holocene fault scarps near tacoma washington usa airborne laser mapping confirms that holocene active faults traverse the puget sound metropolitan area northwestern continental united states the mapping which detects forest floor relief of as little as 15 cm reveals scarps along geophysical lineaments that separate areas of holocene uplift and subsidence along one such line of scarps we found that a fault warped the ground surface between a d 770 and 1160 this reverse fault which projects through tacoma washington bounds the southern and western sides of the seattle uplift the northern flank of the seattle uplift is bounded by a reverse fault beneath seattle that broke in a d 900 930 observations of tectonic scarps along the tacoma fault demonstrate that active faulting with associated surface rupture and ground motions pose a significant hazard in the puget sound region

upper crustal structure in puget lowland washington results from the 1998 seismic hazards investigation in puget sound a new three dimensional 3 d model shows seismic velocities beneath the puget lowland to a depth of 11 kin the model is based on a tomographic inversion of nearly one million first arrival travel times recorded during the 1998 seismic hazards investigation in puget sound ships allowing higher resolution mapping of subsurface structures than previously possible the model allows us to refine the subsurface geometry of previously proposed faults e g seattle hood canal southern whidbey island and devils mountain fault zones as well as to identify structures tacoma lofall and sequim fault zones that warrant additional study the largest and most important of these newly identified structures lies along the northern boundary of the tacoma basin we informally refer to this structure here as the tacoma fault zone although tomography cannot provide information on the recency of motion on any structure holocene earthquake activity on the tacoma fault zone is suggested by seismicity along it and paleoseismic evidence for abrupt uplift of tidal marsh deposits to its north the tomography reveals four large west to northwest trending low velocity basins tacoma seattle everett and port townsend separated by regions of higher velocity ridges that are coincident with fault bounded uplifts of eocene crescent formation basalt and pre tertiary basement the shapes of the basins and uplifts are similar to those observed in gravity data gravity anomalies calculated from the 3 d tomography model are in close agreement with the observed anomalies in velocity cross sections the tacoma and seattle basins are asymmetric the basin floor dips gently toward a steep boundary with the adjacent high velocity uplift locally with a velocity overhang that suggests a basin vetgent thrust fault boundary crustal fault zones grow from minor folds into much larger structures along strike inferred structural relief across the tacoma fault zone increases by several kilometers westward along the fault zone to lynch cove where we interpret it as a zone of south vergent faulting overthrusting tacoma basin in contrast structural relief along the seattle fault zone decreases west of seattle which we interpret as evidence that the n s directed compression is being accommodated by slip transfer between the seattle and tacoma fault zones together the tacoma and seattle fault zones raise the seattle uplift one of a series of east west trending pop up structures underlying puget lowland from the black hills to the san juan islands

interpretation of the seattle uplift washington as a passive roof duplex we interpret seismic lines and a wide variety of other geological and geophysical data to suggest that the seattle uplift is a passive roof duplex a passive roof duplex is bounded top and bottom by thrust faults with opposite senses of vergence that form a triangle zone at the leading edge of the advancing thrust sheet in passive roof duplexes the roof thrust slips only when the floor thrust ruptures the seattle fault is a south dipping reverse fault forming the leading edge of the seattle uplift a 40 km wide fold and thrust belt the recently discovered north dipping tacoma reverse fault is interpreted as a back thrust on the trailing edge of the belt making the belt doubly vergent floor thrusts in the seattle and tacoma fault zones imaged as discontinuous reflections are interpreted as blind faults that flatten updip into bedding plane thrusts shallow monoclines in both the seattle and tacoma basins are interpreted to overlie the leading edges of thrust bounded wedge tips advancing into the basins across the seattle uplift seismic lines image several shallow short wavelength folds exhibiting quaternary or late quaternary growth from reflector truncation several north dipping thrust faults splay thrusts are inferred to core these shallow folds and to splay upward from a shallow roof thrust some of these shallow splay thrusts ruptured to the surface in the late holocene ages from offset soils in trenches across the fault scarps and from abruptly raised shorelines indicate that the splay roof and floor thrusts of the seattle and tacoma faults ruptured about 1100 years ago manuscript received 9 september 2003

