quasi real time fault model estimation for near field tsunami forecasting based on rtk gps analysis application to the 2011 tohoku oki earthquake mw 9 0 1 real time crustal deformation monitoring is extremely important for achieving rapid understanding of actual earthquake scales because the measured permanent displacement directly gives the true earthquake size seismic moment mw information which in turn provides tsunami forecasting we have developed an algorithm to detect estimate static ground displacements due to earthquake faulting from real time kinematic gps rtk gps time series the new algorithm identifies permanent displacements by monitoring the difference of a short term average sta to a long term average lta of the gps time series we assessed the noise property and precision of the rtk gps time series with various baseline length conditions and orbits and discerned that the real time ephemerides based on the international gnss service igs are sufficient for crustal deformation monitoring with long baselines up to 1 000 km we applied the algorithm to data obtained in the 2011 off the pacific coast of tohoku earthquake mw 9 0 to test the possibility of coseismic displacement detections and further we inverted the obtained displacement fields for a fault model the inversion estimated a fault model with mw 8 7 which is close to the actual mw of 9 0 within five minutes from the origin time once the fault model is estimated tsunami waveforms can be immediately synthesized using pre computed tsunami green s functions the calculated waveforms showed good agreement with the actual tsunami observations both in arrival times and wave heights suggesting that the rtk gps data by our algorithm can provide reliable rapid tsunami forecasting that can complement existing tsunami forecasting systems based on seismic observations

the exhaust valve of the north atlantic during glacial periods climate records are marked by large amplitude oscillations believed to be a result of north atlantic na freshwater anomalies which weakened the thermohaline circulation thc and introduced instabilities such oscillations are absent from the present interglacial period with the aid of a semiglobal analytical model it is proposed that the bering strait bs acts like an exhaust valve for the above na freshwater anomalies specifically it is suggested that large instabilities in the thc are only possible during glacial periods because during these periods the bs is closed during interglacial periods when the bs the exhaust valve is open low salinity anomalies are quickly flushed out of the north atlantic by the strong southern ocean winds

real time evolutionary earthquake location for seismic early warning an effective early warning system must provide probabilistic estimates of the location and size of a potentially destructive earthquake within a few seconds after the event is first detected in this work we present an evolutionary real time location technique based on an equal differential time edt formulation and a probabilistic approach for describing the hypocenter estimation the algorithm at each timestep relies on the information from triggered arrivals and not yet triggered stations with just one recorded arrival the hypocentral location is constrained by the voronoi cell around the first triggering station constructed using the travel times to the not yet triggered stations with two or more triggered arrivals the location is constrained by the intersection of the volume defined by the voronoi cells for the remaining not yet triggered stations and the edt surfaces between all pairs of triggered arrivals as time passes and more triggers be come available the evolutionary location converges to a standard edt location synthetic tests performed using the geometry of the irpinia seismic network southern italy isnet and the simulation of an evolutionary location for the 2000 mw 6 6 western tottori japan earthquake indicate that when a dense seismic net work is available reliable location estimates suitable for early warning applications can be achieved after 1 3 sec from the first event detection a further simulation with an mw 6 7 southern greece earthquake shows that at a regional scale the real time location can provide useful constraints on the earthquake position several seconds before a non real time algorithm finally we show that the robustness of the algorithm in the presence of outliers can be effectively used to associate phase arrivals coming from events occurring close in time and we present a preliminary algorithm for event detection

using centroid time delays to characterize source durations and identify earthquakes with unique characteristics the relationship between m 0 and the rupture duration is often difficult to establish this is particularly true for large earthquakes for which the moment rate functions mrf generally have complicated shapes and the estimated durations can vary considerably depending on the methodology used to evaluate the mrf in this work we show that the centroid time delay c provides an alternative estimate of the source duration inverted mrfs often end gradually making the end of coseismic rupture difficult to detect in such cases when the rupture duration is not well defined the time delay c is a useful quantity to represent the first order temporal characteristics of the rupture process variations in stress parameter can be investigated by assuming a standard scaling relationship between the seismic moment m0m0 and c this simple scaling relationship can also be used to identify unusual earthquakes with unique source properties such as events involving complicated rupture processes or earthquakes characterized by unusual rupture velocities stress drops or aspect ratios

