recovering seismic displacements through combined use of 1 hz gps and strong motion accelerometers retrieving displacement from seismic acceleration records is often difficult because unknown small baseline offsets in the acceleration time series will contaminate the doubly integrated record with large quadratic errors one hertz global positioning system gps position estimates and collocated seismic data are available from the 2003 m w 8 tokachi oki hokkaido earthquake after a process of correcting for possible misorientation of the seismic sensors an inversion method is used to simultaneously solve for ground displacement with both data sets as input constraints this inversion method takes into account the presence of unknown offsets in the acceleration record and the relatively large uncertainties in the estimated 1 hz gps positions in this study 117 channels of seismic data were analyzed only 5 of the time does the static displacement retrieved from traditional baseline correction processing without gps information agree with the absolute displacement measured with 1 hz gps to within the errors of the gps data in solving simultaneously for constrained displacements that agree with both the seismic and gps data sets an optimal solution was found that included only one or two step functions in the acceleration records potential explanations for the offsets are analyzed in terms of tilt of the sensor or electronic noise for nine stations clear misorientations of the seismic sensors of more than 20 deg from the reported orientation were found for this size event the 30 sec sampled gps solutions were also a sufficient constraint for establishing the offset errors and recovering reliable displacements the results significantly extend the frequency band over which accelerometer data are reliable for source inversion studies online material plots of constrained seismograms with metadata

love wave dispersion in central north america determined using absolute displacement seismograms from high rate gps 1 we use seismic array processing of high rate gps hrgps displacement time series from the great 2004 mw 9 sumatra andaman earthquake recorded at over 90 nonuniformly distributed hrgps stations in central north america to determine the fundamental love wave phase velocity dispersion curve there these measurements were performed using frequency domain beam forming which we show reduces the effects of gps multipath and common mode noise on the measurement of surface wave phase velocity and azimuth our hrgps based results for surface wave phase velocity agree well with those obtained from 28 broadband seismometers between periods of 20 to 300 s by separating waves based on their apparent velocity beam forming supports the simple model for relative displacement hrgps time series as being the difference between the reference and kinematic station s absolute displacements beam forming also demonstrates that for differential gps processing the infinite apparent velocity beam of an array is composed of the sum of common mode noise and the reference station s absolute displacements multipath and noise we show the infinite apparent velocity beam which we call the generalized spatial filter is similar to the spatial filter commonly used to remove common mode noise from hrgps seismograms and can be used to produce absolute displacement time series for the kinematic stations with reduced common mode noise beam forming also suggests a filtering method complimentary to sidereal filtering to produce gps multipath reduced hrgps time series

the 2002 denali fault earthquake alaska a large magnitude slip partitioned event the mw moment magnitude 7 9 denali fault earthquake on 3 november 2002 was associated with 340 kilometers of surface rupture and was the largest strike slip earthquake in north america in almost 150 years it illuminates earthquake mechanics and hazards of large strike slip faults it began with thrusting on the previously unrecognized susitna glacier fault continued with right slip on the denali fault then took a right step and continued with right slip on the totschunda fault there is good correlation between geologically observed and geophysically inferred moment release the earthquake produced unusually strong distal effects in the rupture propagation direction including triggered seismicity

performance of high rate gps waveforms at long periods moment tensor inversion of the 2003 mw 8 3 tokachi oki earthquake abstract we present a comparison of long period 30 t m w 8 3 with both very broadband seismograms and synthetic waveforms we show that gps provides valuable waveform data between 40 and 160 s periods especially in the near field of the earthquake where seismograms are saturated there are no long period broadband seismic data available in the near field of large earthquakes 100 km for earthquakes m w 7 and 500 km for earthquakes m w 8 the comparison with synthetic seismic displacement waveforms shows that the gps waveforms are performing well at periods of 40 80 s at epicentral distances between 150 and 600 km and at periods of 80 160 s at epicentral distances between 150 and 400 km at longer periods and larger epicentral distances the amplitudes do not always exceed the noise level 2 3 mm but we still observe at selected gps sites that the phase and the amplitude of the surface waves are of good quality up to 1200 km we conclude that gps waveforms in the near field of a large event can be used for seismological applications in this article we recover the focal mechanism of the tokachi oki event by inverting the gps data recorded within 300 km of the epicenter

