tidal modeling of an ancient tide dominated seaway part 1 model validation and application to global early cretaceous aptian tides abstract the utility of deep time global paleotidal modeling is evaluated with a series of modeling experiments focused on the early cretaceous aptian the results from a series of paleobathymetry sensitivity experiments indicate that despite paleogeographic and paleobathymetric uncertainty appropriate use of global paleotidal models complements and enhances stratigraphic and sedimentological methods before being applied to global paleotidal modeling the imperial college ocean model icom is validated for the computation of modern global tides the icom results only deviate slightly from a state of the art published model and were achieved with considerably less computational expense and without data assimilation the results from global paleotidal modeling of the early cretaceous aptian were assessed by comparison with the published geological record icom predicts high mesotidal to macrotidal ranges on the arabian platform around india especially to the north and west along the pacific coast between north and south america northeast of australia and around southeast asia the model predicts low microtidal ranges in the proto south atlantic ocean and weddell sea a further validation test assessed the ability of the model to predict the dominant tidal constituents diurnal or semidiurnal in the aptian lower greensand seaway of southeastern england and northern france during the aptian this region was connected to the boreal proto atlantic and neotethys oceans and now preserves superbly documented tidal deposits the model predicts low microtidal ranges in the proto central atlantic ocean and boreal ocean suggesting that they had little impact on tides in the lower greensand seaway higher tidal amplitudes especially of diurnal once daily tides are predicted in the northwestern neotethys ocean suggesting that this ocean was an important source of tidal energy to the lower greensand seaway sensitivity tests to paleogeographic and paleobathymetric uncertainty indicate that the model predictions are robust the prediction of predominantly diurnal tides is supported by published analyses of large dune scale deposits in the lower greensand of southeast england

effects of lateral viscosity variations on postglacial rebound implications for recent sea level trends global sea level changes have been occurring since the last pleistocene deglaciation recently the contribution of current postglacial rebound to local sea level variations has been removed by means of a radially stratified earth model in order to assess the amount of sea level rise due to recent climatic changes the authors have studied the effects of lateral variations in the viscosity structure on the postglacial uplift rates along the continental margins finite element calculations in cylindrical geometry show that the spread in the cumulative vertical displacement may be affected by 20 in the presence of lateral rheological contrasts but the vertical rates of deformation can attain differences of up to 50 for the different models horizontal deformation rates along continental margins are much more affected by the lateral variations in viscosity and can be used in the future as constraints on mantle rheology

on the origin of el chichon volcano and subduction of tehuantepec ridge a geodynamical perspective the origin of el chichon volcano is poorly understood and we attempt in this study to demonstrate that the tehuantepec ridge tr a major tectonic discontinuity on the cocos plate plays a key role in determining the location of the volcano by enhancing the slab dehydration budget beneath it using marine magnetic anomalies we show that the upper mantle beneath tr undergoes strong serpentinization carrying significant amounts of water into subduction another key aspect of the magnetic anomaly over southern mexico is a long wavelength 150 km high amplitude 500 nt magnetic anomaly located between the trench and the coast using a 2d joint magnetic gravity forward model constrained by the subduction p t structure slab geometry and seismicity we find a highly magnetic and low density source located at 40 80 km depth that we interpret as a partially serpentinized mantle wedge formed by fluids expelled from the subducting cocos plate using phase diagrams for sediments basalt and peridotite and the thermal structure of the subduction zone beneath el chichon we find that 40 of sediments and basalt dehydrate at depths corresponding with the location of the serpentinized mantle wedge whereas the serpentinized root beneath tr strongly dehydrates 90 at depths of 180 200 km comparable with the slab depths beneath el chichon 200 220 km we conclude that this strong deserpentinization pulse of mantle lithosphere beneath tr at great depths is responsible for the unusual location singularity and probably the geochemically distinct signature adakitic like of el chichon volcano

the mw 8 3 illapel earthquake chile preseismic and postseismic activity associated with hydrated slab structures the accumulated stress in subduction zones is discharged with earthquake and aseismic activity the latter is hosted in rheological complex regions characterized by high pore fluid pressure and is often accompanied by repeated earthquakes and earthquake swarms the spatiotemporal analysis of seismic activity can reveal the presence of aseismic transients associated with large earthquakes here we study 20 years of seismicity prior to and after the m w 8 3 earthquake that occurred in a d 2015 in central chile we identified several earthquake swarms before the main shock and repeating aftershocks at the border of the main slip area spatial clustering of the seismic activity shares similar orientation with the main fracture zones observed on the outer rise of the subducting nazca plate our findings suggest that the fracture zones enclosing the rupture are playing a major role in accommodating the pre and post main shock stress evolution we further recognize how fracture regions have acted as barriers to the propagation of large earthquakes in the region

inversion of complex body waves we have developed a method that inverts seismic body waves to determine the mechanism and rupture pattern of earthquakes the rupture pattern is represented as a sequence of subevents distributed on the fault plane this method is an extension of our earlier method in which the subevent mechanisms were fixed in the new method the subevent mechanisms are determined from the data and are allowed to vary during the sequence when subevent mechanisms are allowed to vary however the inversion often becomes unstable because of the complex trade offs between the mechanism the timing and the location of the subevents many different subevent sequences can explain the same data equally well and it is important to determine the range of allowable solutions some constraints must be imposed on the solution to stabilize the inversion we have developed a procedure to explore the range of allowable solutions and appropriate constraints in this procedure a network of grid points is constructed on the i plane where and i are respectively the onset time and the distance from the epicenter of a subevent the best fit subevent is determined at all grid points then the correlation is computed between the synthetic waveform for each subevent and the observed waveform the correlation as a function of and i and the best fit mechanisms computed at each i grid point depict the character of allowable solutions and facilitate a decision on the appropriate constraints to be imposed on the solution the method is illustrated using the data for the 1976 guatemala earthquake

barotropic tides in the global oceans from a nonlinear tidal model assimilating altimetric tides 1 model description and results in this first part of a two part paper we present results from a high resolution data assimilative fully nonlinear barotropic tidal model of the global oceans that excludes the arctic the model assimilates in waters deeper than 1000 m altimetric tides derived from the analysis of 2 years of topex altimetric data it also assimilates tide gage data from coastal tide gages the model domain includes that covered by the altimeter and extends to the antarctic in the first part we present tidal results for the primary semidiurnal m2 s2 n2 and k2 and diurnal k1 o1 p1 and q1 constituents the second part deals with applications kantha et al this issue the model results are compared with observational data from pelagic gages these comparisons show that overall in the open ocean in deep waters away from the margins of the primary basins the model performance is comparable to other tidal models derived using topex data except for m2 and s2 however one advantage of this model compared with those based solely on the analysis of altimetric data is that the altimetry derived tides are subjected to dynamical constraints by the model this results in reduction of subtidal variability often folded into tidal signals by topex data analysis it is also shown that in shallow waters along the margins especially in east asian marginal seas the model differs substantially from these other models in addition to sea surface heights we also present dynamically consistent barotropic currents in the form of tidal ellipses for m2 and k1 constituents since the goal of this research is a global tidal model uniformly valid in both deep and shallow waters we finally present tidal elevations and currents on two well known shallow water areas the northwest european shelf and the northeast american shelf and a semienclosed western pacific marginal sea the bering sea the model results are compared with independent observations and where possible with results from other numerical models the results highlight the importance of bottom topography on the northwest european shelf where accurate bottom topography was included in the model the results are much better than on the northeast american shelf where the digital bathymetric data base 5 dbdb5 topographic database has significant errors results from the bering sea where the topography is more accurate than the dbdb5 compare well with known tides in the region

core mantle boundary shape constraints inferred from the pressure torque acting between the core and the mantle summary in the last few years models of the flow at the top of the earth s core and of the related pressure field have been calculated from the secular variation of the geomagnetic field and core mantle topographies have been computed by seismologists a pressure torque results from the action of the pressure field on the core topography which can theoretically be computed from models of both the pressure field and the core mantle interface small scale features of the flow and of the topography are shown to be capable of contributing strongly to the pressure torque it is thus impossible to calculate the exact value of the torque from the knowledge of only the long wavelength components of the models but the interaction between the large scale components generates by itself torques two orders of magnitude larger than the torques inferred from the irregularities of the length of the day it is nevertheless possible to reconcile the topographic coupling mechanism with the length of the day observations keeping the amplitude of the core topography proposed by seismologists if an orthogonality relation between the geometry of the fluid upwellings and downwellings at the top of the core and the topography is satisfied it is shown how to compute such a topography for a given flow and close to an original topography provided by seismic tomography some consequences of the so inferred link between the fluid flow at the top of the core and the core mantle boundary topography are discussed

marsis remote sounding of localized density structures in the dayside martian ionosphere a study of controlling parameters enhanced topside electron densities in the dayside martian ionosphere have been repetitively observed in areas of near radial crustal magnetic fields for periods of tens of days indicating their long term spatial and temporal stability despite changing solar wind conditions we perform a statistical study of these density structures using the ionospheric mode of the mars advanced radar for subsurface and ionosphere sounding marsis onboard mars express we estimate the apparent extents of these structures relative to the altitude of the surrounding ionosphere the apex of the density structures often lies higher than the surrounding ionosphere median vertical extent of 18 km which indicates upwellings these structures are much wider than they are high with latitudinal scales of several degrees the radar reflector regions are observed above both moderate and strong magnetic anomalies and their precise locations and latitudinal extents match quite well with the locations and latitudinal extents of magnetic structures of given magnetic polarity oblique to vertical fields which happen to be regions where the field lines are open part of the time the majority of the density structures occur in regions where ionospheric plasma is dominant indicating closed field regions shielded from shocked solar wind plasma

