extent is significantly better than existing seismology based point source approaches this approach would also facilitate more rapid tsunami warnings

simple and reliable finite fault solutions for large earthquakes using the w phase the maule m w 8 8 and tohoku m w 9 0 earthquakes 1 we explore the ability of w phase waveform inversions to recover a first order coseismic slip distribution for large earthquakes to date w phase inversions for point sources provide fast and accurate moment tensor solutions for moderate to large events we have applied w phase finite fault inversion to seismic waveforms recorded following the 2010 maule earthquake mw 8 8 and the 2011 tohoku earthquake mw 9 0 firstly a w phase point source inversion was performed to assist us in selecting the data for the finite fault solution then we use a simple linear multiple time window method accounting for changes in the rupture velocity with smoothing and moment minimization constraints to infer slip and rake variations over the fault our results describe well the main features of the slip pattern previously found for both events this suggests that fast slip inversions may be carried out relying purely on w phase records

real time inversion of gps data for finite fault modeling and rapid hazard assessment 1 responses to recent great earthquakes and ensuing tsunamis in sumatra chile and japan with the resulting loss of life and damage to infrastructure demonstrate that our ability to ascertain the full extent of slip of catastrophic earthquakes and their tsunamigenic potential in the first minutes after the initiation of rupture is problematic regional gps networks such as those in western north america and japan are complementary to seismic networks by being able to directly measure displacements close to the source during large earthquakes in real time we report on rapid modeling of two large earthquakes the 2003 mw 8 3 tokachi oki earthquake 100 km offshore hokkaido island using 356 geonet stations and the 2010 mw 7 2 el mayor cucapah earthquake in northern baja california using 95 crtn stations in southern california about 75 km northwest of the epicenter working in a simulated real time mode we invert for finite fault slip in a homogeneous elastic half space using green s functions obtained from okada s formulation we compare two approaches the first starts with a catalog of pre defined faults while the second uses a rapid centroid moment tensor solution to provide an initial estimate of the ruptured fault plane in either case we are able to characterize both earthquakes in less than two minutes reducing the time necessary to obtain finite fault slip and moment magnitude for medium and greater earthquakes compared to traditional methods by an order of magnitude

rapid modeling of the 2011 mw 9 0 tohoku oki earthquake with seismogeodesy 1 rapid characterization of finite fault geometry and slip for large earthquakes is important for mitigation of seismic and tsunamigenic hazards saturation of near source weak motion and problematic integration of strong motion data into displacements make this difficult in real time combining gps and accelerometer data to estimate seismogeodetic displacement waveforms overcomes these limitations by providing mm level three dimensional accuracy and improved estimation of coseismic deformation compared to gps only methods we leverage collocated gps and accelerometer data from the 2011 mw 9 0 tohoku oki japan earthquake by replaying them in simulated real time mode using a novel approach to account for fault finiteness we generate an accurate centroid moment tensor solution independently of any constraint on the slab geometry followed by a finite fault slip model the replay of gps and seismic data demonstrates that robust models could have been made available within 3 min of earthquake initiation

time lapse imaging of coseismic ruptures for the 2019 ridgecrest earthquakes using multiazimuth backprojection with regional seismic data and a 3 d crustal velocity model

high rate coseismic displacements from tightly integrated processing of raw gps and accelerometer data high rate gps and seismic sensors are mutually contributing to seismological applications for capturing earthquake induced coseismic displacements in this study we propose an approach for tightly integrating gps and strong motion data on raw observation level to increase the quality of the derived displacements the performance of the proposed approach is demonstrated using 5 hz high rate gps and 200 hz strong motion data collected during the el mayor cucapah earthquake m w 7 2 2010 april 4 in baja california mexico the new approach not only takes advantages of both gps and strong motion sensors but also improves the reliability of the displacement by enhancing gps integer cycle phase ambiguity resolution which is very critical for deriving displacements with highest quality