itrf2000 a new release of the international terrestrial reference frame for earth science applications 1 for the first time in the history of the international terrestrial reference frame the itrf2000 combines unconstrained space geodesy solutions that are free from any tectonic plate motion model minimum constraints are applied to these solutions solely in order to define the underlying terrestrial reference frame trf the itrf2000 origin is defined by the earth center of mass sensed by satellite laser ranging slr and its scale by slr and very long baseline interferometry its orientation is aligned to the itrf97 at epoch 1997 0 and its orientation time evolution follows conventionally that of the no net rotation nnr nuvel 1a model the itrf2000 orientation and its rate are implemented using a consistent geodetic method anchored over a selection of itrf sites of high geodetic quality ensuring a datum definition at the 1 mm level this new frame is the most extensive and accurate one ever developed containing about 800 stations located at about 500 sites with better distribution over the globe compared to past itrf versions but still with more site concentration in western europe and north america about 50 of station positions are determined to better than 1 cm and about 100 sites have their velocity estimated to at or better than 1 mm yr level the itrf2000 velocity field was used to estimate relative rotation poles for six major tectonic plates that are independent of the trf orientation rate a comparison to relative rotation poles of the nuvel 1a plate motion model shows vector differences ranging between 0 03 and 0 08 m y equivalent to approximately 1 7 mm yr over the earth s surface itrf2000 angular velocities for four plates relative to the pacific plate appear to be faster than those predicted by the nuvel 1a model the two most populated plates in terms of space geodetic sites north america and eurasia exhibit a relative euler rotation pole of about 0 056 0 005 m y faster than the pole predicted by nuvel 1a and located about 10 n 7 e more to the northwest compared to that model

ghost tilt signal during transient ground surface deformation events insights from the september 3 2010 mw7 1 darfield earthquake new zealand 1 this work assesses whether tiltmeters can reliably measure ground tilt in the 2 20 s band similar to that of very long period volcanic earthquakes seismic waves recorded with co located high rate gps borehole seismometer and bubble tiltmeter during the 2010 mw7 1 darfield earthquake in new zealand are used to determine the response of the tiltmeter the joint analysis of this dataset shows that at least for periods within the aforementioned band the observed tilt signal was in fact not related to ground tilt but instead to translational ground acceleration caused by passing s and surface waves if no independent control on translational motion is provided for recorded very long period volcanic earthquakes within the 2 20 s band the signal recorded on bubble tiltmeters may therefore be misinterpreted the use of co located high rate gps data provides such control and is essential to discriminate translational motion from ground tilt on the recorded seismic and tiltmeter signals

guzhangian mid cambrian trilobites from siliceous concretions of the valtorres formation iberian chains ne spain in the carbonate siliciclastic strata of west gondwana e g in the montagne noire france the aftermath of the mid languedocian mid cambrian regression is characterized by a late languedocian major turnover of trilobite families and a furongian early tremadocian radiation related to the stepwise immigration of trilobite invaders from east gondwana under persistent transgressive conditions the scarcity of upper languedocian fossil accumulations in clayey substrates has inspired the sampling of the palaeogeographically most distal parts of the iberian chains spain where diagenetic dissolution of ubiquitous hexactinellid sponge spicules has favoured the formation of siliceous concretions these have yielded the trilobites peronopsis cf insignis oidalagnostus trispinifer proampyx difformis proampyx aculeatus bailiaspis glabrata holocephalina agrauloides by ontogeny holasaphus cf centropyge and a paradoxidid gen et sp indet despite preservation and sampling biases the identification of this taphonomic window in offshore clayey substrates of west gondwana allows the recognition of a strong biogeographical link with baltica and the correlation of the global guzhangian stage and the solenopleura brachymetopa zone of scandinavia with part of the mediterranean upper languedocian substage less

