from transtension to transpression along the northern caribbean plate boundary off cuba implications for the recent motion of the caribbean plate abstract marine geophysical surveys using seabeam single channel seismic reflection gravimetric and magnetic measurements have been conducted along a segment of the northern caribbean transcurrent plate boundary seacarib ii cruise the data allow a better definition of the geometry and the tectonic regime of this major strike slip area they support the following results 1 1 along the southern cuban margin the oriente fault displays a discontinuous trace mainly composed of dextral offset en echelon segments some pull apart basins are located between fault segments cabo cruz basin chivirico and baitiquiri basins in the windward passage area the plate boundary enters into the tortue channel and is not connected with the subduction front off northern hispaniola 2 2 the eastern part of the oriente deep and the santiago promontory are characterised by active compressional tectonics they form the santiago deformed belt described here for the first time this deformed belt can be divided longitudinally into three main segments each one characterised by a particular tectonic style its development is related to a transpressional mechanism along the left lateral oriente strike slip fault our observations suggest that a tectonic and kinematic reorganisation occurred recently in this area probably in the late pliocene which may be compared with the recent geological events recorded on land in the northern caribbean domain the precise knowledge of both geometry and structures along the oriente strike slip fault south of cuba provides new constraints for the recent kinematic evolution along the northern caribbean transcurrent plate boundary it leads us to infer the existence of a convergence component associated with the slip component along the oriente transform fault

tectonometamorphic evolution of the samana complex northern hispaniola implications for the burial and exhumation of high pressure rocks in a collisional accretionary wedge abstract the samana complex exposes a segment of a high p metasedimentary collisional accretionary wedge built during caribbean island arc north america continental margin convergence combined detailed mapping metamorphic mineral assemblages multi equilibrium calculations and thermodynamical modelling of garnet zoning together with isotopic ages allow proposing a tectonothermal evolution of the complex involving three major stages m1 to m3 m1 metamorphism was characterised by a prograde p t path towards the pressure peak in the lawsonite blueschists santa barbara schists and rincon marbles lower structural nappes and garnet blueschists to eclogite facies conditions punta balandra upper nappe this high p metamorphism and related d1 deformation took place from the eocene to late oligocene when the different nappes were buried along a cold subduction zone gradient contemporary to the d2 deformation m2 retrograde metamorphism was associated in all nappes with substantial decompression under nearly isothermal or cooling conditions to the epidote blueschists and greenchists facies conditions d2 deformation produced ene directed folding thrusting and nappe stacking in the complex when nappes went sequentially incorporated to a growing collisional accretionary complex between the late eocene and the earliest miocene d2 deformation is thus responsible for much of the exhumation of the subducted rocks and for the thinning of the nappe pile as the continuity of the p t conditions within the accreted metasedimentary material were in this case preserved the exhumation mechanisms for samana complex high p rocks was most probably driven by underthrusting underplating and erosion non penetrative fabrics associated with d3 and d4 late deformations indicate m3 cooling in the greenschists and subgreenchists facies conditions d5 sinistral strike slip brittle faults cut and laterally displaced the whole nappe pile of the samana complex from the lower miocene to the present

continental crust composition constrained by measurements of crustal poisson s ratio deciphering the geological evolution of the earth s continental crust requires knowledge of its bulk composition and global variability the main uncertainties are associated with the composition of the lower crust seismic measurements probe the elastic properties of the crust at depth from which composition can be inferred of particular note is poisson s ratio this elastic parameter can be determined uniquely from the ratio of p to s wave seismic velocity and provides a better diagnostic of crustal composition than either p or s wave velocity alone1 previous attempts to measure have been limited by difficulties in obtaining coincident p and s wave data sampling the entire crust2 here we report 76 new estimates of crustal spanning all of the continents except antarctica we find that on average increases with the age of the crust our results strongly support the presence of a mafic lower crust beneath cratons and suggest either a uniformitarian craton formation process involving delamination of the lower crust during continental collisions followed by magmatic underplating or a model in which crust formation processes have changed since the precambrian era

transpression and strain partitioning in the caribbean island arc fabric development kinematics and ar ar ages of syntectonic emplacement of the loma de cabrera batholith dominican republic abstract an integrative structural and geochronologic study of the loma de cabrera batholith lcb cordillera central dominican republic and its country rocks reveals the interplay of deformation metamorphism and plutonism produced in the caribbean island arc during late cretaceous oblique convergence the results emphasize the interference between three contemporaneous strain fields 1 a northern and southern domains produced by 40 ar 39 ar in hornblende during sinistral transpressional shearing comparison of the structural data with strain models of oblique plate convergence suggest that the lmsz is a preserved ductile signature of strike slip partitioning within a sinistral transpressional intra oceanic subduction zone in the lcb microstructural data indicate that the magmatic to high temperature solid state deformation initially occurred over a wider band of heterogeneously distributed shear deformation and was partitioned in narrow bands of mid to low temperature deformation connected with the lmsz during the cooling of the batholith field and geochronologic studies also suggest that shortening across the southern domain took place concurrently with sinistral strike slip movement along the crustal scale la guacara and macutico fault zones also consistent with a transpressional setting for the late cretaceous caribbean magmatic arc shear and fault zones were variably reactivated during upper eocene oligocene thrusting and miocene to recent uplift of the cordillera central

current block motions and strain accumulation on active faults in the caribbean the caribbean plate and its boundaries with north and south america marked by subduction and large intra arc strike slip faults are a natural laboratory for the study of strain partitioning and interseismic plate coupling in relation to large earthquakes here we use most of the available campaign and continuous gps measurements in the caribbean to derive a regional velocity field expressed in a consistent reference frame we use this velocity field as input to a kinematic model where surface velocities results from the rotation of rigid blocks bounded by locked faults accumulating interseismic strain while allowing for partial locking along the lesser antilles puerto rico and hispaniola subduction we test various block geometries guided by previous regional kinematic models and geological information on active faults our findings refine a number of previously established results in particular slip rates on the strike slip faults systems bounding the caribbean plate to the north and south and the kinematics of the gonave microplate our much improved gps velocity field in the lesser antilles compared to previous studies does not require the existence of a distinct northern lesser antilles block and excludes more than 3 mm yr of strain accumulation on the lesser antilles puerto rico subduction plate interface which appears essentially uncoupled the transition from a coupled to an uncoupled subduction coincides with a transition in the long term geological behavior of the caribbean plate margin from compressional hispaniola to extensional puerto rico and lesser antilles a characteristics shared with several other subduction systems

