subcontinental scale crustal velocity changes along the pacific north america plate boundary transient tectonic deformation has long been noted within approx100 km of plate boundary fault zones and within active volcanic regions but it is unknown whether transient motions also occur at larger scales within plates relatively localized transients are known to occur as both seismic and episodic aseismic events and are generally ascribed to motions of magma bodies aseismic creep on faults or elastic or viscoelastic effects associated with earthquakes however triggering phenomena and systematic patterns of seismic strain release at subcontinental 1 000 km scale along diffuse plate boundaries have long suggested that energy transfer occurs at larger scale such transfer appears to occur by the interaction of stresses induced by surface wave propagation and magma or groundwater in the crust or from large scale stress diffusion within the oceanic mantle in the decades following clusters of great earthquakes here we report geodetic evidence for a coherent subcontinental scale change in tectonic velocity along a diffuse 1 000 km wide deformation zone our observations are derived from continuous gps global positioning system data collected over the past decade across the basin and range province which absorbs approximately 25 per cent of pacific north america relative plate motion the observed changes in site velocity define a sharp boundary near the centre of the province oriented roughly parallel to the north northwest relative plate motion vector we show that sites to the west of this boundary slowed relative to sites east of it by 1 mm yr 1 starting in late 1999

magnitude scale and quantification of earthquakes despite various shortcomings the earthquake magnitude scale is one of the most fundamental earthquake source parameters to be used for catalogs although use of a uniform scale is desirable it is not always possible because of changes in instrumentation the data reduction method and the magnitude formula the station distribution etc as a result various magnitude scales have been developed and are currently in use recent developments in seismometry and earthquake source theories provide more quantitative source parameters than the magnitude in order to maintain continuity and uniformity of the data it is important to relate these magnitude scales and the new parameters in view of this importance relations between different magnitude scales are examined with an emphasis on the difference in the period of the waves used for the magnitude determination use of several magnitude scales determined at different periods provides a convenient method for characterizing earthquakes the moment magnitude can be used to quantify both shallow and deep earthquakes on the basis of wave energy radiated and provides a uniform scheme

comparison of magnitude estimates for new zealand earthquakes moment magnitude local magnitude and teleseismic body wave magnitude new zealand is one of the more seismically active countries in the world with more than 15 000 earthquakes located each year routine moment tensor analysis of regional seismic data for earthquakes with moment magnitude m w 3 5 4 0 has recently been implemented in new zealand nearly 330 regional moment tensor rmt solutions have been calculated for earthquakes in the new zealand region dating back to late 2003 this complements local magnitude m l the primary magnitude calculated by geonet in new zealand the rmt catalog along with 155 global centroid moment tensor global cmt catalog solutions is used to compare m w with m l for new zealand earthquakes in addition to m w and m l there are more than 330 teleseismic body wave magnitude m b values available from the united states geological survey and international seismological center catalogs for events that also have an m w these are used to examine the relationship between m w m l and m b for new zealand earthquakes there is a clear distinction in the relationship of m l to m w for shallow focus 33 km depth and deep focus 33 km depth earthquakes shallow focus earthquakes show m l to be fairly consistent with m w particularly for events with m w 4 5 and with graphic 1 deep focus earthquakes have m l consistently larger than m w more than a full magnitude unit for some events with graphic 2 m w and m b are in fairly good agreement regardless of the depth whereas m b estimates are consistently smaller than m l for deep events this suggests that m l is overestimated for deep focus events and that the large m ls are not the result of physical properties of the source 1 embed inline graphic 1 gif 2 embed inline graphic 2 gif

gutenberg s surface wave magnitude calibrating function theoretical basis from synthetic seismograms the surface wave magnitude as originally defined by gutenberg 1945 appears to be the most stable quantity rating the strengths of seismic sources it is based on the ground displacement produced by a nearly monochromatic wave train the calibrating function underlying the magnitude definition was obtained from observations of the amplitudes as a function of epicentral distance for a wealth of earthquakes no distinction was made as to focal depths thus the calibrating function depends on one parameter the epicentral distance only subsequent attempts to introduce a focal depth correction were not successful in practice and one and the same calibrating function continues to be applied to events with focal depths ranging from 0 to about 70 km assuming a strike slip point source located inside a standard earth model synthetic seismograms of the fundamental mode sh love wave are computed for a range of focal depths and azimuths amplitude distance curves are obtained and averaged over the azimuths the curves are the basis for improved calibrating functions average depth corrections are obtained and applied to some populations of seismic events the corrected surface wave magnitudes are internally more consistent than the uncorrected ones usually published applying the depth correction to published surface wave magnitudes and considering themb ms relation for a sample of earthquakes and explosions it has been established that for a given intensity of short periodic radiation the 20 s radiation intensity can vary by orders of magnitude while it is known that the 20 s radiation intensity is generally lower for explosions than for earthquakes it turns out to be even lower if the depth correction is applied yielding a clearer separation between both classes of seismic events

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

relationships between m w and other earthquake size parameters in the spanish ign seismic catalog an important part of the preparation and homogenization of the seismic catalog used in the recent seismic hazard assessment study of spain is the development of relationships among the different scales used to measure earthquake size the objective is to convert all earthquake size data in the original catalog to a single magnitude scale the moment magnitude mw in order to have a set of events with an uniform comparable size measurement these new relationships are based on regression analysis between mw and the other units used in the catalog in different epochs the reduced major axis regression scheme is used because it is the most suitable method for symmetric treatment of the variables involved in the fits the new relationships obtained for spain mw as a function of mblg mw as a function of mb and mw as a function of imax are presented and their applicability limits and accuracy are discussed the results obtained could have other practical uses in regional seismicity analysis

ground motion scaling in eastern sicily italy we describe the characteristics of crustal wave propagation in eastern sicily by using the background seismicity of the area we follow the approach de scribed by malagnini hermann and di bona 2000 and malagnini et al 2002 our data set consists of 106 earthquakes recorded by nine three component digital seismic stations between 1994 and 2001 we used only crustal events depths shal lower than 25 km with local magnitudes ranging from 1 0 to 4 3 and hypocentral distances from 10 to 130 km peak ground velocities from 1311 narrow bandpass filtered waveforms are mea sured in thefrequency range 1 0 16 0 hz and regressedtodefinecrustalpropagation excitation and site characteristics with respect to a reference station a subsequent modeling effort is carried out through the use of random vibration theory rvt for obtaining a quantitative evaluation of the apparent geometrical spreading g r and of the crustal quality factor q f an attenuation parameter j0 is also evaluated relative to a reference rock site the attenuation and source parameters estimated in this study are used through the rvt in order to predict the peak horizontal ground acceleration pga and the 5 damping pseudoacceleration spectra psa

homogeneous moment magnitude calibration in switzerland an earthquake catalog containing a uniform size estimate is important for long term seismic hazard assessment in regions of low to moderate seismicity during the update of the earthquake catalog of switzerland ecos we performed regression analyses to convert all earthquake size information in ecos to physically meaningful moment magnitude m w for 34 events in and near switzerland we determined seismic moment thus m w by regional waveform inversion independent m w estimates for the same events do not exist however m w from european mediterranean events obtained in the same way agree with m w from harvard cmt solutions all other size estimates m l m d m b m s and intensities are calibrated relative to these 34 events teleseismic m s and m b from international data centers are directly regressed against m w most observations in ecos consist of local magnitudes m l m d and intensities for local magnitudes we first calibrated the swiss seismological service s m l then we calibrated magnitudes from observatories in neighboring countries france germany italy using only events in the border region e g france switzerland modern instrumental records exist only since the mid 1970s we calibrated the macroseismic dataset which represents by far the largest period in the catalog by determining surface wave magnitude m s for stronger twentieth century swiss earthquakes from analog seismograms these m s which were converted to m w connect intensities and m w after calibration all 20 300 events in ecos have a unified m w including a class type uncertainty estimate based on the original magnitude scale ecos covers the period 250 2001 from 44 n to 51 n and 4 e to 13 e the largest event in ecos is the 1356 m w 6 9 basle earthquake