the potential of high rate gps for strong ground motion assessment abstract we show that high rate global positioning system gps can have a vital role to play in near real time monitoring of potentially destructive earthquakes we do this by investigating the potential of gps in recording strong ground motions from earthquakes in switzerland and japan the study uses finite fault stochastic ground motion simulation based on fourier amplitude spectra and duration models previously developed for both countries allowing comparisons in terms of both fourier and time domain characteristics here the peak ground velocity pgv we find that earthquakes of magnitude m w 5 8 can be recorded by gps in real time at 10 km distance that is their fourier spectrum exceeds the noise of the instruments enough to be used in strong motion seismology postprocessing of gps time series lowers the noise and can improve the minimum observable magnitude by 0 1 0 2 as gps receivers can record at higher rates 10 hz we investigate which sampling rate is sufficient to optimally record earthquake signals and conclude that a minimum sampling rate of 5 hz is recommended this is driven by recording events at short distances below 10 km for magnitude 6 events and below 30 km for magnitude 7 events furthermore the maximum ground velocity derived from gps is compared with the actual pgv for synthetic signals from the stochastic simulations and the 2008 m w 6 9 iwate earthquake the proposed model confirmed by synthetic and empirical data shows that a reliable estimate of pgv for events of about magnitude 7 and greater can be basically retrieved by gps in real time and could be included for instance in shakemaps for aiding postevent disaster management

middle cambrian echinoderms from north spain show echinoderms diversified earlier in gondwana new fossil discoveries in the middle cambrian of spain have considerably expanded our knowledge of the temporal and spatial distribution of some major clades of echinoderms including sucocystid cinctans isorophid edrioasteroids cothurnocystid stylophorans ctenocystoids and a new group of blastozoans eocystitids because many of these taxa appear close to the beginning of the middle cambrian it seems likely that their origins must be placed in the early cambrian these results based on articulated specimens provided from echinoderm lagerstatten agree with the hidden diversity provided from isolated ossicles from other gondwanan areas

rupture directivity of the 3 november 2002 denali fault earthquake determined from surface waves the m w 7 9 earthquake that struck central alaska on 3 november 2002 was preceded 11 days earlier by an mw 6 7 strike slip foreshock on 23 october 2002 both events were predominantly strike slip and ruptured structures associated with the denali fault system previous studies have shown that the mainshock began with failure on a relatively small northeast striking reverse fault before breaking out for 300 km of right lateral strike slip rupture aftershock patterns suggest that the fore shock ruptured a region west of the mainshock which began near the eastern extent of the foreshock sequence and proceeded east southeast to constrain and to quantify source duration and directivity effects we examine surface wave displacement seis mograms and use an empirical green s function egf to isolate and explore main shock rupture kinematics our particular interest lies in large amplitude focussing caused by directivity we observe love and rayleigh wave amplification of two orders of magnitude in the period range from 10 to 33 sec these remarkable directivity enhanced surface waves triggered small earthquakes more than 3000 km from the mainshock rupture

gps seismology application to the 2002 mw 7 9 denali fault earthquake abstract the 2002 denali fault alaska earthquake m w 7 9 caused one or more components of most broadband seismometers in western canada to clip yet did not trigger strong motion instruments thus leaving a substantial gap in the seismic record of this event however the large amplitude surface waves generated by this event were well recorded by the global positioning system gps in the same region out to epicentral distances of more than 3000 km in this article we explore the capabilities of gps seismology specifically how the relative strengths of gps and seismic data sets can be exploited in order to more effectively study earthquake source characteristics and wave propagation effects high rate 1 hz gps data from 23 stations throughout western north america have been analyzed to derive displacement waveforms for this event and the impact of instrumentation gps receiver model and error reduction strategy modified sidereal and spatial filtering on the noise characteristics of displacement time series at each gps site was assessed after applying error reduction methods to gps displacements the final average noise floors of 0 5 cm in the horizontal and 1 5 cm in the vertical indicate that large dynamic displacements are observable by gps we validate the gps displacements by comparing broadband seismic recordings integrated to displacement with gps recordings for four effectively colocated sets of instruments we show excellent agreement between the unclipped seismic and gps recordings of the surface waves from the denali earthquake over the period range of 10 50 sec and for ground displacements exceeding about 1 0 cm thus a large gps displacement data set is now available for western north america an area where records of this event were previously missing or incomplete the final gps seismograms are archived at incorporated research institutions for seismology iris for public use in future studies of the 2002 denali earthquake

