lithospheric dynamics and tectonic stratigraphic evolution of the ebro basin we present analysis of two dimensional modeling of the tectonic subsidence in the ebro basin along three profiles crossing the pyrenees the ebro basin and the catalan coastal range to the east and the iberic cordillera to the west the deformation of the foreland basin during tertiary times is simulated using a lithospheric flexure model incorporating laterally varying elastic thicknesses the deflection of the plate is the combined result of pyrenean loading and the loads exerted by the iberic cordillera and catalan coastal range in the eastern part of the ebro basin no extra driving force on the iberian plate is required the flexural modeling supports the hypothesis that underplating of the iberian plate under the european plate is not associated with subduction of old oceanic lithosphere a good fit with the tertiary basin subsidence data and bouguer anomalies is obtained for an elastic plate with local weakness zones under the ebro basin the inferred lateral variation in the elastic rigidity is consistent with heat flow measurements in northern spain and with major mesozoic extension in the iberic cordillera and valencia trough

very short term earthquake precursors from gps signal interference based on the 2013 nantou and rueisuei earthquakes taiwan abstract we set up a gps network with 17 continuous gps cgps stations in southwestern taiwan to monitor real time crustal deformation we found that systematic perturbations in gps signals occurred just a few minutes prior to the 2013 nantou ml 6 5 and rueisuei ml 6 4 earthquakes in taiwan the anomalous pseudorange readings were several millimeters higher or lower than those in the background time period these systematic anomalies were found as a result of interference of gps l band signals by electromagnetic emissions ems prior to the mainshocks the ems may occur in the form of harmonic or ultra wide band radiation and can be generated during the formation of mode i cracks at the final stage of earthquake nucleation we estimated the directivity of the likely em sources by calculating the inner product of the position vector from a gps station to a given satellite and the vector of anomalous ground motions recorded by the gps the results showed that the predominant inner product generally occurred when the satellite was in the direction either toward or away from the epicenter with respect to the gps network our findings suggest that the gps network may serve as a powerful tool to detect very short term earthquake precursors and presumably to locate a large earthquake before it occurs nevertheless a direct measurement of ems at the site of the gps array is required in future studies to confirm this hypothesis

a physical explanation of the relation between flank uplifts and the breakup unconformity at rifted continental margins rift flank uplifts and the breakup or postrift unconformity are characteristic features of many rifted passive or atlantic type continental margins but are not predicted as primary features of simple lithospheric stretching models the explanations that have been proposed for their origin remain controversial either because they call upon special circumstances or because they are difficult to test plane strain finite element models are used in this paper to explore the dynamics of lithospheric necking during rifting and rupture the results agree with the conceptual interpretation that uplift of the rift boundaries to form flank mountains and uplift of the basin responsible for the breakup unconformity are related consequences of regional isostatic compensation of mass that is redistributed during the necking and rupture phases although the amplitudes of these uplifts depend on the model parameter values the relations between and relative signs of these two effects appear to be fundamental the explanation we propose may have been missed in recent studies because there has been a tendency to concentrate on kinematic stretching models which assume local isostatic equilibrium through out the rifting process such an approach is predicated on the assumption that the lithosphere has an insignificant strength or flexural rigidity during extension which is not true if our explanation is correct

on claimed ulf seismogenic fractal signatures in the geomagnetic field 1 during the last ten years fractal analysis of ultra low frequency ulf geomagnetic field components has been proposed as one of the most promising tools to highlight magnetic precursory signals possibly generated by the preparation processes of earthquakes several papers claim seismogenic changes in the fractal features of the geomagnetic field some months before earthquakes occur the target of the present paper is to put forth a qualitative investigation on the fractal characteristics of ulf magnetic signatures that previous authors have claimed to be related without doubt to strong earthquakes this analysis takes into account both the temporal evolution of the geomagnetic field fractal parameters reported in previous researches and the temporal evolution of global geomagnetic activity running averages of the geomagnetic indices kp and ap are plotted into the original figures from the previous publications this simple analysis shows that the fractal features of the ulf geomagnetic field are closely related to the geomagnetic activity both before and after the earthquake occurs the correlation between the geomagnetic field fractal parameters and geomagnetic activity is clearly shown over both long and short time scales in light of this the present paper shows that fractal behaviors of previously claimed seismogenic ulf magnetic signatures depend mainly on geomagnetic activity due to solar terrestrial interaction therefore previously reported association with the preparation process of the earthquake is dubious

on the seismogenic increase of the ratio of the ulf geomagnetic field components abstract following the paper by fraser smith et al 1990 many scientists have focused their research on the ulf geomagnetic field pulsations in the hope of finding possible anomalous signals caused by the seismic activity thereafter many papers have reported ulf geomagnetic field polarization ratio increases which have been claimed to be related to the occurrence of moderate and strong earthquakes even if there is no firm evidence of correlation between the polarization ratio increase and seismic events these publications maintain that these anomalous increases are without doubt precursors of pending earthquakes furthermore several researchers suggest that these seismogenic signals may be considered a promising approach towards the possibility of developing short term earthquake prediction capabilities based on electromagnetic precursory signatures on the contrary a part of the scientific community emphasizes the lack of validation of claimed seismogenic anomalies and doubt their association with the seismic activity since earthquake prediction is a very important topic of social importance the authenticity of earthquake precursors needs to be carefully checked the aim of this paper is to investigate the reliability of the ulf magnetic polarization ratio changes as an earthquakes precursor several polarization ratio increases of the geomagnetic field which previous researchers have claimed to have a seismogenic origin are put into question by a qualitative investigation the analysis takes into account both the temporal evolution of the geomagnetic field polarization ratio reported in previous papers and the global geomagnetic activity behaviour running averages of the geomagnetic index k p are plotted onto the original figures from previous publications moreover further quantitative analyses are also reported here nine cases are investigated which include 17 earthquakes in seven cases it is shown that the suggested association between the geomagnetic field polarization ratio increases and the earthquake preparation process seems to be rather doubtful more precisely the claimed seismogenic polarization ratio increases are actually closely related to decreases in the geomagnetic activity level furthermore the last two investigated cases seem to be doubtful as well although a close correspondence between polarization ratio and geomagnetic activity cannot be unambiguously demonstrated

detection of ultra low frequency emissions connected with the spitak earthquake and its aftershock activity based on geomagnetic pulsations data at dusheti and vardzia observatories abstract ulf electromagnetic emissions from the spitak armenia earthquake site have been detected observations were carried out at the dusheti and vardzia georgia observatories at distances 120 200 km from the epicentre in a frequency range 0 005 1 hz it is shown that the emission appears several hours before the main shock and some of the powerful aftershocks and is not connected with geomagnetic pulsations of magnetospheric sources