subduction megathrust heterogeneity characterized from 3d seismic data megathrust roughness and structural complexity are thought to be controls on earthquake slip at subduction zones because they result in heterogeneity in shear strength and resolved stress however because active megathrust faults are difficult to observe the causes and scales of complexity are largely unknown here we measured the in situ properties of the megathrust of the middle america subduction zone in a three dimensional seismic reflection volume to determine how fault properties vary we quantify spatial variability in the megathrust roughness overburden and rock physical properties heterogeneity in the megathrust roughness exists at length scales of a few kilometres because the megathrust is dissected by active lower plate normal faults which offset the megathrust and renewed fault roughness spatial variations in the rock physical properties at the plate interface are characterized by correlation length scales of hundreds of metres frontal prism taper historical seismicity and the variation in earthquake stress drop values local to the megathrust are all affected by the heterogeneity at these length scales both geometric and rheological complexities may therefore control the mechanical behaviour of the subduction plate interface which includes earthquake rupture characteristics geometric and rheological complexities may control the mechanical behaviour of megathrusts according to an analysis of the heterogeneity in roughness and rock properties of the middle america megathrust from 3d seismic reflection data

coseismic and postseismic stress changes in a subducting plate possible stress interactions between large interplate thrust and intraplate normal faulting earthquakes 1 a large intraplate normal faulting earthquake mw 7 5 occurred in 1999 in the subducting cocos plate below the downdip edge of the ruptured thrust fault of the 1978 oaxaca mexico earthquake mw 7 8 this situation is similar to the previous case of the 1997 normal faulting event mw 7 1 that occurred beneath the rupture area of the 1985 michoacan mexico earthquake mw 8 1 we investigate the possibility of any stress interactions between the preceding 1978 thrust and the following 1999 normal faulting earthquakes for this purpose we estimate the temporal change of the stress state in the subducting cocos plate by calculating the slip distribution during the 1978 earthquake through teleseismic waveform inversion the dynamic rupture process and the resultant coseismic stress change together with the postseismic stress variations due to plate convergence and the viscoelastic relaxation process to do this we calculate the coseismic and postseismic changes of all stress components in a three dimensional space incorporating the subducting slab the overlying crust and uppermost mantle and the asthenosphere for the coseismic stress change we solve elastodynamic equations incorporating the kinematic fault slip as an observational constraint under appropriate boundary conditions to estimate postseismic stress accumulations due to plate convergence a virtual backward slip is imposed to lock the main thrust zone the effects of viscoelastic stress relaxations of the coseismic change and the back slip are also included the maximum coseismic increase in the shear stress and the coulomb failure stress below the downdip edge of the 1978 thrust fault is estimated to be in the range between 0 5 and 1 5 mpa and the 1999 normal faulting earthquake was found to take place in this zone of stress increase the postseismic variations during the 21 years after the 1978 event modify the magnitude and patterns of the coseismic stress change to some extent but are not large enough to overcome the coseismic change these results suggest that the coseismic stress increase due to the 1978 thrust earthquake may have enhanced the chance of occurrence of the 1999 normal faulting event in the subducting plate if this is the case one of the possible mechanisms could be static fatigue of rock materials around preexisting weak planes involved in the subducting plate and it is speculated that that one of these planes might have been reactivated and fractured because of stress corrosion cracking under the applied stress there for 21 years

the oaxaca mexico earthquake of 1931 lithospheric normal faulting in the subducted cocos plate a study of the great earthquake in oaxaca mexico on 15 january 1931 shows that it was a normal fault earthquake striking east west the lack of evidence of surface faulting near the source region1 and the focal depth of 40 km inferred from body wave modelling suggest that the earthquake occurred within the subducted slab the large size of the earthquake ms 8 0 strongly suggests that the rupture broke through the entire lithosphere of the subducted cocos plate other large normal fault earthquakes in the japanese2 aleutian3 peruvian4 and sumba5 arcs show lithospheric faulting seawards of the trench or very close to it the 1931 event however occurred farther down dip in the slab 150 km landward of the trench below the bottom of what appears to be the seismogenic plate interface we speculate here that large although infrequent normal fault earthquakes such as the 1931 oaxaca earthquake may have a role in decoupling at depth the subducted slab from the upper part of the slab and perhaps from the overriding mexican continental plate the epicentral location of the 1858 michoacan earthquake6 ms 7 5 suggests that it may represent another example of lithospheric normal faulting in the middle american arc such earthquakes for which the periods of recurrence are unknown constitute an extremely high seismic risk to population centres of mexico

large intermediate depth earthquakes and the subduction process this study provides an overview of intermediate depth earthquake phenomena placing emphasis on the larger tectonically significant events and exploring the relation of intermediate depth earthquakes to shallower seismicity especially we examine whether intermediate depth events reflect the state of interplate coupling at subduction zones and whether this activity exhibits temporal changes associated with the occurrence of large underthrusting earthquakes historic record of large intraplate earthquakes m b 7 0 in this century shows that the new hebrides and tonga subduction zones have the largest number of large intraplate events regions associated with bends in the subducted lithosphere also have many large events e g altiplano and new ireland we compiled a catalog of focal mechanisms for events that occurred between 1960 and 1984 with m 6 and depth between 40 and 200 km the final catalog includes 335 events with 47 new focal mechanisms and is probably complete for earthquakes with m b 6 5 for events with m 6 5 nearly 48 of the events had no aftershocks and only 15 of the events had more than five aftershocks within one week of the mainshock events with more than ten aftershocks are located in regions associated with bends in the subducted slab focal mechanism solutions for intermediate depth earthquakes with m 6 8 can be grouped into four categories 1 normal fault events 44 and 2 reverse fault events 33 both with a strike nearly parallel to the trench axis 3 normal or reverse fault events with a strike significantly oblique to the trench axis 10 and 4 tear faulting events 13 the focal mechanisms of type 1 events occur mainly along strongly or moderately coupled subduction zones where a down dip extensional stress prevails in a gently dipping plate in contrast along decoupled subduction zones great normal fault earthquakes occur at shallow depths e g the 1977 sumbawa earthquake in indonesia type 2 events with strike subparallel to the subduction zone and most of them with a near vertical tension axis occur mainly in regions that have partially coupled or uncoupled subduction zones and the observed continuous seismicity is deeper than 300 km the increased dip of the downgoing slab associated with weakly coupled subduction zones and the weight of the slab may be responsible for the near vertical tensional stress at intermediate depth and consequently the change in focal mechanism from type 1 to type 2 events events of type 3 occur where the trench axis bends sharply causing horizontal parallel to the trench strike extensional or compressional intraplate stress type 4 are hinge faulting events for strongly coupled zones we observed temporal changes of intermediate depth earthquake activity associated with the occurrence of a large underthrusting event after the occurrence of a large underthrusting event the stress axis orientation of intermediate depth earthquakes changes from down dip tensional to down dip compressional e g 1960 chile 1974 peru 1982 tonga and 1952 kamchatka earthquakes or the number of large intermediate events decreases for a few years e g 1964 alaska and 1985 valparaiso earthquakes we conclude that even though the stress changes induced by slab pull and slab distortion control the general pattern of intermediate depth seismicity spatial and temporal variations of the intraplate stress associated with interplate coupling are important in controlling the global occurrence of large intermediate depth events

coherent fluctuations of extratropical geopotential height and tropical convection in intraseasonal time scales abstract coherent fluctuations between extratropical circulation and tropical conviction in the intraseasonal time scale are studied possible relationships between 500 mb height field and outgoing longwave radiation olr are examined using correlation complex eof and composite techniques results show that in the 20 70 day bands data there is a systematic evolution of extratropical wavetrains from eurasia across the pacific to north america and the north atlantic in the time scale of 5 to 10 days over the tropics the dominant mode of intraseasonal variation in convection is an east west dipole like feature which propagates from the western indian ocean eastward to the dateline with a quasi period of 40 50 days the space time evolution of these extratropical wavetrains is found to he coherent with the tropical dipolar convection and with the strongest convection over indonesia central pacific in approximate quadrature with the peak phase of the eurasia and pacific north america wavetrains while the

mountain torques and atmospheric oscillations theoretical work and general circulation model gcm experiments suggest that the midlatitude jet stream s interaction with large scale topography can drive intrasea sonal oscillations in large scale atmospheric circulation pat terns in support of this theory we present new observa tional evidence that mountain induced torques play a key role in 15 30 day oscillations of the northern hemisphere circulation s dominant patterns the affected patterns in clude the arctic oscillation ao and the pacific north american pna pattern positive torques both accelerate and anticipate the midlatitude westerly winds at these peri odicities moreover torque anomalies anticipate the onsets of weather regimes over the pacific as well as the break ups of hemispheric scale regimes

oblique reflections in the mars express marsis data set stable density structures in the martian ionosphere the mars advanced radar for subsurface and ionospheric sounding marsis onboard the european space agency s mars express mex spacecraft routinely detects evidence of localized plasma density structures in the martian dayside ionosphere such structures likely taking the form of spatially extended elevations in the plasma density at a given altitude give rise to oblique reflections in the active ionospheric sounder data these structures are likely related to the highly varied martian crustal magnetic field in this study we use the polar orbit of mex to investigate the repeatability of the ionospheric structures producing these anomalous reflections examining data taken in sequences of multiple orbits which pass over the same regions of the martian surface under similar solar illuminations within intervals lasting tens of days presenting three such examples or case studies we show for the first time that these oblique reflections are often incredibly stable indicating that the underlying ionospheric structures are reliably reformed in the same locations and with qualitatively similar parameters the visibility or lack thereof of a given oblique reflection on a single orbit can generally be attributed to variations in the crustal field within the ionosphere along the spacecraft trajectory we show that within these examples oblique reflections are generally detected whenever the spacecraft passes over regions of intense near radial crustal magnetic fields i e with a cusp like configuration the apparent stability of these structures is an important feature that must be accounted for in models of their origin