modeling the rupture process of the 2003 september 25 tokachi oki hokkaido earthquake using 1 hz gps data received 10 september 2004 accepted 3 october 2004 published 3 november 2004 1 high rategpshasthepotentialtorecoverbothdynamic and static displacements accurately we analyze 1 hz gps data recorded during the 2003 tokachi oki earthquake the 1 hz gps displacement waveforms show good agreement with integrated accelerometer records except for low frequency noise that are inherently present in integrated seismic records the gps waveforms were inverted to model the spatio temporal evolution of the fault slip during the rupture the slip is found to propagate downdip in the subduction zone with largest moment release 50 km northwest of the hypocenter the region of largest slip agrees in general with traditional seismic studies indicating that 1 hz gps can be used for finite fault studies the 1 hz gps slip model shows clearer contrast with afterslip distributions than those inferred from strong motion data possibly because 1 hz gps is more sensitive to cumulative slip distribution index terms 1294 geodesy and gravity instruments and techniques 7209 seismology earthquake dynamics and mechanics 7212 seismology earthquake ground motions and engineering citation miyazaki s k m larson k choi k hikima k koketsu p bodin j haase g emore and a yamagiwa 2004 modeling the rupture process of the 2003 september 25 tokachi oki hokkaido earthquake using 1 hz gps data geophys res lett 31 l21603 doi 10 1029 2004gl021457

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

the mw 7 9 denali fault earthquake of 3 november 2002 felt reports and unusual effects across western canada the 3 november 2002 m w 7 9 denali fault earthquake was one of the largest north american earthquakes of the past 100 years this earthquake located 330 km to the west of the yukon alaska border generated 260 reports of shaking and other unusual effects to distances of 3500 km across western canada felt intensity for this earthquake ranged from v at communities in the yukon closest to the epicenter about 350 km distance iv across much of the yukon territory distances of 350 to 750 km iii across much of northern british columbia to ii in southern british columbia and alberta about 2400 km distance in many instances people reported feeling nauseous or seasick and having trouble standing the long period ground motions generated by this earthquake displacements greater than 10 cm were recorded in the yukon caused water to spill from swimming pools generated seiches in lakes and rivers and affected wells instances of dirty well water to distances of 3500 km across western canada

using 1 hz gps data to measure deformations caused by the denali fault earthquake the 3 november 2002 moment magnitude 7 9 denali fault earthquake generated large permanent surface displacements in alaska and large amplitude surface waves throughout western north america we find good agreement between strong ground motion records integrated to displacement and 1 hertz global positioning system gps position estimates collected 140 kilometers from the earthquake epicenter one hertz gps receivers also detected seismic surface waves 750 to 3800 kilometers from the epicenter whereas these waves saturated many of the seismicinstruments in the same region high frequency gps increases the dynamic range and frequency bandwidth of ground motion observations providing another tool for studying earthquake processes

on the temporal character and regionality of the arctic oscillation decadal differences between the 1990s and 1980s in winter jfm sea level pressure and 300 mb zonal winds have an arctic centered character with nearly equal contributions from the atlantic and pacific sectors in contrast the differences between positive and negative arctic oscillation ao composites defined from monthly values of principal components from the same period have similar magnitudes in the pacific and arctic but have an additional large north atlantic oscillation nao signature in the atlantic sector thus arctic changes on decadal scales are more symmetric with the pole than suggested by the standard ao index definition change point analysis of the ao shows that a shift in value near 1989 is an alternate hypothesis to a linear trend analysis of zonal and meridional winds by longitudinal sectors shows the importance of the standing wave pattern in interpreting the ao which supplements the view of the ao as a simple zonal average annular mode