modeling the tectonic development of the tucano and sergipe alagoas rift basins brazil abstract the tucano and sergipe alagoas basins of northeast brazil form part of a regional extensional basin system that was operative during the mesozoic breakup of south america and africa with both basins developing on precambrian crust the synchronous development of the rift basins suggest that they are genetically linked in space and time whereas the offshore sergipe alagoas basin is characterized by a substantial thickness of post rift sediment the tucano basin either failed to develop or at least preserve a significant thickness of post rift sediment observed primary porosities within both pre and syn rift tucano basin sediment imply that significant post rift sedimentation never occurred failure to develop significant post rift subsidence has important thermal and mechanical implications for the reaction of the lithosphere to rifting and can be explained in terms of 1 depth dependent lithospheric extension in which intracrustal detachments allow the extension of the crust to be decoupled from the thinning of the lithospheric mantle 2 small rates of extension that allow the lithosphere to cool during rifting and or 3 lithospheric rifting during which the flexural strength of the lithosphere remains high with respect to points 2 and 3 forward modeling demonstrates that finite rifting rates over a 20 25 m y period are insufficient to cool the lithosphere to the point where post rift subsidence fails to develop an interesting complication arises when the flexural strength of the lithosphere remains large during rifting it tends to suppress the vertical motions of the lithosphere such as those engendered by the cooling of the lithosphere following rifting thereby reducing significantly the amplitude of the post rift subsidence thus the lack of post rift sedimentation within a basin does not necessarily imply that extension has been limited to the crust from our kinematic modeling of the tucano basin the observed negative free air and bouguer gravity anomalies 120 mgals suggest that the flexural strength of the lithosphere has remained sufficiently large to maintain the load of the sediment we can model successfully the observed tucano basin architecture and gravity anomaly irrespective of whether we assume depth dependent or depth independent lithospheric extension primarily because the flexural strength of the lithosphere tends to buffer or suppress the amplitude of the post rift subsidence in contrast the adjacent sergipe alagoas basin is associated with low amplitude gravity anomalies which may reflect a resetting of flexural strength during rifting prior to rifting however there was no appreciable elevation difference between the tucano and sergipe alagoas regions as might be induced by a hot spot for example implying that the flexural strength of the lithosphere was similar the total thickness of the syn and post rift sediments within the sergipe alagoas basin is about the same as the thickness of rift phase sediments in the tucano basin thus the amount of crustal extension responsible for each basin was similar however since the sergipe alagoas basin contains 4 5 km of post rift sediments lithospheric mantle thinning in this region must have been significantly greater than the crustal extension to overcome the effects of flexural bufferring the need for lithospheric mantle thinning to be greater that crustal extension in the sergipe alagoas region was also a result obtained by modeling the development of the ocean continent boundary between brazil and africa from our coupled kinematic and rheological model of lithospheric extension we predict that the ocean continent boundary should form preferentially at the location of greatest crustal and lithospheric mantle thinning that is within the region of maximum depth independent lithospheric extension the ocean continent boundary formed east of the sergipe alagoas basin despite the fact that the tucano basin represents the region of greatest crustal thinning if extension had been uniform with depth beneath these basins the ocean continent boundary should have formed in the tucano basin as it did not some form of intracrustal detachment appears to have been operative to reduce lithospheric mantle thinning beneath the tucano basin while enhancing it beneath the offshore regions of the sergipe alagoas basin

investigating non uniform scaling behavior in ultra low frequency ulf earthquake related geomagnetic signals abstract the scaling properties of the time dynamics of 2000 2001 ulf geomagnetic data in the frequency range between 1 mhz and 10 hz observed at izu peninsula in japan were investigated on the basis of detrended fluctuation analysis dfa which is a powerful method to detect scaling in non stationary time series deviations from uniform power law scaling were identified and quantified our results suggest that a significant non uniform scaling behavior in ulf geomagnetic data could be related to the occurrence of intense seismic clusters these first results could be useful in the framework of short term earthquake prediction

multiscale diagnosis of the north american monsoon system using a variable resolution gcm abstract the onset and evolution of the north american monsoon system during the summer of 1993 were examined from regional to large scales using the national aeronautics and space administration nasa goddard earth observing system geos stretched grid gcm the model s grid spacing for the dynamical core ranges from 0 4 0 5 in latitude longitude over the united states to about 2 5 3 5 at the antipode and the physical package is solved on an intermediate 1 1 uniform grid a diagnostic analysis of the monsoon s onset reveals the development of a positive potential temperature anomaly at the surface that favors a lower level cyclonic circulation while a negative potential vorticity pv anomaly below the tropopause induces an upper level anticyclonic circulation ignoring diabatic effects this pattern is consistent with the superimposition of idealized pv and anomalies as previously discussed in the literature the inclusion of the smaller scale features of the core monsoon in the mod

electromagnetic emissions during dilating fracture of a rock abstract a lot of experiments on electromagnetic emissions emes have been reported under axial compressive fracture shear fracture indentation fracture and stick slip friction in lab and blasting in situ but there are rare reports on the in lab experimental work on emes during dilating fracture of a rock which is helpful in studying and understanding emes related to slow earthquakes and the earthquakes due to volcanic activities and water level changes of reservoirs therefore in the present paper in order to check whether there are detectable emes during dilating fracture of a rock in lab dilating fracture experiments were conducted the dry cuboid specimens of initially intact granodiorite and limestone were tested inside magnetic field free space mffs at room temperature we arranged evenly 20 eme antennas whose resonance frequencies range from 2 5 khz to 540 khz close to rock specimens our experimental results strongly indicate that detectable emes could generate during dilating fracture of a rock they were recorded only associated with some but not all phases of fracture their waveforms often took on the trend that a peak arrived at first and then attenuated sharply and followed by a series of low amplitude oscillations the electromagnetic em signals after eliminating the effects of eme antennae via deconvolution had the maximum peak to peak amplitudes of about 80 0 mv and 40 5 mv for granodiorite and limestone respectively their main spectral components often concentrated in the band of several khz to 60 khz and of several khz to 280 khz the emission of electrons and charged particles from fracture surfaces and or micro fracture electrification could be possible mechanisms for our experimental results

multiple seismo anomalies associated with the m6 1 ludian earthquake on august 3 2014 abstract multiple geophysical parameters including groundwater level water temperature water radon crustal deformation electromagnetic waves and total electron contents tec in the ionosphere are examined together to investigate pre earthquake anomalous phenomena associated with the mw6 1 ludian earthquake on august 3 2014 cross parameter comparison eliminates anomalies that are detected in one parameter only and examine earthquake related phenomena in various fields simultaneously retrieved anomalies show that abnormal decreases of water temperature and radon concentration related to anomalous uplift of groundwater levels appeared about 1 8 days before the earthquake even without contributions from rain significant step like changes are observed from data recorded by strainmeters on july 31 and are consistent with water related anomalies in timing no significant anomalies can be found from electromagnetic data through the preliminary observation in contrast tec appeared positive anomalies 1 3 days before the ludian earthquake although causal mechanisms of the tec anomalies from stressed rocks are not fully understood multiple parameter examination can increase credibility of determination regarding pre earthquake phenomena

magnetic field observations in the near field the 28 june 1992 mw 7 3 landers california earthquake recent reports suggest that large magnetic field changes occur prior to and during large earthquakes two continuously operating proton magne tometers lsbm and ochm at distances of 17 3 and 24 2 km respectively from the epicenter of the 28 june 1992 mw 7 3 landers earthquake recorded data through the earthquake and its aftershocks these two stations are part of a differentially connected array of proton magnetometers that has been operated along the san andreas fault since 1976 the instruments have a sensitivity of 0 25 nt or better and transmit data every 10 min through the goes satellite to the usgs headquarters in menlo park california seismomagnetic offsets of 1 2 0 6 and 0 7 0 7 nt were observed at these sites in comparison offsets of 0 3 0 2 and 1 3 0 2 nt were observed during the 8 july 1986 mt 5 9 north palm springs earthquake which occurred directly beneath the ochm magnetometer site the observations are generally consistent with seismomagnetic models of the earthquake in which fault geometry and slip have the same form as that determined by either inversion of the seismic data or inversion of geodetically determined ground displacements produced by the earthquake in these models right lateral rupture occurs on connected fault seg ments in a homogeneous medium with average magnetization of 2 a m the fault slip distribution has roughly the same form as the observed surface rupture and the total moment release is 1 1 1020 nm there is no indication of dif fusion like character to the magnetic field offsets that might indicate these ef fects result from fluid flow phenomena it thus seems unlikely that these earth quake generated offsets and those produced by the north palm springs earthquake were generated by electrokinetic effects also there are no indications of en hanced low frequency magnetic noise before the earthquake at frequencies be low 0 001 hz