gps estimates of microplate motions northern caribbean evidence for a hispaniola microplate and implications for earthquake hazard summary we use elastic block modelling of 126 gps site velocities from jamaica hispaniola puerto rico and other islands in the northern caribbean to test for the existence of a hispaniola microplate and estimate angular velocities for the gonave hispaniola puerto rico virgin islands and two smaller microplates relative to each other and the caribbean and north america plates a model in which the gonave microplate spans the whole plate boundary between the cayman spreading centre and mona passage west of puerto rico is rejected at a high confidence level the data instead require an independently moving hispaniola microplate between the mona passage and a likely diffuse boundary within or offshore from western hispaniola our updated angular velocities predict 6 8 1 0 mm yr 1 of left lateral slip along the seismically hazardous enriquillo plantain garden fault zone of southwest hispaniola 9 8 2 0 mm yr 1 of slip along the septentrional fault of northern hispaniola and 14 15 mm yr 1 of left lateral slip along the oriente fault south of cuba they also predict 5 7 1 mm yr 1 of fault normal motion in the vicinity of the enriquillo plantain garden fault zone faster than previously estimated and possibly accommodated by folds and faults in the enriquillo plantain garden fault zone borderlands our new and a previous estimate of gonave caribbean plate motion suggest that enough elastic strain accumulates to generate one to two mw 7 earthquakes per century along the enriquillo plantain garden and nearby faults of southwest hispaniola that the 2010 m 7 0 haiti earthquake ended a 240 yr long period of seismic quiescence in this region raises concerns that it could mark the onset of a new earthquake sequence that will relieve elastic strain that has accumulated since the late 18th century

origin of strontium and calcium in pedogenic needle fibre calcite nfc abstract strontium sr and calcium ca isotopic compositions and sr ca ratios have been analysed in different fractions of pedogenic needle fibre calcite nfc from the swiss jura mountains villiers neuch tel switzerland in order to determine their ca sources and to investigate the potential role of fungi in the origin of nfc 87sr 86sr ratios have been measured to trace the ca trapped within different pedogenic carbonate this ratio was compared for previously identified microscopic morphological groups of nfc the bulk soil fine earth

modeling the crust and upper mantle in northern beata ridge caribe norte project the complex tectonic region of ne caribbean where hispaniola and puerto rico are located is bordered by subduction zone with oblique convergence in the north and by incipient subduction zone associated to muertos trough in the south central caribbean basin is characterized by the presence of a prominent topographic structure known as beata ridge whose oceanic crustal thickness is unusual the northern part of beata ridge is colliding with the central part of hispaniola along a transverse ne alignment which constitutes a morphostructural limit thus producing the interruption of the cibao valley and the divergence of the rivers and basins in opposite directions the direction of this alignment coincides with the discontinuity that could explain the extreme difference between west and east seismicity of the island different studies have provided information about beata ridge mainly about the shallow structure from mcs data in this work caribe norte 2009 wide angle seismic data are analyzed along a wnw ese trending line in the northern flank of beata ridge providing a complete tectonic view about shallow middle and deep structures the results show clear tectonic differences between west and east separated by beata island in the haiti basin area sedimentary cover is strongly influenced by the bathymetry and its thickness decreases toward to the island in this area the upper mantle reaches 20 km deep increasing up to 24 km below the island where the sedimentary cover disappears to the east the three seamounts of beata ridge provoke the appearance of a structure completely different where sedimentary cover reaches thicknesses of 4 km between seamounts and moho rises up to 13 km deep this study has allowed to determine the moho topography and to characterize seismically the first upper mantle layers along the northern beata ridge which had not been possible with previous mcs data

actively evolving microplate formation by oblique collision and sideways motion along strike slip faults an example from the northeastern caribbean plate margin abstract the pattern of folding faulting and late quaternary coral reef uplift rates in western and central hispaniola haiti and dominican republic suggest that the elongate gonave microplate a 190 000 km2 area of the northeastern caribbean plate is in the process of shearing off the caribbean plate and accreting to the north american plate late cenozoic transpression between the southeastern bahama platform and the caribbean plate in hispaniola has inhibited the eastward motion of the northeastern corner of the plate transpression is manifested in western and central hispaniola by the formation of regional scale folds that correspond to present day anticlinal topographic mountain chains continuous with offshore anticlinal ridges areas of most rapid quaternary uplift determined from onland coral reefs 125 ka and younger coincide with the axial traces of these folds offshore data suggest recent folding and faulting of the seafloor onshore reef data do not conclusively require late quaternary folding but demonstrate that tectonic uplift rates of the axial areas of the anticlines decrease from the northwest peninsula of haiti 0 37 mm yr to to the central part of the coast of western haiti 0 19 mm yr to the south central part of western haiti 0 mm yr formation of the 1200 km long enriquillo plantain garden walton fault zone as a bypass strike slip fault has isolated the southern edge of the gonave microplate and is allowing continued unimpeded eastward motion of a smaller caribbean plate past the zone of late neogene convergence and quaternary uplift of coral reefs in hispaniola offshore seismic reflection data from the jamaica passage the marine strait separating jamaica and haiti show that the enriquillo plantain garden fault zone forms a narrow but deep active fault bounded trough beneath the passage the active fault is continuous with active faults mapped onshore in western haiti and eastern jamaica the bathymetric deep is present because the jamaica passage fault segment represents a 50 km wide transtensional left step of the fault trace between haiti and jamaica onshore satellite imagery and field observations suggest that the enriquillo plantain garden fault forms a continuous trace extending from central hispaniola east of lake enriquillo dominican republic to the westernmost end of the southern peninsula of haiti the regional lineament corresponds to a recent fault scarp in quaternary alluvium of the clonard pull apart basin in the central part of the southern peninsula of haiti and suggests that at least this part of the lineament has undergone recent slip calmus 1983 has suggested a total offset of 30 50 km of the enriquillo plantain garden fault zone in the southern peninsula of haiti using the apparent offset of lithologic units seismic reflection data from lake enriquillo document recent deformation of quaternary lake sediments where the lineament crosses the lake leveling of the crest of a late holocene coral reef and associated algal tufa around lake enriquillo demonstrate late holocene vertical movement and tilting in a 1500 m wide zone parallel to the fault trend lateral offset is difficult to show in the enriquillo valley area because of rapid recent sedimentation into the valley the pattern of inactive strike slip faults and fold belts of cenozoic age in cuba and the yucatan basin suggest that two elongate microplates were sheared off the proto caribbean plate and accreted to the north american plate by a similar process in paleocene and eocene times age of terminal deformation in western central and eastern cuba is consistent with southeastward younging and migration of arc collision the similarity of the size and sequence of events in cuba suggests that the process of oblique collision and sideways motion of the plate along a new strike slip fault towards a free face may be an important process of microplate formation and interplate transfer in other areas