the relationship between local and moment magnitude in greece during the period 2008 2016 we perform a systematic comparison between local and moment magnitudes in greece for the period 2008 2016 when both magnitudes have been determined using waveform data recorded by the hellenic unified seismic network husn differences between the two magnitudes scales on average do not exceed 0 2 units as has been found in other regions worldwide a recalculation of local magnitude using magnitude residuals for each husn station shows that station site conditions have very little influence on the difference between local and moment magnitude it is therefore more likely that wave propagation effects and in rare cases anomalous source properties are dominant factors in shaping this difference general orthogonal regression is applied to the whole dataset and also to subsets covering different areas of greece or different time period to calibrate the one magnitude scale against the other using a linear model the resulting relationships differ very little suggesting that there is no significant regional temporal variation between local and moment magnitudes while these relationships predict that local magnitude is very close to moment magnitude if both are determined using husn data the comparison with global cmt moment magnitude with m w in the range 4 5 6 2 shows that it is larger than local magnitude by 0 18 units these results are particularly important for converting local magnitudes to equivalent moment magnitudes and thus homogenize the greek earthquake catalog

a new view of italian seismicity using 20 years of instrumental recordings in this paper we show the seismicity of the past 20 years that occurred in italy and surrounding regions hypocentral locations have been obtained by using p and s wave arrival times from the ingv national and several regional permanent seismic networks more than 48 000 events selected from an original data set of about 99 780 are used to reconstruct the most complete seismic picture of the italian region so far the seismicity distribution allows inference on seismotectonics of this complex region of subduction versus continental collision our results clearly reveal the geometry of the adria and the ionian subduction and a continuous normal fault belt in the upper crust following the apennines mountain range the depth of the seismogenic layer is computed from the cut off of seismicity at depth and shows large variations along and across the seismic active regions earthquakes are generated by the different velocity of slab retreat and the subsequent asthenospheric upwelling d 2004 elsevier b v all rights reserved

assessment of gps velocity accuracy for the basin and range geodetic network bargen we assess the accuracy of horizontal velocity estimates from the basin and range geodetic network bargen a continuous gps network that has been in operation since 1996 to make this quantitative assessment we use a procedure that we term the whole error method in this method the measure of the velocity errors is the root mean square rms residual velocity relative to a simple geophysical model this method produces a conservative estimate of the uncertainties since errors in the geophysical models also contribute to the rms residual using estimates from two different bargen subnetworks the northern basin and range and the yucca mountain cluster we determine velocity uncertainties of 0 1 0 2 mm yr 1 since bargen covers a significant fraction of area of the proposed plate boundary observatory component of earthscope our results indicate a good ability of this project to determine highly accurate long term horizontal crustal velocities and deformation rates in this region

new paleoearthquake ages from the western garlock fault implications for regional earthquake occurrence in southern california abstract new paleoseismic investigations on the western segment of the garlock fault at twin lakes california reveal evidence for up to six surface ruptures in the past 5600 years calibrated radiocarbon dates from accelerator mass spectrometer analysis of detrital charcoal constrain the timing of three well defined events at twin lakes to post a d 1450 event a 720 395 b c event g and 3425 2200 b c event i two probable events are also constrained to 625 1525 a d event c and 155 b c a d 615 event e and a possible additional event to 3425 2200 b c and prior to event i our findings offer new insights into mid to late holocene behavior of the western and central segments of the garlock fault and regional fault interactions the timing of the most recent event mre on the western segment likely correlates with the mre at paleoseismic sites on the central segment suggesting that both segments do sometimes rupture together during large earthquakes evidence for events during periods of seismic quiescence on adjacent segments demonstrates that the western and central segments also sometimes rupture independently of one another the occurrence of event g during a lull in seismic strain release at 2 5 ka on faults in the eastern california shear zone ecsz contrasts with other studies that suggest the garlock fault ruptures in phase with ecsz faults our data suggest that seismic strain release on the garlock fault may actually be more in phase with moment release on the mojave section of the san andreas fault and the transverse ranges faults of the los angeles region online material two input files written for the computer program oxcal 4 1 7 and two output files from the oxcal analyses the first input file calibrates and re weights probability density functions pdfs for radiocarbon ages based on stratigraphic ordering and the second input file calculates pdfs for earthquake ages based on radiocarbon ages and stratigraphy bracketing the events

seismic moment tensors of the april 2009 l aquila central italy earthquake sequence summary on 2009 april 6 the central apennines were hit by an mw 6 3 earthquake the region had been shaken since 2008 october by seismic activity that culminated in two foreshocks with mw 4 1 week and a few hours before the main shock we computed seismic moment tensors for 26 events with mw between 3 9 and 6 3 using the regional centroid moment tensor rcmt scheme most of these source parameters have been computed within 1 hr after the earthquake and rapidly revised successively the focal mechanisms are all extensional with a variable and sometimes significant strike slip component this geometry agrees with the ne sw extensional deformation of the apennines known from previous seismic and geodetic observations events group into three clusters those located in the southern area have larger centroid depths and a wider distribution of t axis directions these differences suggest that towards south a different fault system was activated with respect to the sw dipping normal faults beneath l aquila and more to the north

increasing long wavelength relief across the southeastern flank of the sierra nevada california abstract a high degree of correlation between present day relative rock uplift measured using continuous gps geodesy and spatially averaged surface elevations suggests that long wavelength topographic relief is presently increasing along the southeastern flank of the sierra nevada range and within an adjacent portion of the northern basin and range province current estimates for erosion rate are an order of magnitude smaller than the relative rates determined by geodesy thus although the uplift serves to enhance long wavelength relief it cannot be explained entirely as an isostatic response to erosion if uplift rates have been constant through time the duration over which the uplift could have been active

european mediterranean regional centroid moment tensors 1997 2000 the mediterranean region is seismically very active and undergoing rapid deformation earthquakes as strong as m 6 are present but relatively rare on the other hand moderate magnitude seismicity 4 5 m 5 5 is widespread and often damaging an improved knowedge of moderate magnitude earthquakes can contribute significantly to a better understanding of active tectonics in the region harvard centroid moment tensors cmt today represent the most widely used reference for reliable source mechanisms but modelling seismic sources with the cmt technique for earthquakes with magnitude less than m 5 5 5 is quite difficult since 1997 we are using an extension of the standard cmt algorithm to compute regional centroid moment tensors rcmt for moderate magnitude earthquakes mw as low as 4 0 analyzing intermediate period surface waves from regional and teleseismic seismograms we routinely apply the algorithm to european mediterranean seismicity to produce a catalog of seismic moment tensors for events with magnitude between 4 5 and 5 5 which generally are not included in the harvard cmt catalog in this paper we show the results for earthquakes that occurred between 1997 and 2000 consisting of 252 solutions and we discuss the characteristics of the catalog and the areas where these new data are most relevant

mw estimation from crustal coda waves recorded on analog seismograms abstract accurate magnitude determinations are important issues when producing seismicity catalogs aimed at assessing seismic hazard especially in moderate seismicity regions when only a few seismic stations are available the stability of coda wave amplitudes presents great advantages as compared to s lg wave amplitudes for estimating magnitude we develop a method for processing coda waves to determine the moment magnitude m w that is valid both for recent digital short period records and old analog short period seismograms because spectral analyses of paper records are most often not possible we fit the coda envelopes of the raw time signal our empirical representation of the coda envelope is tested with synthetics and its parameters are determined using 109 earthquakes digitally recorded at 12 stations of the laboratoire de detection et de geophysique ldg french velocimetric network between 1997 and 2013 the coda parameters are adapted to the four broad geological zones that can be defined in france within each zone this model matches the observed coda wave envelope for m w between 3 4 and 5 3 synthetic coda signals computed from the regional quality factors q c f within the 0 3 7 hz frequency band of the instrument show that the frequency and regional variation of q c are enough to explain the coda shape of the raw signal this empirical coda model is only valid for events with corner frequency larger than the 1 hz cutoff frequency of the ldg instrument when applying this raw signal envelope model to actual data the site effect at each station must be accounted for from this empirical coda model we obtain stable corrected coda amplitudes that can be directly converted into m w by linear regression

surface deformation in the abruzzi region central italy from multitemporal dinsar analysis summary we investigate the 1992 2000 surface deformation affecting the abruzzi region central italy by exploiting two set of synthetic aperture radar sar data acquired by the ers 1 2 sar sensors from ascending and descending orbits respectively we apply the small baseline subset sbas differential synthetic aperture radar interferometry dinsar technique to the sar data set to estimate the displacement time series and the corresponding velocity maps our dinsar analysis allows us to detect a previously unreported major change in crustal deformation moving from the highest elevation of the central apennines to the adriatic sector that we infer as evidence of a complex tectonic boundary between two adriatic microplates involving a wide interaction zone an extension effect at a rate of about 0 10 10 6 yr 1 is also confirmed by our investigation our findings may have important implications in the seismic hazard assessment within the adriatic region in central italy