active normal faulting and crustal extension a world wide review of fault plane solutions and focal depths for large normal faulting earthquakes on the continents shows that the overwhelming majority of such earthquakes nucleate in the depth range 6 15 km on faults dipping between 30 and 60 in the few cases where levelling or seismic data are good enough these normal faults are shown to be approximately planar from the surface to their nucleation depth at the base of the brittle crust there is evidence that in some cases as a result of the enormous transitory increase in strain rate during large earthquakes rupture continues into the normally ductile lower crust on surfaces with substantially gentler dips these low angle surfaces may be analogous to some of the detachments seen in metamorphic core complexes of the western usa but the nature of the motion on them depends on strain rate as well as on rheological contrasts between the detachments and the blocks on either side such contrasts however are unlikely to introduce substantial curvature to an originally planar shear zone if the observed spread in active normal fault dips is caused by rotation of the faults and the blocks they bound during extension then a maximum value of 1 7 can be accommodated by seismic activity on a single generation of normal faults with continued extension either a new generation of steeper faults cutting the rotated first faults is likely to form or the deformation will continue aseismically on faults dipping at less than 30 large earthquakes have not been observed to nucleate on very low angle 20 normal faults within the continental crust anywhere in the world such faults can of course move aseismically but are unlikely to do so on a large scale within the upper crust in areas where steep normal faults are seismically active thus extensional models that require concentrated simple shear on large sub horizontal faults within the brittle upper crust will also require a spatial separation between aseismic very low angle faulting and seismic highangle faulting since seismogenic high angle faults dominate the topography of extending regions upper crustal very low angle faulting if it occurs on a large scale presumably does so in areas that are relatively fiat

fractal analysis of ulf geomagnetic data associated with the guam earthquake on august 8 1993 this paper presents a fractal analysis of the ulf electromagnetic data obtained at guam observatory during a strong ms 8 0 earthquake occurred on august 8 1993 near the guam island we have already reported the presence of seismogenic ulf emissions for this quake hayakawa et al grl 1996 the chosen period covered four months before and two months after the earthquake it was found that the spectrum of emissions at noon exhibited a power law behavior f which is typical for self organized critical dynamics the slope of the spectrum in the noon sector fluctuates in a range from 2 5 to 0 7 with a tendency to gradually decrease during the process of the earthquake preparation we consider this to be a candidate for a precursory signature the similar effect was found for the night sector we suggest that the focal zone was at the critical stage of self organized criticality process before the quake related to active microfracturing processes followed by the generation of ulf emissions as we detected

carbon enhanced electrical conductivity during fracture of rocks changes in electrical resistance during rock fracture in the presence of a carbonaceous atmosphere have been investigated using nugget sandstone and westerly granite the experiments were performed in an internally heated gas pressure vessel with a load train that produced strain rates between 10 6 and 10 5 s 1 samples were deformed at temperatures of 354 to 502 c and pressures of 100 to 170 mpa in atmospheres of ar or mixtures of 95 co2 with 5 co or 5 ch4 compositions that are well within the field of graphite stability at the run conditions in experiments using nugget sandstone resistance reached a minimum value when the maximum temperature was achieved and good electrode contact was made the resistance then increased as the experiment continued probably due to dry out of the sample a change in the oxidation state of the fe oxide associated with the cement or destruction of current bearing pathways at approximately 200 mpa end load the rock sample failed plots of load and resistance versus time show several interesting features in one experiment for example as the end load reached about 175 mpa resistance stopped increasing and remained fairly constant for a period of approximately 0 5 hour during loading the end load displayed small decreases that were simultaneous with small decreases in resistance when the end load and the displacement indicated rock failure resistance decreased dramatically from 150 m to 100 m in a single experiment the westerly granite also showed a decrease in resistance during dilatancy the nature and distribution of carbon in the run products were studied by electron microprobe and time of flight secondary ion mass spectroscopy top sims carbon observed by mapping with the former is clearly observed on micro cracks that based on the microtexture are interpreted to have formed during the deformation the tof sims data confirm the electron probe observations that carbon is present on fracture surfaces these observations and experimental results lead to the hypothesis that as microfractures open in the time leading up to failure along a fracture carbon is deposited as a continuous film on the new reactive mineral surfaces and this produces a decrease in resistance subsequent changes in resistance occur as connectivity of the initial fracture network is altered by continued deformation such a process may explain some electromagnetic effects associated with earthquakes

the role of surface friction in tropical intraseasonal oscillation abstract the role of surface friction in the tropical intraseasonal oscillation or the madden julian oscillation mjo is investigated by comparing two 4 yr integrations with the goddard atmospheric general circulation model one with the original model design with one added feature to enhance the intensity of the mjo and the other is identical but with surface friction in the tropics replaced by its zonal mean value this comparison indicates that in the second experiment the mjo not only still exists but also exists with similar intensity the oft cited frictional wave cisk fwc interpretation for the origin of the mjo which emphasizes the role of frictionally induced convergence in the surface layer is reassessed in light of these experiments the possibility of the mjo in the second experiment being forced by the middle latitudes is excluded by a third experiment these experiments do not support one of the central ideas in fwc that surface friction plays an instability enhancing role

how normal faulting and sedimentation interact to produce listric fault profiles and stratigraphic wedges abstract in a series of scale experiments we generated listric normal faults by extending models composed of colored sand layers deposited at regular time intervals throughout deformation during syntectonic sedimentation progressive bulk extension along a single set of faults caused domino type tilting of fault blocks underlying tilted faults propagated upwards with constant dips into newly sedimented layers hence fault profiles become progressively more listric tilting of the free surface resulted in asymmetrical depressions and in fan shaped deposits stepwise or continuous geometric models of domino tilting and synchronous sedimentation yield the same structural and stratigraphic features as observed in the sand models the continuous geometric model shows that a critical parameter governing fault curvature is the ratio r between rates of bulk strain and sedimentation both types of models reveal that synchronous sedimentation and bulk extension are capable by themselves of generating listric normal faults

ulf geomagnetic anomalies of possible seismogenic origin observed at teoloyucan station mexico in 1999 2001 intermediate and short time analysis abstract the analysis of ulf geomagnetic field measured at teoloyucan station central mexico 11 35 735 w 19 44 45 100 n 2280 m height is presented in an intermediate 15 days and short time scale the day of the eq occurrence in relation to 7 major earthquakes occurred in mexico in 1999 2001 local changes in the fractal dynamics of the magnetic field are found to be important a pronounced fall of the fractal index is frequently observed prior to the main shock the study of the ulf resonant structure recently discovered in the frequencies fr1 10 2 11 1 mhz and fr2 13 6 14 5 mhz reveals changes in their character probably related to the processes of the earthquakes preparation the success of the observation of the mentioned anomalies specially the fractal index decrease strongly depends on how close is the station from the epicenter and what is the magnitude of the earthquake

does a monsoon climate exist over south america the climatology and the basic state of the summertime circulation and rainfall over south america are studied using assimilation products from the data assimilation system of goddard earth observing system 1 geos1 and satellite derived rainfall results indicate the existence of a regional summer monsoon circulation regime induced by strong diabatic heating over the subtropical south american highland centered at the altiplano plateau sensitivity of the results to the assimilation scheme is tested by comparing that with the national centers for environmental prediction ncep reanalysis and with satellite rainfall estimates results show general agreement between the model produced rainfall anomaly and the satellite estimates as well as consistency between the basic circulation features in the geos 1 and the ncep reanalyses a case study of 1989 90 south american summer monsoon sasm reveals the following characteristics 1 in late spring the onset of sasm is signaled by an abrupt merging of the upper tropospheric double westerly jets one in the subtropics and the other in the subpolar region into a single jet in the midlatitudes this is followed by the establishment of a vortex to the southeast of altiplano and occurrence of heavy precipitation over subtropical eastern brazil 2 during the mature phase of sasm the heavy rainfall zone moves over the altiplano plateau and the southernmost brazilian highland the fully established sasm features are the following a an enhancement of equatorial north atlantic trade wind which emanates from the sahara high and crosses the equator over the south american continent b a buildup of strong northwesterlies along the eastern side of the tropical andes and c development of the south atlantic convergence zone in the southernmost position with strong convective activity meanwhile the upper tropospheric return flow emerges from an anticyclone formed over the altiplano plateau crosses the equator and sinks over northwestern africa 3 the withdrawal of sasm in late summer is signaled by the resplitting of the midlatitude westerly jet at the same time the low level northwest monsoon flow diminishes reducing the moisture supply and leading to the termination of heavy precipitation over the subtropical highland results also show that the above mentioned characteristics of sasm are clearly linked to the tropospheric temperature changes over the central south american highland sensible versus latent heating over the highland are bound to play an important role in the evolution of sasm to provide further support of presence of a monsoon climate over south america sasm is compared and contrasted to the classic east asian summer monsoon easm many similar features including evolution characteristics between the two systems have been identified contrasting aspects of the sasm from the easm are also discussed it is pointed out that a number of monsoonal characteristics of the climate of south america such as the seasonal reversal of the low level wind become apparent only when the strong annual mean wind is removed based on the characteristic features and their evolution the authors conclude that a monsoon climate does exist over south america