lithospheric structure of the texas gulf of mexico passive margin from surface wave dispersion and migrated ps receiver functions the seismic velocity structure beneath texas gulf coastal plain gcp is imaged by migrating ps receiver functions with a seismic velocity model found by fitting surface wave dispersion we use seismic data from a linear array of 22 broadband stations spaced 16 20 km apart a common conversion point ccp stacking technique is applied to earthquake data to improve the s n ratios of receiver functions using an incorrect velocity model for depth migration of a stacked ccp image may produce an inaccurate image of the subsurface to find sufficiently accurate p and s velocity models we first apply a nonlinear modeling technique to fit rayleigh wave group velocity dispersion via very fast simulated annealing vs ranges from 1 5 km s in shallow layers of the gcp to 4 5 km s beneath the llano uplift and just outboard of the balcones fault zone bfz the bfz is characterized by slow velocities that persist to nearly 100 km depth in the stacked image the largest amplitude positive polarity event ranges from the surface at the llano uplift to a maximum depth of 16 km beneath matagorda island we attribute this event to the sediment basement contact which is expected to produce a large impedance contrast another large amplitude and positive polarity event at 35 km depth which likely marks the moho disappears outboard of the luling fault zone the disappearance of the moho beneath the gcp may be due to serpentinization of the upper mantle which would reduce the impedance contrast between the lower crust and upper mantle dramatically

plume mantle source heterogeneity through time insights from the duarte complex hispaniola northeastern caribbean 1 located in the cordillera central of hispaniola the duarte complex offers an opportunity to study an on land fragment of the caribbean colombian oceanic plateau geochemical sr nd isotope and 40ar 39ar radiometric age data combined with detailed mapping have shown that the duarte complex includes two lithostratigraphic units composed of four geochemical groups of metavolcanic rocks group ia low ti high mg basalts and group ib high ti picrites and primitive high mg basalts occur interlayered in the lowermost levels of the lower unit group ii light rare earth element lree enriched picrites ferropicrites and high mg basalts forms the main lava sequence of the lower unit and group iii lree enriched fe ti basalts is present exclusively in the upper unit nd isotope and incompatible trace element patterns are diverse in the duarte complex metavolcanics and are consistent with mantle sources related to a heterogeneous plume mantle melt modeling suggests that an early extensive melting 10 20 of shallow mantle resulted in the formation of relatively depleted group i and ii magmas whereas the late more enriched group iii magmas were the product of deeper low degree 96 ma hence an early cretaceous phase of the caribbean colombian oceanic plateau construction is recorded in hispaniola

crustal thickness and bulk poisson ratios in the dominican republic from receiver function analysis abstract the dominican republic dr comprises the eastern two thirds of the island of hispaniola which is located on the caribbean north american plate boundary previous studies have described the shallow structure and stratigraphy of the island but due to a dearth of broadband seismic data little is known about the lower crust and mantle since august 2014 thirteen broadband three component seismic stations have been deployed temporarily in the dr they are combined with four permanent broadband stations in the dr and three in neighboring haiti to enhance studies of hispaniola s lower crust and upper mantle we report results of a receiver function study using teleseismic data recorded by these stations specifically we compute receiver functions and determine crustal properties via h stacking we propose additional intracrustal and upper mantle layers based on identifications of prominent and coherent p to s converted phases observed in receiver function gathers our results show that crustal thickness varies beneath the island of hispaniola over the range 13 47 km with a median of 24 km and bulk vp vs ratios vary over 1 58 1 99 with median 1 79 receiver function modeling reveals intracrustal discontinuities at station paph port au prince haiti at a depth of 8 0 km station jidr jimani dr 8 8 km depth and sddr sabaneta dr 15 8 km depth additional discontinuities appear in the upper mantle beneath paph 60 1 km depth pcdr punta cana 60 km sdd santo domingo 70 km and sc01 santiago 81 km two north south cross sections show variations in bulk vp vs ratios that are consistent with expectations based upon surface geology but variations in crustal thickness are more scattered and do not conform to expectations from simple tectonic models of hispaniola s formation our stacking results reveal consistency between vp vs ratios in four distinct regions which are consistent with the compositional domains identified by previous studies

seismic hazard along the southern boundary of the gonave microplate block modelling of gps velocities from jamaica and nearby islands northern caribbean summary we use block modelling of gps site velocities from jamaica and nearby islands including hispaniola to test alternative plate boundary geometries for deformation in jamaica and estimate slip rates along the island s major fault zones relative to the caribbean plate gps sites in northern jamaica move 6 0 0 5 mm yr 1 to the wsw constituting a lower bound on the motion of the gonave microplate across its southern boundary in jamaica obliquely convergent motion of all 30 gps sites on and near jamaica relative to the island s e w trending strike slip faults may be partitioned into 2 6 0 6 mm yr 1 of n s shortening across submarine faults south of jamaica and 5 6 mm yr 1 of e w motion guided by geological and seismic information about the strikes and locations of faults in jamaica inverse block modelling of the regional gps velocities rejects plate boundary configurations that presume either a narrow plate boundary in jamaica or deformation concentrated across a restraining bend defined by the topographically high blue mountains of eastern jamaica the best fitting models instead place most deformation on faults in central jamaica the 4 5 mm yr 1 slip rate we estimate for the plantain garden fault and blue mountain restraining bend of southeastern jamaica implies significant seismic hazard for the nearby capital of kingston