segmentation and supercycles a catalog of earthquake rupture patterns from the sumatran sunda megathrust and other well studied faults worldwide abstract after more than 100 years of earthquake research earthquake forecasting which relies on knowledge of past fault rupture patterns has become the foundation for societal defense against seismic natural disasters a concept that has come into focus more recently is that rupture segmentation and cyclicity can be complex and that a characteristic earthquake model is too simple to adequately describe much of fault behavior nevertheless recognizable patterns in earthquake recurrence emerge from long high resolution spatially distributed chronologies researchers now seek to discover the maximum minimum and typical rupture areas the distribution variability and spatial applicability of recurrence intervals and patterns of earthquake clustering in space and time the term supercycle has been used to describe repeating longer periods of elastic strain accumulation and release that involve multiple fault ruptures however this term has become very broadly applied lumping together several distinct phenomena that likely have disparate underlying causes we divide earthquake cycle behavior into four major classes that have different implications for seismic hazard and fault mechanics 1 quasi periodic similar ruptures 2 clustered similar ruptures 3 clustered complementary ruptures rupture cascades and 4 superimposed cycles segmentation is likewise an ambiguous term we identify master segments and asperities as defined by barriers to fault rupture these barriers may be persistent rarely or never traversed frequent occasionally traversed or ephemeral changing location from cycle to cycle we compile a catalog of the historical and paleoseismic evidence that currently exists for each of these types of behavior on major well studied faults worldwide due to the unique level of paleoseismic and paleogeodetic detail provided by the coral microatoll technique the sumatran sunda megathrust provides one of the most complete records over multiple earthquake rupture cycles long historical records of earthquakes along the south american and japanese subduction zones are also vital contributors to our catalog along with additional data compiled from subduction zones in cascadia alaska and middle america as well as the north anatolian and dead sea strike slip faults in the middle east we find that persistent and frequent barriers rupture cascades superimposed cycles and quasi periodic similar ruptures are common features of most major faults clustered similar ruptures do not appear to be common but broad overlap zones between neighboring segments do occur barrier regions accommodate slip through reduced interseismic coupling slow slip events and or smaller more localized ruptures and are frequently associated with structural features such as subducting seafloor relief or fault trace discontinuities this catalog of observations provides a basis for exploring and modeling root causes of rupture segmentation and cycle behavior we expect that researchers will recognize similar behavior styles on other major faults around the world

length of day changes and mountain torque during el nifio abstract values of mountain pressure torque are calculated for the rocky and andes mountains and for the tibetan plateau in order to evaluate their conuibufion to the observed anomalous length of day lod and atmospheric angular momentum aam change during the period from late january to mid february 1983 a period of rapid increase in aam and lod is found to coincide with unusually high values of mountain torque on the rocky mountains associated with a midcontinent high pressure event and a sequence of pacific frontal cyclone lows hitting california a subsequent decrease in aam is not correlated with mountain pressure torquesover the three regions tested thus implicating other regions or other transfer mechanisms

ionospheric storms on mars impact of the corotating interaction region measurements made by the aspera 3 and marsis experiments on mars express have shown for the first time that space weather effects related to the impact of a dense and high pressure solar wind corotating interaction region on mars cause strong perturbations in the martian induced magnetosphere and ionosphere the magnetic barrier formed by pile up of the draped interplanetary magnetic field ceases to be a shield for the incoming solar wind large blobs of solar wind plasma penetrate to the magnetosphere and sweep out dense plasma from the ionosphere the topside martian ionosphere becomes very fragmented consisting of intermittent cold low energy and energized plasmas the scavenging effect caused by the intrusions of solar wind plasma clouds enhances significantly by a factor of 10 the losses of volatile material from mars

dynamic rupture and stress change in a normal faulting earthquake in the subducting cocos plate a large nearly vertical normal faulting earthquake mw 7 1 took place in 1997 in the cocos plate just beneath the ruptured fault zone of the great 1985 michoacan thrust event mw 8 1 dynamic rupture and resultant stress change during the 1997 earthquake have been investigated on the basis of near source strong motion records together with a 3 d dynamic model dynamically consistent waveform inversion reveals a highly heterogeneous distribution of stress drop including patch like asperities and negative stress drop zones zones of high stress drop are mainly confined to the deeper southeastern section of the vertical fault where the maximum dynamic stress drop reaches 280 bars 28 mpa the dynamically generated source time function varies with location on the fault and yields a short slip duration which is caused by a short scalelength of stress drop heterogeneities the synthetic seismograms calculated from the dynamic model are generally consistent with the strong motion velocity records in the frequency range lower than 0 5 hz the pattern of stress drop distribution appears in some sense to be consistent with that of coseismic changes in shear stress resulting from the 1985 thrust event this consistency suggests that the stress transfer from the 1985 event to the subducting plate could be one of the possible mechanisms that increased the chance of the occurrence of the 1997 earthquake

the 8 september 2017 tsunami triggered by the m w 8 2 intraplate earthquake chiapas mexico the 8 september 2017 mw 8 2 earthquake offshore chiapas mexico is the largest earthquake in recorded history in chiapas since 1902 it caused damage in the states of oaxaca chiapas and tabasco including more than 100 fatalities over 1 5 million people were affected and 41 000 homes were damaged in the state of chiapas alone this earthquake an intraplate event on a normal fault on the oceanic subducting plate generated a tsunami recorded at several tide gauge stations in mexico and on the pacific ocean here we report the physical effects of the tsunami on the chiapas coast and analyze the societal implications of this tsunami on the basis of our post tsunami field survey the associated tsunami waves were recorded first at huatulco tide gauge station at 5 04 gmt 12 min after the earthquake we covered ground observations along 41 km of the coast of chiapas encompassing the sites with the highest projected wave heights based on our preliminary tsunami model maximum tsunami amplitudes between 94 5 and 93 0 w runup and inundation distances were measured along eight sites the tsunami occurred at low tide the maximum runup was 3 m at boca del cielo and maximum inundation distance was 190 m in puerto arista corresponding to the coast in front of the epicenter and in the central sector of the gulf of tehuantepec tsunami scour and erosion was evident along the chiapas coast tsunami deposits mainly sand reached up to 32 cm thickness thinning landward up to 172 m distance

earth s variable rotation recent improvements in geodetic data and practical meteorology have advanced research on fluctuations in the earth9s rotation theinterpretation of these fluctuations is inextricably linked with studies of the dynamics of the earth moon system and dynamical processes in the liquid metallic core of the earth where the geomagnetic field originates other parts of the earth9s interior and the hydrosphere and atmosphere fluctuations in the length of the day occurring on decadal time scales have implications for the topography of the core mantle boundary and the electrical magnetic and other properties of the core and lower mantle investigations of more rapid fluctuations bear on meteorological studies of interannual seasonal and intraseasonal variations in the general circulation of the atmosphere and the response of the oceans to such variations

oceanic effects on polar motion determined from an ocean model and satellite altimetry 1993 2001 1 mass redistribution and motion in the oceans are major driving forces of geodetic variations including polar motion length of day geocenter and gravity field changes we examine oceanic contribution to polar motion using estimates from a data assimilating ocean general circulation model and satellite radar altimeter observations the data include model estimates of variations in oceanic mass obp and meridional and zonal velocities sea level anomalies from topex poseidon t p satellite altimeter measurements and steric sea surface height changes deduced from the model are also used to estimate obp effects estimated oceanic contributions from both the model and t p show considerably better agreement with polar motion observations compared with results from previous studies the improvement is particularly significant at intraseasonal timescales both obp and ocean current variations provide important contributions to polar motion at intraseasonal timescales the oceans appear to be a dominant contributor to residual polar motion not accounted for by the atmosphere the oceans also play an important role in seasonal excitation combined obp and ocean current contributions explain much of the residual semiannual variability

overview of recent coastal tectonic deformation in the mexican subduction zone holocene and pleistocene tectonic deformation of the coast in the mexico subudction margin is recorded by geomorphic and stratigraphic markers we document the spatial and temporal variability of active deformation on the coastal mexican subduction margin pleistocene uplift rates are estimated using wave cut platforms at ca 0 7 0 9 m ka on the jalisco block coast rivera north america tectonic plate boundary we examine reported measurements from marine notches and shoreline angle elevations in conjunction with their radiocarbon ages that indicate surface uplift rates increasing during the holocene up to ca 3 0 5 m ka in contrast steady rates of uplift ca 0 5 1 0 m ka in the pleistocene and holocene characterize the michoacan coastal sector south of el gordo graben and north of the orozco fracture zone ofz incorporated within the cocos north america plate boundary significantly higher rates of surface uplift ca 7 m ka across the ofz subduction may reflect the roughness of subducting plate absence of preserved marine terraces on the coastal sector across el gordo graben likely reflects slow uplift or coastal subsidence stratigraphic markers and their radiocarbon ages show late holocene ca last 6 ka bp coastal subsidence on the guerrero gap sector in agreement with a landscape barren of marine terraces and with archeological evidence of coastal subsidence temporal and spatial variability in recent deformation rates on the mexican pacific coast may be due to differences in tectonic regimes and to localized processes related to subduction such as crustal faults subduction erosion and underplating of subducted materials under the southern mexico continental margin

stacking gravity tide observations in central europe for the retrieval of the complex eigenfrequency of the nearly diurnal free wobble summary we have used tidal gravity measurements from six stations in central europe to investigate the resonance in the diurnal tidal band caused by inertial coupling between the mantle and outer core of the earth by the use of stacking it was possible to determine the eigenfrequency and quality factor of this eigenmode commonly called the nearly diurnal free wobble we assessed the effect of systematic errors from the ocean correction to the tidal measurements employing a monte carlo method the observed eigenfrequency is 1 1 434 f 7 cycles per sidereal day and is significantly higher than predicted by theories the observed quality factor is 2 8 0 5 x 10

stress distribution and subduction of aseismic ridges in the middle america subduction zone the regional distribution of stresses associated with the subduction of the cocos plate is inferred from a synthesis of 190 earthquake focal mechanisms body and surface wave analyses of large earthquakes and seismicity distributions broad patterns of consistent behavior are found across the region from the rivera plate boundary in the northwest to the guatemala el salvador border in the southeast and are used as a framework to evaluate evidence for variations in local stresses due to the subduction of two aseismic ridges the tehuantepec ridge and the orozco fracture zone information which bears on the seismic potential at locations of aseismic ridge subduction is particularly important in that no large ms 7 5 earthquakes have occurred historically we identify three major zones with consistent patterns in focal mechanisms and hypocentral distributions of seismicity the first closest to the trench and reflecting the mechanical interaction of the converging plates is a zone of shallow thrust earthquakes extending 100 150 km inland from the trench the second is a zone of normal faulting beginning at about 200 km inland from the trench h 60 km which extends continuously along the entire length of the descending plate throughout the region the third distinct zone exhibits a relatively low level of activity and separates the zones of thrust and normal faulting at about 150 200 km inland from the trench this zone extends from the rivera plate boundary in the northwest to the guatamala region in the southeast at this point the quiet region pinches out and the thrust and normal faulting zones abut and overlap superimposed on this overall pattern we find locally only minor changes in areas of aseismic ridge subduction aside from the prominent seismic slip gaps furthermore on october 25 1981 the playa azul earthquake ms 7 3 occurred in the midregion of the orozco fracture zone body and surface wave analyses of this event show a simple source rupture and shallow thrust fault mechanism as are found elsewhere in the region the seismic moment is mo 1 3 1020 n m the calculated stress drop is 4 5 mpa not extraordinarily high as might be expected in these pervasive seismic gaps an event in the tehuantepec ridge region on january 24 1983 ms 6 7 was a large normal faulting event but further interpretation is ambiguous due to the proximity of other normal faulting we conclude that while aseismic slip may be occurring in the areas of ridge subduction the possibility of large thrust earthquakes cannot be ruled out due to the overall similarities with adjacent regions