variations of elastic plate thickness at continental thrust belts after examining 15 reliable estimates of the elastic thickness of the lithosphere where it underthrusts mountain belts in europe asia and the americas we conclude that the strength of continental lithosphere as a function of depth must be very different from that of oceanic lithosphere depending on the state of stress continental lithosphere may be either very much stronger or very much weaker than would be predicted for oceanic lithosphere of the same thermal age we explain this observation as the result of two competing effects a thicker thermal plate beneath the continents which allows a deeper elastic ductile transition for plates more than 100 million years old and a low activation energy for ductile creep in the continental crust which leads to massive failure of the upper elastic lithosphere at high bending stresses the 100 km values for elastic plate thickness of billion year old lithosphere require a thermal plate thickness of at least 250 km the magnitude of apparent thinning of the elastic plate at high stress is consistent with that calculated from a simple yield envelope which includes a ductile zone in the lower crust the low yield strength of continental materials leads to correlations between effective elastic plate thickness and all of the following dip of the underthrust plate radius of curvature of the thrust front in map view and total length of the mountain belt using insight derived from laboratory experiments on the buckling of spherical shells and drawing analogies with the geophysical characteristics of oceanic subduction zones we arrive at the following sequence of causes and effects the primary variable is the dip of the downgoing plate presumably prescribed by its own excess mass and pressure exerted by dynamic flow in the mantle where this dip is steep the rigidity of the plate is weakened due to inelastic yielding the weakened plate can then buckle at small wavelengths into short arcuate mountain belts thus we believe that the mantle ultimately controls the pattern of surface tectonics but that the nonelastic rheology of the lithosphere is the mechanism by which that control is imposed

statistical analysis of ulf seismomagnetic phenomena at kakioka japan during 2001 2010 to clarify and verify the ultralow frequency ulf seismomagnetic phenomena we have performed statistical studies on the geomagnetic data observed at the kakioka kak station japan during 2001 2010 we investigated the energy of ulf geomagnetic signals of the frequency around 0 01 hz using wavelet transform analysis to minimize the influences of artificial noises and global geomagnetic perturbations we used only the geomagnetic data observed at nighttime lt 2 30 a m to 4 00 a m and utilized observations from a remote station kanoya as a reference statistical results of superposed epoch analysis have indicated that ulf magnetic anomalies are more likely to appear before sizable earthquake events es 108 rather than after them especially 6 15 days before the events further statistical investigations show clearly that the ulf geomagnetic anomalies at kak station are more sensitive to larger and closer events finally we have evaluated the precursory information of ulf geomagnetic signals for local sizable earthquakes using molchan s error diagram the probability gain is around 1 6 against a poisson model the above results have indicated that the ulf seismomagnetic phenomena at kak clearly contain precursory information and have a possibility of improving the forecasting of large earthquakes

the origin of monsoons abstract the monsoon is interpreted as an intertropical convergence zone itcz substantially away more than 10 from the equator and the existence of the itcz does not have to rely on land sea contrast land sea contrast can provide a favorable longitudinal location for the itcz but this role can be replaced by sea surface temperature contrast in the longitudinal direction thus the interpretation of the monsoon presented herein differs from the long held fundamental belief that its basic cause is land sea thermal contrast on the continental scale in the sense that the existence of landmass is not considered a necessary condition for monsoons through general circulation model experiments support has been found for this interpretation the asian and australian summer monsoon circulations are largely intact in an experiment in which asia maritime continent and australia are replaced by ocean with sea surface temperature sst taken from that of the surrounding oceans thus in these areas land sea c

potential relationships between seismo deformation and seismo conductivity anomalies abstract this study examines the relationships between seismo deformation and seismo conductivity anomalies during two m6 earthquakes that occurred on march 27th and june 2nd 2013 in taiwan the hilbert huang transform is applied on surface displacement data to remove the effects of noise semi annual and annual cycles and the long term plate movements the residual displacements have similar orientations when earthquake related stress accumulates in the crust once the accumulated stress approaches the threshold for fault rupture the orientations of the residual displacements generally become random except in a small region near the epicenter interestingly high conductivity anomalies which can be detected from the 3 component magnetic data via the magnetic transfer function exist in places very close to this small region near the epicenter spatial and temporal correlations between the high conductivity anomalies and the small region of seismo deformation anomalies suggest that electric charges may migrate and become trapped in the region during seismogenic processes due to differential stress accumulation these electric charges form a high conductivity material that affects the parkinson vector of the geomagnetic field

two dimensional p t t modelling and the dynamics of extension and inversion in the betic zone se spain abstract the internal zone of the betic cordilleras offers a unique opportunity to study the dynamics of lithospheric processes at mid crustal levels which controlled the formation and evolution of the southeastern margin of iberia in this paper we present the result of two dimensional numerical modelling of p t t paths related to latest oligocene and early miocene extension and inversion in the betic zone the ages of p t t loops are constrained by an extensive data set of geothermo barometric and geochronological data including 40 ar 39 ar laser probe data we investigate the thermo mechanical evolution of the betic zone using numerical models for simple shear pure shear and combined shear the wernicke simple shear model fails to explain the observed temperatures in excess of 500 c and is not consistent with the occurrence of intrusions of ultramafic rocks in the western betics however the delaminated simple shear model with low angle faults located only at lower crustal levels is found to be consistent with the p t t data after a heating phase associated with a finite extension of 80 km rapid cooling occurred reflecting inversion of the extensional structure by nw se to n s directed compression palaeo rheological models for the latest oligocene early miocene times demonstrate the important role of the detachments produced during crustal extension for the dynamics of the subsequent inversion phase the modelling strongly suggest that inversion locked after 60 km of finite convergence after locking of the inversion overthrusting in a northward direction occurred which is compensated by pure shear deformation in the lower crust in the southeastern part of the betic zone

global measurements of stratospheric mountain waves from space temperatures acquired by the cryogenic infrared spectrometers and telescopes for the atmosphere crista during shuttle mission sts 66 have provided measurements of stratospheric mountain waves from space large amplitude long wavelength mountain waves at heights of 15 to 30 kilometers above the southern andes mountains were observed and characterized with vigorous wave breaking inferred above 30 kilometers mountain waves also occurred throughout the stratosphere 15 to 45 kilometers over a broad mountainous region of central eurasia the global distribution of mountain wave activity accords well with predictions from a mountain wave model the findings demonstrate that satellites can provide the global data needed to improve mountain wave parameterizations and hence global climate and forecast models

