a robust maximum likelihood earthquake location method for early warning this study proposes a robust method that estimates a reliable earthquake location from only a small number of p wave arrival times the method is based on the maximum likelihood estimation from differential p wave arrivals we formulate the problem using a probability density function pdf of the residual between observed and predicted differential p wave travel times between two seismic stations and construct the likelihood function from the sum of the products of the independent pdfs the hypocenter is determined by an iterative grid search algorithm that finds the point with the largest probability on successively finer grids to reduce the effect from outliers possibly concealed within a small number of observations the student s t distribution is used for the pdf of the location likelihood the jackknife resampling technique is also used to discriminate outliers from the observations the robustness of the method is tested using the monte carlo experiments that locate 10 000 events from small numbers of p wave arrivals observed within an epicentral distance of 100 km including both arrival time error and velocity model error the earthquakes are located within an epicentral distance of 8 5 10 8 km and 20 6 33 1 km for events inside the seismic network and outside the network respectively using only five p wave arrivals including a large arrival time error between 1 and 5 s this shows that this method can estimate the location of the event reliably with only a few p wave arrivals even when contaminated by an outlier therefore it is believed that this location method could significantly improve the robustness of an earthquake early warning system

near real time mapping of peak ground acceleration and peak ground velocity following a strong earthquake during a disastrous earthquake the early assessment and timely reporting of the peak ground acceleration pga and peak ground velocity pgv maps will be crucial in an effective emergency response operation in this study we first derive an empirical relationship between m l and m w the pga and pgv attenuation relationships are deduced with data from the taiwan strong motion instrumentation program tsmip and the taiwan rapid earthquake information release system treirs site corrections of the attenuation relationships for shallow and large earthquakes in taiwan region are also obtained peak values of earthquake strong ground motion can be well determined in taiwan as soon as the earthquake location is determined and magnitudes are calculated by the treirs this peak ground motion value information can be immediately turned into the calculated pga and pgv maps that can be issued within two minutes of the earthquake origin time during any disastrous earthquake these maps are found to be very useful for immediate seismic damage assessment and dispatching of emergency response missions manuscript received 1 december 2000

a threshold based earthquake early warning system for offshore events in southern iberia the south of the iberian peninsula is situated at the convergence of the eurasian and african plates this region experiences large earthquakes with long separation in time the best known of which was the great 1755 lisbon earthquake which occurred sw of san vicente cape sw iberian peninsula the high risk of damaging earthquakes has recently led carranzaet al geophys res lett 40 2013 to investigate the feasibility of an eews in this region analysis of the geometry for the iberian seismic networks and the san vicente cape area led the authors to conclude that a threshold based approach which would not require real time location of the earthquake might be the best option for an eews in sw iberia in this work we investigate this hypothesis and propose a new eew approach that extends standard p wave threshold based single station analysis to the whole network the proposed method enables real time estimation of the potential damage at stations that are triggered by p waves and those which are not triggered with the advantage of greater lead times for release of alerts results of tests made with synthetic data mimicking the scenario of the great 1755 lisbon earthquake and those conducted by applying the new approach to available recordings indicate that an eew estimation of the potential damage associated with an event in the san vicente cape area can be obtained for a very large part of the iberian peninsula

on the estimation of seismic intensity in earthquake early warning systems 1 the infamous tokai earthquake which by some accounts is overdue is expected to be a magnitude 8 event that will cause unprecedented damage in regions of japan to mitigate hazards from large earthquakes in japan an earthquake early warning eew system was developed that is able to determine hypocentral locations from p arrival data within a few seconds and then transmit this information before the onset of large ground motions from the later arrival of s waves we introduced a new source parameter for seismic intensity magnitude that can be estimated from the real time p wave data during the early stages of fault rupture for most earthquakes m 6 5 the use of this parameter results in a significant improvement in the uncertainty in the estimated seismic intensity compared to estimates derived from earthquake magnitude a pre established relation between the p and s wave seismic intensity therefore enables an eew system to issue a rapid and reasonably reliable prediction of the amount of ground shaking that may be expected from the damaging s waves

scaling wind stirring effects in an oceanic bulk mixed layer model with application to an ogcm of the tropical pacific the mixed layer depth mld plays an important role in the climate system through its influences on sea surface temperature sst the kraus turner niiler hereafter referred to as ktn bulk mixed layer ml model is designed for describing the mld and has been adopted widely by many ocean modeling however large biases exist in the mld simulation using the original ktn model in the tropical pacific this is partly due to the uncertainties in representing wind stirring effect in the model which is scaled by a parameter m 0 traditionally m 0 is taken as a constant uniformly in space in this study the m 0 is estimated as spatially and seasonally varying through its inverse calculation from a balance equation describing the turbulent kinetic energy tke budget of the ml it is illustrated that the m 0 is spatially varying over the tropical pacific the derived m 0 fields are then embedded into an ocean general circulation model ogcm compared with the observations and the global ocean data assimilation system godas analyses the mld simulations in the ogcm with varying m 0 are substantially improved in the tropical pacific ocean on seasonal and interannual time scales additionally the pacific subtropical cells stcs become intensified accompanied with the strengthening of upwelling in the eastern equatorial pacific thus more realistic simulations are obtained in spatially and seasonally varying m 0 case compared with the constant m 0 case as the related cooling effect from the upwelling is enhanced the simulated sst is slightly cooled down in the eastern equatorial pacific further applications and implications are also discussed