climate driven deformation of the solid earth from grace and gps 1 grace data indicate large seasonal variations in gravity that are assumed to be related to climate driven fluxes of surface water seasonal redistribution of surface mass should deform the earth and our calculations using grace data suggest vertical deformations of 13 mm in the region of greatest flux the amazon river basin to test the grace gravity hydrology connection we analyzed gps data acquired from sites in this region after accounting for degree 1 variations not observable with grace we find that annual deformation measured with gps correlates highly with predictions calculated from grace measurements these results confirm the variations in surface water sensed by grace which are significantly larger than those predicted by some hydrology models the results also demonstrate that grace can be an important tool for monitoring deformation of the earth and suggest that combined analysis of grace and gps may be a useful approach for estimation of geocenter variations

vs30 κ regional attenuation and mw from accelerograms application to magnitude 3 5 french earthquakes summary we investigate recordings from weak to moderate earthquakes with magnitudes ranging between about 3 and 5 recorded by the french accelerometric network s wave spectra are modelled as a product of source propagation and site terms inverting large data sets of multiple earthquakes recorded at multiple stations allows us to separate the three contributions source parameters such as moment magnitude corner frequency and stress drop are estimated for each earthquake we provide the first complete and homogeneous catalogue of moment magnitudes for france for the events with magnitude greater than 3 that occurred between 1996 and 2006 stress drops are found to be regionally dependent as well as magnitude dependent and range from about 0 1 mpa 1 bar to about 30 mpa 300 bars the attenuation parameters show that in france on a nationwide scale variations of attenuation properties do exist site transfer functions are also computed giving the level of amplification at different frequencies with respect to the response of a generic rock site characterized by an average 30 m s wave velocity vs30 of 2000 m s 1 from these site terms we compute the high frequency fall off parameter modelled as exp f with f the frequency for 76 stations we also determine rock stations vs30 and we show the vs30 relationship for 21 rock stations

influence of anthropogenic groundwater unloading in indo gangetic plains on the 25 april 2015 mw 7 8 gorkha nepal earthquake groundwater usage in the indo gangetic plains exceeds replenishment of aquifers leading to substantial reduction in the mass such anthropogenic crustal unloading may promote long term fault slip or may modulate seismic activity in the adjoining himalayan region our simulation using gravity recovery and climate experiment data and hydrological models of such a process indicates that the thrust earthquakes on the main himalayan thrust mht including the recent 25 april 2015 mw 7 8 gorkha nepal earthquake are probably influenced by the anthropogenic groundwater unloading process in the gangetic plains the groundwater withdrawal leading to crustal unloading in the gangetic plains causes a significant component of horizontal compression which adds to the secular interseimic compression at the seismogenic depth 5 20 km on the mht beneath the himalayan arc and at hypocentral depth of the 2015 gorkha nepal earthquake this effect enhances the coulomb stress on the locked zone of mht

a completeness analysis of the national seismic network of italy accepted for publication in journal of geophysical research copyright 2009 american geophysical union further reproduction or electronic distribution is not permitted

gps constraints on vertical crustal motion in the northern basin and range 1 we estimated vertical velocities using an array of 12 continuous gps stations forming part of the pbo nucleus network we analyzed data spanning the period 1996 through 2006 the array has an aperture 400 km and crosses a major active intracontinental normal fault system in the northern basin and range province the root mean square rms of vertical rates relative to a local no net vertical frame is 0 3 mm yr indicating high relative rate precision the rms difference between rates based on t 7 year sub strands of the total data set and the full 10 year rate estimates varies as 2 4 t 1 3 mm yr the net vertical rate observed across the greater wasatch fault zone is consistent with the predictions of elastic half space dislocation models only when the deep slipping part of the fault has very shallow dip 30

continuous gps measurements of contemporary deformation across the northern basin and range province we have acquired and analyzed data from the northern basin and range nbar continuous gps network since july 1996 the rms residual with respect to the best fitting lines through the individual station position estimates is 2 3 mm in the horizontal and 6 10 mm in the vertical after the first 395 days of operation uncertainties in horizontal velocity estimates are 1 2 mm yr 1 relative motion among nbar sites located in eastern nevada and in utah is small but east west extension is significant assuming uniform strain accumulation across the whole network the relative motion observed across the wasatch fault zone is 2 2 mm yr east west relative motions among stations in western nevada and california in contrast are dominated by northwest right lateral shear we infer an integrated deformation across the northern basin and range of 11 2 mm yr northwest these rates are consistent with previous geodetic measurements our gps velocity estimates however reveal a possibly abrupt transition from east west extension in eastern nevada and utah to right lateral shear in western nevada this transition is roughly coincident with the central nevada seismic belt and is consistent with the right oblique focal mechanisms of the 1954 dixie valley and fairview peak earthquakes the transition also appears to correlate spatially with a transition in upper mantle structure

active megadetachment beneath the western united states geodetic data interpreted in light of seismic imaging seismicity xenolith studies and the late quaternary geologic history of the northern great basin suggest that a subcontinental scale extensional detachment is localized near the moho to first order seismic yielding in the upper crust at any given latitude in this region occurs via an m7 earthquake every 100 years here we develop the hypothesis that since 1996 the region has undergone a cycle of strain accumulation and release similar to slow slip events observed on subduction megathrusts but yielding occurred on a subhorizontal surface 5 10 times larger in the slip direction and at temperatures 800 c net slip was variable ranging from 5 to 10 mm over most of the region strain energy with moment magnitude equivalent to an m7 earthquake was released along this megadetachment primarily between 2000 0 and 2005 5 slip initiated in late 1998 to mid 1999 in northeastern nevada and is best expressed in late 2003 during a magma injection event at moho depth beneath the sierra nevada accompanied by more rapid eastward relative displacement across the entire region the event ended in the east at 2004 0 and in the remainder of the network at about 2005 5 strain energy thus appears to have been transmitted from the cordilleran interior toward the plate boundary from high gravitational potential to low via yielding on the megadetachment the size and kinematic function of the proposed structure in light of various proxies for lithospheric thickness imply that the subcrustal lithosphere beneath nevada is a strong thin plate even though it resides in a high heat flow tectonic regime a strong lowermost crust and upper mantle is consistent with patterns of postseismic relaxation in the southern great basin deformation microstructures and low water content in dunite xenoliths in young lavas in central nevada and high temperature microstructures in analog surface exposures of deformed lower crust large scale decoupling between crust and upper mantle is consistent with the broad distribution of strain in the upper crust versus the more localized distribution in the subcrustal lithosphere as inferred by such proxies as low p wave velocity and mafic magmatism

modeling deformation induced by seasonal variations of continental water in the himalaya region sensitivity to earth elastic structure strong seasonal variations of horizontal and vertical positions are observed on gps time series from stations located in nepal india and tibet china we show that this geodetic deformation can be explained by seasonal variations of continental water storage driven by the monsoon for this purpose we use satellite data from the gravity recovery and climate experiment to determine the time evolution of surface loading we compute the expected geodetic deformation assuming a perfectly elastic earth model we consider green s functions describing the surface deformation response to a point load for an elastic homogeneous half space model and for a layered nonrotating spherical earth model based on the preliminary reference earth model and a local seismic velocity model the amplitude and phase of the seasonal variation of the vertical and horizontal geodetic positions can be jointly adjusted only with the layered earth model while an elastic half space model fails emphasizing the importance of using a realistic earth elastic structure to model surface displacements induced by surface loading we demonstrate based on a formal inversion that the fit to the geodetic data can be improved by adjusting the layered earth model therefore the study also shows that the modeling of geodetic seasonal variations provides a way to probe the elastic structure of the earth even in the absence of direct measurements of surface load variations

regional moment tensor determination in the european mediterranean area initial results the broadband seismic network in the european mediterranean area provides high quality data we invert these regional three component data for the source parameters of moderate to strong earthquakes in the entire european mediterranean area regional seismograms have a good signal to noise ratio even for moderate sized events that are too small for teleseismic analysis the magnitude threshold for source parameter determination can thus be significantly lowered the threshold depends on the average event station distances within dense broadband networks we analyze mw 3 0 earthquakes in areas far from broadband seismic stations the lower bound is mw 4 5 4 8 still considerably lower than the teleseismic analysis threshold about mw 5 0 5 3 for larger events we perform rapid moment tensor analysis using near real time data solutions are posted within hours after event occurrence in a second step we merge near real time and later available data to obtain a regional moment tensor catalog of moderate to large earthquakes for the entire european mediterranean area within less than 1 year we have analyzed 67 earthquakes ranging in size from mw 2 9 to 7 5 the solutions cover the seismically active areas of the european mediterranean area particularly important are solutions for slowly deforming regions where large earthquakes that could be analyzed with teleseismic data occur infrequently the solutions are reliable for events with independent source parameter estimates the agreement is generally high the solutions are robust variations in epicentral parameters source depth or exact choice of stations do not affect source parameter estimates strongly the moment magnitudes provide a unified estimate of earthquake size for the european mediterranean area we perform regression analyses to link our moment magnitudes with local body and surface wave magnitudes