interseismic plate coupling and strain partitioning in the northeastern caribbean summary the northeastern caribbean provides a natural laboratory to investigate strain partitioning its causes and its consequences on the stress regime and tectonic evolution of a subduction plate boundary here we use gps and earthquake slip vector data to produce a present day kinematic model that accounts for secular block rotation and elastic strain accumulation with variable interplate coupling on active faults we confirm that the oblique convergence between caribbean and north america in hispaniola is partitioned between plate boundary parallel motion on the septentrional and enriquillo faults in the overriding plate and plateboundary normal motion at the plate interface on the northern hispaniola fault to the east the caribbean north america plate motion is accommodated by oblique slip on the faults bounding the puerto rico block to the north puerto rico subduction and to the south muertos thrust with no evidence for partitioning the spatial correlation between interplate coupling strain partitioning and the subduction of buoyant oceanic asperities suggests that the latter enhance the transfer of interplate shear stresses to the overriding plate facilitating strike slip faulting in the overriding plate the model slip rate deficit together with the dates of large historical earthquakes indicates the potential for a large m w7 5 or greater earthquake on the septentrional fault in the dominican republic similarly the enriquillo fault in haiti is currently capable of a m w7 2 earthquake if the entire elastic strain accumulated since the last major earthquake was released in a single event today the model results show that the puerto rico lesser antilles subduction thrust is only partially coupled meaning that the plate interface is accumulating elastic strain at rates slower than the total plate motion this does not preclude the existence of isolated locked patches accumulating elastic strain to be released in future earthquakes but whose location and geometry are not resolvable with the present data distribution slip deficit on faults from this study are used in a companion paper to calculate interseismic stress loading and together with stress changes due to historical earthquakes derive the recent stress evolution in the ne caribbean

the northern caribbean plate boundary in the jamaica passage structure and seismic stratigraphy multibeam bathymetry data and multichannel seismic reflection profiles have been collected at the end of 2012 along the enriquillo plantain garden fault zone epgfz in the jamaica passage between jamaica and hispaniola analysis of the data set reveals the tectonic evolution and the stratigraphic complexity of the northern caribbean boundary stratigraphic correlations with previous marine and on land studies are proposed to place the identified seismic sequences in their regional tectonic history two distinct crustal domains are interpreted typical stratigraphic sequences for the rifted blocks of the eastern cayman trough margin are identified in five basins of the jamaica passage highlighting the eastward limit of the cayman trough margin these inherited basins are deformed and folded during a first phase of compression that could correspond to the regional tectonic rearrangement recorded in the early miocene about 20 ma a distinct crustal domain that we propose to relate to the carib beds caribbean typical reflectors a b and v is identified in the southern part of the jamaica passage indicating that the caribbean large igneous province could extend up to the extreme northeast part of the lower nicaragua rise the left lateral epgfz currently cuts across two pre existing basins the morant and matley basins during the activity of the epgfz these basins are deformed and folded indicating a second phase of compression in contrast the navassa basin located in the middle of the jamaica passage results from the strike slip motion of the epgfz and is interpreted as an asymmetrical basin bordered by the epgfz only on its northern side

segmentation and kinematics of the north america caribbean plate boundary offshore hispaniola we explored the submarine portions of the enriquillo plantain garden fault zone epgfz and the septentrional oriente fault zone sofz along the northern caribbean plate boundary using high resolution multi beam echo sounding and shallow seismic reflection the bathymetric data shed light on poorly documented or previously unknown submarine fault zones running over 200 km between haiti and jamaica epgfz and 300 km between the dominican republic and cuba sofz the primary plate boundary structures are a series of strike slip fault segments associated with pressure ridges restraining bends step overs and dogleg offsets indicating very active tectonics several distinct segments 50 to 100 km long cut across pre existing structures inherited from former tectonic regimes or bypass recent morphologies formed under the current strike slip regime along the most recent trace of the sofz we measured a strike slip offset of 16 5 km which indicates steady activity for the past 1 8 ma if its current gps derived motion of 9 8 2 mm yr has remained stable during the entire quaternary

seamarc ii mapping of transform faults in the cayman trough caribbean sea seamarc ii maps of the southern wall of the cayman trough between honduras and jamaica show zones of continuous well defined fault lineaments adjacent and parallel to the wall both to the east and west of the cayman spreading axis these lineaments mark the present active traces of transform faults which intersect the southern end of the spreading axis at a triple junction the swan islands transform fault to the west is dominated by two major lineaments that overlap with right stepping sense across a large push up ridge beneath the swan islands the fault zone to the east of the axis named the walton fault is more complex containing multiple fault strands and a large pull apart structure the walton fault links the spreading axis to jamaican and hispaniolan strike slip faults and it defines the southern boundary of a microplate composed of the eastern cayman trough and western hispaniola the presence of this microplate raises questions about the veracity of caribbean plate velocities based primarily on cayman trough opening rates

complex rupture during the 12 january 2010 haiti earthquake initially the devastating mw 7 0 12 january 2010 haiti earthquake seemed to involve straightforward accommodation of oblique relative motion between the caribbean and north american plates along the enriquillo plantain garden fault zone here we combine seismological observations geologic field data and space geodetic measurements to show that instead the rupture process involved slip on multiple faults primary surface deformation was driven by rupture on blind thrust faults with only minor deep lateral slip along or near the main enriquillo plantain garden fault zone thus the event only partially relieved centuries of accumulated left lateral strain on a small part of the plate boundary system together with the predominance of shallow off fault thrusting the lack of surface deformation implies that remaining shallow shear strain will be released in future surface rupturing earthquakes on the enriquillo plantain garden fault zone as occurred in inferred holocene and probable historic events we suggest that the geological signature of this earthquake broad warping and coastal deformation rather than surface rupture along the main fault zone will not be easily recognized by standard palaeoseismic studies we conclude that similarly complex earthquakes in tectonic environments that accommodate both translation and convergence such as the san andreas fault through the transverse ranges of california may be missing from the prehistoric earthquake record