aragonite to calcite transformation during fresh water diagenesis of carbonates insights from pore water chemistry dissolved strontium and calcium concentrations in fresh water lenses fwl and associated mixing zones mz on two small holocene ooid sand islands in the schooner cays bahamas were monitored during a 1 yr period to quantitatively analyze the transformation of aragonite to calcite the observed characteristics of this mass transfer are functions of climate and hydrology aragonite to calcite transformation in all hydrologic zones is primarily associated with meteoric recharge the transformation occurs throughout the fwl and in the mz to relative salinities of 19 and 36 sea water on the two islands rates of transformation are rapid in all zones and are greatest in the fwl a limestone composed of 100 calcite should form from an aragonite precursor within 4 700 to 15 600 yr in the fwl and within 8 700 to 60 000 yr in the upper mz efficiencies of transformation can vary between hydrologic zones due to pco2 effects yet the efficiency of the entire system fwl mz is high 87 this indicates that most caco3 derived from aragonite dissolution is reprecipitated as calcite somewhere in the fresh water system or upper mixing zone co2 effects fresh water sea water mixing and the differing solubilities between aragonite and calcite all drive the mass transfer the latter is the most significant accounting for up to nine times more mass transfer than co2 effects and at least ten times more mass transfer than fresh water sea water mixing differing solubilities should also cause mass transfer to occur throughout the hydrologic cycle but it apparently becomes ineffective after the rainy season possibly due to the inhibition of calcite precipitation

magnitude estimation for the 2011 tohoku oki earthquake based on ground motion prediction equations this study investigates whether real time strong ground motion data from seismic stations could have been used to provide an accurate estimate of the magnitude of the 2011 tohoku oki earthquake in japan ultimately such an estimate could be used as input data for a tsunami forecast and would lead to more robust earthquake and tsunami early warning we collected the strong motion accelerograms recorded by borehole and free field surface kiban kyoshin network stations that registered this mega thrust earthquake in order to perform an off line test to estimate the magnitude based on ground motion prediction equations gmpes gmpes for peak ground acceleration and peak ground velocity pgv from a previous study by eshaghi et al in the bulletin of the seismological society of america 103 2013 derived using events with moment magnitude m 5 0 1998 2010 were used to estimate the magnitude of this event we developed new gmpes using a more complete database 1998 2011 which added only 1 year but approximately twice as much data to the initial catalog including important large events to improve the determination of attenuation parameters and magnitude scaling these new gmpes were used to estimate the magnitude of the tohoku oki event the estimates obtained were compared with real time magnitude estimates provided by the existing earthquake early warning system in japan unlike the current operational magnitude estimation methods our method did not saturate and can provide robust estimates of moment magnitude within 100 s after earthquake onset for both catalogs it was found that correcting for average shear wave velocity in the uppermost 30 m v text s 30 improved the accuracy of magnitude estimates from surface recordings particularly for magnitude estimates of pgv mpgv the new gmpes also were used to estimate the magnitude of all earthquakes in the new catalog with at least 20 records results show that the magnitude estimate from pgv values using borehole recordings had the smallest standard deviation among the estimated magnitudes and produced more stable and robust magnitude estimates this suggests that incorporating borehole strong ground motion records immediately available after the occurrence of large earthquakes can provide robust and accurate magnitude estimation

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

the potential for earthquake early warning in italy using elarms abstract the new italian national seismic network insn is a dense network of broadband stations deployed for monitoring italian seismicity the network consists of 250 stations with a typical station spacing of 40 km earthquake early warning is the rapid detection of an event in progress assessment of the hazard it poses and transmission of a warning ahead of any significant ground motion we explore the potential for using the insn real time network for the purpose of earthquake early warning we run the elarms early warning methodology off line using a data set of more than 200 events with magnitudes between 2 5 and 6 0 a scaling relation for magnitude determination from the dominant period of the first seconds of signal following the p onset is developed from the data set the standard deviation in the magnitude estimates using this approach is 0 4 magnitude units and all event magnitude estimates are within 0 75 magnitude units of the true magnitude given the existing distribution of seismic stations it takes an average of 10 sec after event initiation before the p wave has been detected at four stations if we require a detection at four stations before issuing the first alert then the blind zone within which no warning would be available has a radius of 37 km the elarms methodology can provide a warning earlier than this but with a greater uncertainty an assessment of past damaging earthquakes across italy shows that applying elarms with the existing seismic network could provide warning to population centers in repeats of past events for example in a repeat of the 1980 irpinia earthquake naples could receive an 15 sec warning the variations in the size of the blind zone and warning times for different regions can be used as a guide to selecting strategic locations for future station deployments

magnitude determination using strong ground motion attenuation in earthquake early warning 1 we use 1661 strong motion accelerograms with peak ground acceleration pga larger than 80 gal 1 gal 1 0 cm s2 from 77 earthquakes recorded by the taiwan strong motion instrumentation program tsmip stations to derive a strong motion attenuation relationship this relationship can be used to dynamically define a mpga magnitude for earthquakes using earthquake locations determined by earthquake early warning process the mpga magnitude using this strong motion attenuation relationship corresponds well with mw given a sufficient number of pga readings mems micro electro mechanical systems acceleration sensor could be widely used for ground motion monitoring purposes thus we propose that once a large earthquake has begun that we might be able to use strong near field tens of kilometers pga values to quickly estimate the earthquake s magnitude which would improve earthquake early warning

a new method of quickly estimating epicentral distance and magnitude from a single seismic record rapid estimation of the epicentral distance and magnitude is of fundamental importance for early earthquake detection and warning systems we present a novel method of estimating the epicentral distance from a single seismic record in a short amount of time in order to quantitatively evaluate the difference in observed seismic waveforms we introduced a simple function with the form of bt exp at and determined a and b in terms of the least squares method by fitting this function to the initial part of the waveform envelope we have found that log b is inversely proportional to log where is the epicentral distance this relation holds true regardless of the earthquake magnitude by using this relation we can roughly estimate the epicentral distance nearly immediately after the p wave arrival then we can readily estimate the magnitude from the maximum amplitude observed within a given short time interval after the p wave arrival by using an empirical magnitude amplitude relation that includes the epicentral distance as a parameter manuscript received 11 january 2002