instantaneous geodetic positioning at medium distances with the global positioning system we evaluate a new method of global positioning system gps data analysis called instantaneous positioning at spatial scale lengths typical of interstation spacings in a modern crustal motion network this method is more precise and versatile than traditional gps static and kinematic processing of multi epoch batches of data the key to instantaneous positioning is the ability to resolve integer cycle phase ambiguities with only a single epoch of dual frequency phase and pseudorange data rendering receiver cycle slips irrelevant we estimate three dimensional relative coordinates and atmospheric zenith delay parameters independently every 30 s over a 12 week period for baseline distances of 50 m 14 km and 37 km horizontal precision of a single epoch coordinate solution is about 15 mm and vertical precision is about 7 8 times worse removing that component of each time series which repeats with a period of exactly 1 sidereal day and thus manifests signal multipath reduces the scatter by about 50 in all components solution averaging of the high frequency time series can be performed using any number of measurement epochs to further improve coordinate precision we demonstrate that the daily coordinates estimated with instantaneous positioning are more precise by 20 50 per coordinate component than those estimated with 24 hour batch processing spectral analysis of the single epoch solutions indicates that the flicker noise characteristic of gps time series observed in lower frequency bands also affects gps solutions in the frequency band 0 01 mhz to 10 mhz we argue that the flicker noise is induced by tropospheric effects since modern gps receivers are capable of observing at frequencies as high as 10 hz our technique significantly overlaps and complements the frequency band of broadband seismology and benefits other research areas such as earthquake geodesy volcanology and gps meteorology

impact of 3 d earth structure on w phase cmt parameters we investigate the impact of un modeled 3d structural heterogeneity on inverted w phasesource parameters we generate a large dataset of synthetic seismograms accounting for theearths 3d structure for 250 earthquakes globally distributed the w phase algorithm is thenused to invert for earthquake cmt parameters assuming a spherical earth model the im pact of lateral heterogeneity is assessed by comparing inverted source parameters with thoseused to compute the 3d synthetics results show that the 3d structure mainly affects centroidlocation while the effect on the other source parameters remains small centroid mislocationspresent clear geographical patterns in particular w phase solutions for earthquakes in southamerica are on average biased 17 km to the east of the actual centroid locations this ef fect is significantly reduced using an azimuthally well balanced distribution of seismologicalstations source parameters are generally more impacted by mantle heterogeneity while thescalar moment of shallow earthquakes seems to be mainly impacted by the crustal structure shallow earthquakes present a variability ofmr andmr moment tensor elements result ing both from the small amplitude and a larger uncertainty of the associated green s functions

earthquake source parameters from gps measured static displacements with potential for real time application 1 we describe a method for determining an optimal centroid moment tensor solution of an earthquake from a set of static displacements measured using a network of global positioning system receivers using static displacements observed after the 4 april 2010 mw 7 2 el mayor cucapah mexico earthquake we perform an iterative inversion to obtain the source mechanism and location which minimize the least squares difference between data and synthetics the efficiency of our algorithm for forward modeling static displacements in a layered elastic medium allows the inversion to be performed in real time on a single processor without the need for precomputed libraries of excitation kernels we present simulated real time results for the el mayorcucapah earthquake the only a priori information that our inversion scheme needs is a crustal model and approximate source location so the method proposed here may represent an improvement on existing early warning approaches that rely on foreknowledge of fault locations and geometries citation o toole t b a p valentine and j h woodhouse 2013 earthquake source parameters from gpsmeasured static displacements with potential for real time application geophys res lett 40 6 0 65 doi 10 1029 2012gl054209