correlated errors in geodetic time series implications for time dependent deformation analysis of frequent trilateration observations from the two color electronic distance measuring networks in california demonstrate that the noise power spectra are dominated by white noise at higher frequencies and power law behavior at lower frequencies in contrast earth scientists typically have assumed that only white noise is present in a geodetic time series since a combination of infrequent measurements and low precision usually preclude identifying the time correlated signature in such data after removing a linear trend from the two color data it becomes evident that there are primarily two recognizable types of time correlated noise present in the residuals the first type is a seasonal variation in displacement which is probably a result of measuring to shallow surface monuments installed in clayey soil which responds to seasonally occurring rainfall this noise is significant only for a small fraction of the sites analyzed the second type of correlated noise becomes evident only after spectral analysis of line length changes and shows a functional relation at long periods between power and frequency of 1 where is frequency and 2 with 2 this type of correlated noise is termed random walk noise and its source is mainly thought to be small random motions of geodetic monuments with respect to the earth s crust though other sources are possible because the line length changes in the two color networks are measured at irregular intervals power spectral techniques cannot reliably estimate the level of 1 noise rather we also use here a maximum likelihood estimation technique which assumes that there are only two sources of noise in the residual time series white noise and random walk noise and estimates the amount of each from this analysis we find that the random walk noise level averages about 1 3 mm yr and that our estimates of the white noise component confirm theoretical limitations of the measurement technique in addition the seasonal noise can be as large as 3 mm in amplitude but typically is less than 0 5 mm because of the presence of random walk noise in these time series modeling and interpretation of the geodetic data must account for this source of error by way of example we show that estimating the time varying strain tensor a form of spatial averaging from geodetic data having both random walk and white noise error components results in seemingly significant variations in the rate of strain accumulation spatial averaging does reduce the size of both noise components but not their relative influence on the resulting strain accumulation model

seismicity and crustal structure beneath the western ligurian sea derived from local earthquake tomography abstract in this paper we present and comment on the results of a tomographic inversion of p arrival times of local earthquakes to better understand the structure and features of the ligurian sea an oceanic basin originated in the oligocene miocene this tomographic inversion is the last step in a long and careful revision of the data available for the ligurian sea an accurate catalogue derived from a controlled compilation of data from the numerous stations monitoring seismic activity in this young oceanic basin has been used for computation of a one dimensional 1d reference model a high quality subset of the new catalogue has been used for the non linear 3d tomographic inversion by iteratively solving the coupled hypocenter velocity problem in a least square sense careful analysis of the resolution capability of the used data set has revealed the better resolved features for interpretation the resulting 3d model shows a high velocity layer extending from the northeastern side of the model where it lays about 30 km deep to the southwestern part where it shallows to 15 km the shallow part of this high velocity body is located near the original area of the opening of the ligurian sea that took place between the oligocene and early miocene its velocity is comparable with that of an oceanic moho around 7 8 km s a lens shaped high velocity body about 25 km long located at a depth of 8 15 km is interpreted as a series of ophiolitic bodies intruded into the upper crust

reassessment of earthquakes 1900 1999 in the eastern mediterranean and the middle east summary we have reappraised locations and surface wave magnitudes of earthquakes this century in the eastern mediterranean and the middle east between 10 and 44 n and 18 and 70 e the results are presented in an improved parametric catalogue of shallow earthquakes h 40 km large enough ms 6 0 to be of interest in seismotectonics and earthquake engineering a considerable number of early events of 6 ms 7 2 not included in other catalogues have been identified and their magnitudes assessed we find that iss isc locations are systematically shifted by 10 30 km to the north or northeast of their macroseismic epicentres also we derived a regional average relationship between log m0 and ms we show that the correlation of magnitude with epicentral intensity is very weak as is expected and a source of error in frequency relations

local and duration magnitudes in northwestern italy and seismic moment versus magnitude relationships in the present work we develop some local magnitude scales for northwestern italy based on vertical short period records this study is motivated by the possibility of applying the computed scales to an instrumental catalog of more than 25 000 local earthquakes as this region has been continuously monitored by 12 short period vertical component 1c stations since the mid 1980s furthermore a digital network of three component 3c broadband or 5 second sensors has monitored northwestern italy since 1996 today a significant number of earthquakes have been simultaneously recorded by both networks allowing the calibration of the 1c local scale by using magnitudes computed according to a scale derived for the 3c digital network moreover because station sant anna di valdieri houses both a 3c code stv2 and 1c code stv sensors the magnitude scales for the two networks can be developed using the same reference station the magnitude scale m l log a log r 100 0 0054 r 100 3 s is derived for the 3c digital network with the requirement that the correction s of station stv2 is zero this scale is based on 10 057 maximum amplitudes 2822 earthquakes computed from horizontal synthesized wood anderson seismograms in the hypocentral distance 10 to 310 km and in the range 0 m l 5 with respect to an carlier magnitude scale derived for the 3c network constraining the sum of all the station corrections to zero the magnitudes predicted by the previous equations show an average bias of 0 2 0 1 which can be ascribed to the different constraint applied to the station corrections the magnitudes predicted by the scale for the 3c network are used to calibrate magnitude scales based on either total duration or maximum amplitude from synthesized wood anderson seismograms computed for each short period vertical recording the magnitude scale obtained considering maximum amplitudes from vertical short period recordings is m l log a log r 100 0 0041 r 100 3 s the reliability of the obtained magnitude scales is assessed using 827 earthquakes different from those we considered in the regression analysis finally the following seismic moment versus local magnitude relations are valid in the western alps in the range 0 where m l3c is the local magnitude computed starting from the horizontal component of broadband flat frequency response from 0 033 to 50 hz or semibroadband flat frequency response from 0 2 to 40 hz sensors and m l1c is the magnitude computed starting from the vertical short period recordings 1 embed graphic 1 gif

local and duration magnitude determination for the italian earthquake catalog 1981 2002 this research has been supported in part by project gndt2000 2002 coordinated by a amato and g selvaggi and funded by italian civil protection

a new global mode of earth deformation seasonal cycle detected we have detected a global mode of earth deformation that is predicted by theory precise positioning of global positioning system sites distributed worldwide reveals that during february to march the northern hemisphere compresses and the southern hemisphere expands such that sites near the north pole move downward by 3 0 millimeters and sites near the equator are pulled northward by 1 5 millimeters the opposite pattern of deformation occurs during august to september we identify this pattern as the degree one spherical harmonic response of an elastic earth to increased winter loading of soil moisture snow cover and atmosphere data inversion shows the load moment s trajectory as a great circle traversing the continents peaking at 6 9 1022 kilogram meters near the north pole in winter indicating interhemispheric mass exchange of 1 0 1016 0 2 1016 kilograms

evidence of bias in estimations of earthquake size magnitudes of earthquakes determined using traditional methods show systematic deviations dependent on tectonic setting from accurate estimates of earthquake size magnitudes are overestimated for most of the continental earthquakes underestimated for mid oceanic ridges and differences of varying sign are obtained for subduction zones this is important in evaluating the seismic risk or consideration of effects such as the seismic versus aseismic strain release as seismic moments determined from magnitudes can be wrong by as much as a factor of four