reply to comment by p rydelek et al on earthquake magnitude estimation from peak amplitudes of very early seismic signals on strong motion records 1 based on the analysis of mediterranean near source strong motion records zollo et al 2006 hereinafter referred to as zln showed that peak displacement amplitudes of initial pand s wave seismic signals scales with the earthquake size in the moment magnitude range 4 6 1 9 in figure 1 we report data distribution vs magnitude and hypocentral distance note that the distance distribution of analyzed events for japan figure 1 is clearly different from that for the mediterranean med earthquakes given by zln whereas most of med records occur at an hd 40 km 10 at odds with rwh we did not apply any cut off at m 5 5 on hypocentral distance for small and moderate events indeed this may introduce a bias on the estimation of attenuation law parameters retrieved from both small and large earthquakes records we follow the zln procedure involving among others sensitivity correction p and s phase identification double integration filtering in a frequency band 0 075 3 hz peaks are read on the modulus of displacement expressed in meters starting from the pwave and s wave picked arrivals we measure peaks within a 2 second window for the p arrival we also test the method with 4 second windows 11 the distance attenuation effect is corrected for by assuming a simple log linear model wu and zhao 2006 zln the amplitudes are normalized to a reference distance of 10 km i e the same as for zln in the mediterranean study to facilitate comparison though rwh show data normalized at a distance of 20 km zln figures 2a and 2b the use of a different normalization distance does not change the slope of the log peak vs magnitude relationships and thus does not alter the graphical interpretation 12 in figure 2 we show the relation between the logarithm of distance normalized peak displacement for p and s waves in different time windows vs final magnitude of the events following zln statistical significance was geophysical research letters vol 34 l20303 doi 10 1029 2007gl030560 2007 click here for full article

peak ground velocity shakemaps derived from geodetic slip models summary we develop a methodology to derive fast and reliable peak ground velocity pgv shakemaps from kinematic finite source models of earthquake rupture inferred from geodetic static displacements the temporal variations in slip on the fault are based on the simple assumption that larger slip takes longer time to accumulate assuming constant rupture and slip velocities slip is distributed in time to produce a variable rise time model sensitivity tests on finite source models of the 1994 mw 6 7 northridge california earthquake show that distribution of peak ground velocities derived using 3 0 km s 1 rupture velocity and 76 8 cm s 1 slip velocity matches to a large extent observed pgv suggesting that rapid assessment of strong ground motions derived from geodetic data can aid emergency response particularly in areas with sparse seismic station coverage

real time moment magnitude and stress drop with implications for real time shaking prediction abstract despite the potentially dramatic effect of the stress drop on ground motion intensity currently available earthquake early warning systems that deliver peak ground motion predictions do not account for the effect of this parameter to address this issue a new evolutionary algorithm for determining stress drop and moment magnitude in real time is described it consists of two distinct modules one processes data recorded by individual stations and another computes event average stress drops and moment magnitudes to speed up the analysis the real time algorithm deviates from standard procedures of stress drop determination in several ways because these time saving measures come at the price of accuracy a quality control parameter is introduced which quantifies the discrepancy between the observed and modeled ground motion the results of implementing the algorithm offline using kik borehole data from japan are presented it is shown that it is possible to recover the moment magnitudes and the stress drops in real time two example timelines of seismic moment and stress drop are presented these show that the source parameters of small to moderate earthquakes may be estimated quite accurately within 5 to 10 s since the first trigger whereas those of larger magnitudes i e m w 6 take 20 30 s finally ground motion prediction equations for the velocity s root mean square and peak ground velocity are presented once the epicenter seismic moment and stress drop are determined using a few stations nearest to the epicenter their values can be input into those equations to get the ground motion intensity at sites further away from it