buoyancy driven flow in a confined aquifer with a vertical gradient of permeability we examine the injection of fluid of one viscosity and density into a horizontal permeable aquifer initially saturated with a second fluid of different viscosity and density the novel feature of the analysis is that we allow the permeability to vary vertically across the aquifer this leads to recognition that the interface may evolve as either a rarefaction wave that spreads at a rate proportional to t a shock like front of fixed length or a mixture of shock like regions and rarefaction wave type regions the classical solutions in which there is no viscosity ratio between the fluids and in which the formation has constant permeability lead to an interface that spreads laterally at a rate proportional to t 1 2 however these solutions are unstable to cross layer variations in the permeability owing to the vertical shear which develops in the flow causing the structure of the interface to evolve to the rarefaction wave or shock like structure in the case that the viscosities of the two fluids are different it is possible that the solution involves a mixture of shock like and rarefaction type structures as a function of the distance above the lower boundary using the theory of characteristics we develop a regime diagram to delineate the different situations we consider the implications of such heterogeneity for the prediction of front locations during text co 2 sequestration if we neglect the permeability fluctuations the model always predicts rarefaction type solutions while even modest changes in the permeability across a layer can introduce shocks this difference may be very significant since it leads to the text co 2 plume occupying a greater fraction of the pore space between the injector and the leading edge of the text co 2 front in a layer of the same mean permeability this has important implications for estimates of the fraction of the pore space that the text co 2 may access

large scale natural gradient tracer test in sand and gravel cape cod massachusetts 3 hydraulic conductivity variability and calculated macrodispersivities hydraulic conductivity k variability in a sand and gravel aquifer on cape cod massachusetts was measured and subsequently used in stochastic transport theories to estimate macrodispersivities nearly 1500 k measurements were obtained by borehole flowmeter tests and permeameter analyses of cores the geometric mean for the flowmeter tests 0 11 cm s is similar to that estimated from other field tests the mean for the permeameter tests 0 035 cm s is significantly lower possibly because of compaction of the cores the variance for the flowmeter 0 24 is also greater than that for the permeameter 0 14 geostatistical analyses applying negative exponential models with and without nuggets reveal similar spatial correlation structures for the two data sets estimated correlation scales range from 2 9 to 8 m in the horizontal and from 0 18 to 0 38 m in the vertical estimates of asymptotic longitudinal dispersivity b 35 0 78 m are similar in magnitude to that observed in the natural gradient tracer test 0 96 m previously conducted at this site

fractured shale gas systems the first commercial united states natural gas production 1821 came from an organic rich devonian shale in the appalachian basin understanding the geological and geochemical nature of organic shale formations and improving their gas producibility have subsequently been the challenge of millions of dollars worth of research since the 1970s shale gas systems essentially are continuous type biogenic predominant thermogenic or combined biogenic thermogenic gas accumulations characterized by widespread gas saturation subtle trapping mechanisms seals of variable lithology and relatively short hydrocarbon migration distances shale gas may be stored as free gas in natural fractures and intergranular porosity as gas sorbed onto kerogen and clay particle surfaces or as gas dissolved in kerogen and bitumen five united states shale formations that presently produce gas commercially exhibit an unexpectedly wide variation in the values of five key parameters thermal maturity expressed as vitrinite reflectance sorbed gas fraction reservoir thickness total organic carbon content and volume of gas in place the degree of natural fracture development in an otherwise low matrix permeability shale reservoir is a controlling factor in gas producibility to date unstimulated commercial production has been achievable in only a small proportion of shale wells those that intercept natural fracture networks in most other cases a successful shale gas well requires hydraulic stimulation together the devonian antrim shale of the michigan basin and devonian ohio shale of the appalachian basin accounted for about 84 of the total 380 bcf of shale gas produced in 1999 however annual gas production is steadily increasing from three other major organic shale formations that subsequently have been explored and developed the devonian new albany shale in the illinois basin the mississippian barnett shale in the fort worth basin and the cretaceous lewis shale in the san juan basin in the basins for which estimates have been made shale gas resources are substantial with in place volumes of 497 783 tcf the estimated technically recoverable resource exclusive of the lewis shale ranges from 31 to 76 tcf in both cases the ohio shale accounts for the largest share

petroleum reservoir characterization using downhole microseismic monitoring imaging of microseismic data is the process by which we use information about the source locations timing and mechanisms of the induced seismic events to make inferences about the structure of a petroleum reservoir or the changes that accompany injections into or production from the reservoir a few key projects were instrumental in the development of downhole microseismic imaging most recent microseismic projects involve imaging hydraulic fracture stimulations which has grown into a widespread fracture diagnostic technology this growth in the application of the technology is attributed to the success of imaging the fracture complexity of the barnett shale in the fort worth basin texas and the commercial value of the information obtained to improvecompletions and ultimately production in the field the use of commercial imaging in the barnett is traced back to earlier investigations to prove the technology with the cotton valley imaging project and earlier experiments at the m site in the piceance