depositional and tectonic framework of the rift basins of lake baikal from multichannel seismic data recent multichannel seismic reflection data from lake baikal located in a large active continental rift in central asia image three major stratigraphic units totaling 3 5 to 7 5 km thick in four subbasins a major change in rift deposition and faulting between the oldest and middle rift units probably corresponds to the change from slow to fast rifting in early pliocene time inferred from on land studies a minor modification of fault patterns characterizes the youngest unit a brief comparison of the basins of lake baikal with those of the east african rift system highlights differences in structural style that can be explained by differences in age and evolution of the surrounding basement rocks

geoelectric signals in china and the earthquake generation process we present original apparent resistivity records for stations located in the chinese provinces of hebei and sichuan along with seismicity patterns fault maps and limited hydrologic data these records are part of a 30 year database of geoelectric signals that have been recorded in china by a nationwide network of more than 100 stations set up by the state seismological bureau of the people s republic of china the database includes the time period during which the m 7 8 1976 tangshan and m 7 2 1976 songpan earthquakes occurred resistivity data recorded in and around the epicentral region of the tangshan event show coherent changes both temporal and in areal distribution years and months before and after the earthquakes a regional change in water table occurred more than 3 years prior to the tangshan earthquake the resistivity and water table signals appear to correlate in the 2 to 3 year period prior to the earthquake rainfall records from the region around tangshan extending to the cities of beijing and tianjin do not appear to account for the resistivity changes regional seismicity and active fault patterns in north china indicate that deformation occurs mainly along the borders of large tectonic blocks the source region for the geoelectric signals appears to lie within a large shear zone at the edge of a tectonic block undergoing rotation the tangshan epicentral area is thus only part of a larger zone of deformation we suggest that dilational strain associated with the opening of fractures may lower resistivity and water table for shallow crustal depths such as those monitored by the chinese geoelectric network dilation and resistivity changes are expected to begin at stress levels well below the peak values of the seismic cycle our study suggests that in some cases the areal extent of geoelectric signals may be significantly larger than that of the eventual earthquake source dimension the chinese geoelectric database offers an opportunity to improve our understanding of possible geoelectric precursors to earthquakes

transient electric variations associated with large intermediate depth earthquakes in south aegean abstract a telluric station was installed on crete in the south aegean in order to investigate the existence of transient electric variations before large near intermediate depth earthquakes during the experiment two transient electric variations not correlated with geomagnetic variations were recorded and associated with two time isolated intermediate depth earthquakes with local magnitude m l 5 8 and 4 8 respectively finally a qualitative discussion on the form of the electric signal based on the charge dislocation model is presented

anomalous behaviors of geomagnetic diurnal variations prior to the 2011 off the pacific coast of tohoku earthquake mw9 0 there have been many reports on ultra low frequency ulf electromagnetic phenomena associated with earthquakes in a very wide frequency range in this study unusual behaviors of geomagnetic diurnal variations prior to the 2011 off the pacific coast of tohoku earthquake mw9 0 have been reported ratios of diurnal variation range between the target station esashi esa which is about 135 km from the epicenter and the remote reference station kakioka kak about 302 km distant to the epicenter have been computed the results of 10 day running mean of the ratios showed a clear anomaly exceeding the statistical threshold in the vertical component about 2 months before the mega event this anomaly is unique over a 3 year background and the further stochastic test indicates that this anomaly is unlikely a random anomaly which is highly suggestive of correlation with the mega event the original records of geomagnetic fields of the esa station also exhibit continuous anomalous behaviors for about 10 days in the vertical component approximate 2 months prior to the mw9 0 earthquake

reduction of systematic forecast errors in the ecmwf model through the introduction of an envelope orography day 1 forecast errors in the ecmwf model geopotential height fields during wintertime show a distinctive and highly reproducible signature with negative biases over the major mountain barriers these biases are largest on days when the 500mb flow over the mountains is strong and they tend to shift position from day to day so as to remain close to the region where the jet stream crosses the mountain barrier these systematic errors evolve through the forecast interval until by day 10 they assume an equivalent barotropic structure which strongly resembles the upper level stationary wave pattern but has the opposite sign which indicates that the model does not have sufficient presumably orographic forcing to maintain the stationary waves the time evolution of the systematic error pattern is investigated by means of a series of experiments with a barotropic model in which the observed mean wintertime 300 mb flow is perturbed by a steady forcing derived from the day 1 forecast error pattern the day 10 error patterns as simulated by the barotropic model bear a strong similarity to the observed ones the forcing in the vicinity of the northern rockies makes a particularly large contribution to the simulated day 10 error pattern whereas that in the himalaya region appears to be relatively less important the impact of an enhanced orography upon the climate of the ecmwf model is investigated by carrying out a pair of extended integrations out to 50 days the control run is based on the conventional average type orography used for operational forecasting the other run is based on an envelope orography constructed by adding to the conventional grid square averaged orography an increment proportional to the standard deviation of the sub grid scale variance results for this one rather short pair of integrations suggest that the envelope orography may be capable of yielding a more realistic simulation of the observed wintertime flow pattern particularly with respect to features in the pacific and western north american sectors certain aspects of the zonally averaged circulation are also more realistic in this envelope simulation a series of 21 successive ten day forecast integrations has also been carried out with this envelope orography from february 1982 data results indicate that the introduction of the envelope orography results in a slight degradation of the short range forecasts together with a distinct improvement of the forecast beyond four days the beneficial impact towards the end of the forecast interval appears to be large enough to increase the forecast usefulness by perhaps as much as half a day

on the anomalous changes of seismicity and geomagnetic field prior to the 2011 mw 9 0 tohoku earthquake abstract in xu et al 2013 it has just been reported that approximately 2 months prior to the m w 9 0 tohoku earthquake that occurred in japan on 11 march 2011 anomalous variations of the geomagnetic field have been observed in the vertical component at a measuring station about 135 km from the epicenter for about 10 days 4 14 january 2011 here we show that this observation is in striking agreement with independent recent results obtained from natural time analysis of seismicity in japan in particular this analysis has revealed that an unprecedented minimum of the order parameter fluctuations of seismicity was observed around 5 january 2011 thus pointing to the initiation at that date of a strong precursory seismic electric signals activity accompanied by the anomalous geomagnetic field variations starting from this date natural time analysis of the subsequent seismicity indicates that a strong main shock was expected in a few days to one week after 08 40 lt on 10 march 2011

radio emission associated with rock fracture possible application to the great chilean earthquake of may 22 1960 stress induced piezoelectric fields produce freely propagating electromagnetic radiation when microscopic rock fractures occur in quartz bearing rocks a laboratory study is presented which shows that electromagnetic emissions are produced when microfractures occur in westerly granite a detailed model is presented for the emission process which allows an estimate of the total radiated power from an individual microfracture on the basis of these results a case is presented that an unusual radio emission seen on several widely separated radio astronomy receivers in the northern hemisphere on may 16 1960 was due to a stress induced microfracture along the chilean fault this radio event occurred 6 days prior to the great chilean earthquake of may 22 1960 and may have been a precursor to one of the largest earthquakes of this century

challenges in the detection of ionospheric pre earthquake total electron content anomalies peta for earthquake forewarning various studies have investigated the link between seismic activity and ionospheric precursory phenomena many of these retrospective case studies have supported the existence of pre earthquake ionospheric anomalies by examining past earthquake events using a variety of analytical methods based on existing methodologies however the conversion of a retrospective analysis to a prospective forewarning scenario is not a straightforward process the obstacles to its potential adoption stem mainly from assumptions made during data analysis and interpretation in this study several parameters pertaining to existing approaches for the detection of these ionospheric anomalies are highlighted and discussed in particular ionosphere total electron content tec a detailed examination is conducted to understand the roles that each of these parameters play in the detection process and the consequent difficulties when adopting them in a prospective analysis these issues include accounting for variations in ionosphere characteristics owing to different measurement platforms e g ground and space based observations and statistical methods e g standard deviation envelopes used in detecting anomalies furthermore the necessity of excluding space weather contributions in the underlying tec fluctuations poses a challenge in determining the validity of observed ionospheric anomalies the notion of an earthquake preparation zone is also evaluated in the context of the ionosphere along with its implications in a forewarning scenario these issues need to be addressed in current research in order to enable its possible application in earthquake forewarning