comment on earthquake magnitude estimation from peak amplitudes of very early seismic signals on strong motion records by aldo zollo maria lancieri and stefan nielsen an early warning system should determine the loca tion and magnitude of an earthquake as rapidly as possiblein order to broadcast an alarm to regions that will undergosevere ground shaking it was recently claimed by zollo etal 2006 that earthquake size could be determined fromonly the first 2 seconds of p or s wave strong motion data this represents a fraction of the rupture time for larger m 7 events using this relatively short amount of data themethod of analysis was to find the peak ground displace ment pgd which was reported to scale with earthquakemagnitude such rapid information would play an importantand much needed role in an earthquake early warning eew system here we perform a similar analysis onstrong motion data from the kik net and k net arrays injapan and find no compelling evidence that the peak grounddisplacement during the first couple of seconds of p wave isrelated to the eventual size of a large earthquake

earthquake early warning for bucharest romania novel and revised scaling relations 1 the accumulation of strong earthquakes with resembling source mechanisms in the romanian vrancea zone se carpathians allows for designing a simple cheep and robust earthquake early warning eew system for bucharest with leading times of about 25 s a previously established scaling relation for eew predicts in the range from 1 2 s a ten times higher ground motion amplitude in bucharest than the maximum p wave acceleration measured in the epicentral area using additional weak and strong motion data we find that ground shaking in bucharest is generally overestimated by this relation by a factor of two however the predicted amplitudes are within the 95 confidence interval of our revised relation additional predictive laws for eew are determined for different ground motion parameters the application of our scaling relations to the october 27 2004 vrancea earthquake m w 6 0 supports the feasibility of the approach for eew in romania

tsunami early warning within five minutes tsunamis are most destructive at near to regional distances arriving within 20 30 min after a causative earthquake effective early warning at these distances requires notification within 15 min or less the size and impact of a tsunami also depend on sea floor displacement which is related to the length l width w mean slip d and depth z of the earthquake rupture currently the primary seismic discriminant for tsunami potential is the centroid moment tensor magnitude m w cmt representing the product lwd and estimated via an indirect inversion procedure however the obtained m w cmt and the implied lwd value vary with rupture depth earth model and other factors and are only available 20 30 min or more after an earthquake the use of more direct discriminants for tsunami potential could avoid these problems and aid in effective early warning especially for near to regional distances previously we presented a direct procedure for rapid assessment of earthquake tsunami potential using two simple measurements on p wave seismograms the predominant period on velocity records t d and the likelihood t 50 ex that the high frequency apparent rupture duration t 0 exceeds 50 55 s we have shown that t d and t 0 are related to the critical rupture parameters l w d and z and that either of the period duration products t d t 0 or t d t 50 ex gives more information on tsunami impact and size than m w cmt m wp and other currently used discriminants these results imply that tsunami potential is not directly related to the product lwd from the seismic faulting model as is assumed with the use of the m w cmt discriminant instead information on rupture length l and depth z as provided by t d t 0 or t d t 50 ex can constrain well the tsunami potential of an earthquake we introduce here special treatment of the signal around the s arrival at close stations a modified real time m wpd rt magnitude and other procedures to enable early estimation of event parameters and tsunami discriminants we show that with real time data currently available in most regions of tsunami hazard event locations m b and m wp magnitudes and the direct period duration discriminant t d t 50 ex can be determined within 5 min after an earthquake occurs and t 0 t d t 0 and m wpd rt within approximately 10 min this processing is implemented and running continuously in real time within the early est earthquake monitor at ingv rome http early est rm ingv it we also show that the difference m b log10 t d t 0 forms a rapid discriminant for slow tsunami earthquakes the rapid availability of these measurements can aid in faster and more reliable tsunami early warning for near to regional distances