constraints on surface deformation in the seattle wa urban corridor from satellite radar interferometry time series analysis summary we apply differential insar dinsar time series techniques to the urban corridor between tacoma seattle and everett wa using 93 interferograms from three satellites ers 1 ers 2 and radarsat 1 between 1992 and 2007 our goal is to study local tectonic geomorphic and groundwater processes consequently we remove long wavelength 50 100 km deformation signals from unwrapped interferograms by comparing surface velocities generated via the time series technique at more than two million points within the overlapping region between two independent ers tracks we estimate the uncertainty of relative surface velocity measurements to be 0 5 mm yr 1 in the vertical we estimate the uncertainty of relative displacement measurements to be 5 4 mm given our comparisons of dinsar derived time series to gps data a result that is consistent both with previous dinsar time series analysis and with the uncertainty expected from gps displacements projected onto the radar line of sight active tectonic deformation at shallow depths on the region s numerous east west structures is absent over the 11 5 yr of sar data examined assuming that the south dipping thrust beneath seattle and tacoma takes up 3 mm yr 1 of north south shortening our data indicate that the fault must be currently locked to a depth of greater than 10 km we also document extensive groundwater related deformation throughout much of the study region most notably we identify sharp linear deformation gradients near federal way wa and running between sumner wa and steilacoom wa these features may mark the locations of previously unmapped fault splays that locally control groundwater movement we find no slow landslide deformation on any of the numerous mapped slide complexes within seattle although regions of known active landsliding such as along perkins lane in seattle exhibit radar phase de correlation these observations are consistent with relatively infrequent and rapid landslide deformation within seattle

seismic reflection images beneath puget sound western washington state the puget lowland thrust sheet hypothesis seismic reflection data show that the densely populated puget lowland of western washington state is underlain by subhorizontal paleogene and neogene sedimentary rocks deformed by west and northwest trending faults and folds from south to north beneath the lowland features seen on the seismic data include the horizontally stratified 3 5 km thick tacoma sedimentary basin the seattle uplift with south dipping 20 strata on its south flank and steeply 50 to 90 north dipping strata and the west trending seattle fault on its north flank the 7 5 km thick northward thinning seattle sedimentary basin the antiformal kingston arch and the northwest trending transpressional southern whidbey island fault zone swif interpreting the uplifts as fault bend and fault propagation folds leads to the hypothesis that the puget lowland lies on a north directed thrust sheet the base of the thrust sheet may lie at 14 to 20 km depth within or at the base of a thick block of basaltic crescent formation its edges may be right lateral strike slip faults along the base of the cascade range on the east and the olympic mountains on the west our model suggests that the seattle fault has a long term slip rate of about 0 25 mm year and is large enough to generate a m7 6 to 7 7 earthquake

tectonic contraction across los angeles after removal of groundwater pumping effects after the 1987 whittier narrows and 1994 northridge earthquakes revealed that blind thrust faults represent a significant threat to metropolitan los angeles a network of 250 continuously recording global positioning system gps stations was deployed to monitor displacements associated with deep slip on both blind and surface faults here we augment this gps data with interferometric synthetic aperture radar imagery to take into account the deformation associated with groundwater pumping and strike slip faulting after removing these non tectonic signals we are left with 4 4 mm yr 1 of uniaxial contraction across the los angeles basin oriented n 36 degrees e perpendicular to the major strike slip faults in the area this indicates that the contraction is primarily accommodated on thrust faults rather than on the northeast trending strike slip faults we have found that widespread groundwater and oil pumping obscures and in some cases mimics the tectonic signals expected from the blind thrust faults in the 40 km long santa ana basin groundwater withdrawal and re injection produces 12 mm yr 1 of long term subsidence accompanied by an unprecedented seasonal oscillation of 55 mm in the vertical direction and 7 mm horizontally