alleviation of a systematic westerly bias in general circulation and numerical weather prediction models through an orographic gravity wave drag parametrization systematic westerly biases in the northern hemisphere wintertime flow of the meteorological office 15 layer operational model and 11 layer general circulation model are described evidence that the failure to parametrize subgrid scale orographic gravity wave drag may account for such biases is presented this evidence is taken from aircraft studies surface pressure drag measurements and studies of the zonally averaged momentum budget a parametrization scheme is described in which the surface stress is proportional to the near surface wind speed and static stability and to the variance of subgrid scale orography the stress is absorbed in the vertical by considering the influence of such gravity wave activity on static stability and vertical wind shear a richardson number dependent wave breaking formulation is devised and the vertical stress profile determined by a saturation hypothesis whereby the breaking waves are maintained at marginal stability it is shown that wave breaking preferentially occurs in the boundary layer and in the lower stratosphere results from a simple zonally symmetric model show how the adjustment to thermal wind balance with a wave drag in the stratosphere warms polar regions by adiabatic descent and decelerates the mean westerlies in the troposphere the influence of the parametrization scheme on integrations of the 11 layer model is described and found to be generally beneficial in a discussion of the reasons why this problem has only recently emerged it is suggested that the satisfactory northern hemisphere winter circulations of previous coarser general circulation models were due to a compensation implied by underestimating both the surface drag and the horizontal flux of momentum by explicitly resolved large scale eddies

the mechanics of continental extension and sedimentary basin formation a simple shear pure shear flexural cantilever model abstract deep seismic reflection data and earthquake seismology show the fundamental importance of major crustal faults during extension of continental lithosphere controlling the development of rifted sedimentary basins major basement faults are generally planar and extend down to 10 15 km depth corresponding to the base of the seismogenic layer beneath this depth deformation gives way to distributed ductile shear in the lower crust and lithospheric mantle a mathematical model is described of the geometric thermal and flexural isostatic response of the lithosphere to extension by planar faulting of the upper crust and plastic distributed deformation in the lower crust and mantle during faulting upper crustal footwall and hanging wall blocks behave as two mutually self supporting flexural cantilevers their response to isostatic forces induced by extension generates footwall uplift and hanging wall collapse for extension on multiple faults interference of footwall uplift and hanging wall collapse gives rise to the familiar block rotations of rift tectonics the flexural cantilever model is able to predict crustal structure and sedimentary basin geometry for faults of arbitrary spacing horizontal displacement and polarity the effects of fault spacing fault polarity and the amount of extension as well as erosion of footwall uplift on crustal structure and basin geometry during both syn rift and post rift stages of basin evolution are explored models of passive rifting involving lithosphere extension in response to the build up of far field tectonic forces and decompression induced partial melting of the upper asthenosphere and lower lithosphere appear to conform to the main geological observations the role of active rifting driven by locally derived deviatoric tensional forces generated by mantle plumes remains uncertain

modelling the connection between earthquake preparation processes and crustal electromagnetic emission abstract the steadily increasing amount of information available today on the natural electromagnetic emission eme of the radio frequency band associated with seismic events raises the problem of the origin of this phenomenon a natural hypothesis is that eme is due to earthquake preparation processes the present paper is concerned with substantiating a model that postulates eme to be caused by cracking of surficial crustal layers in the zone of earthquake preparation the crust is assumed to have ordered hierarchical structure individual elements of that structure are formed of blocks of different scales and obey principles of similarity between the blocks are soft interlayers with a finite strength limit a regular periodic structure with a cubic lattice is studied as a result eme intensity as a function of magnitude is evaluated methodological recommendations are given for organization of field observations of eme in relation to earthquake prediction

impact of orographically induced gravity wave drag in the gla gcm the influence of gravity wave drag gwd parametrization has been investigated in the goddard laboratory for atmospheres general circulation model with the resolution of 4 latitude 5 longitude in the horizontal and 17 sigma layers in the vertical the simulations showed several overall beneficial effects in the extended range forecast as well as the seasonal simulation for both winter and summer conditions the key results include the following 1 the mid latitude westerlies which were shifted poleward equatorward in northern southern winter have been corrected consequently the systematic bias of low high sea level pressure over the north south polar region has been largely eliminated 2 there is a significant improvement in the simulation of the winter hemisphere stationary waves this can be attributed to the gwd induced rossby wave propagation over the northern pacific region as the storm track is simulated better precipitation distribution improves remarkably 3 in cooperation with the improved regional zonal mean flow an adjustment of the mean meridional circulation is found over the asian summer monsoon region leading to an improvement in the precipitation distribution 4 spurious absorption of gravity waves at the model top 10 mb has been removed by applying an open upper boundary condition the vertical propagation of the tropospherical gravity wave into the upper stratosphere and mesosphere over mid latitudes of the northern hemisphere in winter is consistent with observational studies as well as the middle atmospheric dynamics

the effect of moist convection on the tropospheric response to tropical and subtropical zonally asymmetric torques tropospheric winds can be altered by vertical transfers of momentum due to orographic gravity waves and convection previous work showed that in dry models such zonally asymmetric torques produce a pattern of tropical ascent that is well described by linear dynamics together with meridional shifts of the midlatitude jet here a series of idealizedmodels is used to understand the effects of moisture on the tropospheric responseto tropical and subtropical zonally asymmetric upper tropospheric torques the vertical motion response to a torque is shown to be amplified by the reduction in effective static stability that occurs in moist convecting atmospheres this amplification occurs only in precipitating regions and the magnitude of subsidence in nonprecipitating regions saturates when clear sky radiative cooling balances induced adiabatic warming for basic statesinwhichprecipitationisconcentrated inan intertropicalconvergence zone itcz most of the vertical motion response is thus confined within the basic state itcz even when the torqueisremotefromtheitcz tropicalandsubtropicaltorquesperturbtheextratropicalbarocliniceddyfield and the convectively coupled equatorial wave field resulting changes in momentum flux convergence by transient eddies induce secondary meridional overturning circulations that modify the zonal mean response to a torque the net effect allows tropical torques to merge a double itcz into a single equatorial itcz the response of tropical transient eddies is highly sensitive to the representation of convection so the zonal mean response to a torque is similarly sensitive even when the torque is located in the subtropics

on the three dimensional propagation of stationary waves abstract a locally applicable nonzonally averaged conservation relation is derived for quasi geostrophic stationary waves on a zonal flow a generalization of the eliassen palm relation the flux which appears in this relation constitutes it is argued a useful diagnostic of the three dimensional propagation of stationary wave activity this is illustrated by application to a simple theoretical model of a forced rossby wave train and to a northern hemisphere winter climatology results of the latter procedure suggest that the major forcing of the stationary wave field derives from the orographic effects of the tibetan plateau and from nonorographic effects diabatic heating and or interaction with transient eddies in the western north atlantic and north pacific oceans and siberia no evidence is found in the data for wave trains of tropical origin forcing by the orographic effects of the rocky mountains seems to be of secondary importance