continuous gps measurements of postglacial adjustment in fennoscandia 1 geodetic results 1 data collected under the auspices of the bifrost gps project yield a geographically dense suite of estimates of present day three dimensional 3 d crustal deformation rates in fennoscandia johansson et al 2002 a preliminary forward analysis of these estimates milne et al 2001 has indicated that models of ongoing glacial isostatic adjustment gia in response to the final deglaciation event of the current ice age are able to provide an excellent fit to the observed 3 d velocity field in this study we revisit our previous gia analysis by considering a more extensive suite of forward calculations and by performing the first formal joint inversion of the bifrost rate estimates to establish insight into the physics of the gia response in the region we begin by decomposing a forward prediction into the three contributions associated with the ice ocean and rotational forcings from this analysis we demonstrate that recent advances in postglacial sea level theory in particular the inclusion of rotational effects and improvements in the treatment of the ocean load in the vicinity of an evolving continental margin involve peak signals that are larger than the observational uncertainties in the bifrost network the forward analysis is completed by presenting predictions for a pair of fennoscandian ice histories and an extensive suite of viscoelastic earth models the former indicates that the bifrost data set provides a powerful discriminant of such histories the latter yields bounds on the assumed constant upper and lower mantle viscosity nu um nu lm specifically we derive a 95 confidence interval of 5 x 10 20 less than or equal to nu um less than or equal to 10 21 pa s and 5 x 10 21 less than or equal to nu lm less than or equal to 5 x 10 22 pa s with some preference for elastic lithospheric thickness in excess of 100 km the main goal of the bayesian inverse analysis is to estimate the radial resolving power of the bifrost gps data as a function of depth in the mantle assuming a reasonably accurate ice history we demonstrate that this resolving power varies from similar to 200 km near the base of the upper mantle to similar to 700 km in the top portion of the lower mantle we conclude that the bifrost data are able to resolve structure on radial length scale significantly smaller than a single upper mantle layer however these data provide little constraint on viscosity in the bottom half of the mantle finally elements of both the forward and inverse analyses indicate that radial and horizontal velocity estimates provide distinct constraints on mantle viscosity

determination of amplitude and duration magnitudes and site residuals from short period seismographs in northern california abstract equations for determining amplitude magnitude mx and duration magnitude mf that employ all calibrated instruments in the usgs short period telemetered seismic network in northern california ncsn were developed and tested against a set of 1276 earthquakes from 1986 to 1990 that were analyzed on the caltech usgs processing system cusp the expressions for decay of amplitude and record duration in these equations are functions of distance alone sensitivity corrections for both mx and mf are simply the logarithms of the ratios of the magnification of the reference instrument to that of the instrument actually used component corrections were chosen so as to minimize the dependence of instrument site residuals on instrument component mf site residuals were found to be closely linked to mx site residuals in a manner that suggests both depend primarily on site amplification both mx and mf site residuals vary systematically with bedrock lithology older well consolidated rocks produce negative residuals smaller amplitudes and shorter durations and younger unconsolidated rocks produce positive residuals larger amplitudes and longer durations average station magnitude residuals are virtually independent of distance from the epicenter to at least 800 km and mx mf averaged over 0 5 unit magnitude intervals is less than 0 05 from m 0 5 to m 5 5 comparison of mx and mbk m l uc berkeley for 293 events in both the cusp data set and the berkeley catalog shows that calculated mx s are marginally larger than the corresponding mbk s mx mbk averages about 0 04 the characteristics of the standard wood anderson seismograph employed to calculate mx are free period 0 8 sec damping constant 0 8 and static magnification 2080

instantaneous deformation from continuous gps contributions from quasi periodic loads summary continuous gps cgps coordinate time series are known to experience repeating deformation signals with seasonal and other periods it is unlikely that these signals represent perfect sinusoids with temporally constant amplitude we develop an analysis method that accommodates temporal variations in the amplitudes of sinusoidal signals we apply the method to simulated coordinate time series to numerically explore the potential consequences of neglecting decadal variation in amplitude of annual motions on the residual error spectra of cgps measurements as well as potential bias in estimates for secular site velocity we find that secular velocity bias can be appreciable for shorter time series and that residual error time series of longer duration may contain significant power in a broad band centred on semiannual frequency if temporal variation in the amplitude of annual motions is not accounted for in the model used to reduce the observations to residuals it may be difficult to differentiate the bandpass filtered signature of mismodelled loading signals from power law noise using residual error spectra for shorter time series we provide an example application to a 9 yr coordinate time series for a cgps station located in southern california at carbon creek control structure cccs which is known to experience large amplitude seasonal motions associated with the santa ana aquifer system

precariously balanced rocks and ground motion maps for southern california groups of precariously balanced rocks are effectively low resolution strong motion seismoscopes that have been operating on solid rock outcrops for thousands of years and once the methodology has been developed can provide important information about seismic risk in one zone near victorville only 30 km from the nearest point on the san andreas fault more than 50 precarious rocks have been documented widespread rock varnish suggests that many of these rocks have been in their current unstable positions for thousands of years we have established the mechanical basis for rough estimates of the horizontal accelerations necessary to topple these rocks using field observations and numerical and physical modeling to verify that zones of precarious rocks do not occur near historic earthquakes searches using binoculars were made along roads with occasional foot surveys near large earthquakes based on these reconnaissance searches we conclude that no precarious rock zones are found within 15 km of zones of high energy release of historic large earthquakes to document the occurrence of precarious rocks in southern california road surveys were carried out along major roads four zones of precarious rocks and seven other zones of somewhat less precarious rocks have been documented published probabilistic ground motion maps for southern california are compared with the occurrence of zones of precarious and semi precarious rocks the results are encouraging and suggest that eventually studies of precarious rocks will provide important constraints on the assumptions on which the maps are based results from studies of precarious rocks may eventually provide important information for siting and design of sensitive structures such as hospitals and power plants precarious rocks give a direct indication of past ground shaking in contrast to the indirect inference provided by fault trenching studies which may be subject to uncertainties in the actual time history of slip due to the fault e g fault creep slow earthquakes or unknown dynamic stress drop it is concluded that precarious rocks warrant further study and quantitative analysis

strain rates in northwestern italy from spatially smoothed seismicity 1 this work presents seismic strain rate maps for the western alps and northern apennines northern italy as derived from an earthquake catalog collecting both historical and instrumental data strain rates are calculated on the basis of the rate of seismic moment release using the anderson method unlike previous applications which determined the total strain rate associated with specific seismogenic sources we have employed an innovative zoneless approach based on a spatially smoothed seismicity method in addition a monte carlo simulation procedure is applied to allow for uncertainty in the input data e g magnitude to moment conversion seismogenic thickness maximum earthquake magnitude strain rate maps are developed by summing the moments of the earthquakes reported in the catalog and by using two different earthquake recurrence relations our results indicate that deformation rates are quite high ranging from about 2 to 12 10 9 yr 1 in the northern apennines and from 0 5 to 6 10 9 yr 1 in the western alps these values however are 1 order less than those derived from global positioning system measurements suggesting that a portion of the recent deformation in northwestern italy is related to aseismic processes the discrepancies between seismic and geodetic strain rates may also indicate that the record of seismicity may not provide a sufficient time window for assessment of secular rates of moment release or secular deformation rates and rates of recurrence of large magnitude earthquakes in the study area

duration magnitude scale and site residuals for northern morocco the first empirical duration magnitude m d formula is developed and tested for the northern morocco seismic network nmsnet this relationship is obtained by relating the ign instituto geografico national madrid body waves mblg ign to the duration and the epicentral distance at 25 analogue stations of the nmsnet for 479 earthquakes with 2 5 mb 5 4 from march 1992 to february 2001 m d estimates are significantly more precise while introducing a correction term for each of these stations csta j the magnitude for the i th event m d i is the mean value of individual m d ij 0 14 1 63 log 10 tau ij 0 031 triangle ij csta j

a method for calibration of the local magnitude scale based on relative spectral amplitudes and application to the san juan bautista california area we develop and use a spectral empirical green s function approach to estimate the relative source amplitudes of earthquakes near san juan bautista california we isolate the source amplitudes from path effects by comparing the recorded spectra of pairs of events with similar location and focal mechanism without computing the path effect with this method we estimate the relative moments of 1600 m 1 5 4 local earthquakes and we use these moments to recalibrate the duration magnitude scale in this region the estimated moments of these small earthquakes increase with catalog magnitude m d roughly proportionally to 101 1 m d slightly more slowly than a moment magnitude scaling of 101 5 m w this more accurate magnitude scaling can be used in analyses of the local earthquakes such as comparisons between the seismic moments and geodetic observations electronic supplement 1 additional description and figures showing estimated source amplitudes obtained with different parameters and observed amplitudes of some earthquakes with large misfits 1 http www bssaonline org lookup suppl doi 10 1785 0120160141 dc1