large scale lithospheric detachment of the downgoing cocos plate the 8 september 2017 earthquake mw 8 2 abstract on 8 september 2017 a great earthquake m w 8 2 took place in the mexican subduction zone in the tehuantepec gap where no large subduction earthquakes have taken place since 1902 however the 8 september earthquake did not occur on the contact between the cocos and north american plates the centroidal hypocentral depths reported by different agencies including the national seismological service range from 45 to 47 4 km placing it immediately beneath the down dip limit of the interplate locked zone the source mechanism reflects down dip tensional faulting the inversion of the fault process shows a rupture that initiated at the bottom of the lithosphere and propagated upward breaking through the entire subducted lithosphere an unusually long complex and copious aftershock sequence followed the main event the relocated aftershocks in the first 20 days following the main event delineate a 160 km long fault sub parallel to the oceanic trench immediately beneath the interplate contact the aftershocks also concentrate in secondary intraslab faults 50 km down dip from the mainshock rupture revealing that pervasive tensional stresses are present within the subducted plate this deformation pattern suggests a large scale tensional regime in the slab apparently induced by its own gravitational weight that pulls it away from the strongly coupled interplate contact other large intraplate earthquakes in the vicinity in 1931 m w 7 8 and 1999 m w 7 5 also reflect this detachment of the downgoing cocos plate that sinks into the mantle under its own gravitational weight the slab detachment suggests that the up dip segment of the plate interface near the isthmus of tehuantepec is locked and possibly primed for a megathrust earthquake such as the m w 8 6 that took place in 1787 on an adjacent segment of the mexican subduction zone

hydrological and oceanic effects on polar motion from grace and models 1 terrestrial water storage tws and ocean bottom pressure obp are major contributors to the observed polar motion excitations second only to atmospheric mass movement however quantitative assessment of the hydrological and oceanic effects on polar motion remains unclear because of the lack of global observations in this paper hydrological and oceanic mass excitations to polar motion are investigated using monthly tws and obp derived from the gravity recovery and climate experiment grace for january 2003 until december 2008 the results from this analysis are compared with hydrological model excitations from the european center for medium range weather forecasts ecmwf and oceanic model excitations obtained from the jet propulsion laboratory jpl using estimating the circulation and climate of the ocean ecco results show that the grace derived obp and tws better explain the geodetic residual polar motion excitations for the px component at the annual period while the grace obp and ecmwf hydrological angular momentum agree better with the geodetic residuals for the annual py excitation grace ocean and hydrology excitations better explain the geodetic residuals for the semiannual py excitation however the jpl ecco and ecmwf models better explain the intraseasonal geodetic residual of polar motion excitation in the px and py components the grace data demonstrate much higher intraseasonal variability than either the models or the geodetic observations

a study of ground motion excitation based on the earthquake of september 8 2017 evidence that normal faults influence the stress parameter we performed a study of ground motion modeling based on multiple linear regression and random vibration theory using the earthquake sequence of september 8 2017 mw 8 2 our results show that there is high attenuation in the region of oaxaca chiapas and central mexico however the peak amplitude excitations of normal fault earthquakes are higher than those of thrust fault earthquakes the earthquake sequence involved a large number of events but not all the seismic events were aftershocks because many earthquakes had different rupture styles the thrust events follow a simple scaling relation with a constant stress parameter but the normal fault events are difficult to represent with a constant self similar model our best result consists of a q 0 240 pm 032 with a frequency dependent factor of 0 63 pm 0 05 the excitation term is well determined with a stress parameter of 80 bars for the thrust faults but for the normal faults the stress parameter is at least 180 bars with a non self similar model our results show that it is necessary to include new ground motion prediction equations in seismic hazard analysis for meganormal faults which have not previously been considered in subduction zones

maven observations of energy time dispersed electron signatures in martian crustal magnetic fields energy time dispersed electron signatures are observed by the mars atmosphere and volatile evolution maven mission in the vicinity of strong martian crustal magnetic fields analysis of pitch angle distributions indicates that these dispersed electrons are typically trapped on closed field lines formed above strong crustal magnetic sources most of the dispersed electron signatures are characterized by peak energies decreasing with time rather than increasing peak energies these properties can be explained by impulsive and local injection of hot electrons into closed field lines and subsequent dispersion by magnetic drift of the trapped electrons in addition the dispersed flux enhancements are often bursty and sometimes exhibit clear periodicity suggesting that the injection and trapping processes are intrinsically time dependent and dynamic these maven observations demonstrate that common physical processes can operate in both global intrinsic magnetospheres and local crustal magnetic fields

double seismic zones and stresses of intermediate depth earthquakes data from japanese local seismograph networks suggest that the stresses in double seismic zones are in plate compression for the upper zone and in plate tension for the lower zone the stresses do not necessarily appear to be down dip it may therefore be possible to identify other double seismic zones on the basis of data which indicate that events with differing orientations of in plate stresses occur in a given segment of slab a global survey of published focal mechanisms for intermediate depth earthquakes suggests that the stress in the slab is controlled at least in part by the age of the slab and the rate of convergence old and slow slabs are under in plate tensile stresses and the amount of in plate compression in the slab increases with increasing convergence rate or decreasing slab age young and fast slabs are an exception to this trend all such slabs are down dip tensile since these slabs all subduct under continents they may be bent by continental loading double seismic zones are not a feature common to all subduction zones and are only observed in slabs which are not dominated by tensile or compressive stresses unbending of the lithosphere and upper mantle phase changes are unlikely to be the causes of the major features of double zones although they may contribute to producing some of their characteristics sagging or thermal effects possibly aided by asthenospheric relative motion may produce the local deviatoric stresses that cause double zones

analysis of the trade off between hypocentral depth and source time function focal depth determination for shallow 60 km intermediate size ms 6 5 to 7 5 earthquakes continues to be problematic for these events the depth phases i e pp and sp are not distinctly separated in time and thus synthetic modeling of wave shapes becomes necessary unfortunately the uniqueness of the solution is not easily determined because of the trade off between various focal parameters we have investigated the trade off between depth and source function both theoretically and experimentally the changes in the green s function caused by an incorrect assumed depth can almost always be compensated by changes in the source function producing the same observed seismogram thus there is considerable trade off between depth and the source function perturbing the depth from the true depth leads to a more complicated source function the simplest source function then pinpoints the true depth we have used two different measures of simplicity the varimax norm v max and the half absolute moment time t 1 2 both measures successfully characterize the complications that appear in the source functions for incorrect assumed depths the true depth of an event can be interpreted from the resultant v max versus depth and t 1 2 versus depth curves thus we have a technique that determines the depth range of faulting in a systematic quantitative fashion our observations from the synthetic study have been applied to an outer rise event off the coast of central chile 16 october 1981 ms 7 2 to an event in southern mexico 24 october 1980 ms 7 0 and to the borrego mountain event in southern california 9 april 1968 ms 6 4 resulting in faulting depth ranges of 0 to 20 5 km 60 to 70 5 km and 10 to 14 5 km respectively

dynamic response of the martian ionosphere to an interplanetary shock mars express and maven observations multipoint observations from the mars advanced radar for subsurface and ionosphere sounding marsis instrument on board mars express and the mars atmosphere and volatile evolution maven mission reveal a dynamic response of the martian ionosphere to abrupt variations in the upstream solar wind plasma on 2 february 2017 maven located upstream from the martian bow shock encountered a cir related interplanetary shock with a sudden enhancement in the dynamic pressure marsis operating in the upper ionosphere at 478 km altitudes and 78 solar zenith angles observed a sharp increase in the local magnetic field magnitude 1 min after the shock passage at maven the time lag is roughly consistent with the expected propagation time of a pressure pulse from the bow shock to the upper ionosphere at the fast magnetosonic speed subsequently remote soundings recorded disturbed signatures of the topside ionosphere below mars express

zonal contributions to global momentum variations on intraseasonal through interannual time scales the authors separate the variability in a 13 year time series of daily values of the relative angular momentum of the atmosphere m into three frequency bands intraseasonal seasonal and interannual two methods are used to achieve this separation and the amount of variance attributable to intraseasonal fluctuations in particular is sensitive to the choice made seasonal time scales clearly dominate the global momentum series included in this frequency band is a notable dip in the series early in almost every calendar year to localize the sources of the frequency band dependent fluctuations in m they decompose the data into series of angular momentum values within each of 46 equal area zonal belts over the globe and form covariances between these belt series and m seasonal variations in m represent the residual of opposing contributions from the subtropical jets of the northern and southern hemispheres both intraseasonal and interannual variations in m result mostly from behavior in the tropics

a possible stress interaction between large thrust and normal faulting earthquakes in the mexican subduction zone abstract a large nearly vertical normal faulting earthquake mw 7 1 took place in 1997 in the subducting cocos plate just beneath the ruptured fault zone of the 1985 michoacan mexico earthquake mw 8 1 we investigate the possibility of stress interaction between the two large events through a 3d analysis of coseismic stress change that was due to the first event taking into consideration the postseismic change and the dynamic rupture process of the second event in the middle portion of the subducting plate at depths below 30 km the calculated coseismic increase in the vertical shear stress and in the coulomb failure stress beneath the high stress drop zones of the 1985 earthquake is in the order of 0 4 to 0 8 mpa it was also found that the 1997 earthquake took place in the zone of maximum coseismic stress increase possible postseismic stress changes due to the subduction process or to the loading of the overriding continental lithosphere and from aseismic slip would enhance the coseismic stress change and hence the possibility of occurrence of a normal faulting earthquake in the subducting plate the dynamic rupture pattern of the 1997 event seems to be consistent with the inferred stress interactions introduction a large nearly vertical normal faulting earthquake mw 7 1 occurred on 11 january 1997 beneath the mi choacan segment of the mexican subduction zone santoyo