time dependent land uplift and subsidence in the santa clara valley california from a large interferometric synthetic aperture radar data set 1 we invert 115 differential interferograms derived from 47 synthetic aperture radar sar scenes for a time dependent deformation signal in the santa clara valley california the time dependent deformation is calculated by performing a linear inversion that solves for the incremental range change between sar scene acquisitions a nonlinear range change signal is extracted from the ers insar data without imposing a model of the expected deformation in the santa clara valley cumulative land uplift is observed during the period from 1992 to 2000 with a maximum uplift of 41 18 mm centered north of sunnyvale uplift is also observed east of san jose seasonal uplift and subsidence dominate west of the silver creek fault near san jose with a maximum peak to trough amplitude of 35 mm the pattern of seasonal versus long term uplift provides constraints on the spatial and temporal characteristics of water bearing units within the aquifer the silver creek fault partitions the uplift behavior of the basin suggesting that it acts as a hydrologic barrier to groundwater flow while no tectonic creep is observed along the fault the development of a low permeability barrier that bisects the alluvium suggests that the fault has been active since the deposition of quaternary units

origin and evolution of the seattle fault and seattle basin washington analysis of seismic reflection data reveals that the seattle basin washington is markedly asymmetric and consists of 9 10 km of eocene and younger deposits the basin began as a discrete geologic element in the late eocene 40 ma the result of a reorganization in regional fault geometry and kinematics in this reorganization dextral offset on the puget fault south east of seattle stepped eastward and the seattle fault began as a restraining transfer zone north vergent reverse or thrust faulting on the seattle fault forced flexural subsidence in the seattle basin to the north offset on the seattle fault and subsidence of the seattle basin have continued to the present

coda attenuation in the area of el chichon volcano chiapas mexico abstract coda wave attenuation is investigated using the single scattering approximation on analog records from stations of a telemetered network situated close to el chichon volcano in southern mexico as well as from temporary stations deployed during 1982 the single scattering model was applied to the envelope of coda waves to characterize the coda decay rate we obtained values of q c which according to the filter settings of the seismographs and the average period measured in the traces correspond to frequencies of about 1 3 0 3 hz results indicate apparently larger attenuation than observed with similar techniques in other regions of mexico including the mexican volcanic belt within the limitation imposed by the data the spatial distribution of coda q with respect to the volcanic edifice was investigated for paths sampling the near vicinity of the volcano a value of approximately q c 30 was obtained the highest attenuation results are obtained for volumes with a slight e w tendency with q c values of 28 and 25 respectively the location of a gravity high as well as microseismic activity correlates well with this result which is interpreted as due to the probable presence of an intrusive magma body lower attenuation is obtained for volumes sampling deeper than the moho reaching a value of q c 87 suggesting that rocks below this boundary play a major role in controlling the overall attenuation of paths traversed by coda waves the results also suggest a decrease in attenuation towards the south and north possibly reflecting a decrease in magmatic processes in both of these directions

active shortening of the cascadia forearc and implications for seismic hazards of the puget lowland 1 margin parallel shortening of the cascadia forearc is a consequence of oblique subduction of the juan de fuca plate beneath north america strike slip thrust and oblique crustal faults beneath the densely populated puget lowland accommodate much of this north south compression resulting in large crustal earthquakes to better understand this forearc deformation and improve earthquake hazard assessment we here use seismic reflection surveys coastal exposures of pleistocene strata potential field data and airborne laser swath mapping to document and interpret a significant structural boundary near the city of tacoma this boundary is a complex structural zone characterized by two distinct segments the northwest trending eastern segment extending from tacoma to carr inlet is formed by the broad 11 5 km southwest dipping 11 20 rosedale monocline this monocline raises crescent formation basement about 2 5 km resulting in a moderate gravity gradient we interpret the rosedale monocline as a fault bend fold forming above a deep thrust fault within the rosedale monocline inferred quaternary strata thin northward and form a growth triangle that is 4 1 to 6 6 km wide at its base suggesting 2 3 mm yr of slip on the underlying thrust the western section of the 40 km long north dipping tacoma fault extending from hood canal to carr inlet forms the western segment of the tacoma basin margin structural relief on this portion of the basin margin may be several kilometers resulting in steep gravity and aeromagnetic anomalies quaternary structural relief along the tacoma fault is as much as 350 400 m indicating a minimum slip rate of about 0 2 mm yr the inferred eastern section of the tacoma fault east of carr inlet crosses the southern part of the seattle uplift has variable geometry along strike and diminished structural relief the tacoma fault is regarded as a north dipping backthrust to the seattle fault so that slip on a master thrust fault at depth could result in movement on the seattle fault the tacoma fault or both