an automatic processing system for broadcasting earthquake alarms in japan most of the damage caused by large earthquakes is concentrated within areas less than about 100 km from the focal regions we have developed an earthquake alarm system that determines earthquake parameters within a few seconds of the p wave s arrival at the closest station and then transmits the earthquake information before the s wave arrival in areas of possible serious earthquake damage since an earthquake alarm system requires the determination of reliable earthquake parameters as quickly as possible it is unreasonable to wait until waveform data from numerous stations have been collected for analysis for this reason we have developed a novel method of determining the hypocentral location by using the arrival times for only a few stations as well as the lack of p wave arrivals at other stations at a given time the use of not yet arrived data makes it possible not only to determine reliable hypocenter parameters within a few seconds but also to detect erroneous arrival time readings and remove them automatically since the available waveform data increases with time the system was designed to redetermine earthquake parameters every second our method was deployed in a real time system starting in july 2002 the real time system locates 10 20 events per day which includes a few felt earthquakes occurring in and around japan it was shown from the waveform data for about 100 felt earthquakes that almost all the events except those far from the network could be located within a few seconds when most of seismic energy has not even arrived at some stations close by we recently started widespread broadcasting of earthquake information in real time by using a satellite transmission system

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

wavelet based methods for rapid calculations of magnitude and epicentral distance an application to earthquake early warning system the purpose of this study is to demonstrate the use of wavelet transform wt as the common processing tool for earthquake s rapid magnitude determination and epicentral estimation the goal is to use the same set of wavelet coefficients that characterize the seismogram and especially its p wave portion to use one technique wt for double use magnitude and location estimation wavelet magnitude estimation wme is used to derive a scaling relation between earthquake s magnitude and wavelet coefficients for south aegean using data from 469 events with magnitudes from 3 8 to 6 9 the performance of the proposed relation was evaluated using data from 40 additional events with magnitude from 3 8 to 6 2 in addition the epicentral estimation is achieved by a new proposed method wavelet epicentral estimation wepe which is based on the combination of wavelet azimuth estimation and two stations sub array method following the performance investigation of wepe method we present results and simulations with real data from characteristic events that occurred in south aegean both methods can be run in parallel providing in this way a suitable core of a regional earthquake early warning system in south aegean

real time seismic warning with a two station subarray one of the most basic problems in seismology is earthquake location in particular the ability to quickly locate a large potentially devastating earthquake is of fundamental importance in a real time warning system where speed is a key factor in determining the level of success of such systems we have developed a simple method that uses only the two earliest p wave arrival times in a seismic array assuming a simple velocity model these arrivals are used to construct a hyperbolic curve on which the approximate epicenter of the earthquake is expected to lie epicentral location along this hyperbola is further constrained by using the fact that the p waves arriving at the other stations in the array are not first arrivals when applied to p wave seismic data from the hector mine earthquake in california and a smaller event in the central united states model results show agreement with actual earthquake locations although there is an inherent uncertainty in the subarray method of locating large earthquakes this may be an acceptable trade off in an early warning system in view of the time a few to tens of seconds saved by not waiting for other p arrivals whereas the main goal of this report is to present the location method we also show that the station closest to the hector mine earthquake had recorded about 0 3 and 1 mm of ground motion within 2 and 3 sec respectively of the arrival of the p waves thus indicating that a large event had occurred manuscript received 18 september 2003

real time detection location and characterization of rockslides using broadband regional seismic networks we propose a new real time approach to detect locate and estimate the volume of rockslides by analyzing waveforms acquired from broadband regional seismic networks the identification of signals generated by rockslides from other sources such as natural and or induced earthquakes is accomplished by exploiting the ratio between local magnitudes ml and duration magnitudes md we found that signals associated with rockslides have ml md 0 8 while for earthquakes ml md 1 in addition we derived an empirical relationship between md and rockslide volumes obtaining a preliminary characterization of rockslide volume within seconds after their occurrence the key points of this study are presented by testing the hypothesis on a recent rockslide event that occurred in northern italy we discuss also the potential evolution of the methodology for early warning and or rapid response purposes

development of an earthquake early warning system based on earthworm application to southwest iberia abstract the main aim of this study is to demonstrate the feasibility of an earthquake early warning system eews to warn of potentially destructive earthquakes in the cape san vicente sv and gulf of cadiz gc areas in the southwest iberian peninsula based on real time broadband stations existing in the region historic earthquakes in this region include the 1755 lisbon m w 8 5 and 1969 sv m w 7 8 events this study illustrates the design configuration and first results of an eews prototype based on the u s geological survey earthworm tools and developed at the institut cartografic i geologic de catalunya icgc system main functionalities are real time data acquisition processing p wave picking event detection earthquake hypocentral location and magnitude estimation from previously calculated peak displacement p d and predominant period c of the p wave signal data archiving and earthquake early warning dissemination the prototype was put into operation after a setup period during which several simulations were carried out to establish the optimal settings after the first year of operation one felt earthquake occurred in the area of study location and magnitude results are fairly good compared with the instituto geografico nacional ign catalog lead times obtained are on the order of tens of seconds for the majority of targets which are long enough to mitigate damage for a large area of the southern coasts of portugal and spain due to the gc and sv earthquakes preliminary results for this prototype demonstrate the possibility of a regional reliable and effective eews in southwest iberia