a simulation of the 1982 1983 el nino a general circulation model of the equatorial pacific ocean was used to simulate the 1982 1983 el nino event the wind data set used to force the model is that of florida state university fsu the results are presented here and compared with those from other simulations the model results show that the simulation is successful in reproducing the major features of the 1982 1983 el nino such as the disappearance of the equatorial undercurrent the pattern and magnitude of the sea surface temperature anomaly and the variations of the thermocline however there is a delay of about 2 3 months in these events in the model compared with those observed this is attributed to the wind stress forcing during 1982 in the eastern equatorial pacific which is more intense in the fsu wind data set than in the national meteorological center data set along the south american coast the model results show a persistent cooling before a slight warming in april 1983 during the event which is not understood

geometry and state of stress of the wadati benioff zone in the gulf of tehuantepec mexico 1 data recorded in the gulf of tehuantepec and published moment tensor solutions were used to infer the geometry of the wadati benioff zone w b zone and the stress distribution of the subducted cocos plate from northwest to southeast the subducted slab gently increases its dip bends up at depths of the order of 100 km and about 240 km inland from the trench then unbends and increases its dip toward the southeast below chiapas contour lines of equal depth at 50 and 100 km show a significant contortion of the w b zone west of the isthmus of tehuantepec and coincide with significant changes in the topographic features of the crust we calculated a vp vs ratio of 1 75 for the whole area and a moho depth in the gulf of tehuantepec of 28 5 3 5 km near the trench along the coupling zone t axes of interplate and intraplate earthquakes are oblique to the interface and parallel to the dip direction of the subducted plate respectively at depths greater than 50 km the t axes are roughly horizontal best fit stresses using the gephart and forsyth 1984 code resulted in the following variation of the minimum stresses t axes from northwest to southeast as plunge azimuth 3 40 37 to 3 28 72 then to 3 11 54 and finally to 3 27 35 we also analyzed recordings from the 30 september 1999 oaxaca earthquake mw 7 5 and its aftershocks we inferred an approximate fault area of 80 by 30 km inside the subducted cocos plate

mars ionospheric interaction with comet c 2013 a1 siding spring s coma at their closest approach as seen by mars express on 19 october 2014 mars experienced a close encounter with comet c 2013 a1 siding spring using data from the mars advanced radar for subsurface and ionosphere sounding marsis on board mars express mex we assess the interaction of the martian ionosphere with the comet s coma and possibly magnetic tail during the orbit of their closest approach the topside ionospheric electron density profile is evaluated from the altitude of the peak density of the ionosphere up to the mars express altitude we find complex and rapid variability in the ionospheric profile along the mex orbit not seen even after the impact of a large coronal mass ejection before closest approach large electron density reductions predominate which could be caused either by comet water damping or comet magnetic field interactions after closest approach a substantial electron density rise predominates moreover several extra topside layers are visible along the whole orbit at different altitudes which could be related to different processes as we discuss

persistent anomalies blocking and variations in atmospheric predictability abstract we consider regimes of low frequency variability in large scale atmospheric dynamics the model used for the study of these regimes is the fully nonlinear equivalent barotropic vorticity equation on the sphere with simplified forcing dissipation and topography twenty five modes are retained in a spherical harmonics expansion of the streamfunction solutions are studied as a function of the nondimensional intensity of the forcing and dissipation multiple stationary solutions are obtained as a result of nonlinear interaction between waves mean flow and orography the number of modes retained in the analysis permits these multiple equilibria to appear for realistic values of the forcing the equilibria exhibit blocked and zonal flow patterns bearing a marked resemblance to synoptically defined zonal and blocked northern hemisphere midlatitude flows wave wave interactions influence strongly the stability properties of the equilibria and the time evolution of nonequilibrium solutions time depe

friction and mountain torque estimates from global atmospheric data abstract seasonal zonal surface torques between the atmosphere and the earth are estimated and compared using data from a number of independent sources the mountain torque is computed both from surface pressure data and from isobaric height data the friction torque is estimated from the oceanic stress data of hellerman and rosenstein results for the total torque are inferred from atmospheric angular momentum data finally the globally integrated total torque is compared with astronomical observations of the earth s rotation rate these comparisons help us to assess the quality of the different results zonal torques are also computed using results from a gfdl general circulation model of the atmosphere a comparison with the corresponding results inferred from real data is presented and interpreted in terms of model accuracy

radar soundings of the ionosphere of mars we report the first radar soundings of the ionosphere of mars with the marsis mars advanced radar for subsurface and ionosphere sounding instrument on board the orbiting mars express spacecraft several types of ionospheric echoes are observed ranging from vertical echoes caused by specular reflection from the horizontally stratified ionosphere to a wide variety of oblique and diffuse echoes the oblique echoes are believed to arise mainly from ionospheric structures associated with the complex crustal magnetic fields of mars echoes at the electron plasma frequency and the cyclotron period also provide measurements of the local electron density and magnetic field strength

possible feedback path for low frequency atmospheric oscillations abstract equatorial low frequency oscillations with periods of 1 2 months are being intensively studied by many investigators a strong equatorial dipole pattern is observed in which atmospheric variables such as temperate wind and pressure are out of phase between the indian ocean indonesia region and the western pacific while it is generally thought that the oscillations make a complete circuit around the earth from their excitation region in the equatorial indian ocean western pacific the signal is more difficult to observe over the south america atlantic africa sector using analyses of four year of satellite derived microwave radiance data evidence is presented here for the possibility of a feedback route in the southern hemisphere the observed propagation path extends from the central equatorial pacific across lower south america and heads equatorward after passing south of africa the response route finally reenters the equatorial indian ocean with the correct phase to enhance the primary e

marsis observations of the martian nightside ionosphere dependence on solar wind conditions despite the absence of solar radiation on the martian nightside a weak irregular and variable ionosphere is produced there the nightside ionosphere is thought to be maintained by two main sources dayside nightside plasma transport and electron precipitation observations by mars express mex and mars global surveyor mgs have shown that these plasma sources are either hindered or favored by the presence of strong crustal magnetic fields and that these effects are modulated by external parameters such as the solar wind dynamic pressure and the orientation of the interplanetary magnetic field imf these external drivers are expected to influence the supply of plasma to the nightside and thus the formation of the irregular nightside ionosphere we here present a statistical study of the martian ionosphere at solar zenith angle greater than 107 from november 2005 to may 2006 using remote measurements of ionospheric echoes with the mars advanced radar for subsurface and ionospheric sounding marsis radar sounder onboard mex and using mgs based proxies for the solar wind dynamic pressure and the imf clock angle we find that the peak densities increase with the dynamic pressure and also that cases of very high peak density are almost always associated with westward imf orientation we find that using mex aspera 3 electron data these cases often seem to be linked to accelerated electrons plasma transport is known to be important in the near nightside on the other hand electron precipitation prevails when the dynamic pressure is high enough to compress the ionosphere and in vertical field regions where the imf orientation matters

causes of rapid motions of the earth s pole analysis of new highly accurate geodetic data reveals rapid motions of the earth s pole with peak to peak variations of 0 002 to 0 020 seconds of arc fluctuating on timescales between two weeks and several months comparison with meteorological excitation estimates shows that these motions are at least partially driven by surface air pressure changes as modified by the response of sea level to atmospheric loading such geodetic measurements thus potentially provide a novel means of observing the dynamics of the atmosphere and oceans at very low spatial wavenumbers

barotropic wave propagation and instability and atmospheric teleconnection patterns abstract a global barotropic model linearized about the 300 mb climatological mean january flow is perturbed by applying a series of localized forcings distributed throughout the tropics and subtropics structures which resemble the observed pacific north american and east atlantic teleconnection patterns noted by wallace and gutzler 1981 tend to recur in the responses similar patterns are found to result from the dispersion of isolated initial perturbations placed at a variety of locations in the tropics and midlatitudes it is shown that these structures are related to the most rapidly growing mode associated with barotropic instability of the zonally varying climatological basic state in the absence of damping this mode has an e folding time of about a week and a period close to 50 days in localized regions the instantaneous growth rates can be competitive with those of baroclinic instability these episodes of rapid local barotropic growth are interspersed with intervals in which the local

slab pull and slab push earthquakes in the mexican chilean and peruvian subduction zones we studied intermediate depth earthquakes in the chile peru and mexican subduction zones paying special attention to slab push down dip compression and slab pull down dip extension mechanisms although slab push events are relatively rare in comparison with slab pull earthquakes quite a few have occurred recently in peru a couple slab push events occurred in 1991 and one slab pull together with several slab push events occurred in 1970 near chimbote in mexico several slab push and slab pull events occurred near zihuatanejo below the fault zone of the 1985 michoacan event in central chile a large m 7 1 slab push event occurred in october 1997 that followed a series of four shallow mw 6 thrust earthquakes on the plate interface we used teleseismic body waveform inversion of a number of mw 5 9 slab push and slab pull earthquakes in order to obtain accurate mechanisms depths and source time functions we used a master event method in order to get relative locations we discussed the occurrence of the relatively rare slab push events in the three subduction zones were they due to the geometry of the subduction that produces flexure inside the downgoing slab or were they produced by stress transfer during the earthquake cycle stress transfer can not explain the occurence of several compressional and extensional intraplate intermediate depth earthquakes in central chile central mexico and central peru it seemed that the heterogeneity of the stress field produced by complex slab geometry has an important influence on intraplate intermediate depth earthquakes 2002 elsevier science b v all rights reserved