extent and duration of the 2003 cascadia slow earthquake 1 inversion of continuous gps measurements from the pacific northwest show the 2003 cascadia slow earthquake to be among the largest of ten transients recognized here twelve stations bracketing slow slip indicate transient slip propagated bi directionally from initiation in the southern puget basin reaching 300 km along strike over a period of seven weeks this event produced for the first time resolvable vertical subsidence and horizontal displacement reaching six mm in southern washington state inverted for non negative thrust slip a maximum of 3 8 cm of slip is inferred centered at 28 km depth near the sharp arch in the subducting juan de fuca plate nearly all slip lies shallower than 38 km inverted slip shows a total moment release equal to mw 6 6 and a high degree of spatial localization rather than near uniform slip this suggests rupture concentrated along asperities holds for slow earthquakes as well as conventional events

gps deformation in a region of high crustal seismicity n cascadia forearc we estimate the rate of crustal deformation in the central and northern cascadia forearc based on a combination of existing global positioning system gps velocity data along the cascadia subduction zone gps strain rates and velocities show that the northwestern washington southwestern british columbia region is currently shortening at 3 3 5 mm yr 31 in a n s direction in good agreement with inference from crustal earthquake statistics on the longterm the shortening rate is 5 6 mm yr 31 providing that the subduction related interseismic loading of the margin is purely elastic compared to the velocity of the oregon forearc with respect to north america v 7m m yr 31 this indicates that most of the forearc motion is accommodated in the puget georgia basin area corresponding to the main concentration of crustal seismicity the difference between the current and long term shortening rates may be taken up during subduction megathrust earthquakes thus these events could produce a sudden increase of n s compression in the puget sound region and could trigger major seattle fault type crustal earthquakes published by elsevier science b v

satellite radar interferometry time series analysis of surface deformation for los angeles california 1 the los angeles california metropolitan area is a tectonically active region with surface deformation that is a combination of fault related tectonics plus a variety of natural and anthropogenic signals we apply the small baseline subset sbas algorithm to produce an interferometric synthetic aperture radar insar time series analysis for the los angeles area using data acquired by the ers satellites from late 1995 into 2002 the result is a space time deformation product that can be exploited to view not only the smoothly varying long term surface motion but also its time varying patterns large seasonal oscillations of the santa ana aquifer observed in southern california integrated gps network scign data are accurately matched in the insar time series moreover correlations of the insar time series with an annual sinusoid allows us to investigate the dynamics of the hydrologic system index terms 1243 geodesy and gravity space geodetic surveys 1294 geodesy and gravity instruments and techniques 1803 hydrology anthropogenic effects citation lanari r p lundgren m manzo and f casu 2004 satellite radar interferometry time series analysis of surface deformation for los angeles california geophys res lett 31 l23613 doi 10 1029 2004gl021294

evidence for late holocene earthquakes on the utsalady point fault northern puget lowland washington trenches across the utsalady point fault in the northern puget lowland of washington reveal evidence of at least one and probably two late holocene earthquakes the teeka and duffers trenches were located along a 1 4 km long 1 to 4 m high northwest trending southwest facing topographic scarp recognized from airborne laser swath mapping glaciomarine drift exposed in the trenches reveals evidence of about 95 to 150 cm of vertical and 200 to 220 cm of left lateral slip in the teeka trench radiocarbon ages from a buried soil a horizon and overlying slope colluvium along with the historical record of earthquakes suggest that this faulting occurred 100 to 400 calendar years b p a d 1550 to 1850 in the duffers trench 370 to 450 cm of vertical separation is accommodated by faulting 210 cm and folding 160 to 240 cm with probable but undetermined amounts of lateral slip stratigraphic relations and radiocarbon ages from buried soil colluvium and fissure fill in the hanging wall suggest the deformation at duffers is most likely from two earthquakes that occurred between 100 to 500 and 1100 to 2200 calendar years b p but deformation during a single earthquake is also possible for the two earthquake hypothesis deformation at teeka trench in the first event involved folding but not faulting regional relations suggest that the earthquake s were m 6 7 and that offshore rupture may have produced tsunamis based on this investigation and related recent studies the maximum recurrence interval for large ground rupturing crustal fault earthquakes in the puget lowland is about 400 to 600 years or less