5hz gps seismology of the el mayor cucapah earthquake estimating the earthquake focal mechanism summary high rate 5hz gps records observed in the near field following the magnitude 7 2 el mayor cucapah earthquake that occurred in northern mexico on 2010 april 4 are compared with broad band seismograms the high rate gps displacement records are consistent with the twice integrated strong motion seismic records in the near field where broad band seismograms are clipped due to strong shaking agreement degrades at distances greater than about 150 km from the epicentre where displacement amplitudes approach the noise level of gps seismograms using high rate gps data the focal mechanism of the main shock is estimated and is shown to be consistent with teleseismic estimates the result is seen as confirmation that high rate gps observed at near field stations can be applied together with teleseismic seismometers to yield better information about earthquake rupture properties and parameters

early palaeozoic peri gondwana terranes new insights from tectonics and biogeography following the late neoproterozoic early cambrian breakup of the supercontinent rodinia gondwana evolved as one of the principal continental masses on earth embracing most of south america africa australasia antarctica much of western europe and parts of asia around its margins were various other terranes that had varying tectonic and biogeographical affinities with the main continental block this book incorporates a series of reviews and multidisciplinary research papers that together explore the tectonic palaeogeographical and palaeobiogeographical evolution of the elements that made up the peri gondwanan collage the stratigraphical scope of the coverage embraces the late precambrian through early devonian providing a comprehensive overview of structural stratigraphical and biological evolution through this significant interval of earth history integration of these various processes throughout the volume will be of broad based interest to a wide range of geoscientists

source process of the 3 november 2002 denali fault earthquake central alaska from teleseismic observations 1 the november 3 2002 denali fault earthquake which is the largest inland event ever recorded in central alaska occurred along an arcuate segment of the right lateral strike slip denali fault we use first motion p wave polarities and inversions of teleseismic p waveforms for a fixed focal mechanism to constrain the rupture process we find clear evidence for a substantial reverse component near the hypocenter at the beginning of the rupture twenty five seconds later rupture propagated unilaterally to the east on a strike slip fault and released most of the seismic moment along an asperity located 170 km east of the hypocenter with a maximum slip of 8 m this earthquake had a duration of 120 s and ruptured more than 300 km in length correlation with gravity anomalies suggests a relation between moment distribution and physical properties of subsurface rock units that may support a weaker middle fault segment marked by fewer aftershocks

detecting multiple surface waves excited by the 2011 tohoku oki earthquake from geonet observations abstract multiple surface waves circling the earth excited by the 2011 m w 9 0 tohoku oki earthquake were well recorded by both global and regional broadband bb seismometer networks in this study we explore the ability of kinematic solutions of global positioning system gps observations from geonet to reveal the phases of multiple surface waves even though multipath effects and common mode errors are not reduced the wave packages of g 2 g 3 of love waves and r 2 r 3 of rayleigh waves are clearly identified from the raw gps displacement time series in the 100 500 s periods which show great coherency with bb seismograms in both amplitude and time the arrival times of these wave packages tally with the synthetic value by the group velocities from the global dispersion model we consider that kinematic solutions of continuous gps measurement can act as a supplementary tool for studying global surface wave dispersion