seismic gaps and recurrence periods of large earthquakes along the mexican subduction zone a reexamination abstract seismic gaps and recurrence periods of large shallow interplate earthquakes along the mexican subduction zone are reexamined after combining information from a catalog of nineteenth century9s earthquakes some relocated epicenters of the early part of this century source parameters of recent large earthquakes and redetermined magnitudes of great shallow earthquakes of this century tehuantepec and michoacan gaps have not experienced a large shock in this century and perhaps none in the past century they are either aseismic or have anomalously large repeat times guerrero jalisco and ometepec regions presently appear to have a high seismic potential observed average repeat times of large earthquakes m s 7 4 in six regions east central and west oaxaca san marcos petatlan and colima are between 32 to 56 yr data of this century indicate that the strain is released mostly in large events m s 7 4 a simple dislocation model with parameters obtained from the studies of recent earthquakes explains the observed recurrence periods quite well the b value for this zone is not meaningful an observation which is of significance for seismic risk estimation most of seismic moment or equivalently seismic energy release since 1800 appears to occur for 15 yr followed by relative quiescence in the next 15 yr

the latitude height structure of 40 50 day variations in atmospheric angular momentum abstract quasi periodic variations in the relative angular momentum of the atmosphere on time scales of around 40 50 days have been observed by langley et al 1981 a description of the two dimensional latitude height structure of the winds responsible for these changes is constructed here from five years of nmc twice daily global analyses using cross spectral and amplitude phase eigenvector techniques we find these variations are associated with wavelike motions in the tropical upper troposphere that propagate and downward in phase within the tropics a coherently connected midlatitude northern hemisphere component is also present whose phase is essentially independent of height we believe the tropical component to be the zonally averaged part of the motions described by madden and julian 1971 1972 the northern hemisphere midlatitude component may be a direct response to the tropical motions or both motions may be the common response to an as yet unidentified tropical forcing

rupture process of the 2011 tohoku oki earthquake and absolute elastic strain release 1 on 11 march 2011 the tohoku oki earthquake in eastern japan and the devastating tsunami that followed it caused severe damage and numerous deaths to clarify the rupture process of the earthquake we inverted teleseismic p wave data applying a novel formulation that takes into account the uncertainty of green s function which has been a major error source in waveform inversion the estimated seismic moment is 5 7 1022 nm mw 9 1 associated with a fault rupture 440 km long and 180 km wide along the plate interface the source process is characterized by asymmetric bilateral rupture propagation but we also found continuous slips up dip from the hypocenter which led to a large maximum slip 50 m long slip duration 90 s and a large stress drop 20 mpa the long slip duration large stress drop extensional normal faulting aftershocks in a previously compressional stress regime and low angle normal slips at approximately the depth of the plate interface suggest that the earthquake released roughly all of the accumulated elastic strain on the plate interface owing to exceptional weakening of the fault the stress accumulated on the plate interface was about 20 mpa near the trench and 0 10 mpa in the down dip source region

a striking example of the atmosphere s leading traveling pattern abstract conventional and complex empirical orthogonal function eof techniques show that for at least four months during the fall and winter of 1979 80 a large amplitude large scale traveling flow anomaly existed in the troposphere and stratosphere this feature evolved in a cyclic manner exhibiting an average period of about 23 days its phase propagation was toward the west while its amplitude was concentrated in a broad envelope centered over canada the phenomenon was equivalent barotropic in the troposphere and increased in amplitude with altitude it represented about 25 of the variance of geopotential heights in the troposphere and stratosphere for the months of november through march the meridional and zonal structure of the zonal wavenumber one component of the traveling anomaly is similar to that of the theoretical 16 day wave however it is distinct from that theoretical mode in that its period is longer and in the troposphere zonal wave two makes a large contribution to its structur

first measurements of the ionospheric plasma escape from mars before the phobos mission the magnetosphere of mars was relatively unexplored basically all data on the charged particle environment of mars had come from the soviet mars missions mars 2 3 4 and 5 here we report the results of an ion composition experiment on board the soviet phobos 2 spacecraft which allowed us to determine the loss of plasma from the ionosphere of mars because mars has a very small intrinsic magnetic field the ion outflow had been expected to be similar to that of venus surprisingly there were many similarities between the ionospheric outflow from mars and the earth the ion loss from mars results from both ion pick up that results from mass loading of the solar wind in the martian boundary layer and ionospheric o beams of energies up to several kev possibly from upward acceleration processes similar to those observed above the earth s auroral oval a preliminary estimate of the ionospheric outflow from mars indicates that the planet is losing oxygen at a rate of 3 x 1025 ions s 1 this corresponds to an evacuation of its present total atmospheric oxygen content contained in co2 and o2 in less than 100 million years

link between plate fabric hydration and subduction zone seismicity in alaska subduction carries water into the earth where it can influence seismicity analysis of the structure of the alaskan subduction zone suggests fluid delivery is influenced by faults in the oceanic plate that formed at the mid ocean ridge

tidal despinning of the mantle inner core superrotation and outer core effective viscosity dissipation of tidal energy in the oceans causes a net transfer of angular momentum from the spin of the earth to the relative orbital motions of the moon and sun these torques couple directly to the mantle and cause it to despin viscous coupling across the outer core is an effective means of communicating this change to the inner core the ekman time scale for dissipation of transient fluid motions associated with unsteady torques is much shorter than the time scale for adjustment of inner core and mantle rotational velocities in the steady couette flow regime the relative amplitude and phase of rotational variations in this system with respect to the applied torques are given in terms of core viscosity and torque variation frequency any short period variations in mantle torques will leave the inner core largely unchanged and the influence of long period and secular torques applied to the mantle is efficiently transmitted to the inner core the system response to a steady tidal torque applied to the mantle leaves the inner core with a small excess rotational velocity relative to the mantle proportional to the product of outer core viscosity and the applied mantle torque recent estimates of an inner core super rotation of 1 degree year imply an effective outer core viscosity of 10 3 pa s glacial cycle variations in tidal torques somewhat complicate this picture but do not yield significantly different viscosity estimates however they do imply that the differential rotation velocity varies by roughly a factor of 2 over a 100 kyr glacial cycle the tidal shear strain may also contribute to development of anisotropy in the inner core

seismic source characteristics of the intraslab 2017 chiapas mexico earthquake mw8 2 abstract inversion of the parameters characterising the seismic source of the instraslab 2017 chiapas mexico earthquake mw 8 2 shows a simple rupture process with a unidirectional propagation and directivity towards the north west and a duration of the rupture process around 75 s the initial point source values of strike dip and rake are 316 80 and 91 respectively the focal mechanism indicates a normal fault type within the oceanic cocos plate with an almost vertical fault plane for a focal depth of 59 km the seismic data was obtained from 51 seismic stations of the global seismic network iris for the epicentral distances between 30 and 90 in the finite fault inversion 75 seismic signals between p and sh waves were used the epicenter is on the southeast margin of the large slip zone which extends 75 km to the northwest this large slip zone is located to the south of the city of arriaga the scalar seismic moment was estimated at 2 55 10 21 n m equivalent to a moment magnitude of mw 8 2 the maximum dislocation or slip is 14 5 m as a coseismic effect a local tsunami was generated recorded by several tidal gauges and offshore buoys the deformation pattern shows a coastal uplift and subsidence

slab1 0 a three dimensional model of global subduction zone geometries 1 we describe and present a new model of global subduction zone geometries called slab1 0 an extension of previous efforts to constrain the two dimensional non planar geometry of subduction zones around the focus of large earthquakes slab1 0 describes the detailed non planar three dimensional geometry of approximately 85 of subduction zones worldwide while the model focuses on the detailed form of each slab from their trenches through the seismogenic zone where it combines data sets from active source and passive seismology it also continues to the limits of their seismic extent in the upper mid mantle providing a uniform approach to the definition of the entire seismically active slab geometry examples are shown for two well constrained global locations models for many other regions are available and can be freely downloaded in several formats from our new slab1 0 website http on doi gov d9arbs we describe improvements in our two dimensional geometry constraint inversion including the use of average active source seismic data profiles in the shallow trench regions where data are otherwise lacking derived from the interpolation between other active source seismic data along strike in the same subduction zone we include several analyses of the uncertainty and robustness of our three dimensional interpolation methods in addition we use the filtered subduction related earthquake data sets compiled to build slab1 0 in a reassessment of previous analyses of the deep limit of the thrust interface seismogenic zone for all subduction zones included in our global model thus far concluding that the width of these seismogenic zones is on average 30 larger than previous studies have suggested

enhanced atmospheric oxygen outflow on earth and mars driven by a corotating interaction region 1 solar wind controls nonthermal escape of planetary atmospheric volatiles regardless of the strength of planetary magnetic fields for both earth with a strong dipole and mars with weak remnant fields the oxygen ion o outflow has been separately found to be enhanced during corotating interaction region cir passage here we compared the enhancements of o outflow on earth and mars driven by a cir in january 2008 when sun earth and mars were approximately aligned the cir propagation was recorded by stereo ace cluster and mars express mex during the cir passage cluster observed enhanced flux of upwelling oxygen ions above the earth s polar region while mex detected an increased escape flux of oxygen ions in the martian magnetosphere we found that 1 under a solar wind dynamic pressure increase of 2 3 npa the rate of increase in martian o outflow flux was 1 order higher than those on earth and 2 as a response to the same part of the cir body the rate of increase in martian o outflow flux was on the same order as for earth the comparison results imply that the dipole effectively prevents coupling of solar wind kinetic energy to planetary ions and the distance to the sun is also crucially important for planetary volatile loss in our inner solar system

the 1977 sumba earthquake series evidence for slab pull force acting at a subduction zone the great 1977 sumba earthquake occurred at the eastern sunda trench just west of the collision of australian continental lithosphere with the island arc the length of the aftershock zone of this normal faulting earthquake is about 200 km aftershocks are concentrated 65 115 km east of the main shock epicenter with very few aftershocks in a 50 km long segment that spans the main shock epicenter relocated hypocenters and focal mechanism data are consistent with normal faulting throughout the upper 28 km of the oceanic lithosphere there is no evidence for thrust faulting of the deeper aftershocks these data imply that the neutral bending surface must be at least 35 40 km deep a second aftershock zone about 180 km northwest of the main shock became active immediately following the main shock but events were concentrated during days 50 52 this zone is a 70 km long lineation that trends toward the main shock epicenter and reflects right lateral strike slip faulting within the subducted oceanic plate seismicity exists to a depth of about 650 km in the very old plate beneath the sunda banda arc and that plate s negative buoyancy causes very large slab pull forces great interface thrust earthquakes are absent at the sumba region and slab pull forces are inferred to have partially decoupled the subducted plate from the overriding plate this decoupling permits slab pull stresses to be guided updip to the region of the sumba main shock such shallow acting slab pull provides a bending moment at the trench and explains the deformation and timing observed for the entire sumba earthquake series in this model slab pull forces stretch the subducted plate until the increasing stresses at the shallow subduction zone lead to a subduction zone earthquake postseismically the released oceanic plate undergoes a pulse of downdip strain returning the plate to a less extended state the moment of this downdip plate motion could exceed the seismic moment of the main shock