crust and mantle structure across the basin and range colorado plateau boundary at 37 n latitude and implications for cenozoic extensional mechanism we present new evidence on the seismic velocity and density of the crust and upper mantle along a 200 km long transect across the eastern basin and range and western colorado plateau at 37 n latitude receiver functions computed from the p waveforms recorded with 10 portable broadband stations deployed along the transect were used to estimate crustal thickness variations the crust is 30 35 km thick within the eastern basin and range and increases over a distance of 100 km at the western edge of the colorado plateau reaching a maximum of approximately 45 km east of the hurricane fault the timing of crustal multiples within the reciever functions were used to estimate the v p v s of the crust along the profile and we found that the western colorado plateau crust is characterized by a high poisson s ratio 0 28 0 29 indicative of a crust with an average mafic composition we estimated the upper mantle lid thickness along our profile based on teleseismic p wave travel times and constraints provided by gravity data our data and available geophysical constraints are most consistent with a lithosphere that thickens from an average thickness of 60 km beneath the basin and range to 100 km beneath the western colorado plateau although the basin and range lithosphere may have significant thickness variations the thick strong mafic crust and thicker mantle lid under the colorado plateau can account for the relative geologic stability and subdued magmatism of the plateau during laramide compression and cenozoic extension compared to surrounding regions the crustal and lithospheric thinning across the tectonic boundary occurs over a short distance 100 km suggesting it is a geologically young feature produced by a predominantly mechanical response to late cenozoic extension our new lithosphere model at 37 n latitude is consistent with the existence in early cenozoic time of a flat subducted slab at 100 km depth and a relict sevier laramide 50 60 km thick crustal welt and 60 100 pure shear extension values of 1 6 2 0 during the late cenozoic

age and spreading history of the cayman trough as determined from depth heat flow and magnetic anomalies the opening of the cayman trough records aspects of relative motion between the north american and caribbean plates essential to accurate reconstruction of caribbean evolution assessment of opening rates based upon basement subsidence analysis as well as magnetic anomaly interpretation shows that the trough may have opened at one third to one half previously proposed rates depths to basement show that the crust has subsided away from the present axis in two stages a younger stage characterized by substantial and asymmetric greater to the east subsidence preceded by an older stage of slight increases of depth with distance depth to age relations calculated from subsidence curves which accommodate lateral as well as vertical cooling of the accreting slab indicate that the trough has opened at an overall rate of less than 15 mm yr since 25 30 ma and at 20 30 mm yr prior to 30 ma marine magnetic anomalies show lineations perpendicular to the trough including a distinct central anomaly but the pattern is neither well defined nor symmetrical about the present axis however partial anomaly sequences can be identified on both sides of the axis and the distribution of these sequences indicates that spreading may have involved frequent short ridge jumps mostly eastward the overall rate of opening as indicated by this interpretation of the magnetics is about 15 and 30 mm yr since and prior to 26 ma both subsidence and magnetics indicate that the trough opened by at least 45 50 ma

the effect of ocean tides on the earth s rotation as predicted by the results of an ocean tide model the published ocean tidal angular momentum results of seiler 1991 are used to predict the effects of the most important semidiurnal m2 s2 n2 diurnal k1 o1 p1 and long period mf mf mm and ssa ocean tides on the earth s rotation the separate as well as combined effects of ocean tidal currents and sea level height changes on the length of day ut1 and polar motion are computed the predicted polar motion results reported here account for the presence of the free core nutation and are given in terms of the motion within the rotating body fixed terrestrial reference frame of the celestial ephemeris pole so that they can be compared directly to the results of observations outside the retrograde diurnal tidal band the summed effect of the semidiurnal and diurnal ocean tides studied here predict peak to peak polar motion amplitudes as large as 2 mas within the retrograde diurnal tidal band the resonant enhancement caused by the free core nutation leads to predicted polar motion or equivalently nutation amplitudes as large as 9 mas at the unobservable retrograde k1 tidal frequency

transpressional rupture of an unmapped fault during the 2010 haiti earthquake the enriquillo plantain garden strike slip fault accommodates the relative motion between the north american and caribbean plates and was thought to have ruptured during the 2010 haiti earthquake satellite data instead indicate that a blind thrust fault possibly related to the haitian fold thrust belt was responsible and caused some contractional deformation on 12 january 2010 a mw 7 0 earthquake struck the port au prince region of haiti the disaster killed more than 200 000 people and caused an estimated 8 billion in damages about 100 of the country s gross domestic product1 the earthquake was initially thought to have ruptured the enriquillo plantain garden fault of the southern peninsula of haiti which is one of two main strike slip faults inferred to accommodate the 2 cm yr 1 relative motion between the caribbean and north american plates2 3 here we use global positioning system and radar interferometry measurements of ground motion to show that the earthquake involved a combination of horizontal and contractional slip causing transpressional motion this result is consistent with the long term pattern of strain accumulation in hispaniola the unexpected contractional deformation caused by the earthquake and by the pattern of strain accumulation indicates present activity on faults other than the enriquillo plantain garden fault we show that the earthquake instead ruptured an unmapped north dipping fault called the leog ne fault the leog ne fault lies subparallel to but is different from the enriquillo plantain garden fault we suggest that the 2010 earthquake may have activated the southernmost front of the haitian fold and thrust belt4 as it abuts against the enriquillo plantain garden fault as the enriquillo plantain garden fault did not release any significant accumulated elastic strain it remains a significant seismic threat for haiti and for port au prince in particular

effects of water and melt on seismic velocities and their application to characterization of seismic reflectors the effects of a silicate melt and water on seismic velocities are compared at relatively small fluid fraction less than 20 vol on the basis of a theoretical model of composite materials to show that the two fluids are clearly characterized by the velocity ratio vp vs for a silicate melt vp vs increases with increasing fluid fraction when a significant reflection is expected vp vs becomes much larger than 2 for water vp vs decreases as the fluid fraction increases to 10 vol then it increases but it remains similar to a solid state value about 1 8 unless the amount of water exceeds 15 vol this will be a good measure to distinguish between two candidates for seismic reflectors partially molten rocks and rocks containing free water if a reflector can be treated as a thin low velocity layer the velocity ratio in it can be estimated from the frequency dependence of reflection coefficient