millimeter level ultra long period multiple earth circling surface waves retrieved from dense high rate gps network abstract high rate gps networks have proven to be capable of continuously recording strong ground motion which is valuable for studying earthquake rupture processes and seismic hazard mitigation previous studies of high rate gps usually resolved dynamic ground displacements of some major seismic phases stronger than a few millimeters in this study we explore the feasibility of retrieving much weaker ground motions sub millimeter in long duration records by stacking high rate gps network we processed data of the 2011 tohoku oki earthquake recorded by more than 600 high rate gps stations of the plate boundary observatory pbo and analyzed kinematic displacement results with seismic array methods from these high rate gps seismograms we identified abundant seismic phases not only including clear body waves such as multiple s waves s ss sss ssss traveling along minor major great circle arc and ssssss beyond 360 degrees but also the r1 r5 rayleigh waves and g1 g6 love waves some of which travel around the earth multiple times many of these seismic phases have not been reported by previous high rate gps studies the group velocity dispersion curves extracted from multiple earth circling love waves of high rate gps are consistent with those of broadband seismic records in the period from 150 to 600 s which can sample the mantle structure down to top of the lower mantle thus important for understanding interaction between upper mantle and lower mantle so the dense high rate gps networks should be useful for deep mantle research as an additional valuable dataset with the development of multi system gnss and the more precise modeling of error sources high rate gnss data should have great potential for accurately detecting more geodynamic processes with much wider bandwidth in geoscience studies

slip history of the 2003 san simeon earthquake constrained by combining 1 hz gps strong motion and teleseismic data 1 the slip history of the 2003 san simeon earthquake is constrained by combining strong motion and teleseismic data along with gps static offsets and 1 hz gps observations comparisons of a 1 hz gps time series and a co located strong motion data are in very good agreement demonstrating a new application of gps the inversion results for this event indicate that the rupture initiated at a depth of 8 5 km and propagated southeastwards with a speed 3 0 km sec with rake vectors forming a fan structure around the hypocenter we obtained a peak slip of 2 8 m and total seismic moment of 6 2 10 18 nm we interpret the slip distribution as indicating that the hanging wall rotates relative to the footwall around the hypocenter in a sense that appears consistent with the shape of the mapped fault trace index terms 1242 geodesy and gravity seismic deformations 7205 7212 seismology earthquake ground motions and engineering 8123 tectonophysics dynamics seismotectonics citation ji c k m larson y tan k w hudnut and k choi 2004 slip history of the 2003 san simeon earthquake constrained by combining 1 hz gps strong motion and teleseismic data geophys res lett 31 l17608 doi 10 1029 2004gl020448

surface waves of the 2011 tohoku earthquake observations of taiwan s dense high rate gps network 1 surface waves generated by the 2011 mw 9 0 tohoku japan earthquake were recorded by both the high rate gps and broadband seismic stations in taiwan in this study we investigate the precision of high rate gps displacements and estimate the feasibility of using gps for seismology study in taiwan one hertz observations of 210 continuous gps stations in taiwan and neighboring islands were processed using a precise point positioning technique to estimate the absolute epoch by epoch positions generated by the tohoku earthquake modified sidereal filtering was used to correct for near daily periodical variations of high rate position time series that may be influenced by multipath effects and a band pass filter was used to remove noises from marginal frequencies for all the 210 stations the gps precision after modified sidereal filtering improved from 8 2 to 7 4 mm in the horizontal and from 19 5 to 12 7 mm in the vertical components except for about 20 of the data with large position errors after applying the band pass filter in the teleseismic frequency band 0 008 0 08 hz excluding 54 stations with noisy data 156 continuous gps stations were selected surface wave displacements derived from both high rate gps and broadband seismometers are highly consistent and the correlation coefficients are enhanced by a band pass filter 0 008 0 08 hz from 0 85 to 0 95 in the horizontal and from 0 58 to 0 85 in the vertical components we consider continuous gps can be used as an alternative approach to study characteristics of surface wave propagation in taiwan

ability of 1 hz gps data to infer the source process of a medium sized earthquake the case of the 2008 iwate miyagi nairiku japan earthquake 1 we demonstrate the ability of 1 hz global positioning system gps data to infer a medium sized m6 class earthquake source process through an inversion study of the 2008 iwate miyagi nairiku japan earthquake m 6 9 1 hz gps waveforms for this earthquake are compared and show good agreement with strong motion waveforms ground motions are well recorded at a sufficient number of gps stations in and around source region allowing us to perform waveform inversion using 1 hz gps data only the 1 hz gps inversion result shows fairly good agreement with a joint inversion of geodetic and strong motion data such as the seismic moment mw 6 9 cumulative slip distribution and rupture propagation such agreements demonstrate that 1 hz gps is able to infer the dynamic features of the rupture process as well as permanent or static slip even for a m6 class medium sized earthquake