shape of the subducted rivera and cocos plates in southern mexico seismic and tectonic implications the geometry of the subducted rivera and cocos plates beneath the north american plate in southern mexico was determined based on the accurately located hypocenters of local and teleseismic earthquakes the hypocenters of the teleseisms were relocated and the focal depths of 21 events were constrained using a body wave inversion scheme the suduction in southern mexico may be approximated as a subhorizontal slab bounded at the edges by the steep subduction geometry of the cocos plate beneath the caribbean plate to the east and of the rivera plate beneath north america to the west the dip of the interplate contact geometry is constant to a depth of 30 km and lateral changes in the dip of the subducted plate are only observed once it is decoupled from the overriding plate on the basis of the seismicity the focal mechanisms and the geometry of the downgoing slab southern mexico may be segmented into four regions 1 the jalisco region to the west where the rivera plate subducts at a steep angle that resembles the geometry of the cocos plate beneath the caribbean plate in central america 2 the michoacan region where the dip angle of the cocos plate decreases gradually toward the southeast 3 the guerrero oaxaca region bounded approximately by the onshore projection of the orozco and o gorman fracture zones where the subducted slab is almost subhorizontal and underplates the upper continental plate for about 250 km and 4 the southern oaxaca and chiapas region in southeastern mexico where the dip of the subduction gradually increases to a steeper subduction in central america these drastic changes in dip do not appear to take place on tear faults suggesting that smooth contortions accommodate these changes in geometry the inferred 80 and 100 km depth contours of the subducted slab lie beneath the southern front of the trans mexican volcanic belt suggesting it is directly related to the subduction thus the observed nonparallelism with the middle american trench is apparently due to the changing geometry of the rivera and cocos plates beneath the north american plate in southern mexico and not to zones of weakness in the crust of the north american plate as some authors have suggested

intraseasonal oscillations in the global atmosphere i northern hemisphere and tropics abstract we have examined systematically oscillatory modes in the northern hemisphere and in the tropics the 700 mb heights were used to analyze extratropical oscillations and the outgoing longwave radiation to study tropical oscillations in convection all datasets were band pass filtered to focus on the intraseasonal is band of 10 120 days leading spatial patterns of variability were obtained by applying eof analysis to these is data the leading principal components pcs were subjected to singular spectrum analysis ssa ssa is a statistical technique related to eof analysis but in the time domain rather than the spatial domain it helps identify nonlinear oscillations in short and noisy time series in the northern hemisphere there are two important modes of oscillation with periods near 48 and 23 days respectively the 48 day mode is the most important of the two it has both traveling and standing components and is dominated by a zonal wavenumber two the 23 day mode has the spatial stru

background seismicity rate at subduction zones linked to slab bending related hydration tectonic properties strongly control variations in seismicity among subduction zones in particular fluid distribution in subduction zones influences earthquake occurrence and it varies among subduction zones due to variations in fluid sources such as hydrated oceanic plates however the relationship between variations in fluid distribution and variations in seismicity among subduction zones is unclear here we divide earth s subduction zones into 111 regions and estimate background seismicity rates using the epidemic type aftershock sequence model we demonstrate that background seismicity rate correlates to the amount of bending of the incoming oceanic plate which in turn is related to the hydration of oceanic plates via slab bending related faults regions with large bending may have high seismicity rates because a strongly hydrated oceanic plate causes high pore fluid pressure and reduces the strength of the plate interface we suggest that variations in fluid distribution can also cause variations in seismicity in subduction zones

long term variability of mars exosphere based on precise orbital analysis of mars global surveyor and mars odyssey a long term perspective on mars exosphere variability at 405 km is provided by merging together density data derived from precise orbit determination of the mars global surveyor and mars odyssey mo satellites extending from 2001 to 2010 these data are heavily weighted toward afternoon local times at high latitudes in the southern hemisphere clear long term solar and annual variations are well captured by empirical formulas residuals from the empirical fit show evidence for relative depletions in exosphere density around mars closest approach to earth which would be consistent with a scavenging mechanism that is dependent on solar wind dynamic pressure superimposed on this variation with mars sun distance are positive density residuals during mars year my 25 my27 and my29 that are apparently due to elevated dust levels in mars middle atmosphere however during my24 my26 and my28 there are dust level increases without any corresponding increase in exosphere density we suspect that this inconsistency is related to a variable ability to sense the response to dust related effects imposed by the high latitude limitations of our measurements combined with interference between the mechanisms that translate middle atmosphere heating to an exosphere response evidence also supports the hypothesis that winter helium bulge effects contributed to the inferred interannual density variability during the 2007 2009 solar minimum period when the o he transition height likely resided near the 405 km orbit of mo

source process of the chiapas mexico intermediate depth earthquake mw 7 2 of 21 october 1995 abstract on 21 october 1995 we recorded with a local array an earthquake that occurred at a depth of 165 km in the subduction zone of chiapas the harvard focal mechanism solution indicates a normal fault responding to the down dip tension of the subducted oceanic crust this is the first intermediate depth earthquake well recorded with accelerographs and seismometers in southeastern mexico peak ground accelerations pga range from 21 to 436 cm sec 2 at hypocentral distances of 174 to 256 km respectively the recorded pgas are larger than those of the copala guerrero earthquake of 14 september 1995 which was a shallow 16 km thrust fault with a similar magnitude m w 7 4 the large pga generated by the chiapas earthquake are probably due to an enhancement of the signals produced by the up ward intraslab propagation of energy and are similar to those observed from other intermediate depth earthquakes in the subduction zone of japan molas and yamazaki 1995 the duration of the strongest shaking increases from about 10 sec in the southeast at the town of san vicente close to the tacana volcano to nearly 20 sec in the northwest in the city of tuxtla gutierrez located near the epicenter teleseismic p wave inversion using the harvard focal mechanism solution indicates that the seismic moment was released in three events with a total duration of about 20 sec the results of the inversion indicate that the rupture propagated from the northwest to the southeast along a 30 km distance from spectral analysis we calculate a total seismic moment release of 5 2 0 5 10 19 n m equivalent to an m w 7 1 magnitude event using three sources with an average depth of 150 km we were able to reach a reasonable match of the first 40 sec of the displacement records recorded at the broadband seismic stations of huatulco huig and pinotepa nacional pnig for the station located in tuxtla gutierrez tuxd we used two sources since only the first 5 sec were modeled the amplitude spectrum at teleseismic distances follows a typical brune9s 1970 2 model we obtained a corner frequency of 0 045 hz from the spectra which is equivalent to a source radius of 15 km and a stress drop of 65 bars assuming a circular fault

geometry and state of stress of the downgoing cocos plate in the isthmus of tehuantepec mexico the seismicity in the isthmus of tehuantepec mexico is anomalously active compared with other parts of the middle american subduction zone the results of a microearthquake study conducted in this region show that the slab changes dip from an almost subhorizontal geometry west of longitude 96 w to a dip of about 45 to 50 to the east of this longitude the change in dip occurs gradually in a broad flexure of the subducting slab that takes place over 150 km this geometry of the slab is reminiscent of that in southern peru the change in dip however takes place more gently in tehuantepec in addition to the change in the dip of the subducted cocos plate a rapid increase is observed in the maximum depth extent of the subducted slab in the region of subhorizontal subduction focal depths are consistently shallower than about 80 km whereas earthquakes as deep as 200 km are found where the subducted slab dips at a steeper angle both the change in the dip of the slab and of the maximum depth of intermediate depth earthquakes appear to correlate with the presence of the tehuantepec fracture zone which separates two distinct provinces of the oceanic cocos plate the age and the crustal thickness of the cocos plate increase to the southeast of the tehuantepec fracture zone relative to its northwestern counterpart in tehuantepec the dip and maximum depth of the subducted slab appears to be correlated with the age of the oceanic plate as has been observed in other subduction zones of the world

length of day variations caused by el nino southern oscillation and quasi biennial oscillation two prominent interannual atmospheric fluctuations the el nino southern oscillation in the troposphere ocean system and the quasi biennial oscillation in the equatorial stratosphere account for most of the observed interannual length of day lod variation from 1964 through 1987 with a relative contribution of about 2 to 1 thus the atmosphere lod connection extends from seasonal and shorter periods to interannual periods up to about 10 years

tidal variations of earth rotation we have rederived the periodic variations of the earth s rotation due to the tidal deformation of the earth by the sun and moon and included all terms with amplitudes 0 002 milliseconds 1 mm this series applies to the mantle plus crust and oceans which rotate together for characteristic tidal periods the parameter which scales the rotational series is k c where k is that fraction of the love number which causes the tidal variation in the moment of inertia of the coupled mantle and oceans while c is the dimensionless polar moment of inertia of the coupled units if the whole earth minus oceans were coupled rotationally then k 0 30 and c 0 33 ocean tides increase k by 0 04 decoupling of the fluid core from the mantle decreases k by 0 06 while c cmantle 0 29 since neither pressure viscous nor hydromagnetic coupling locks the fluid to the mantle for periods less than 5 to 25 years from the analysis of lunar laser ranging data we find that k c at monthly and fortnightly frequencies equals 0 99 0 15 and 0 99 0 20 as compared with a theoretical value of 0 94 0 04 in addition we have estimated theoretically the effects of ocean tides on earth rotation nutation and polar motion using models based on the laplace tidal equations