automated near realtime cmt inversion the earthquake research institute eri of the university of tokyo has completely automated the process of determining source mechanisms of earthquakes using waveform data the solutions are automatically distributed using the internet without being checked the process is initiated by receipt of e mail giving the origin time and location of an earthquake to determine the source mechanism we apply the harvard centroid moment tensor cmt inversion method to long period body wave data the portion of the seismogram from the first arrival to the initial surface wave the method has been successfully applied since october 1993 to all of the major earthquakes in the world for which we received event e mail 108 of the 242 cmt solutions in 1994 were determined within 6 hours of the event with an average delay of 3 8 hours for local events e g events around japan it is also possible to determine cmt solutions within 30 minutes from the occurrence of the earthquakes using an efficient dialup data retrieval system operated by eri

probabilistic estimation of earthquake growth to a catastrophic one 1 we propose a method to estimate the probability of earthquake growth to a catastrophic one immediately after observing its initiation for practical usage in an earthquake early warning system this method is essentially an application of the conditional probability theory where the magnitude frequency relation plays a crucial role we apply it to the nankai trough region japan where a catastrophic earthquake is expected in the near future based on the historical catalogue we estimate the probability density of magnitude using a bayesian approach we then estimate the probability of earthquake growth to a catastrophic one if the observed earthquake magnitude reaches 6 5 the estimated probability that the final magnitude exceeds 7 5 is 25 41 according to previous studies the time taken for the magnitude to increase from 6 5 to 7 5 is approximately 10 15 seconds our method is highly beneficial in that it enables an earlier alarm to be issued

magnitude determination using initial p waves a single station approach 1 prompted by recent success in the research and application of earthquake early warning systems we conducted an investigation into the relationship between the magnitudes of earthquakes and the properties of the first three seconds of the p waves at a single station using waveforms at station nacb of the broadband array in taiwan for seismology from 46 earthquakes within 100 km epicentral distance we found a linear correlation between the magnitudes and the logarithmic characteristic periods of the initial p waves for earthquakes up to magnitude 6 5 we also detected a deterministic relationship between the magnitudes and the peak amplitudes of the initial p waves for earthquakes of magnitude m 6 5 while further study needs to be done on the behavior of the initial p wave peak amplitudes from larger earthquakes we propose here that the characteristic periods and peak amplitudes of the first three seconds of the p waves be used jointly in onsite single station earthquake early warning operations

an automatic seismic event processing for detection and location the p m c c method we present a new method for automatic detection and location of seismic events recorded on a network it is based on a progressive study of the interstation correlation functions which leads to a consistent set of time delays when a seismic phase is present three different examples are processed on networks of different sizes

determination of earthquake early warning parameters τ c and pd for southern california summary we explore a practical approach to earthquake early warning in southern california by determining a ground motion period parameter c and a high pass filtered displacement amplitude parameter pd from the initial 3 s of the p waveforms recorded at the southern california seismic network stations for earthquakes with m 4 0 at a given site we estimate the magnitude of an event from c and the peak ground motion velocity pgv from pd the incoming threecomponent signals are recursively converted to ground acceleration velocity and displacement the displacements are recursively filtered with a one way butterworth high pass filter with a cut off frequency of 0 075 hz and a p wave trigger is constantly monitored when a trigger occurs c and pd are computed we found the relationship between c and magnitude m for southern california and between pd and pgv for both southern california and taiwan these two relationships can be used to detect the occurrence of a major earthquake and provide onsite warning in the area around the station where onset of strong ground motion is expected within seconds after the arrival of the p wave when the station density is high the methods can be applied to multistation data to increase the robustness of onsite early warning and to add the regional warning approach in an ideal situation such warnings would be available within 10 s of the origin time of a large earthquake whose subsequent ground motion may last for tens of seconds

a new trigger criterion for improved real time performance of onsite earthquake early warning in southern california we have implemented and tested an algorithm for onsite earthquake early warning eew in california using the infrastructure of the southern california seismic network scsn the algorithm relies on two parameters derived from the initial 3 sec of p waveform data at a single seismic sensor period parameter c and high pass filtered displacement amplitude p d previous studies have determined empirical relationships between c and the moment magnitude m w of an earthquake and between p d and the peak ground velocity pgv at the site of observation in 2007 seven local earthquakes in southern california with 4 0 m l 4 7 have triggered the calculation of m w and pgv by the eew algorithm while the mean values of estimated parameters were in the expected range the scatter was large in particular for the smallest events during the same time period the eew algorithm produced a large number of false triggers due to low trigger thresholds to improve the real time performance of the onsite approach we have developed a new trigger criterion that is based on combinations of observed c and p d values this new criterion removes 97 of previous false triggers and leads to a significant reduction of the scatter in magnitude estimates for small earthquakes

interannual planetary wave breaking in the presence of ekman pumping and mean flow a two layer planetary geostrophic model is adopted to study the breaking of planetary waves in the presence of ekman pumping and the associated mean flow the governing equation for the interface is a quasi linear equation which is solved analytically by the method of characteristics the waves are forced by annual or interannual upwelling or downwelling along the eastern boundary of a subtropical gyre it is found that the time and position at which breaking occurs is mainly determined by the speed and depth of the eastern boundary perturbation while the intensity of a breaking front is mainly determined by the amplitude of the perturbation