a revised dislocation model of interseismic deformation of the cascadia subduction zone 1 cas3d 2 a new three dimensional 3 d dislocation model is developed to model interseismic deformation rates at the cascadia subduction zone the model is considered a snapshot description of the deformation field that changes with time the effect of northward secular motion of the central and southern cascadia forearc sliver is subtracted to obtain the effective convergence between the subducting plate and the forearc horizontal deformation data including strain rates and surface velocities from global positioning system gps measurements provide primary geodetic constraints but uplift rate data from tide gauges and leveling also provide important validations for the model a locked zone based on the results of previous thermal models constrained by heat flow observations is located entirely offshore beneath the continental slope similar to previous dislocation models an effective zone of downdip transition from locking to full slip is used but the slip deficit rate is assumed to decrease exponentially with downdip distance the exponential function resolves the problem of overpredicting coastal gps velocities and underpredicting inland velocities by previous models that used a linear downdip transition a wide effective transition zone etz partially accounts for stress relaxation in the mantle wedge that cannot be simulated by the elastic model the pattern of coseismic deformation is expected to be different from that of interseismic deformation at present 300 years after the last great subduction earthquake the downdip transition from full rupture to no slip should take place over a much narrower zone

resolving vertical tectonics in the san francisco bay area from permanent scatterer insar and gps analysis using a combination of gps measured horizontal velocities of 200 sites and 115 487 range change rates determined with the permanent scatterer interferometric synthetic aperture radar insar method in the san francisco bay area we resolve vertical motions in the region at sub mm yr precision the highest displacement rates are due to nontectonic processes such as active landslides subsidence and rebound over aquifers and rapid settling of unconsolidated sediments along the bay margins residual displacement rates are determined by removing the contribution of the gps derived horizontal velocity field from the insar range change rates to isolate vertical tectonic rates we use only those insar measurements made on material that was not quaternary substrate which is susceptible to nontectonic and seasonally varying ground motions the insar residuals indicate significant uplift over the southern foothills of the active mount diablo anticlinorium the mission hills stepover region of the hayward and calaveras faults and the central and southern santa cruz mountains located along a restraining bend of the san andreas fault

space geodesy subsidence and flooding in new orleans a subsidence map of the city offers insight into the failure of the levees during hurricane katrina

a dislocation model of strain accumulation and release at a subduction zone strain accumulation and release at a subduction zone are attributed to stick slip on the main thrust zone and steady aseismic slip on the remainder of the plate interface this process can be described as a superposition of steady state subduction and a repetitive cycle of slip on the main thrust zone consisting of steady normal slip at the plate convergence rate plus occasional thrust events that recover the accumulated normal slip because steady state subduction does not contribute to the deformation at the free surface deformation observed there is completely equivalent to that produced by the slip cycle alone the response to that slip is simply the response of a particular earth model to embedded dislocations for a purely elastic earth model the deformation cycle consists of a coseismic offset followed by a linear in time recovery to the initial value during the interval between earthquakes for an elastic viscoelastic earth model elastic lithosphere over a viscoelastic asthenosphere the postearthquake recovery is not linear in time records of local uplift as a function of time indicate that the long term postseimic recovery is approximately linear suggesting that elastic earth models are adequate to describe the deformation cycle however the deformation predicted for amore simple elastic half space earth does not reproduce the deformation observed along the subduction zones in japna at all well if stick slip is restricted to the main thrust zone as recognized earlier by shimazaki seno and kato the uplift profiles could be explained if stick slips were postulated to extend along the plate interface beyond the main thrust zone to a depth of perhaps 100 km but independent evidence suggests that stick slip at such depths if unlikely less