lithosphere dynamics and tectono stratigraphic evolution of the mesozoic betic rifted margin southeastern spain abstract quantitative subsidence analysis demonstrates that mesozoic sediments in the eastern betic cordilleras have been deposited on a thermally subsiding rifted margin the dynamics of rifting are related to regional trans tension in the atlantic realm modelling of this phase of rifting at the southern iberian margin shows that the associated stretching of the lithosphere significantly altered its geometrical and mechanical structure and exerted a major control on subsequent convergence tectonics the mesozoic stretching led to the formation of a ramp at the margin due to strong lateral variations in the effective elastic thickness eet of the lithosphere and the thickness of the crust in a direction perpendicular to the margin the existence of a ramp structure in the late mesozoic at the iberian margin which is also supported by stratigraphic and structural data is important for the style of subsequent deformation of the lithosphere in late cretaceous tertiary times the lateral variations in eet inferred from forward modelling of rifted margin stratigraphy could explain the observed multiple collapse of the betic margin and the partitioning of deformation between the converging units involved in the betic orogeny modelling of depth dependent palaeo rheological profiles of the margin shows that the mechanical properties of the lithosphere after stretching differed distinctly from those before stretching lithospheric deformation in the betic cordilleras during the tertiary orogeny seems therefore to be largely controlled by the previous rifting phase a comparison of the palaeo and present day rheologies in terms of estimates for eet during late cretaceous and present times indicates that the mechanical properties of the lithosphere underlying the betic orogen were also affected by rifting during late oligocene aquitanian times this phase of rifting is coeval with extension in the valencia trough the gulf of lions and the west european rift system which supports a causal relation with regional lithospheric processes the lateral and spatial variations in thermo mechanical properties of the lithosphere underlying the betics therefore reflect the dynamics of lithospheric extension on a larger scale

detachment faulting and the evolution of passive continental margins major detachment faults play a key role in the lithospheric extension process in the basin and range province and may also be important in other continental extension terranes such detachment faulting leads to an inherent asymmetry of extensional structure and of uplift subsidence patterns detachment models developed for the formation of metamorphic core complexes can also be applied to the formation of passive continental margins we therefore suggest the existence of upper plate and lower plate passive margins these give rise to a complementary asymmetry of opposing margins after continental breakup transfer faults offset marginal features and allow margins to switch from upper plate to lower plate characteristics along strike

improvement of orographic gravity wave parameterization using a mesoscale gravity wave model abstract parameterization of gravity waves due to subgrid scale orography is now included in most existing large scale models of the atmosphere parameterization schemes however have so far been evaluated mainly in view of the overall performance of the large scale models this may lead to an inappropriate assessment of the schemes since errors from various sources may interact with one another to avoid this situation an approach is taken in which a numerical model that explicitly resolves gravity waves is used to evaluate the performance of the schemes for this purpose a mesoscale two dimensional nonlinear anelastic nonhydrostatic model is developed and used to numerically simulate gravity waves for a variety of orographic conditions regarding a subdomain of the mesoseale model as the horizontal grid interval of a large scale model two vertical profiles of gravity wave drag are compared one for the subdomain averaged values of the drag simulated by the mesoseale model and the other for the drag c

results of ultra low frequency magnetic field measurements during the guam earthquake of 8 august 1993 we report the results of measurements of ultra low frequency magnetic noise during a large earthquake ms 7 1 at guam of 8 august 1993 depth 60 km the ulf observing system is located in the guam island about 65 km from the epicenter several distinct features of this analysis are summarized 1 we have proposed rather sophisticated statistical analyses monthly mean standard deviation in order to estimate the wave intensity and polarization i e ratio z h 2 a comparison between the ulf wave activity and kp is useful in distinguishing between the space geomagnetic pulsations and non space emissions 3 then the use of the ratio z h is found to be of essential importance in discrimating the emissions presumably of seismic origin from space plasma waves 4 the statistical analysis of the temporal evolution of this ratio has yielded that it shows a broad maximum only about one month before the earthquake and this suggests that the emissions during this period are very likely to be magnetic precursors 5 the temporal variation of z component is similar to that for the loma prieta earthquake such that it shows a broad maximum ten days two weeks before the earthquake and another increase a few days before the earthquake 6 the emissions presumably associated with the earthquake are of noise like nature and their main frequency is 0 02 0 05 hz with maximum intensity 0 1 nt

a finite difference technique to incorporate spatial variations in rigidity and planar faults into 3 d models for lithospheric flexure summary we present a finite difference formulation for 3 d elastic flexure of the lithosphere which is solved by a direct matrix method to incorporate the effect of spatial variations in rigidity additional terms for the bi harmonic 3 d flexure equation have been derived from a variational displacement formulation as used in finite element methods additionally planar faults are treated as discontinuities these are implemented by an additional degree of freedom for fault heave and a coupled continuum equation for zero differential tilting across the fault the 3 d finite difference results have been tested for line loads point loads and disc loads by analytical solutions and for spatial variation in effective elastic thickness eet by 2 d finite difference solutions fault related flexure patterns are compared to the 2 d analytical broken plate model developed by vening meinesz 1950 we subsequently apply the 3 d fault model to investigate fault controlled 3 d basement geometries in lake tanganyika east africa we show that our model is capable of predicting 3 d basement geometries characteristically observed in rifted basins the modelling results indicate that fault controlled upper crustal flexure patterns are associated with low values for eet a comparison with regional scale model studies showing a superposition of high eet flexure effects supports a multilayered rheological control on continental rifting

low frequency magnetic field measurements near the epicenter of the ms 7 1 loma prieta earthquake the authors report the results of measurements of low frequency magnetic noise by two independent monitoring systems prior to the occurrence of the m sub s 7 1 loma prieta earthquake of 17 october 1989 their measurements cover 25 narrow frequency bands in the more than six decade frequency range 0 01 hz 32 khz with a time resolution varying from a half hour in the ulf range 0 01 10 hz to one second in the elf vlf range 10 hz 32 khz the ulf system is located near corralitos about 7 km from the epicenter the elf vlf system is located on the stanford campus about 52 km from the epicenter analysis of the elf vlf system is located on the stanford campus about 52 km from the epicenter analysis of the elf vlf data has revealed no precursor activity that they can identify at this time however the ulf data have some distinctive and anomalous features first a narrow band signal appeared in the range 0 05 0 2 hz around september 12 and persisted until the appearance of the second anomalous feature which consisted of a substantial increase in the noise background starting on 5 october and covering almost the entire frequency range of the ulf system third there was an anomalousmore dip in the noise background in the range 0 2 5 hz starting one day ahead of the earthquake finally and perhaps most compelling there was an increase to an exceptionally high level of activity in the range 0 01 0 5 hz starting approximately three hours before the earthquake there do not appear to have been any magnetic field fluctuations originating in the upper atmosphere that can account for this increase further while the systems are sensitive to motion seismic measurements indicate that there were no significant shocks preceding the quake thus the various anomalous features in the data and in particular the large amplitude increase in activity starting three hours before the quake may have been magnetic precursors less

experimental study on characteristics of surface potential and current induced by stress on coal mine sandstone roof abstract rocks generate voltage and current when subjected to load hence the study of their characteristics is critical to the prevention and management of mine dynamic disasters and their secondary impacts to investigate the characteristics of surface potential and current induced by stress on coal mine sandstone roof an experimental scheme for determining the mechanical electrical characteristics of rocks is constructed the aforementioned system tests the evolution rules of current and voltage generated by the coal mine sandstone roof at different loading rates the formation mechanism and coupling rules with mechanical properties of sandstone are also analysed experimental results show that although loading rates may differ the variations of pressure stimulated current psc and pressure stimulated voltage psv curves are similar throughout the loading process the psc is divided into three stages rapid growth slow growth and peak on the other hand the psv curve exhibits a double peak characteristic the loading rate changes the current and voltage growth rates and peak values when combined with mechanical properties it can be observed that the psc is related to the effective elastic modulus whereas the psv is related to micro crack and macro crack events in rocks the current and voltage generated by the coal mine sandstone roof subjected to load are consistent with stress the mechanical electrical properties of sandstone indicate that the change processes in the psc and psv result from the coupling effects of various mechanisms in the compaction stage these are mainly caused by the piezoelectric effect of sandstone in the elastic plastic deformation stage they are primarily generated by the electric dipoles formed by micro cracks in the sandstone fracture deformation stage the change processes are mainly caused by the crack tip discharge this study provide an experimental basis and practical results that reflect the microscale process and electrical precursors of sandstone fracturing