rapid determination of earthquake magnitude using gps for tsunami warning systems 1 the 26 december 2004 sumatra earthquake mw 9 2 9 3 generated the most deadly tsunami in history yet within the first hour the true danger of a major oceanwide tsunami was not indicated by seismic magnitude estimates which were far too low mw 8 0 8 5 this problem relates to the inherent saturation of early seismic wave methods here we show that the earthquake s true size and tsunami potential can be determined using global positioning system gps data up to only 15 min after earthquake initiation by tracking the mean displacement of the earth s surface associated with the arrival of seismic waves within minutes displacements of 10 mm are detectable as far away as india consistent with results using weeks of data after the event these displacements imply mw 9 0 0 1 indicating a high tsunami potential this suggests existing gps infrastructure could be developed into an effective component of tsunami warning systems

real time high rate co seismic displacement from ambiguity fixed precise point positioning application to earthquake early warning 1 nowadays more and more high rate real time gps data become available that provide a great opportunity to contribute to earthquake early warning eew system in terms of capturing regional surface displacements as an independent information source useful for promptly estimating the magnitude of large destructive earthquake in our study we demonstrate the performance of the real time ambiguity fixed precise point positioning ppp approach using 5 hz gps data collected during el mayor cucapah earthquake mw 7 2 4 april 2010 the ppp based displacements show to agree with accelerometer based displacement at centimeter level the key for successfully obtaining high precision displacements is the efficient ambiguity resolution ppp with ambiguity fixing can result in correct permanent co seismic offsets and correct recovery of moment magnitude and fault slip inversion at levels comparable to post processing

an analysis of ground shaking and transmission loss from infrasound generated by the 2011 tohoku earthquake 1 the 2011 mw9 0 tohoku earthquake generated infrasound that was recorded by nine infrasonic arrays most arrays recorded a back azimuth variation with time due to the expanse of the source region we use ray tracing to predict group velocities and back azimuth wind corrections a japan accelerometer network recorded ground shaking in unprecedented spatial resolution we back projected infrasound from arrays is44 kamchatka and is30 tokyo to the source region and compare these results with acceleration data is44 illuminates the complex geometry of land areas that experienced shaking is30 illuminates two volcanoes and a flat area around the city of sendai where the maximum accelerations occurred the arrays and epicentral region define three source receiver profiles the observed broadband energy transmission loss tl follows an exponential decay law the best fitting model which has parameters that are interpreted to include the effects of geometric spreading scattering and the maximum ratio of the effective sound speed in the stratosphere to that at the ground accounts for stratospheric wind speed yields a 65 variance reduction relative to predictions from a traditional tl relationship this model is a simplified version of the model of le pichon et al 2012 which yields an 83 variance reduction for a single frequency implying that fine scale atmospheric structure is required to explain the tl for stratospheric upwind propagation our results show that infrasonic arrays are sensitive to ground acceleration in the source region of megathrust earthquakes the tl results may improve infrasonic amplitude scaling laws for explosive yield

predicting and monitoring long term compaction in unconsolidated reservoir sands using a dual power law model we propose a model for predicting the long term creep compaction of unconsolidated sand reservoirs prior to significant depletion the model is based upon linear viscoelasticity theory whereby deformation is decoupled into instantaneous and time dependent components the instantaneous component of deformation is modeled using a power law function of effective pressure model parameters are solved by conducting a constant strain rate laboratory experiment the time dependent deformation is modeled using a power law function of time associated model parameters are solved by conducting a creep strain test at the anticipated in situ effective pressure in total application of the model involves measurement of three model parameters obtained by conducting two different laboratory experiments we illustrate the model utilizing samples from unconsolidated sand reservoirs in the wilmington field in california and an offshore field in the gulf of mexico we show that the stiffness change associated with the porosity reduction predicted by the model is large and could be monitored using p wave velocity this should make compaction observable with 4d seismic surveys of the example fields