structure and evolution of the magnitogorsk forearc basin identifying upper crustal processes during arc continent collision in the southern urals the southern urals of russia contain a well preserved example of a paleozoic arc continent collision in which the intraoceanic magnitogorsk volcanic arc and its forearc basin sediments accreted to the east european craton during the devonian the magnitogorsk arc records the evolution from incipient intraoceanic subduction to a mature arc and by comparing its surface geological features with those in active arc continent collision settings it is possible to identify upper crustal processes that were active in the southern urals the arc edifice can be divided into western and eastern volcanic fronts that were active during different stages of arc evolution and for which two distinct phases of forearc basin development can be recognized the late lower to middle devonian aktau formation represents a remnant of the intraoceanic to collisional forearc basin to the irendyk volcanic front whereas the middle devonian to lower carboniferous ulutau koltubanian and zilair formations were deposited in a suture forearc basin to the east magnitogorsk volcanic front it was not until the late devonian that these two basins were joined structural mapping combined with reflection seismic profiling shows these basins to be affected by open nonlinear volcanic basement cored synsedimentary folds the karamalytash anticline appears to have the geometry of a growth fold that formed during deposition of sediments in the suture forearc basin the forearc region is affected by minor thrusting that involves the volcanic basement although it is not clear if these thrusts reactivate preexisting trench parallel faults synsedimentary deformation slumping and olistostrome development were common throughout the suture forearc basin history but were especially widespread during the late devonian when the full thickness of the continental crust is interpreted as having arrived at the subduction zone

crustal structure and fault geometry of the 2010 haiti earthquake from temporary seismometer deployments haiti has been the locus of a number of large and damaging historical earthquakes the recent 12 january 2010 mw 7 0 earthquake affected cities that were largely unprepared which resulted in tremendous losses it was initially assumed that the earthquake ruptured the enriquillo plantain garden fault epgf a major active structure in southern haiti known from geodetic measurements and its geomorphic expression to be capable of producing m 7 or larger earthquakes global positioning systems gps and interferometric synthetic aperture radar insar data however showed that the event ruptured a previously unmapped fault the leog ne fault a north dipping oblique transpressional fault located immediately north of the epgf following the earthquake several groups installed temporary seismic stations to record aftershocks including ocean bottom seismometers on either side of the epgf we use data from the complete set of stations deployed after the event on land and offshore to relocate all aftershocks from 10 february to 24 june 2010 determine a 1d regional crustal velocity model and calculate focal mechanisms the aftershock locations from the combined dataset clearly delineate the leog ne fault with a geometry close to that inferred from geodetic data its strike and dip closely agree with the global centroid moment tensor solution of the mainshock but with a steeper dip than inferred from previous finite fault inversions the aftershocks also delineate a structure with shallower southward dip offshore and to the west of the rupture zone which could indicate triggered seismicity on the offshore trois baies reverse fault we use first motion focal mechanisms to clarify the relationship of the fault geometry to the triggered aftershocks

morphology structure and tectonic evolution of the mona canyon northern mona passage from multibeam bathymetry side scan sonar and seismic reflection profiles 1 the submarine mona canyon is a rift between puerto rico and hispaniola of the greater antilles an integrated marine geophysical data set including multibeam bathymetry side scan sonar imagery single channel and multichannel seismic reflection profiles is used to evaluate the morphology structure and tectonic evolution of the mona canyon a structural restoration of the central mona canyon indicates that extension in the rift initiated in the middle oligocene approximately 30 ma a minimum total extension of 6 1 km and a minimum longitudinal strain of 11 4 across the central mona canyon are calculated the overall extension is proposed to have occurred over two phases phase i occurred from the middle oligocene to late miocene and was a slow 0 09 mm yr stage of at least 1 7 km of opening phase ii was most likely controlled by the impact of the subducted southeast portion of the bahamas platform beneath the northeastern caribbean plate margin phase ii was a more rapid 0 4 mm yr stage of extension of at least 4 4 km that occurred from the late pliocene to the recent as the se bahamas collision warped the middle and upper slope of the northern puerto rico margin along its advancing path and slowed the eastward movement of hispaniola relative to puerto rico the upper reaches of the mona canyon form the trailing edge of the puerto rico virgin islands block as it pulls away from a pinned hispaniola the mona reentrant marks the trailing edge of a northern hispaniola forearc sliver that forms due to increased coupling between the subducting north america plate and the overriding plate

morphotectonics of the central muertos thrust belt and muertos trough northeastern caribbean multibeam bathymetry data acquired during the 2005 spanish r v hesperides cruise and reprocessed multichannel seismic profiles provide the basis for the analysis of the morphology and deformation in the central muertos trough and muertos thrust belt the muertos trough is an elongated basin developed where the venezuelan basin crust is thrusted under the muertos fold and thrust belt structural variations along the muertos trough are suggested to be a consequence of the overburden of the asymmetrical thrust belt and by the variable nature of the venezuelan basin crust along the margin the insular slope can be divided into three east west trending slope provinces with high lateral variability which correspond to different accretion stages 1 the lower slope is composed of an active sequence of imbricate thrust slices and closed fold axes which form short and narrow accretionary ridges and elongated slope basins 2 the middle slope shows a less active imbricate structure resulting in lower superficial deformation and bigger slope basins 3 the upper slope comprises the talus region and extended terraces burying an island arc basement and an inactive imbricate structure the talus region is characterized by a dense drainage network that transports turbidite flows from the islands and their surrounding carbonate platform areas to the slope basins and sometimes to the trough in the survey area the accommodation of the ongoing east west differential motion between the hispaniola and the puerto rico virgin islands blocks takes place by means of diffuse deformation the asymmetrical development of the thrust belt is not related to the geological conditions in the foreland but rather may be caused by variations in the geometry and movement of the backstop the map view curves of the thrust belt and the symmetry of the recesses suggest a main north south convergence along the muertos margin the western end of the investigator fault zone comprises a broad band of active normal faults which result in high instability of the upper insular slope