impact of fault parameter uncertainties on earthquake recurrence probability examined by monte carlo simulation an example in central taiwan abstract the region around taiwan is well known for its unique geological setting which has resulted in a high seismicity the central geological survey taiwan cgst has launched a series of investigation on characterizing the active faults on the island the cgst revealed that there are 33 active faults and their fault parameters are suggested in the latest publication in 2010 however the uncertainties of return period and earthquake magnitude are not provided the main objective of the paper is to study the impact of unspecified parameter uncertainties on recurrence earthquake probabilities in addition a numerical approach involving the use of monte carlo simulation was proposed to estimate the exceedance probabilities in which the parameter uncertainties were taken into account the meishan fault in central taiwan with the best estimate return period of 162 years and earthquake magnitude of 7 1 was used as an example the analyses verified the impact of parameter uncertainties on the exceedance probability in fault induced earthquake recurrence when uncertainty is high the exceedance probability associated with large magnitudes is high it was also observed that the probabilistic analysis in this study can generate a realistic continuous distribution of exceedance probabilities that cannot be obtained by a deterministic approach the best estimate distribution of exceedance probability was established by enveloping the curves estimated by both deterministic and probabilistic approaches accordingly the best estimate exceedance probability for a 7 5 magnitude earthquake recurring in 2011 2060 induced by the meishan fault in central taiwan was estimated as 11

3 d seismic velocity structure of the crust and the uppermost mantle in the northeastern japan arc 3 d seismic velocity structure of the crust and the uppermost mantle beneath the northeastern japan arc is investigated by using arrival time data from local earthquakes we use a velocity model composed of three layers corresponding to the upper crust the lower crust and the uppermost mantle respectively taking into account the observed regional variation of pn velocity the uppermost mantle is further divided into three parts by two pn velocity boundaries near the coasts of the japan sea and the pacific ocean the velocities within the upper crust the lower crust and the three parts of the uppermost mantle are assumed to be constant locations of two pn velocity boundaries and depth distributions of the conrad and the moho discontinuities are expressed by continuous functions of unknown parameters station corrections and hypocenters are also introduced to be unknowns these unknown parameters are determined by inverting arrival time data of p and s wave first arrivals and clear later arrivals of pg and p waves the pn velocity boundary between the land and the pacific ocean is located approximately along the pacific coastline and that between the land and the japan sea is nearly along the japan sea coastline the conrad and the moho discontinuities are at depths ranging from 14 to 20 km and from 27 to 36 km respectively the conrad and the moho depths have similar spatial distributions they are deep beneath the land and become shallower toward the western and the eastern coastlines beneath the land they are shallow in the central part of the tohoku district and become deeper toward both the north and the south directions in the north they become shallow again

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

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

meteoric versus burial control on porosity evolution of the smackover formation whole rock 13c 18o and sr compositions of the uppermost ooid grainstones of the smackover formation at black creek field in mississippi reveal characteristics of a meteoric system in this area the trend in 13c signatures indicates that meteoric water acquired its low carbon values at a soil zone and was buffered completely with the host rock before entering the meteoric lens identical 18o data suggest that allochems stabilized at the same temperatures in waters of similar 18o compositions during early meteoric diagenesis that is calcitization continued to completion before the onset of burial sr concentrations reveal differential transformation mechanisms low sr values in the phreatic zones are attributed to slow stabilization by exchange with the bulk solution high sr compositions in the vadose zone resulted from rapid incremental transformation meteoric cementation was sparse therefore grainstones entered the burial realm with all of their porosity intact modification of porosity was a burial process and was directly related to the intensity of chemical compaction which itself was controlled by three factors 1 the degree of early cementation 2 grain type and 3 grain size early cemented intervals experienced low to moderate compaction regardless of grain size or grain type in the absence of early cementation grain type and grain size were the dominant factors of porosity control coarse grained intervals that were composed of micritic grains experienced less compaction than fine grained oolitic intervals average volumetric percentages of cements as determined by point counting of 63 samples are as follows 1 marine and meteoric cements 1 5 2 prebitumen calcite 6 5 3 saddle dolomite 1 4 postbitumen calcite 4 3 5 pyrobitumen 1 total cement sum of 1 5 total burial cement sum of 2 5 and total burial carbonate cement volumes sum of 2 4 average 14 13 and 12 respectively out of an original porosity of 40 13 porosity units were lost by cementation and 27 porosity units were reduced by compaction mechanical and chemical present day intergranular porosity of these grainstones is zero whether they belonged to the vadose zone or the phreatic interval burial cementation and compaction destroyed all intergranular porosity regardless of early diagenetic overprint or textural variables the reservoir became compartmentalized during burial some intervals were active producers of calcium carbonate others were passive recipients

quick and reliable determination of magnitude for seismic early warning this article reports efforts toward using real time earthquake monitoring by the taiwan central weather bureau to meet the needs of seismic early warning twenty three sets of strong motion data from moderate earthquakes m 5 0 in the taiwan area are used to demonstrate the feasibility of this goal for earthquakes larger than ml 5 epicenters can be reliably determined in about 15 sec after the arrival of the p wave at the nearest station the earthquake magnitude m l cannot be determined in the same time frame due to incomplete recording of shear waves at some stations however the magnitude based on the first 10 sec of signal ml10 can be related to ml as follows ml 1 28 ml10 0 85 0 13 our results show that the real time strong motion system routinely used by the cen tral weather bureau can be used to determine epicenters and magnitudes in about 30 sec after occurrence of earthquakes in taiwan such information hopefully can be used to reduce damage to society

evaluation of the real time earthquake information system in japan 1 the real time earthquake information system reis of the japanese seismic network is developed for automatically determining earthquake parameters within a few seconds after the p waves arrive at the closest stations using both the p wave arrival times and the timing data that p waves have not yet arrived at other stations reis results play a fundamental role in the real time information for earthquake early warning in japan we show the rapidity and accuracy of reis from the analysis of 4 050 earthquakes in three years since 2005 44 percent of the first reports are issued within 5 seconds after the first p wave arrival and 80 percent of the events have a difference in epicenter distance less than 20 km relative to manually determined locations we compared the formal catalog to the estimated magnitude from the real time analysis and found that 94 percent of the events had a magnitude difference of 1 0 unit