martian magnetic storms the response of mars to the major space weather events called interplanetary coronal mass ejections icmes is of interest for both general planetary solar wind interaction studies and related speculations on their evolutionary consequences especially with respect to atmosphere escape various particle and field signatures of icmes have been observed on phobos 2 mars global surveyor mgs mars express mex and now mars atmosphere and volatile evolution maven of these maven s combined instrumentation and orbit geometry is particularly well suited to characterize both the event drivers and their consequences however maven has detected only moderate disturbances at mars due in large part to the general weakness of the present solar cycle nevertheless the strongest event observed by maven in march 2015 provides an example illustrating how further insights can be gained from available models here we first look more closely at what previously run bats r us mhd simulations of the combined maven observations tell us about the march 2015 event consequences we then use analogous models to infer those same responses including magnetic field topology changes and ionospheric consequences to a hypothetical extreme icme at mars based on stereo a measurements in july 2012 the results suggest how greatly enhanced yet realistic solar wind pressure magnetic field and convection electric field combine to produce strong magnetospheric coupling with important consequences for upper atmosphere and ionosphere energization

the 30 50 day mode at 850 mb during monex abstract the analyzed wind field at 850 mb during the summer monsoon experiment monex is subjected to a time series analysis to confirm the existence of a peak in the time range of 30 50 days having established that this study presents a mapping of the motion field for this time scale in this short paper we illustrate the steady meridional propagation of a train of troughs and ridges that seem to form near the equator and dissipate near the himalayas the meridional scale of this mode is around 300 km and its meridional speed of propagation is 0 75 latitude per day the amplitude of the wind for this mode is around 3 6 m s 1 the salient contributions here are the mapping and the demonstration of a very regular behavior of this mode its existence is here noted from a period well before the onset of monsoon i e from early may to late july three major storms during monex were noted to form within the trough line of this system and the period of major cessation of rains over the indian subconti

scardec a new technique for the rapid determination of seismic moment magnitude focal mechanism and source time functions for large earthquakes using body wave deconvolution accurate and fast magnitude determination for large shallow earthquakes is of key importance for post seismic response and tsumami alert purposes when no local real time data are available which is today the case for most subduction earthquakes the first information comes from teleseismic body waves standard body wave methods give accurate magnitudes for earthquakes up to mw 7 7 5 for larger earthquakes the analysis is more complex because of the non validity of the point source approximation and of the interaction between direct and surface reflected phases the latter effect acts as a strong high pass filter which complicates the magnitude determination we here propose an automated deconvolutive approach which does not impose any simplifying assumptions about the rupture process thus being well adapted to large earthquakes we first determine the source duration based on the length of the high frequency 1 3 hz signal content the deconvolution of synthetic double couple point source signals depending on the four earthquake parameters strike dip rake and depth from the windowed real data body wave signals including p pcp pp sh and scs waves gives the apparent source time function stf we search the optimal combination of these four parameters that respects the physical features of any stf causality positivity and stability of the seismic moment at all stations once this combination is retrieved the integration of the stfs gives directly the moment magnitude we apply this new approach referred as the scardec method to most of the major subduction earthquakes in the period 1990 2010 magnitude differences between the global centroid moment tensor cmt and the scardec method may reach 0 2 but values are found consistent if we take into account that the global cmt solutions for large shallow earthquakes suffer from a known trade off between dip and seismic moment we show by modelling long period surface waves of these events that the source parameters retrieved using the scardec method explain the observed surface waves as well as the global cmt parameters thus confirming the existing trade off for some well instrumented earthquakes our results are also supported by independent studies based on local geodetic or strong motion data this study is mainly focused on moment determination however the scardec method also informs us about the focal mechanism and source depth and can be a starting point to study systematically the complexity of the stf

mars plasma system response to solar wind disturbances during solar minimum this paper is a phenomenological description of the ionospheric plasma and induced magnetospheric boundary imb response to two different types of upstream solar wind events impacting mars in march 2008 at the solar minimum a total of 16 mars express orbits corresponding to five consecutive days is evaluated solar terrestrial relations observatory b stereo b at 1 au and mars express and mars odyssey at 1 644 au detected the arrival of a small transient interplanetary coronal mass ejection icme like on the 6 and 7 of march respectively this is the first time that this kind of small solar structure is reported at mars s distance in both cases it was followed by a large increase in solar wind velocity that lasted for 10 days this scenario is simulated with the wang sheeley arge wsa enlil cone solar solar wind model at mars the icme like event caused a strong compression of the magnetosheath and ionosphere and the recovery lasted for 3 orbits 20 h after that the fast stream affected the upper ionosphere and the imb which radial and tangential motions in regions close to the subsolar point are analyzed moreover a compression in the martian plasma system is also observed although weaker than after the icme like impact and several magnetosheath plasma blobs in the upper ionosphere are detected by mars express we conclude that during solar minimum and at aphelion small solar wind structures can create larger perturbations than previously expected in the martian system

the 2017 mexico tsunami record numerical modeling and threat assessment in costa rica an mw 8 2 earthquake and tsunami occurred offshore the pacific coast of mexico on 2017 09 08 at 04 49 utc costa rican tide gauges have registered a total of 21 local regional and far field tsunamis the quepos gauge registered 12 tsunamis between 1960 and 2014 before it was relocated inside a harbor by late 2014 where it registered two more tsunamis this paper analyzes the 2017 mexico tsunami as recorded by the quepos gauge it took 2 h for the tsunami to arrive to quepos with a first peak height of 9 35 cm and a maximum amplitude of 18 8 cm occurring about 6 h later as a decision support tool this tsunami was modeled for quepos in real time using commit community model interface for tsunami with the finer grid having a resolution of 1 arcsec 30 m however the model did not replicate the tsunami record well probably due to the lack of a finer and more accurate bathymetry in 2014 the national tsunami monitoring system of costa rica sinamot was created acting as a national tsunami warning center the occurrence of the 2017 mexico tsunami raised concerns about warning dissemination mechanisms for most coastal communities in costa rica due to its short travel time

geodetic data inversion using a bayesian information criterion for spatial distribution of fault slip summary we developed a new inversion method to reconstruct static images of seismic sources from geodetic data using akaike s bayesian information criterion abic coseismic surface displacements are generally related with a slip distribution on a fault surface by linear integral equations parametric expansion of the fault slip distribution by a finite number of known basis functions yields a set of observation equations expressed in a simple vector form incorporating prior constraints on the smoothness of slip distribution with the observation equations we construct a bayesian model with unknown hyperparameters the optimal values of the hyperparameters which control the structure of the bayesian model are objectively determined from observed data by using abic once the values of hyperparameters are determined we can use the maximum likelihood method to find the optimal distribution of fault slip we examined the validity of this method through a numerical experiment using theoretical data with random noise we analysed geodetic data associated with the 1946 nankaido earthquake ms 8 2 by using this method the result shows that the fault slip distribution of this earthquake has two main peaks of 4 and 6 m located off kii peninsula and muroto promontory these two high slip areas are clearly separated by a low slip zone extending along kii strait such a slip distribution corresponds with the fact that the rupture process of this earthquake in the western part is notably different from that in the eastern part

the slope of sea level along the equator during the 1982 1983 el nino observed deviations of monthly mean sea level at seven island stations along the equator in the pacific have been superimposed on the mean dynamic topography to determine the variations of the east west slope of sea surface topography during the 1982 1983 el nino the normal east west slope is eliminated in january 1983 when the bulk of warm water flowing eastward has reached the coast of south america the sea surface remains essentially flat from january to june 1983 although zonal winds are very weak until april only the slope requires several months to be reestablished and in october and november sea level along the entire equator is 10 cm or more below normal indicating a net loss of warm water from the equatorial pacific

source rupture process of the tecoman colima mexico earthquake of 22 january 2003 determined by joint inversion of teleseismic body wave and near source data the spatial and temporal slip distribution of the tecoman colima mexico earthquake is estimated from near source strong motion and teleseismic body wave data to perform a stable inversion we applied smoothing constraints and determined their optimal relative weights on the observed data using an optimized akaike s bayesian information criterion abic the source parameters are as follows strike dip slip 300 20 93 seismic moment m 2 3 1020 n m source duration 30 sec along strike distance 35 km along dip distance 70 km we found that the rupture process can be divided into three stages the rupture nucleated near the hypocenter stage i then it broke the first asperity centering about 15 km southwest from the epicenter stage ii and the rupture propagated to the northeast and the second asperity was broken stage iii we also estimated the shear stress change due to the rupture process of the mainshock on and around the major fault zone it appears that one cluster of aftershocks for the first 5 days which took place in and adjacent to the zones of stress increased due to the fault rupture during the mainshock but overall correlation between the aftershock location and the stress pattern is not clear manuscript received 14 may 2003

transient layers in the topside ionosphere of mars 1 radar soundings from the marsis instrument on board the mars express spacecraft have shown that distinct layers can occur in the topside ionosphere of mars well above the main photo ionization layer these layers appear as cusps or sometimes steps in plots of the time delay as a function of frequency usually only one topside layer is observed typically at altitudes from 180 to 240 km however occasionally an additional layer occurs at even higher altitudes the layers are transient features and are present about 60 of the time near the subsolar point decreasing with increasing solar zenith angle to less than 5 at the terminator and the nightside the transient nature of the layers suggests that they are produced by a dynamical process most likely involving an interaction with the solar wind in the upper levels of the ionosphere

detection of earthquake swarms at subduction zones globally insights into tectonic controls on swarm activity earthquake swarms are characterized by an increase in seismicity rate that lacks a distinguished mainshock and does not obey omori s law at subduction zones they are thought to be related to slow slip events sses on the plate interface earthquake swarms in subduction zones can therefore be used as potential indicators of slow slip events however the global distribution of earthquake swarms at subduction zones remains unclear here we present a method for detecting such earthquake sequences using the space time epidemic type aftershock sequence etas model we applied this method to seismicity m 4 5 recorded in the anss catalog at subduction zones during the period 1995 2009 we detected 453 swarms which is about 6 7 times the number observed in a previous catalog foreshocks of some large earthquakes are also detected as earthquake swarms in some subduction zones such as at ibaraki oki japan swarm like foreshocks and ordinary swarms repeatedly occur at the same location given that both foreshocks and swarms are related to sses on the plate interface these regions may have experienced recurring sses we then compare the swarm activity and tectonic properties of subduction zones finding that swarm activity is positively correlated with curvature of the incoming plate before subduction this result implies that swarm activity is controlled either by hydration of the incoming plate or by heterogeneity on the plate interface due to fracturing related to slab bending