comparisons of ground motions from colocated and closely spaced one sample per second global positioning system and accelerograph recordings of the 2003 m 6 5 san simeon california earthquake in the parkfield region the 2003 san simeon california earthquake m 6 5 generated a set of colocated and closely spaced high rate 1 sample per second global positioning system gps positions and ground motions from digital accelerographs in the park field region at epicentral distances of 50 to 70 km the waveforms of displacements derived from the 13 gps receivers in the region have dominant periods between about 7 and 18 sec the waveforms are similar in shape with a systematic change in waveform as a function of distance from the source the gps motions are smaller than the accelerograph motions for periods less than about 2 sec from this we conclude that the 1 sample per sec gps receivers provide a good representation of ground motion at periods longer than about 2 sec perhaps more important for earth quake engineering is that the accelerograph data are similar to the gps data for periods as long as 30 sec if not longer this means that data from digital accelero graphs can provide reliable relative displacement response spectra at the periods needed in the design of large structures at least for earthquakes with magnitudes of 6 5 or above at distances within 70 km we combine the colocated or very closely spaced gps and accelerograph data sets in the frequency domain to obtain a single broadband time series of the ground motion at each accelerograph station these broadband ground motions may be useful to seismologists in unraveling the dynamic process of fault rupture and to engineers for designing large structures with very long period response

southern california permanent gps geodetic array spatial filtering of daily positions for estimating coseismic and postseismic displacements induced by the 1992 landers earthquake the june 28 1992 m w 7 3 landers california earthquake was the first earthquake to be surveyed by a continuously operating global positioning system gps array the coordinate time series of seven sites are evaluated for station displacements during an interval of 100 days centered on the day of the earthquake we employ a new spatial filtering technique that removes common mode errors from the coordinate time series this approach provides precise estimates of site specific displacements compared to the cumbersome method of analyzing baselines between pairs of stations all sites indicate significant coseismic horizontal displacements of 5 65 mm with uncertainties of 1 2 mm horizontal displacements are in general agreement with elastic dislocation models in particular for sites closer to the epicenter vertical displacements range from 13 to 7 mm with uncertainties of 2 4 mm the observed vertical displacements in all cases show 5 10 mm more subsidence than expected from geodetic and seismic geologic models significant postseismic horizontal displacements totaling 6 2 mm 10 20 of the coseismic displacement are detected at the three sites closest to the epicenter these displacements are modeled as a short term exponential relaxation with a decay time of 22 10 days superimposed on a longer term linear interseismic trend scaling the observed coseismic and postseismic displacements at one of the sites with the distance to the epicenter provides a measure of site strain which agrees well with the direction and magnitude determined from more precise laser strain meter data the time series do not show any detectable preseismic displacements

effects of earthquake ground motion on tracking characteristics of new global navigation satellite system receivers we use a shake table capable of large 7 g three dimensional accelerations with large payloads to simulate ground motion reconstructed from acceleration data collected during the february 2010 mw 8 8 maule chile earthquake the tracking performance of five modern geodetic gnss receiver and antenna combinations was investigated while undergoing simulated seismic shaking at three two levels of amplification individual system performance was characterized by the number of tracked gnss observations the l1 and l2 gps signal tracking was significantly impacted for the majority of the receiver models during simulations with maximum accelerations of 4 g and the tracking performance for all of the tested receiver types was significantly impaired during the 7 g simulations results show improved tracking when only the antenna was shaken suggesting that vibration induced oscillator phase noise may contribute significantly to tracking degradation during shaking