diachronous uplift and recycling of sedimentary basins during cenozoic tectonic transpression northeastern caribbean plate margin abstract four marine sedimentary sequences of late cretaceous to pleistocene age crop out in the 320 km long 1 to 30 km wide peralta rio ocoa belt of hispaniola haiti and dominican republic the four sedimentary sequences are dominated by marine turbiditic rocks ranging up to 11 5 km in apparent thickness and exhibit mainly northwest to southeast belt parallel paleocurrents the three younger sequences are generally in fault or unconformable contact with the underlying sequence from northwest to southeast the four belts become progressively wider younger less metamorphosed less folded and faulted and lower in topographic elevation we interpret the three younger sequences as a syn tectonic stratigraphic record of diachronous northwest to southeast transpressional closure of a coniacian danian back arc basin represented by the oldest exposed sedimentary sequence at the northwest end of the belt and inferred at depth beneath the three younger sequences using the stratigraphic record we infer the following three stages in the closure of the back arc basin and the overlying younger basins stage one latest cretaceous to early late eocene closure a minimum of 11 km of paleocene turbidites and limestone in the padre las casas area and a minimum of 11 5 km of early eocene to early late eocene pelagic limestone mudstone sandstone and siltstone in the peralta and sierra el numero areas was deposited in an elongate basin derived from the first stage of latest cretaceous early late eocene closure and erosion of the coniacian danian back arc basin to the northwest paleocene eocene turbidites in both areas contain large amounts of reworked campanian paleocene microfauna and exhibit northwest to southeast belt parallel paleocurrents syn deformational features in eocene sedimentary rocks in the peralta and sierra el numero area indicate that convergent deformation accompanied sedimentation witschard and dolan 1990 stage two middle eocene to early miocene closure up to 8 6 km of middle eocene to early miocene turbidites debris flows and olistostromes of the rio ocoa group of the dominican republic were deposited in an elongate basin derived from middle eocene to early miocene closure uplift and erosion of the peralta group to the west and northwest turbidites contain reworked eocene faunas and lithologies similar to those in the underlying peralta group and exhibit northwest to southeast belt parallel paleocurrents erosion of late cretaceous island arc and overlying paleogene carbonate rocks of the cordillera central provided additional belt perpendicular sources of coarser grained conglomerate and olistostromes following deposition of the rio ocoa group both the peralta and the rio ocoa group were deformed in a southwest verging fold and thrust belt during the early miocene stage three middle miocene to recent closure up to 1 5 km of middle miocene to pleistocene sandstone conglomerate and reefal limestone of the ingenio caei group of the dominican republic were deposited in an elongate basin above a pronounced angular unconformity developed on the older deformed rocks of the rio ocoa group sediments of the ingenio caei group were derived from middle miocene to recent closure uplift and erosion of the rio ocoa and peralta groups to the northwest onshore exposures of the ingenio caei group can be correlated with submerged strata seen on seismic reflection profiles across the offshore san pedro basin recent submarine clastic sedimentation in the san pedro basin is dominated by northwest to southeast influx of clastic turbidites derived from active erosion of onshore exposures of the rio ocoa and ingenio caei groups middle miocene to recent sediments of the san pedro basin are being actively shortened by northward to northeastward directed underthrusting along the muertos trench underthrusting at the muertos trench is suggested to represent ongoing closure of the back arc basin thought to be deeply buried beneath the san pedro basin tectonic transpression along the closing back arc basin marks one edge of an actively deforming microplate within the north america caribbean strike slip plate boundary zone

crustal and uppermost mantle structure in the middle east assessing constraints provided by jointly modelling ps and sp receiver functions and rayleigh wave group velocity dispersion curves

precambrian crustal evolution seismic constraints from the canadian shield whether or not plate tectonic processes operated on a younger hotter earth remains ambiguous seismic data from new networks in the hudson bay region of the canadian shield where the precambrian geological record spans more than 2 billion years offer fresh scope to address this problem using receiver function analyses we show that the crust of the rae domain which exhibits ages of paleo to neoarchean 3 9 2 7 ga is likely felsic to intermediate in composition average vp vs 1 73 and seismically transparent with a sharp moho there is little evidence for modern style plate tectonics and based on the simplicity and spatial extent of the felsic crust models favouring vertical tectonic processes such as crustal delamination or plume activity appear better suited to the results data from the hearne domain which exhibits widespread 2 7 ga granite and greenstone geology show a more complex crust with higher vp vs ratios consistent with a greater mafic component the trans hudson orogen tho proposed to be a himalayan scale mountain belt during the paleoproterozoic is thought to have formed during the 1 8 ga collision of the superior and churchill plates results from the quebec baffin island segment of the tho appear to map out the first order shape of the underthrusting superior plate with elevated vp vs ratios likely representing the rifted margin of the superior craton consistently thicker crust is observed beneath central and southern baffin island 43 km coincident with widespread high grade metamorphic surface geology these features can be explained by crustal thickening due to stacking of accreted terranes during continent continent collision analogous to the present day tibetan plateau followed by erosion when reviewed in light of age and compositional constraints from the geological record our seismic observations point towards secular crustal evolution from non plate tectonic during the paleo to mesoarchean evolving towards fully developed modern style plate tectonics during the paleoproterozoic

the poisson ratio of the australian crust geological and geophysical implications the poisson ratio which depends on the vp vs ratio provides much tighter constraints on the crustal composition than either the compressional or the shear velocity alone the crustal poisson ratio can be determined from the joint analysis of the travel times of waves converted at the moho and of crustal multiples reflected at the top of the moho we have analyzed the records of the permanent stations installed on the australian continent complemented by the data of the skippy experiment the results reveal substantial variations in the poisson ratio in the different tectonic units for the proterozoic crust an increase of the poisson ratio with increasing crustal thickness is systematically observed while for the phanerozoic crust the poisson ratio tends to decrease for increasing crustal thicknesses these observations are in remarkable agreement with the results of the deep seismic soundings that were performed in the former soviet union the variations observed in the proterozoic provinces can perhaps be explained by underplating of mafic materials at the base of the crust fl 2000 elsevier science b v all rights reserved