seasonal subsidence and rebound in las vegas valley nevada observed by synthetic aperture radar interferometry analyses of areal variations in the subsidence and rebound occurring over stressed aquifer systems in conjunction with measurements of the hydraulic head fluctuations causing these displacements can yield valuable information about the compressibility and storage properties of the aquifer system historically stress strain relationships have been derived from paired extensometer piezometer installations which provide only point source data because of the general unavailability of spatially detailed deformation data areal stress strain relations and their variability are not commonly considered in constraining conceptual and numerical models of aquifer systems interferometric synthetic aperture radar insar techniques can map ground displacements at a spatial scale of tens of meters over 100 km wide swaths insar has been used previously to characterize larger magnitude generally permanent aquifer system compaction and land subsidence at yearly and longer timescales caused by sustained drawdown of groundwater levels that produces intergranular stresses consistently greater than the maximum historical stress we present insar measurements of the typically small magnitude generally recoverable deformations of the las vegas valley aquifer system occurring at seasonal timescales from these we derive estimates of the elastic storage coefficient for the aquifer system at several locations in las vegas valley these high resolution measurements offer great potential for future investigations into the mechanics of aquifer systems and the spatial heterogeneity of aquifer system structure and material properties as well as for monitoring ongoing aquifer system compaction and land subsidence

ground motion measurement in the lake mead area nevada by differential synthetic aperture radar interferometry time series analysis probing the lithosphere rheological structure 1 we measure ground motion around the lake mead nevada using synthetic aperture radar interferometry the lake water level has fluctuated through time since impoundment in 1935 to quantify the deformation due to water level variations over the past decade and to constrain the crust and mantle rheological parameters in the lake area we analyze 241 interferograms based on 43 ers images acquired between 1992 and 2002 all interferograms have a high coherence due to arid conditions most of them show strong atmospheric artefacts tropospheric phase delays are estimated and corrected for each interferogram by analyzing the phase elevation correlation corrections are validated using data from the era40 global atmospheric reanalysis corrected interferograms are inverted pixel by pixel to solve for the time series of ground motion in the lake area temporal smoothing is added to reduce random atmospheric artefacts the observed deformation is nonlinear in time and spreads over a 50 50 km2 area we observe a 16 mm subsidence between 1995 and 1998 due to an 11 m water level increase followed by an uplift due to the water level drop after 2000 we model the deformation taking into account the loading history of the lake since 1935 a simple elastic model with parameters constrained by seismic wave velocities does not explain the amplitude of the observed motion the two layer viscoelastic model proposed by kaufmann and amelung 2000 with a mantle viscosity of 1018 pa s adjusts well the data amplitude and its spatiotemporal shape

radar interferogram filtering for geophysical applications the use of sar interferometry is often impeded by decorrelation from thermal noise temporal change and baseline geometry power spectra of interferograms are typically the sum of a narrow band component combined with broad band noise we describe a new adaptive filtering algorithm that dramatically lowers phase noise improving both measurement accuracy and phase unwrapping while demonstrating graceful degradation in regions of pure noise the performance of the filter is demonstrated with sar data from the ers satellites over the jakobshavns glacier of greenland

persistent scatterer selection using maximum likelihood estimation 1 we present here a new insar persistent scatterer selection method using maximum likelihood estimation to identify persistent scattering pixels which results in a denser network of reliable phase measurements than do existing methods we analyze the phase of each pixel in a series of interferograms and estimate the relative strength of any slowly fluctuating component of the radar echo from a dominant scatterer to the background scattering within a pixel we find a fairly dense network of scatterers with stable phase characteristics in areas where conventional insar fails due to decorrelation we examined data over two vegetated regions in the san francisco bay area the average phases of these pixels clearly show the slip along the hayward fault and set upper bounds on any slip along the bay area segment of the san andreas fault

main genetic types and geological characteristics of iron rich ore deposits in china the proven total reserves of iron ores in china are relatively abundant but the iron ores mainly belong to low grade ores the reserves of high grade iron ores are rare and only possess 4 6 of the total proven reserves of iron ores among them the high grade ores for steelmaking and for iron smelting are even rarer and only amount to 1180 million tones which make up 2 27 of the proven reserves of iron ores in china the main genetic types of iron deposits of high grade ores in china include hydrothermal reformed type in sedimentary metamorphosed iron deposits bif weathered leaching type in sedimentary metamorphosed iron deposits bif iron deposits related to continental volcano intrusive activities iron deposits related to marine vo l canic intrusive activities skarn iron deposits hydrothermal iron deposits among these iron deposit types of high grade iron ores the skarn iron deposits and iron deposits related to marine volcanic intrusive activities are relatively important and have favorable ore prospecting potential