accuracy of high rate gps for seismology 1 we built a device for translating a gps antenna on a positioning table to simulate the ground motions caused by an earthquake the earthquake simulator is accurate to better than 0 1 mm in position and provides the ground truth displacements for assessing the technique of high rate gps we found that the root mean square error of the 1 hz gps position estimates over the 15 min duration of the simulated seismic event was 2 5 mm with approximately 96 of the observations in error by less than 5 mm and is independent of gps antenna motion the error spectrum of the gps estimates is approximately flicker noise with a 50 decorrelation time for the position error of 1 6 s we find that for the particular event simulated the spectrum of surface deformations exceeds the gps error spectrum within a finite band more studies are required to determine whether a generally optimal bandwidth exists for a target group of seismic events

rapid resolution of crustal motion at short ranges with the global positioning system on the basis of the analysis of global positioning system gps data collected at the u s geological survey kennedy ranch house alinement array near parkfield california in november 1990 and february 1991 we assess the temporal resolution of crustal deformation for gps receiver systems operating as strain meters and provide guidelines for achieving millimeter level precision with short range kinematic type gps measurements site occupation of about one half hour is sufficient for day to day repeatability of submillimeter precision in relative position during good satellite geometry signal multipath effects which dominate dispersive baseline errors are essentially averaged out and need not be modeled however as occupation times decrease baseline solutions are increasingly sensitive to multipath effects which together with nondispersive receiver measurement noise are of millimeter to centimeter magnitude in epoch by epoch solutions on repeatedly monitored baselines we can account for both of these noise sources separately the mostly random receiver noise is effectively suppressed by low pass filters with corner frequencies of about 20 mhz the multipath noise is filtered using the fact that it essentially repeats from day to day residual errors in filtered 1 s epoch by epoch solutions are below 2 mm during periods of good satellite geometry hence for a continuously monitored baseline actual deformation in excess of this threshold can be detected with a time lag comparable to the group delay of the low pass filter i e typically within a minute in terms of strain along a typical short baseline of 1 km sampled once per second we can detect 1 2 s in l min with multipath modeling without multipath modeling it takes 10 min to resolve the same magnitude of deformation in 30 min we can detect 0 1 s independent of multipath modeling these results have important implications for kinematic type gps surveys for millimeter level precision without impractical multipath modeling it is necessary to occupy a site during good satellite geometry for a period longer than that of the multipath signature our experience in both benign and difficult multipath environments indicates that approximately 10 min are sufficient the measurements at the kennedy ranch house alinement array suggest that this segment of the san andreas fault appears to be virtually locked at the surface during the 3 month period between the two surveys

detection of arbitrarily large dynamic ground motions with a dense high rate gps network 1 we describe the detection of teleseismic surface waves from the 3 november 2002 mw 7 9 denali fault earthquake in alaska with a dense network of 1 hz gps stations in southern california about 3900 km from the event relative horizontal displacements with amplitudes in excess of 15 mm and duration of 700 seconds agree with integrated velocities recorded by nearby broadband seismometers with an rms difference of 2 3 mm the displacements are derived from independent 1 hz instantaneous positions demonstrating that a gps network can provide direct measurements of arbitrarily large dynamic and static ground horizontal displacements at periods longer than 1 s and amplitudes above 2 mm with an inherent precision signal to noise that improves indefinitely with amplitude without clipping and in real time high rate real time gps networks can enhance earthquake detection and seismic risk mitigation and support other applications such as intelligent transportation and civil infrastructure monitoring

gps applications for geodynamics and earthquake studies geodetic measurements obtained with the global positioning system gps are increasingly more widely applied in geophysical studies in this paper we review the changes to the technology of gps geodesy over the last five years that are responsible for this increased applicability we survey geophysical investigations employing gps to measure coseismic postseismic and interseismic deformation plate motion and crustal deformation at plate boundaries volcano deformation and the deformation associated with glacial isostatic adjustment and its application to sea level studies we emphasize the use of gps determinations for the modeling of this wide variety of geophysical phenomena we also discuss the recent advent of permanent gps networks for regional geophysical studies as well as the possible future of gps surveying in light of the recent advances