bivergent thrust wedges surrounding oceanic island arcs insight from observations and sandbox models of the northeastern caribbean plate at several localities around the world thrust belts have developed on both sides of oceanic island arcs e g java timor panama vanuatu and the northeastern caribbean in these localities the overall vergence of the backarc thrust belt is opposite to that of the forearc thrust belt for example in the northeastern caribbean a north verging accretionary prism lies to the north of the eastern greater antilles arc hispaniola and puerto rico whereas a south verging thrust belt called the muertos thrust belt lies to the south researchers have attributed such bivergent geometry to several processes including reversal of subduction polarity subduction driven mantle fl ow stress transmission across the arc gravitational spreading of the arc and magmatic infl ation within the arc new observations of deformational features in the muertos thrust belt and of fault geometries produced in sandbox kinematic models along with examination of published studies of island arcs lead to the conclusion that the bivergence of thrusting in island arcs can develop without reversal of subduction polarity without subarc mantle fl ow and without magmatic infl ation we suggest that the eastern greater antilles arc and comparable arcs are simply crustalscale bivergent or doubly vergent thrust wedges formed during unidirectional subduction sandbox kinematic modeling suggests in addition that a broad retrowedge containing an imbricate fan of thrusts develops only where the arc behaves relatively rigidly in such cases the arc acts as a backstop that transmits compressive stress into the backarc region further modeling shows that when arcs behave as rigid blocks the strike slip component of oblique convergence is accommodated entirely within the prowedge and the arc the retrowedge hosts only dip slip faulting frontal thrusting the existence of large retrowedges and the distribution of faulting in an island arc may therefore be evidence that the arc is relatively rigid the rigidity of an island arc may arise from its mafi c composition and has implications for seismic hazard analysis

historical perspective on seismic hazard to hispaniola and the northeast caribbean region 1 we evaluate the long term seismic activity of the north american caribbean plate boundary from 500 years of historical earthquake damage reports the 2010 haiti earthquakes and other earthquakes were used to derive regional attenuation relationships between earthquake intensity magnitude and distance from the reported damage to the epicenter for hispaniola and for puerto rico and the virgin islands the attenuation relationship for hispaniola earthquakes and northern lesser antilles earthquakes is similar to that for california earthquakes indicating a relatively rapid attenuation of damage intensity with distance intensities in puerto rico and the virgin islands decrease less rapidly with distance we use the intensity magnitude relationships to systematically search for the location and intensity magnitude mi which best fit all the reported damage for historical earthquakes many events occurred in the 20th century along the plate boundary segment from central hispaniola to the nw tip of puerto rico but earlier events from this segment were not identified the remaining plate boundary to the east to guadeloupe is probably not associated with m 8 historical subduction zone earthquakes the may 2 1787 earthquake previously assigned an m 8 8 25 is probably only mi 6 9 and could be located north west or sw of puerto rico an mi 6 9 earthquake on july 11 1785 was probably located north or east of the virgin islands we located mi 8 historical earthquakes on april 5 1690 february 8 1843 and october 8 1974 in the northern lesser antilles within the arc we speculate that the december 2 1562 mi 7 7 and may 7 1842 mi 7 6 earthquakes ruptured the septentrional fault in northern hispaniola if so the recurrence interval on the central septentrional fault is 300 years and only 170 years has elapsed since the last event the recurrence interval of large earthquakes along the hispaniola subduction segment is likely longer than the historical record intra arc m 7 0 earthquakes may occur every 75 100 years in the 410 km long segment between the virgin islands and guadeloupe

caribbean island arc rifting and back arc basin development in the late cretaceous geochemical isotopic and geochronological evidence from central hispaniola this work froms part of the mcyt projects bte 2002 00326 and cgl2005 02162 bte and also received aid from the cartographic project of the dominican republic funded by the sysmin program of the european union careful reviews from j geldmacher a c kerr and an anonymous reviewer are much appreciated

tectonic evolution of the caribbean the development of the caribbean is discussed in terms of modern tectonic theory the nature of the site on which the caribbean formed is examined and the development of the rifted margins of the caribbean is described constraints on caribbean evolution from the relative motions of north and south america are briefly examined and the caribbean oceanic plateau is discussed the great island arc system of the caribbean is addressed in detail emphasizing the way the great arc of the caribbean was segmented the role of central america in caribbean history is briefly considered

relationship between environmental change and human activities in the period of the shijiahe culture tanjialing site jianghan plain china abstract a new 3 3 m long archaeological sedimentary profile from tanjialing hubei province was examined for pollen toc tn and 13 c org content the results contribute to a better understanding of the interaction between environment and human activities in the late neolithic jianghan plain discussed in the context of archaeological record and published available data during the early shijiahe culture 4 6 4 4 ka bp a mixed broadleaved evergreen and deciduous forest mainly consisting of evergreen quercus pinus cyclobalanopsis liquidambar and ulmus developed at tanjialing the high values of toc tn and c n suggests that the organic matter is mainly from allochthonous terrestrial plants combined with 13 c org analysis c 3 plants occupied the area and the climate was warm and humid with less human disturbance during this period the abrupt rise of toc tn and c n content and decrease of 13 c org combined with the local spread of typha and cyperaceae show that this area witnessed a short term water regime expansion event during the early period of the shijiahe culture in the mid period of the shijiahe culture 4 4 4 2 ka bp a significant rise in herbs especially poaceae and a remarkable decline in broadleaved trees imply an increasingly intensified human interference the continuous decline of toc tn and c n content indicates the reduction of allochthonous organic matter from terrestrial plants all proxies responses suggest decreasing effective moisture and temperature during this stage in the early and middle period of the shijiahe culture the warm and wet climate was favorable for agriculture which promoted the prosperity of the shijiahe culture and shijiahe ancient city played an important role in the defense against flood and invasion chronic drought around 4 2 ka bp not only hindered the development of local agriculture but also hindered the ditch system work leading to the fall of the shijiahe culture the defense function of the ancient city vanished due to dry climate and groundwater decline therefore the ancient city was abandoned the extreme events flood extreme drought etc related to the climate transformation played an important role in the legendary yu zheng sanmiao war