synthesis of wood anderson seismograms from broadband digital records abstract wood anderson torsion seismograms are synthesized by convolution with cosited broadband digital seismograph recordings and compared with the photographically recorded wood anderson seismograms at berkeley and mt hamilton the objective is to use routinely the synthesized seismograms to determine local magnitude comparison of local magnitude values calculated from both synthesized and photographic seismograms shows that the variation in local magnitude between the two types of seismograms is less than the variation among the photographic seismograms consequently broadband digital recordings can provide reliable local magnitude estimates without introducing significant bias it is shown that the static magnification of standard t s 0 8 sec wood anderson torsion seismographs determined from measurement of the free period and tilt sensitivity is 2080 60 and not 2800 as often reported this discrepancy is due to the erroneous assumption that the taught wire suspension in a wood anderson seismograph does not distort significantly thus leading to an incorrect estimate of the radius of gyration and consequently to a theoretical geometrical magnification of 2800

ongoing drought induced uplift in the western united states the western united states has been experiencing severe drought since 2013 the solid earth response to the accompanying loss of surface and near surface water mass should be a broad region of uplift we use seasonally adjusted time series from continuously operating gps stations to measure this uplift which we invert to estimate mass loss the median uplift is 4 mm with values up to 15 mm in california s mountains the associated pattern of mass loss which ranges up to 50 cm of water equivalent is consistent with observed decreases in precipitation and streamflow we estimate the total deficit to be about 240 gt equivalent to a 10 cm layer of water over the entire region or the annual mass loss from the greenland ice sheet

regional magnitude scaling transportability and ms mb discrimination at small magnitudes data sets of mb pn and mb lg measurements are presented for three continental regions in order to investigate scaling relationships with moment magnitude w and event discrimination at small magnitudes compilations of published measurements are provided for eastern north american and central asian earthquakes and new measurements are reported for earthquakes located in western united states statistical tests on w mb relationships show that the mb lg scale of nurru 1973 is transportable between tectonic regions and a single unified w mb lg relationship satisfies observations for m 6 5 in all regions a unified relationship is also developed for nuclear explosions detonated at the nevada test site and test sites of the former soviet union regional mb for explosions scale at higher rates than for earthquakes and of significance is the finding that mb pn for explosions scales at a higher rate than mb lg a model is proposed where differences in scaling rates are related to effects of spectral overshoot and near field rg scattering on the generation of pn and lg waves by explosions for earthquakes mb pn and mb lg scale similarly showing rates near 1 0 or 2 3 log1omo seismic moment

tectonothermal processes and mechanical strength in a recent orogenic belt northern apennines 1 this paper investigates the seismic cutoff temperature at the maximum depth of seismicity across a young orogenic belt the northern apennines by attempting to take account of the different tectonothermal processes which have occurred in the region since the last 20 myr the analysis of seismicity over a period of 20 years 1981 2002 in combination with the thermal regime shows that the western part of the northern apennines peri tyrrhenian zone is characterized by extensional tectonics few earthquakes generally shallow and of low magnitude and high surface heat flux the entire crust of the eastern part of the orogenic belt external zone is affected by seismic activity of moderate magnitude and low heat flux earthquakes increase both in number and energy released in the inner portion of the belt internal zone where events with larger focal depth indicate subduction the cutoff potential temperature at the largest depth of seismicity is 550 c for the internal zone in the external zone of the orogen the temperature at the maximum depth of seismicity is about 550 c this result agrees with recent work on the thermal structure and seismicity of several continental areas the limiting temperature in the peri tyrrhenian zone can instead exceed 750 c a possible explanation is that the deepest earthquakes might be associated to magma movement the overall earthquake spatial distribution across the orogen appears related to the long term rheology which varies roughly in the same direction of tectonic transport of the chain this consistency appears also from the b value of the frequency magnitude relation which can be interpreted in relation to the rheological properties of the medium the b value seems to be inversely correlated to the expected mechanical strength of the crust and increases eastward in the direction of tectonic transport the largest number of shocks and magnitude of the internal zone happen where a sharp lateral change of strength should occur

statistical modeling of the 1997 1998 colfiorito earthquake sequence locating a stationary solution within parameter uncertainty abstract the umbria marche region of italy is a seismically active region that experienced a strong sequence of earthquakes during 1997 1998 with a cluster of magnitude m 5 events during which the average event rate increased from the long term level by several orders of magnitude using maximum likelihood ml inversion of the epidemic type aftershock sequences model to characterize the seismicity of this region over 22 years we find in agreement with previous studies the event rate during the sequence is underpredicted based on simulations with the large m 5 events fixed however by sampling the parameter space around the ml solution within the inversion uncertainty and comparing the simulated event rate with that of the real data we are able to find near maximum likelihood parameters that provide a reasonable match to both the long term average event rate and the rate during the sequence we use the shape of the interevent time histogram to infer that the events in the sequence are probably mostly aftershocks of the large events rather than an increased occurrence of background events we suggest that event rate comparisons can be useful as an additional constraint on the selection of parameters from within the 95 confidence interval of the ml fit our results demonstrate the extra constraint can greatly improve the match between a stationary model and finite catalog data and that care is needed before adding further parameters to ascribe nonstationarity to time dependent event rate changes

erosion rates for pinnacles formed in soft sediments and implications for constraining seismic hazard models abstract we provide estimates of the rates of natural modification of badlands pinnacles formed in soft sediments at two sites in new zealand and assess the utility of pinnacles for constraining seismic hazard models one of the sites is in a humid temperate environment and the other is in a semiarid environment rates of pinnacle modification of 30 270 mm yr equivalent to 3 27 m century are estimated by comparison of images acquired one to two decades apart the primary mode of modification is the progressive narrowing of the pinnacle column by precipitation induced erosion along with consequent loss of height as the columns become thin and unstable additional damage may have been produced by earthquake shaking for specific pinnacles but in general this is likely to be trivial given that 1 estimates of the levels of peak ground acceleration pga required to shake down the pinnacles at the two sites are at least a factor of 5 13 greater than the pgas predicted or measured from regional earthquakes during the time periods of observation in other words they would only be significantly damaged by major local earthquakes and 2 a fragile pinnacle has actually formed in the time periods of observation the pinnacle modification rates are rapid enough that they would not have existed one to two centuries ago or would have been of substantially different geometries as such pinnacles are unlikely to be useful for constraining seismic hazard models for return periods greater than a few decades at least in the context of the new zealand environment

real time determination of seismic moment tensor for the italian region this work has been funded by the 2005 2007 dpc s4 and 2008 2010 dpc s3 italian civil protection contracts

constraints on ground accelerations inferred from unfractured hoodoos near the garlock fault california abstract in the absence of long term instrumental data the presence of fragile geologic features near active faults can provide physical limits on the level of ground shaking that could potentially have significant implications for seismic hazards this paper introduces a multidisciplinary investigation that uses unfractured hoodoos in seismically active regions to constrain the level of ground accelerations at those locations although there is a large uncertainty associated with the age of the hoodoos because of their rapidly eroding nature they can still be useful in providing physical limits on ground motions associated with recent large events here we consider the fragilities of two hoodoos in the red rock canyon region within a few kilometers of the garlock fault which is an active strike slip fault in a transtensional region with at least a few large earthquakes in the holocene the hoodoos at these sites could be evidence of median or relatively low ground motions associated with large transtensional strike slip earthquakes results of our field and laboratory tests on two hoodoos provide constraints on peak ground accelerations pgas of and using the u s geological survey s usgs probabilistic seismic hazard psh deaggregation the dominant earthquake contributing to the hazard at the site of the hoodoos for the recurrence intervals of 475 975 and 2475 years is located at a distance of 4 8 km and has a magnitude of 7 63 consistent with the observed paleoearthquake evidence on the garlock fault the pgas corresponding to these three return periods are 0 26 0 40 and respectively therefore the survival of the more fragile hoodoo during a presumably large event on the garlock fault in the past 550 years would be consistent with the 2008 seismic hazard level if the ground motions during that event were below the median value

climate driven vertical acceleration of icelandic crust measured by continuous gps geodesy earth s present day response to enhanced glacial melting resulting from climate change can be measured using global positioning system gps technology we present data from 62 continuously operating gps instruments in iceland statistically significant upward velocity and accelerations are recorded at 27 gps stations predominantly located in the central highlands region of iceland where present day thinning of the iceland ice caps results in velocities of more than 30 mm yr and uplift accelerations of 1 2 mm yr2 we use our acceleration estimates to back calculate to a time of zero velocity which coincides with the initiation of ice loss in iceland from ice mass balance calculations and arctic warming trends we show through a simple inversion a direct relationship between ice mass balance measurements and vertical position and show that accelerated unloading is required to reproduce uplift observations for a simple elastic layer over viscoelastic half space model