magnitude period scaling relations for japan and the pacific northwest implications for earthquake early warning scaling relations between the predominant period of p wave arrivals and earthquake magnitude are explored using datasets from the pacific northwest and japan and compared with previous observations in southern california allen and kanamori 2003 we find the same scaling for events in all three geologically diverse regions the sensitivity of the predominant period observation to magnitude can be optimized using various frequency bands for different magnitude ranges and in dif ferent regions the ability to estimate the magnitude using the first few seconds of the p wave offers a methodology for earthquake early warning the accuracy of magnitude estimates increases with the number of stations reporting predominant period observations the most significant improvements in the magnitude estimate occur when the number of reporting stations increased from one to four as in south ern california we find that the average absolute magnitude error is 0 5 magnitude units when the closest four stations to the epicenter are used

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

quick estimation of the magnitude and epicentral distance using the p wave for earthquakes in iran abstract a reliable estimation of the earthquake magnitude and epicentral distance within a few seconds after the p wave arrival is of great importance for earthquake early warning systems this study aims to investigate the relations between the envelope of the initial part of the p wave with epicentral distance and magnitude of the earthquakes related to the tectonic conditions of iran to this end the accelerometer waveforms of 17 earthquakes with moment magnitudes less than 7 8 and epicentral distances less than 150 km are considered a simple function with the form of y bt exp at is fitted to the initial part of the waveform envelope on time windows of 2 3 4 and 5 s by the least squares method which is constructed simply by keeping the past maximum amplitude at every moment parameters a and b are obtained to scale magnitude and epicentral distance as well the results show that log is proportional to log b in which denotes the epicentral distance the distance scaling relations for all of the time windows indicate standard deviations between 0 16 and 0 17 km for log comparing to the adopted relation in the early warning system of the japan meteorological agency results illustrate a relatively distinct slope and intercept which arises from differences in tectonic structure and features of the earthquake sources in two areas the same process for records with epicentral distances less than 50 km is also repeated results indicate smaller standard deviations between 0 13 and 0 14 km for four time windows considering the arrangement of hazardous faults in many populated districts of iran including tehran utilization of the obtained relations is recommended for distances less than 50 km moreover the current study represents two distance dependent relations between magnitudes with p max and a p max within the initial 3 s of p wave arrivals with standard deviations of 0 42 and 0 46 magnitude units respectively

short term earthquake prediction current status of seismo electromagnetics abstract loss of human lives as a result of earthquakes is caused overwhelmingly by the collapse of buildings within less than a few minutes of main shocks the most urgent countermeasure consists of two key elements one is strengthening of weak structures and the other is short term earthquake prediction short term prediction needs precursors although some promising precursors are reported the prevailing views in japan and elsewhere are overly pessimistic the pessimism largely roots in the fact that short term precursors are generally non seismic and tools developed for seismology are not designed to detect them nonetheless nationally funded large scale earthquake prediction programs always emphasize the need to reinforce seismometer networks they do not take into account the views of those in the science community who point to the importance of non seismic precursors while there are well founded causes to be skeptical the situation needs to be improved one reason for skepticism is that the observations of precursors have not yet been perfect enough and another is that some important fundamental aspects of non seismic precursors are still unresolved we review some of these problems

isotope signatures associated with early meteoric diagenesis the environments in which carbonate diagenesis proceeds have been documented in previous studies of holocene and late pleistocene sediments and limestones on barbados west indies variations in the carbon and oxygen isotopic composition of limestones produced during early freshwater diagenesis have been observed in this study to occur in specific patterns six potentially useful patterns emerge when one views stable isotope data within a stratigraphic framework 1 the subaerial exposure surface is characterized by strongly 12c enriched limestones 13c compositions of underlying limestones grow progressively heavier with increasing depth 2 the subaerial exposure surface may also be marked by slight 18o enrichment 3 an abrupt shift in 18o values may differentiate sediments above the exposure surface from those below 4 sediments altered in the marine meteoric mixing zone may be characterized by positive covariance between their 18o and 13c compositions 5 the vadose phreatic boundary may be marked by a sharp increase in 13c values in the seaward portions of a fresh groundwater system and 6 samples contemporaneously altered in a single fresh groundwater system within an areally restricted region should display a narrow range of 18o and a wide range of 13c compositions analysis of samples from five palaeozoic and mesozoic formations which contained petrographic evidence of early freshwater diagenesis showed that isotope patterns similar to those observed in barbados limestones have been preserved in rocks as old as mississippian these isotope patterns could prove to be useful for identifying diagenetically induced porosity trends in carbonate rocks they might be used to identify limestones diagenetically altered in meteoric environments to identify mixing zone cements and dolomites and to trace the regional and vertical distributions of early meteoric groundwater systems in ancient carbonate formations

locating earthquakes with amplitude application to real time seismology earthquakes are traditionally located using travel times however since the ground motion amplitude generally decays with the distance from the source it should also be possible to locate earthquakes using amplitude data amplitudes are affected by many factors other than the distance so that we do not expect to be able to locate the epicenter the location of the initial rupture very accurately with amplitude data however locating earthquakes with amplitudes has its own merits 1 for postearthquake emergency services it is often more important to know the spatial distribution of strong motion parameters such as peak acceleration and peak velocity than the rupture initiation point itself national research council 1991 this is especially true for thrust earthquakes e g 1971 san fernando earthquake 1987 whittier narrows earthquake or events with large rupture zones 2 the amplitudes are usually much easier to determine than the arrival times especially for events with complex rupture patterns or with immediate foreshocks in which event association can be difficult for application to real time earthquake information systems such as cube caltech usgs broadcast of earthquakes kanamori et al 1991 the amplitude method could provide a quick and robust way to send useful information for emergency operations here we report a few examples and propose a method for future implementation in a cube type system