on the characteristics of earthquake stress release variations in japan abstract the amount of stress released during earthquakes is a fundamental characteristic of the earthquake rupture process as such it represents a key parameter for improving our understanding of earthquake source physics and for reliable ground motion prediction large earthquake populations usually show variations in stress release as large as three orders of magnitude but the underlying mechanisms have remained largely elusive and particularly the dependence of stress release on earthquake size is still a matter of debate here i use a unique dataset from japan encompassing earthquakes of a wide magnitude range and spatial coverage to show that stress release variations of crustal earthquakes are strongly correlated with heat flow variations indicating that they are thermally controlled in contrast subcrustal events depict highest stress release in regions of strong subduction interface coupling and overall less pronounced variability as compared with crustal earthquakes stress release is overall only weakly dependent on earthquake size but at local scales i e within individual earthquake sequences the dependence can be very strong and apparently varies with stress regime accounting for these systematic variations reduces the stress release variability on local scale by a factor of two to three as compared with the full earthquake population a finding that is of key significance in the endeavor to reduce the uncertainties in future ground motion predictions

the 2011 mw 9 0 tohoku earthquake comparison of gps and strong motion data near field ground motion data are available in semi real time either from modern strong motion or continuous global positioning system gps networks allowing robust solutions for earthquake source parameters which are useful for rapid disaster assessment and early warning these wide applications require the ground motion data to cover a very broad frequency band that however is usually not available this paper presents a case study on the 2011 m w 9 0 tohoku earthquake showing how the ground motion information from geodetic and seismic instrumentations is complementary and suggesting the joint use of both types of data particularly when the network coverage is sparse first the strong motion records from the two japanese networks k net and kik net are analyzed using an automatic empirical baseline correction tool the static coseismic displacement data are obtained by double integration and then used to derive the permanent slip distribution on the earthquake fault comparisons with the corresponding gps based solutions yield a quantitative estimation of uncertainties of the empirical baseline correction furthermore a dozen nearby gps and strong motion station pairs are selected to demonstrate that the information in their time series agrees with each other finally methods for combining both types of ground motion observation systems are discussed and the wide applicability of this approach is highlighted

fast determination of earthquake magnitude and fault extent from real time p wave recordings s u m m a r y this work is aimed at the automatic and fast characterization of the extended earthquake source through the progressive measurement of the p wave displacement amplitude along the recorded seismograms we propose a straightforward methodology to quickly characterize the earthquake magnitude and the expected length of the rupture and to provide an approximate estimate of the average stress drop to be used for earthquake earlywarning and rapid response purposes we test the methodology over a wide distance and magnitude range using a massive japan earthquake accelerogram data set our estimates of moment magnitude source duration length and stress drop are consistent with the ones obtained by using other techniques and analysing the whole seismic waveform in particular the retrieved source parameters follow a self similar constant stress drop scaling median value of stress drop 0 71 mpa for the m 9 0 2011 tohoku oki event both magnitude and length are underestimated due to limited available p wave time window ptws and to the low frequency cut off of analysed data we show that in a simulated real time mode about 1 2 seconds would be required for the source parameter determination of m 4 5 events 3 10 seconds for m 6 7 and 30 40 s for m 8 8 5 the proposed method can also provide a rapid evaluation of the average slip on the fault plane which can be used as an additional discriminant for tsunami potential associated to large magnitude earthquakes occurring offshore

a threshold based earthquake early warning using dense accelerometer networks most earthquake early warning systems eews developed so far are conceived as either regional network based or on site stand alone systems the recent implementation of nationwide high dynamic range dense accelerometer arrays makes now available potentially in real time unsaturated waveforms of moderate to large magnitude earthquakes recorded at very short epicentral distances 10 20 km this would allow for a drastic increase of the early warning lead time for example the time between the alert notification and the arrival time of potentially destructive waves at a given target site by analysing strong motion data from modern accelerograph networks in japan taiwan and italy we propose an integrated regional on site early warning method which can be used in the very first seconds after a moderate to large earthquake to map the most probable damaged zones the method is based on the real time measurement of the period c and peak displacement pd parameters at stations located at increasing distances from the earthquake epicentre the recorded values of early warning parameters are compared to threshold values which are set for a minimum magnitude 6 and instrumental intensity vii according to the empirical regression analyses of strong motion data at each recording site the alert level is assigned based on a decisional table with four alert levels defined upon critical values of the parameters pd and c which are set according to the error bounds estimated on the derived prediction equations given a real time evolutionary estimation of earthquake location from first p arrivals the method furnishes an estimation of the extent of potential damage zone as inferred from continuously updated averages of the period parameter and from mapping of the alert levels determined at the near source accelerometer stations the off line application of the method to strong motion records of the m w 6 3 2009 central italy earthquake shows a very consistent match between the rapidly predicted within a few seconds from the first recorded p wave and observed damage zone the latter being mapped from detailed macroseismic surveys a few days after the event the proposed approach is suitable for italy where during the last two decades a dense network of wide dynamic range accelerometer arrays has been deployed by the department of civil protection dpc the istituto nazionale di geofisica e vulcanologia ingv and other regional research agencies