an earthquake catalog for seismic hazard assessment in ecuador building a unified and homogeneous earthquake catalog is a preliminary step for estimating probabilistic seismic hazard in a country ecuador a territory of 600 km 500 km is characterized by an active seismicity both in the shallow crust and in the subduction zone several international and local earthquake catalogs are available covering different time and spatial windows characterized by different magnitude types and uncertainties after a careful analysis of each catalog in particular for completeness and uncertainty levels we propose a priority scheme for merging the instrumental catalogs moreover several historical earthquakes are analyzed to estimate epicentral location and magnitude completing the solutions obtained in a previous publication once the historical earthquakes are appended to the instrumental catalog the resulting catalog covers five centuries in the cordillera region next homogenization of magnitudes and removal of aftershocks is performed different options are studied and the impact on the recurrence curve is evaluated for the cordillera region within 2 5 and 1 latitude the average occurrence of an earthquake with m w 6 0 is 10 20 years based on the historical catalog

calibration of an ml scale in northwestern turkey from 1999 izmit aftershocks a local magnitude scale is derived for northwestern turkey using data collected by a temporary network installed by the german task force for earthquakes after the 1999 izmit earthquake m w 7 4 and the permanent sapanca bolu network we computed wood anderson seismograms for over 5353 arrivals at 27 three component stations from 530 earthquakes the hypocentral distances considered range from 5 to 140 km with the best represented range being from 5 to 70 km we inverted the measured amplitudes following both the nonparametric richter s 1958 and parametric bakun and joyner 1984 approaches these methods yield consistent magnitude values and station corrections however the calculated nonparametric distance correction log a implies that ground motion attenuation is higher than what is accounted for by the equation calibrated in central california in the range 5 62 km the best fit is provided by log a log r 17 0 00960 r 17 2 this equation is obtained constraining the geometrical spreading parameter n to 1 the calculated value of k 0 00960 confirms that in this range of distance seismic waves could propagate through a low q volume station corrections which allow for a significant reduction of m l residuals range between 0 5 magnitude units suggesting a strong influence of local site effects on the amplitude of ground motion in accord with the obtained attenuation and station corrections the magnitudes of the considered events range from 0 4 to 4 8

on the increase of background seismicity rate during the 1997 1998 umbria marche central italy sequence apparent variation or fluid driven triggering abstract we investigate the temporal evolution of background seismicity rate in the umbria marche sector of the northern apennines that was struck by the 1997 1998 colfiorito seismic sequence specifically we apply the epidemic type aftershock sequences etas model to separate the background seismicity rate from the coseismic triggered rate of earthquake production analyzed data are extracted from the catalogo della sismicita italiana csi1 1 catalog of italian seismicity 1981 2002 which contains for the study area 12 163 events with m l 1 5 the capability of the etas model to match the observed seismicity rate is tested by analyzing the model residuals and by applying two nonparametric statistical tests the runs and the kolmogorov smirnov tests to verify the fit of residuals to poisson hypothesis we first apply the etas model to the seismicity that occurred in the study area during the whole period covered by the csi1 1 catalog our results show that the etas model does not explain the temporal evolution of seismicity in a time interval defined by change points identified from time evolution of residuals and encompassing the colfiorito seismic sequence we therefore restrict our analysis to this period and analyze only those events belonging to the 1997 1998 seismic sequence we again obtain the inadequacy of a stationary etas model with constant background rate to reproduce the temporal pattern of observed seismicity we verify that the failure of the etas model to fit the observed data is caused by the increase of the background seismicity rate associated with the repeated colfiorito mainshocks we interpret the inferred increase of background rate as a consequence of the perturbation to the coseismic stress field caused by fluid flow and or pore pressure relaxation in particular we show that the transient perturbation caused by poroelastic relaxation can explain the temporal increase of background rate that therefore represents a fluid signal in the seismicity pattern

national seismic hazard model for new zealand 2010 update a team of earthquake geologists seismologists and engineering seis mologists has collectively produced an update of the national probabilistic seismic hazard psh model for new zealand national seismic hazard model or nshm the new nshm supersedes the earlier nshm published in 2002 and used as the hazard basis for the new zealand loadings standard and numerous other end user applica tions the new nshm incorporates a fault source model that has been updated with over 200 new onshore and offshore fault sources and utilizes new new zealand based and international scaling relationships for the parameterization of the faults the dis tributed seismicity model has also been updated to include post 1997 seismicity data a new seismicity regionalization and improved methodology for calculation of the seismicity parameters probabilistic seismic hazard maps produced from the new nshm show a similar pattern of hazard to the earlier model at the national scale but there are some significant reductions and increases in hazard at the regional scale the national scale differences between the new and earlier nshm appear less than those seen between much earlier national models indicating that some degree of consis tency has been achieved in the national scale pattern of hazard estimates at least for return periods of 475 years and greater online material table of fault source parameters for the 2010 national seismic hazard model

the 1356 basel earthquake an interdisciplinary revision summary within historical times one of the most damaging events in intra plate europe was the 1356 basel earthquake given its significance for assessing regional seismic hazard in central europe an interdisciplinary project was launched in 2005 to re explore this event our effort aimed to incorporate techniques from history seismology archaeology paleoseismology and engineering new and reinterpreted historical data from basel and its surroundings plus archaeological findings on buildings that survived the event and still exist enabled this macroseismic assessment palaeoseismological studies combined with historical evidence provided additional data for the surrounding areas archaeology offers sparse information on some castles and churches sometimes supported by historical records a contemporary source allows some reconstruction of the stronger fore and aftershocks this expanded information base improves our sense of the event s damage and consequences for the city of basel the relatively abundant archaeological data allowed us to assess statistically the macroseismic intensity at ix although the pattern of damage was scattered data points for the expected area of damage around basel are not distributed regularly the absence of historical and archaeological findings for southern germany might be due to archival problems future investigation may improve this situation our results confirm that the basel earthquake was the most destructive known for central europe intensities up to viii are found within a radius of about 30 km analysing the macroseismic field confirms our former assessment of the event and shows an epicenter located about 10 km south of basel the most probable range for the moment magnitude mw is between 6 7 and 7 1

scenario based seismic risk analysis an engineering approach to the development of source and site specific ground motion time histories in areas of low seismicity modern engineering design methods require ground motion time histories as input for non linear dynamic structural analysis non linear dynamic methods of analysis are increasingly applied in the context of probabilistic risk assessments and for cost effective design of critical infrastructures in current engineering practice artificial time histories matching deterministic design spectra or probabilistic uniform hazard spectra are most frequently used for engineering analysis the intermediate step of generation of response spectra can lead to a biased estimate of the potential damage from earthquakes because of insufficient consideration of the true energy content and strong motion duration of earthquakes thus assessment of seismic risk may seem unrealistic an engineering approach to the development of three component ground motion time histories has been established which enables consideration of the typical characteristics of seismic sources regional ground motion attenuation and the main geotechnical characteristics of the target site therefore the approach is suitable for use in scenario based risk analysis a larger number of time histories are required for representation of the seismic hazard near field effects are implemented in the stochastic source model using engineering approximations the approach is suggested for use in areas of low seismicity where ground motion records of larger earthquakes are not available uncertainty analysis indicates that ground motions generated by individual earthquakes are well constrained and that the usual lognormal model is not the best choice for predicting the upper tail of the distribution of the ground motions

an evaluation of the scsn moment tensor solutions robustness of the mw magnitude scale style of faulting and automation of the method we have generated moment tensor solutions and moment magnitudes m w for 1700 earthquakes of local magnitude m l 3 0 that occurred from september 1999 to november 2005 in southern california the method is running as an automated real time component of the southern california seismic network scsn with solutions available within 12 min of event nucleation for local events the method can reliably obtain good quality solutions for m w with m l 3 5 and for the moment tensor for events with m l 4 0 the method uses the 1d time domain inverse code tdmt invc software package dreger 2003 the green s functions have been predetermined for various velocity profiles in southern california which are used in the inversion of observed three component broadband waveforms 10 100 sec using data from at least four stations moment tensor solutions have an assigned quality factor dependent on the number of stations in the inversion and the goodness of fit between synthetic and observed data if a minimum quality factor is attained the m l or m w is 5 0 or greater and if the event is in the southern california reporting regions the m w will be the official scsn cisn magnitude the m w from the high quality solutions determined from our method generally correlate very well with reviewed m l except in regions at the perimeter of the network the m w reported here indicates the scsn m l systematically underestimates the magnitude in the mexicali region of baja california mono lakes area coso region and the brawley seismic zone and overestimates the magnitude in the coastal ranges comparisons of the moment tensors determined using this model are made with harvard centroid moment tensors generated for larger earthquakes in the california region and recent 3d models for events in the los angeles region with excellent correlation most of the earthquakes with good quality solutions exhibit strike slip faulting in particular along the major late quaternary strike slip faults thrust faulting on east west striking planes is observed along the southern edge of the transverse ranges while northwest striking thrust faulting is observed in the coastal ranges normal faulting is most common in baja california and southern sierra nevada including the western basin and range region poor quality solutions with unreliable m w are caused by excessive background noise in the waveforms small events m l 4 0 can be affected by ambient noise or teleseisms but larger events can also have unreliable solutions if they follow a recent large regional event