japan unified high resolution relocated catalog for earthquakes juice crustal seismicity beneath the japanese islands abstract we have generated a high resolution catalog called the japan unified high resolution relocated catalog for earthquakes juice which can be used to evaluate the geometry and seismogenic depth of active faults in japan we relocated 1 1 million hypocenters from the nied hi net catalog for events which occurred between january 2001 and december 2012 to a depth of 40 km we apply a relative hypocenter determination method to the data in each grid square in which entire japan is divided into 1257 grid squares to parallelize the relocation procedure we used a double difference method incorporating cross correlating differential times as well as catalog differential times this allows us to resolve in detail a seismicity distribution for the entire japanese islands we estimated location uncertainty by a statistical resampling method using jackknife samples and show that the uncertainty can be within 0 37 km in the horizontal and 0 85 km in the vertical direction with a 90 confidence interval for areas with good station coverage our seismogenic depth estimate agrees with the lower limit of the hypocenter distribution for a recent earthquake on the kamishiro fault 2014 mj 6 7 which suggests that the new catalog should be useful for estimating the size of future earthquakes for inland active faults

real time monitoring of moment magnitude by waveform inversion 1 an instantaneous measure of the moment magnitude mw of an ongoing earthquake is estimated from the moment rate function mrf determined in real time from available seismic data using waveform inversion integration of the mrf gives the moment function from which an instantaneousmw is derived by repeating the inversion procedure at regular intervals while seismic data are coming in we can monitor the evolution of seismic moment and mw with time the final size and duration of a strong earthquake can be obtained within 12 to 15 minutes after the origin time we show examples of mw monitoring for three large earthquakes at regional distances the estimated mw is only weakly sensitive to changes in the assumed source parameters depending on the availability of seismic stations close to the epicenter a rapid estimation of the mw as a prerequisite for the assessment of earthquake damage potential appears to be feasible

one minute after strong motion map effective epicenter and effective magnitude abstract this article reports the recent progress on real time seismic monitoring in taiwan particularly the real time strong motion monitoring by the taiwan central weather bureau9s telemetered seismic network cwbsn which is presently aiming at rapid reporting immediately after a large earthquake occurrence if rapid reporting can be achieved before the arrival of the strong shaking earthquake early warning will become possible cwbsn has achieved the generation of the intensity map epicenter and magnitude within 1 min of the occurrence of a large earthquake both rapid reporting and early warning are principally applied to large m 5 events the requirement of on scale waveform recording prompted cwbsn in 1995 to integrate strong motion sensors e g force balance accelerometers into its telemetered seismic monitoring system time domain recursive processing is applied to the multi channel incoming seismic signals by a group of networked personal computers to generate the intensity map from the isoseismal contours an effective epicenter is immediately identified that resides in the middle of the largest usually the 100 gal contour curve of the intensity map an effective magnitude is also defined that can be derived immediately from the surface area covered by the largest usually the 100 gal contour curve for a large event with a finite rupture surface the epicenter and magnitude so derived are more adequate estimates of the source location and of the strength of destruction the effective epicenter gives the center of the damage area it stands in contrast with the conventional epicenter location which only gives the initial point of rupture nucleation the effective magnitude reflects more closely the earthquake damage potential instead of the classical magnitude definition that emphasizes the total energy release the cwbsn has achieved in obtaining the above crucial source information well within 1 min this time can further be reduced to better than 30 sec as illustrated by the example in this article showing that earthquake early warning is indeed an achievable goal the rapid reporting and early warning information is electronically transmitted to users to allow rapid response actions with or without further human intervention

deep structure of the northeastern japan arc and its relationship to seismic and volcanic activity evidence for possible deep seated magmatic activity beneath northeastern japan can be obtained from seismic observations tomographic inversions of p wave velocity data show low velocity zones distributed in the crust and upper mantle beneath active volcanoes in or around these zones anomalously low frequency micro earthquakes perhaps caused by magmatic activity are found at depths of 25 40 km distinct s wave reflectors corresponding to the upper surfaces of magma bodies are found at depths of 10 18 km large crustal earthquakes also occur around the low velocity zones these observations reveal the distribution of magma reservoirs at depths and elucidate its relation with shallow seismicity beneath volcanic arcs

simultaneous estimation of attenuation structure source parameters and site response spectra application to the northeastern part of honshu japan abstract we have developed an inversion method for estimating q structure by the use of a large number of waveform data from earthquakes we divide an area to be analyzed into small blocks and simultaneously estimate the q value in each block source parameters for each event and site response spectrum for each station the source spectrum is assumed to be expressed by the 2 model and values of corner frequencies and low frequency levels of source spectra are estimated amplitudes are calculated by taking the orientation of focal mechanism solutions into account a trade off among estimated parameters is tested by numerical experiments using three sets of artificial data in a case when artificial data include error of 15 in the orientation of the p axis of focal mechanism solutions the inverted result shows that the original checkerboard pattern of q structure is well reconstructed although estimated q 1 values are about 10 higher than those of the original one the result without the corrections for radiation effect shows that the checkerboard pattern is only reconstructed in the blocks having a sufficient number of ray paths we applied this inversion method to a real data set in the northeastern part of honshu japan estimated q p structure shows that low q p regions are distributed beneath the volcanic front and they move towards the west with increasing depth previous studies of three dimensional seismic velocity structure in this area show that p wave low velocity regions exist in the crust beneath the volcanic front and they are inclined towards the west in the mantle wedge the low q p regions estimated in this study coincide in general with the p wave low velocity regions