magnitude estimation using the first three seconds p wave amplitude in earthquake early warning 1 pd is the peak amplitude of displacement in the first three seconds after the arrival of the p wave we investigated the attenuation of pd with the hypocentral distance r in southern california as a function of magnitude m and obtained the following relationship log pd 3 463 0 729 m 1 374 log r 0 305 given an earthquake location determined by the p wave arrival times at stations close to the epicenter this relationship can be used to define a so called pd magnitude of earthquakes our result shows that for earthquakes in southern california the pd magnitudes agree with the catalog magnitudes with a standard deviation of 0 18 for events less than magnitude 6 5 therefore pd is a robust measurement for estimating the magnitudes of earthquakes and has practical application in earthquake early warning systems citation wu y m and l zhao 2006 magnitude estimation using the first three seconds p wave amplitude in earthquake early warning geophys res lett 33 l16312 doi 10 1029 2006gl026871

application of real time gps to earthquake early warning 1 we explore the use of real time high rate gps displacement data for earthquake early warning using 1 hz displacement waveforms from the april 4 2010 mw 7 2 el mayor cucapah earthquake we compare these data to those provided by the broadband velocity and accelerometer instrumentation of the southern california seismic network the unique information provided by the gps based displacement timeseries is the permanent static displacement using a simple algorithm that can be applied in real time we extract the static offset shortly after the s wave arrival around the time of the observed peak shaking at the same site and before shaking at more distant locations these data can be used as they become available to provide a robust estimate of the earthquake magnitude which ranges from 6 8 to 7 0 in this case we therefore conclude that real time high rate gps can provide a useful and independent assessment of earthquake magnitude for the purpose of earthquake early warning and real time earthquake information systems in general including tsunami warning systems

tsunami early warning using earthquake rupture duration 1 effective tsunami early warning for coastlines near a tsunamigenic earthquake requires notification within 5 15 minutes we have shown recently that tsunamigenic earthquakes have an apparent rupture duration t0 greater than about 50 s here we show that t0 gives more information on tsunami importance than moment magnitude mw and we introduce a procedure using seismograms recorded near an earthquake to rapidly determine if t0 is likely to exceed t 50 or 100 s we show that this duration exceedance procedure can be completed within 3 10 min after the earthquake occurs depending on station density and that it correctly identifies most recent earthquakes which produced large or devastating tsunamis this identification forms a complement to initial estimates of the location depth and magnitude of an earthquake to improve the reliability of tsunami early warning and in some cases may make possible such warning

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

automatic imaging of earthquake rupture processes by iterative deconvolution and stacking of high rate gps and strong motion seismograms by combining the complementary advantages of conventional network inversion and backprojection methods we have developed an iterative deconvolution and stacking ids approach for imaging earthquake rupture processes with near field complete waveform data this new approach does not need any manual adjustment of the physical empirical constraints such as restricting the rupture time and duration and smoothing the spatiotemporal slip distribution therefore it has the ability to image complex multiple ruptures automatically the advantages of the ids method over traditional linear or nonlinear optimization algorithms are demonstrated by the case studies of the 2008 wenchuan and 2011 tohoku earthquakes for such large earthquakes the ids method is considerably more stable and efficient than previous inversion methods additionally the robustness of this method is demonstrated by comprehensive synthetic tests indicating its potential contribution to tsunami and earthquake early warning and rapid response systems it is also shown that the ids method can be used for teleseismic waveform inversions for the two major earthquakes discussed here the ids method can provide without tuning any physical or empirical constraints teleseismic rupture models consistent with those derived from the near field gps and strong motion data