bayesian inference on earthquake size distribution a case study in italy abstract this article is focused on the study of earthquake size statistical distribution by using bayesian inference the strategy consists in the definition of an a priori distribution based on instrumental seismicity and modeled as a power law distribution by using the observed historical data the power law is then modified in order to obtain the posterior distribution the aim of this article is to define the earthquake size distribution using all the seismic database available i e instrumental and historical catalogs and a robust statistical technique we apply this methodology to the italian seismicity dividing the territory in source zones as done for the seismic hazard assessment taken here as a reference model the results suggest that each area has its own peculiar trend while the power law is able to capture the mean aspect of the earthquake size distribution the posterior emphasizes different slopes in different areas our results are in general agreement with the ones used in the seismic hazard assessment in italy however there are areas in which a flattening in the curve is shown meaning a significant departure from the power law behavior and implying that there are some local aspects that a power law distribution is not able to capture

magnitude problems in historical earthquake catalogues and their impact on seismic hazard assessment summary areliablehistoricalearthquakecatalogueisahighlycriticalcomponentinanyregionalseismic hazard analysis although many of the various catalogues used for constructing national or regional seismic hazard maps in europe cover much of the same territory and use standardized parameters somediscrepancieshavebeenrevealedbetweendifferentcatalogues switzerland s ecos catalogue compiled by the swiss seismological service sed and italy s cpti04 catalogue compiled by the cpti working group spatially overlap each other to a large extent and employ a uniform moment magnitude scale mw however a careful review of these two catalogues has revealed significant inconsistencies in the moment magnitude mw 1 the moment magnitudes used for the same earthquakes were found to differ which could potentially have a substantial impact on any regional seismic hazard assessment that is based on these catalogues this type of inconsistency often arises when different regression relationships are used to convert other magnitude scales or event intensity into mw which can cause many of the event magnitudes in one catalogue to be systematically biased higher or lower with respect to those in another catalogue in this case the magnitudes of small to medium historical earthquakes in italy s cpti04 catalogue are systematically higher than those in switzerland s ecos catalogue 2 an abnormally high frequency of large magnitude events was observed for some of the time periods particularly if most of the available data was on intensity this has been observed in both the cpti04 and ecos catalogues for the time period prior to 1975 and is possibly due to a bias during the intensity to magnitude conversion 3 a systematic bias in magnitude resulted in biased estimations for the a and b values of the gutenberg richter magnitude frequency relationships all of these issues can lead to skewed seismic hazard results or inconsistencies in the seismic hazard from different studies by constructing seismic hazard models based on the ecos and cpti04 catalogues we can evaluate the impact of these inconsistencies on the regional seismic hazard the results show that the seismic hazard from the two models can disagree by as much as a factor of three at some locations which demonstrates the importance of developing consistent and unbiased earthquake catalogues across neighbouring countries

crustal loading near great salt lake utah two sites of the bargen gps network are located 30 km south of great salt lake gsl lake level records since mid 1996 indicate seasonal water elevation variations of 0 3 m amplitude superimposed on a roughly decadal feature of amplitude 0 6 m using an elastic green s function and a simplified load geometry for gsl we calculate that these variations translate into radial crustal loading signals of 0 5 mm seasonal and 1 mm decadal the horizontal loading signals are a factor of 2 smaller despite the small size of the expected loading signals we conclude that we can observe them using gps time series for the coordinates of these two sites the observed amplitudes of the variations agree with the predicted decadal variations to 0 5 mm the observed annual variations however disagree this difference may be caused by some combination of local precipitation induced site motion unmodeled loading from other nearby sources errors in the gsl model and atmospheric errors

implications of transient deformation in the northern basin and range western united states transient deformation events observed in global positioning system gps data from the basin and range extensional province may illuminate qualitatively similar transient events observed in subduction zones and other tectonic environments we model gps time series at 22 sites using a combination of hyperbolic tangent function analysis and elastic load deformation estimated from climatological data we identify two transient events 2000 4 and 2004 4 with roughly similar timing and displacement to those described previously by other researchers the first few years of gps observations adopted as a reference state in earlier studies are found to be anomalous our results differ from previous studies in two respects first a significant component of northward transient motion occurs during both events despite a reversal of sign in east component motion second sites move coherently in the eastern as well as the western basin and range surface mass loading the largest source of transient stress forcing in the region exhibits no evidence of a simple relationship to the deformation transients prior studies inferred slip on a single megadetachment at the moho but that hypothesis assumes negligible ductile deformation of the lower crust and a dry olivine rheology for the uppermost mantle recent measurements of crustal quartz abundance and effective elastic thickness suggest both assumptions are unlikely basin and range transients can be reconciled with the frictional slip mechanism widely accepted for subduction zone transients provided that slip is occurring on discontiguous detachment surfaces at midcrustal depths

age of unstable bedrock landforms southwest of yucca mountain nevada and implications for past ground motions we determine minimum exposure ages for unstable outcrops at three sites in amargosa desert southwestern nevada including a site at the southern end of yucca mountain varnish microlamination dating techniques provide minimum exposure ages of 12 5 36 k y for the unstable outcrops of welded tuff including a 24 k y age for the south yucca mountain site the youngest exposure age 12 5 k y is found at the site located only 10 km from the death valley furnace creek fault suggesting outcrops may be more frequently modified when close to major active earthquake sources a simplistic stability assessment of the south yucca mountain outcrops suggests peak ground accelerations pgas may not have exceeded about 1 g uncertainty bounds 0 5 2 g in at least 24 k y a pga of 1 g is consistent with the predicted 24 k y return period pgas from the near decade old yucca mountain probabilistic seismic hazard psh model except for the ninety fifth percentile and above we gain confidence in our interpretations by additionally observing 1 minimal damage to the south yucca mountain outcrops from a recent moderate earthquake that is estimated to have produced a pga of less than 0 1 g there i e motions less than 0 5 g do not significantly damage the outcrops and 2 severe damage to similar volcanic outcrops associated with pgas of the order 0 5 1 g near a nuclear blast site from the 1960s these observations support our suggestion that pgas greater than 0 5 1 g have not occurred at the south yucca mountain site for a time period of at least 24 k y significant seismic events that substantially modify the outcrops and produce associated rubble fields may therefore occur on longer time scales

seismic moment from regional surface wave amplitudes applications to digital and analog seismograms accurate consistent earthquake size estimates are fundamental for seismic hazard evaluation in central europe seismic activity is low and long term seismicity available as intensities from written historical records has to be included for meaningful assessments we determined seismic moments m 0 of 25 stronger twentieth century events in switzerland from surface wave amplitude measurements these m 0 can be used to calibrate intensity moment relations applicable to preinstrumental data we derived the amplitude moment relation using digital data from 18 earthquakes in and near switzerland where independent m 0 estimates exist the surface wave amplitudes were measured at empirically determined distance varying reference periods t for amplitudes measured at t the distance attenuation term of the surface wave magnitude relation s log a t max 1 66 log is independent of distance for log m 0 m s c e we get log m 0 s 14 90 uncertainties of 0 3 for the 14 90 constant correspond to a factor of 2 m 0 uncertainty which was verified with independent data our relation allows fast direct m 0 determination for current earthquakes and after recalibration of the constant the relation can be applied anywhere we applied our relation to analog seismograms from early instrumental earthquakes in switzerland that were collected from several european observatories amplitude measurements from scans were performed at large amplifications and corrected for differences between t and actual measurement periods the resulting magnitudes range from m w 4 6 to 5 8 for the largest earthquake in switzerland during the twentieth century uncertainties for the early instrumental events are on the order of 0 4 magnitude units online material moment tensor analysis of 14 recent earthquakes