test of a threshold based earthquake early warning method using japanese data most of existing earthquake early warning systems are regional or on site systems a new concept is the integration of these approaches for the definition of alert levels and the estimation of the earthquake potential damage zone pdz the key element of the method is the real time simultaneous measurement of initial peak displacement p d and period parameter c in a 3 s window after the first p wave arrival time at accelerometer stations located at increasing distances from the epicenter as for the on site approach the recorded values of p d and c are compared to threshold values which are set for a minimum magnitude m 6 and instrumental intensity i mm vii according to empirical regression analysis of strong motion data from different seismic regions at each recording site the alert level is assigned based on a decisional table with four entries defined by threshold values of the parameters p d and c a regional network of stations provides the event location and transmits the information about the alert levels recorded at near source stations to more distant sites before the arrival of the most destructive phase we present the results of performance tests of this method using ten m 6 japanese earthquakes that occurred in the period 2000 2009 and propose a very robust methodology for mapping the pdz in the first seconds after a moderate to large earthquake the studied cases displayed a very good matching between the rapidly predicted earthquake pdz inferred from initial p peak displacement amplitudes and the instrumental intensity map the latter being mapped after the event using peak ground velocity and or acceleration or from field macroseismic surveys

rapid estimation of earthquake source and ground motion parameters for earthquake early warning using data from a single three component broadband or strong motion sensor we propose a new algorithm to rapidly determine earthquake source and ground motion parameters for earthquake early warning eew this algorithm uses the acceleration velocity and displacement waveforms of a single three component broadband bb or strong motion sm sensor to perform real time earthquake noise discrimination and near far source classification when an earthquake is detected the algorithm estimates the moment magnitude m epicentral distance and peak ground velocity pgv at the site of observation the algorithm was constructed by using an artificial neural network ann approach our training and test datasets consist of 2431 three component sm and bb records of 161 crustal earthquakes in california japan and taiwan with 3 1 m 7 6 at 115 km first estimates become available at t 0 0 25 s after the p pick and are regularly updated we find that displacement and velocity waveforms are most relevant for the estimation of m and pgv while acceleration is important for earthquake noise discrimination including site corrections reduces the errors up to 10 the estimates improve by an additional 10 if we use both the vertical and horizontal components of recorded ground motions the uncertainties of the predicted parameters decrease with increasing time window length t 0 larger magnitude events show a slower decay of these uncertainties than small earthquakes we compare our approach with the c algorithm and find that our prediction errors are around 60 smaller however in general there is a limitation to the prediction accuracy an eew system can provide if based on single sensor observations

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

burial diagenesis and thermochemical sulfate reduction smackover formation southeastern mississippi salt basin the smackover formation in the southeastern mississippi salt basin has been buried from 3 03 to 6 06 km and subjected to temperatures of 100 to 200c pre hydrocarbon migration burial diagenesis is characterized by precipitation of calcite cement followed by saddle dolomite and late anhydrite these phases formed at temperatures of less than 100c the oxygen isotopic composition of calcite ranges from minus 5 to minus 8 4 pdb and carbon isotopic composition ranges from 3 5 to 6 0 pdb the sulfur isotopic composition of late anhydrites ranges from 18 1 to 19 1 cdt post hydrocarbon migration burial diagenesis is dominated by replacement of previously formed late anhydrite by calcite or calcite plus elemental sulfur and precipitation of post bitumen calcite cement these diagenetic phases formed at temperatures above 150c and are present only in the deep part of the basin the oxygen isotopic compositions of calcites that replace anhydrite range from minus 3 0 to minus 4 0 pdb and carbon isotopic compositions range from minus 2 0 to 4 2 pdb the oxygen isotopic compositions of post bitumen calcites range from minus 3 4 to minus 5 6 pdb and carbon isotopic compositions range from minus 1 6 to minus 16 3 pdb two samples of elemental sulfur have sulfur isotopic compositions of 15 8 and 16 1 cdt the high temperature replacement of anhydrite by calcite more the presence of post bitumen calcite cement the sulfur isotopic composition of sulfates and elemental sulfur and high concentration of hydrogen sulfide indicate that rapid thermochemical reduction of solid sulfates is taking place in the deep part of the mississippi salt basin at temperatures as low as 150c less

skeletal aragonite neomorphism quantitative modelling of a two water diagenetic system abstract the neomorphism of skeletal aragonite occurs by the simultaneous dissolution of aragonite and precipitation of calcite along thin solution films which may have an associated zone of partly dissolved aragonite chalky zone it has been proposed that pore waters at neomorphic calcite aragonite contact zones neomorphic fronts may be partly isolated from bulk pore waters and thus retain primary geochemical signatures to varying degrees iterative computer programs were developed that simulate aragonite neomorphism in two water diagenetic systems using stable isotope and trace element data neomorphism of aragonitic mollusks from the purbeck group of southern england late jurassic to early cretaceous was associated with a decrease in strontium concentration from approximately 5100 ppm to 500 ppm modelling results indicate a high bulk water rock ratio and minimal if any isolation of the neomorphic front waters for the purbeck group mollusks and also for some pleistocene corals partial isolation of neomorphic front waters from bulk pore waters is uncommon based on published data on the geochemistry of neomorphic calcites however partial isolation does occur in some thick low porosity shells such as the gastropod strombus gigas pleistocene process based modelling of fluid rock interaction provides a means for better interpreting trace element and stable isotope data in diagenetic carbonates sensitivity analysis results indicate that water rock ratios cannot be determined at much better than order of magnitude accuracies because of uncertainties over initial pore water composition fractionation factors and distribution coefficients

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