early magnitude and potential damage zone estimates for the great mw 9 tohoku oki earthquake the mw 9 0 2011 tohoku oki earthquake has reopened the discussion among the scientific community about the effectiveness of earthquake early warning for large events a well known problem with real time procedures is the parameter saturation which may lead to magnitude underestimation for large earthquakes here we measure the initial peak ground displacement and the predominant period by progressively expanding the time window and distance range to provide consistent magnitude estimates m 8 4 and a rapid prediction of the potential damage area this information would have been available 35 s after the first p wave detection and could have been refined in the successive 20 s using data from more distant stations we show the suitability of the existing regression relationships between early warning parameters and magnitude provided that an appropriate p wave time window is used for parameter estimation we interpret the magnitude under estimation as a combined effect of high pass filtering and frequency dependence of the main radiating source during the rupture process

a window into the complexity of the dynamic rupture of the 2011 mw 9 tohoku oki earthquake the 2011 mw 9 tohoku oki earthquake recorded by over 1000 near field stations and multiple large aperture arrays is by far the best recorded earthquake in the history of seismology and provides unique opportunities to address fundamental issues in earthquake source dynamics here we conduct a high resolution array analysis based on recordings from the usarray and the european network the mutually consistent results from both arrays reveal rupture complexity with unprecedented resolution involving phases of diverse rupture speed and intermittent high frequency bursts within slow speed phases which suggests spatially heterogeneous material properties the earthquake initially propagates down dip with a slow initiation phase followed by sustained propagation at speeds of 3 km s the rupture then slows down to 1 5 km s for 60 seconds a rich sequence of bursts is generated along the down dip rim of this slow and roughly circular rupture front before the end of the slow phase an extremely fast rupture front detaches at about 5 km s towards the north finally a rupture front propagates towards the south running at about 2 5 km s for over 100 km key features of the rupture process are confirmed by the strong motion data recorded by k net and kik net the energetic high frequency radiation episodes within a slow rupture phase suggests a patchy image of the brittle ductile transition zone composed of discrete brittle asperities within a ductile matrix the high frequency is generated mainly at the down dip edge of the principal slip regions constrained by geodesy suggesting a variation along dip of the mechanical properties of the mega thrust fault or their spatial heterogeneity that affects rise time

w phase source inversion for moderate to large earthquakes 1990 2010 rapid characterization of the earthquake source and of its effects is a growing field of interest until recently it still took several hours to determine the first order attributes of a great earthquake e g m w 7 5 even in a well instrumented region the main limiting factors were data saturation the interference of different phases and the time duration and spatial extent of the source rupture to accelerate centroid moment tensor cmt determinations we have developed a source inversion algorithm based on modelling of the w phase a very long period phase 100 1000 s arriving at the same time as the p wave the purpose of this work is to finely tune and validate the algorithm for large to moderate sized earthquakes using three components of w phase ground motion at teleseismic distances to that end the point source parameters of all m w 6 5 earthquakes that occurred between 1990 and 2010 815 events are determined using federation of digital seismograph networks global seismographic network broad band stations and sts1 global virtual networks of the incorporated research institutions for seismology data management center for each event a preliminary magnitude obtained from w phase amplitudes is used to estimate the initial moment rate function half duration and to define the corner frequencies of the passband filter that will be applied to the waveforms starting from these initial parameters the seismic moment tensor is calculated using a preliminary location as a first approximation of the centroid a full cmt inversion is then conducted for centroid timing and location determination comparisons with harvard and global cmt solutions highlight the robustness of w phase cmt solutions at teleseismic distances the differences in m w rarely exceed 0 2 and the source mechanisms are very similar to one another difficulties arise when a target earthquake is shortly e g within 10 hr preceded by another large earthquake which disturbs the waveforms of the target event to deal with such difficult situations we remove the perturbation caused by earlier disturbing events by subtracting the corresponding synthetics from the data the cmt parameters for the disturbed event can then be retrieved using the residual seismograms we also explore the feasibility of obtaining source parameters of smaller earthquakes in the range 6 0 mw 6 5 results suggest that the w phase inversion can be implemented reliably for the majority of earthquakes of mw 6 or larger

evidence of large scale repeating slip during the 2011 tohoku oki earthquake 1 the repetition of slip during rupture process of earthquake is a debate issue which had never been confirmed clearly in the past big events due to the lack of dense near field observations and limited resolution in time of source model the 2011 m9 0 tohoku oki earthquake generated a wealth seismic records which provided us an unprecedented opportunity to study the rupture evolution of giant earthquake at a high spatio temporal resolution here we use teleseismic local strong motion and near field coseismic geodetic data to investigate the source rupture process of this event based on the parallel inversion technique the results reveal a broad slip zone with remarkable large scale repeating slip during the earthquake the inverted source model shows several time periods of energy release with three main peaks these energy bursts and temporal rupture snapshots suggest repetition of a large scale slip on the biggest asperity this rupture behavior resulted in 50 m slips on the slip zone and prolonged the entire rupture process for a long duration of 160 seconds the proposed source model is in a good agreement with the aftershock distribution and can interpret the characteristics of local strong motions further investigations of repeating slip during this event are crucial which will deeply transform earthquake science from dynamic point of view

earthquake magnitude estimation from early radiated energy 1 from inspection of a large set of japanese events we investigate the scaling of the early radiated energy inferred from the squared velocity integral iv2 with the final magnitude of the event we found that the energy can only discriminate whether the event has a magnitude larger or smaller than 5 8 and in the latter case it can allow for real time magnitude estimation however by normalizing iv2 for the rupture area the initial slip scales with the magnitude between 4 m 7 following the expected scaling laws we show that the ratio between the squared peak displacement and iv2 is a proxy for the slip following the same scaling but it can be directly derived from the data without any assumption on the rupture area the scaling relationship between initial slip and magnitude can be used for early warning applications when integrated in a probabilistic evolutionary approach

earthquake magnitude estimation from peak amplitudes of very early seismic signals on strong motion records 1 we show that the low pass filtered peak amplitudes of initial p and s wave seismic signals recorded in the vicinity of an occurring earthquake source correlates with the earthquake magnitude and may be used for real time estimation of the event size in seismic early warning applications the earthquake size can be therefore estimated using only a couple of seconds of signal from the p or s wave onsets i e while the rupture itself is still propagating and rupture dimension is far from complete we argue that dynamic stress release and or slip duration on the fault in the very early stage of seismic fracture scales both with the observed peak amplitude and with the elastic energy available for fracture propagation the probability that a fracture grows to a larger size should scale with the energy initially available citation zollo a m lancieri and s nielsen 2006 earthquake magnitude estimation from peak amplitudes of very early seismic signals on strong motion records geophys res lett 33 l23312 doi 10 1029 2006gl027795

stochastic inversion by matching to large numbers of pseudo wells abstractwe have developed a 1d stochastic algorithm for estimating reservoir properties based on matching large numbers of pseudo wells to seismic angle stacks the pseudo wells are part deterministic and part stochastic 1d stratigraphic profiles with consistent elastic and reservoir properties pseudo wells are sampled from a prior distribution defined by the geological interpretation a rock physics model and a model for the vertical statistics that provides close control of the lithofacies proportions a new set of pseudo wells typically 103 104 tied to the local stratigraphy is constructed for each seismic trace synthetics derived from the pseudo wells using extended elastic impedance are matched to either one or two seismic angle stacks and the best matches are selected and averaged to provide a joint estimate of reservoir properties and impedances and the associated uncertainties the algorithm has been tested on a number of data sets and validated by blind well ties the algorithm is 1d with