results of ulf magnetic field measurements near the epicenters of the spitak ms 6 9 and loma prieta ms 7 1 earthquakes comparative analysis the characteristics of the ulf magnetic field emissions measured at two magnetic observatories in the republic of georgia prior to and after the ms 6 9 earthquake that occurred near spitak armenia on december 7 1988 are compared with the apparently similar emissions associated with the ms 7 1 earthquake that occurred near loma prieta california on october 17 1989 the main features of the spitak measurements according to observations made at the dusheti station 128 km to the spitak epicenter as compared with the loma prieta measurements which were made at corralitos california 7 km to the loma prieta epicenter are the following 1 the intensity of ulf background activity started growing 3 to 5 days before the spitak earthquake whereas the corresponding increase in activity began 12 days before the loma prieta earthquake 2 a substantial ulf emission burst was recorded at dusheti starting 4 hours prior to the main shock a similar large burst of ulf activity commenced 3 hours before the loma prieta event and continued until the occurrence of the main shock 3 ulf activity remained high for about two weeks after the spitak earthquake and for several months after the loma prieta earthquake 4 ulf noise bursts were observed 1 to 6 hours before powerful aftershocks at spitak during the period of enhanced activity but there was no conclusive link between the ulf noise at corralitos and the after shocks a major difference in the ulf activity preceding the two earthquakes is a difference in amplitude 0 2 nt at spitak and 5 nt at loma prieta but this is easily explained as being caused by the different distances of the observation stations from the epicenters

geomagnetic variations possibly associated with the pisco earthquake on 15 august 2007 peru abstract on 15 august 2007 pisco earthquake magnitude 8 0 hit the central coast of peru near the magdas ancon anc station geomagnetic data from anc and other reference stations have been analyzed to detect any signature related to this great earthquake results indicate the presence of annual geomagnetic variations in the vertical component at anc and huancayo hua stations in the vicinity of the epicenter of pisco earthquake these variations have a quasi sinusoidal waveform with amplitudes of about 10 and 5 nt for anc and hua stations respectively they appeared clearly during the period preceding the onset of the pisco earthquake especially at anc station by using hua eusebio eus and kourou kou as reference stations in the vicinity and away from the epicenter of pisco earthquake a clear disappearance of the diurnal variation of the vertical component was observed at anc station during the day of earthquake moreover the pisco earthquake and another earthquake on 29 march 2008 near anc station were found to occur concurrently with the depressions in the polarization ratio z h of pc 3 10 45 s amplitude such anomalous variations appear to be a result of changes in the crustal stress field and the lithospheric conductivity in the studied region

seismic profiling the continental lithosphere deep seismic reflection profiling is successfully being used worldwide to study the structure of the continental crust1 7 the moist8 profile recorded by birps british institutions reflection profiling syndicate was the first to show that the structure of the upper mantle could also be imaged given a powerful source and long recording times birps has recently acquired an ultra deep seismic reflection line drum deep reflections from the upper mantle the drum line was designed specifically to investigate the reflectivity of the lower continental lithosphere and was therefore recorded to a two way time twt of 30 s giving a depth of penetration into the lithosphere of 110 km this profile has now revealed strong reflections which are unequivocally from the lower lithosphere well below the base of the crust and which are as far as we are aware the deepest and most continuous structures imaged in the upper mantle by multi channel seismic reflection profiling

generation of ulf electromagnetic emissions by microfracturing microfracturing electrification is discussed as a possible explanation of ulf electromagnetic emissions observed before and after earthquakes using a space time simple model of microfracture progression it is possible to compare theoretical results and observed results with special reference to the intensity spectrum and temporal development of ulf magnetic field variations

frictional discharge plasma and seismo electromagnetic phenomena abstract although several mechanisms of precursory electromagnetic emissions of earthquakes have been proposed there has been no in situ observation of electromagnetic phenomena occurring at the frictional contacts during rock frictions from an experiment simulating the motion of an asperity on a fault surface we report the generation of photon emissions around frictional contacts between natural rock minerals spectroscopic analysis clarified that the photon emissions are caused by dielectric breakdown of ambient gases electric discharge plasma due to frictional electrification the plasmas were found to occur under normal stress of 4 mpa and sliding speed of 10 2 m s this indicates that plasma generations do not require high normal stresses needed to fracture rocks and sliding speeds as high as seismic rates 1 m s thus frictional discharges could occur at microscopic asperities at the onset of the slips of earthquakes and might be one of the sources of the seismo electromagnetic emission

seismomagnetic effect generated by the october 1989 ml 7 1 loma prieta california earthquake a differentially connected array of proton magnetometers operated within the epicentral region of the october 18 1989 ml 7 1 loma prieta earthquake for 12 years from 1974 to 1986 the closest magnetometer station was located 7 3 km from the epicenter of the earthquake and within 3 km of the site where anomalous ulf magnetic noise measurements were observed following the earthquake the magnetometers were reinstalled with sensors replaced in the original undisturbed sensor holders comparison of pre 1986 total intensity magnetic field data with data obtained during the months following the earthquake indicate local offsets of about 1 nt may have been generated at stations nearest the epicenter tests on other continuous differenced data from 1983 to present indicate that offsets determined could be biased by as much as 0 7 nt the offsets can be approximately fit with a simple seismomagnetic model of the earthquake for which 1 9 m of right lateral and 1 3 m of dip slip southwest side up occurred on a fault patch between 6 km and 18 km deep and 45 km long the total rock magnetization is assumed to be 1 5 a m since the offset has persisted following the earthquake an alternate explanation in terms of electokinetic effects is unlikely even though transient ground water flow occurred following the earthquake comparison of pre 1986 and similar post seismic total magnetic field noise does not indicate any change caused by aliasing of ulf 0 01 hz 10 hz magnetic noise in the vicinity of the loma prieta earthquake

ulf electromagnetic precursors for an earthquake at biak indonesia on february 17 1996 ulf electromagnetic emissions associated with a large earthquake occurred at biak island indonesia at 5h 59m ut on february 17 1996 magnitude mw 8 2 and depth 20 km from usgs catalog have been investigated on the basis of ulf magnetic observations at two stations biak and darwin in australia about 1 200 km apart though a simple analysis of magnetic field intensity horizontal and vertical magnetic field components at both stations was found to be closely correlated with geomagnetic kp activity a detailed analysis of the difference of h and z components at the two stations the polarization analysis z h and fractal analysis frequency spectrum slope at these two stations has yielded that the ulf emissions in the frequency range from 5 mhz to 30 mhz about 1 5 1 0 months before the quake are likely to be a precursory signature of the quake with its intensity on the order of 0 2 0 3 nt

normal vs strike slip faulting during rift development in east africa the malawi rift kinematic analysis of neogene and quaternary faults demonstrates that the direction of extension in the malawi rift rotated from east northeast to southeast rift development commenced with the formation of half grabens bounded by northwest north and northeast striking normal faults owing to slightly oblique rifting the northwest striking faults in the northernmost rift segment show a small dextral oblique slip component whereas north and northeast oriented faults in the central part of the rift display a sinistral oblique slip component this first event resulted in block faulting and basin subsidence which is largely responsible for the present day basin morphology of lake malawi a major change in fault kinematics occurred because of rotation of the extension direction and permutation of the principal compressive and intermediate axes the structural pattern inherited from the first rifting phase was no longer suitably oriented to accommodate extensional deformation and strike slip faulting assumed a major role the strike slip regime amplified uplift of basement ridges within the rift in regions of local transpression but it also created alluvial basins because of local transtension this new kinematic style is compatible with the recent seismicity older faults that show mainly the first deformational increment are restricted to the outermost parts of the rift toward the center the faults depict an increase in strike slip components of movement suggesting deformation propagation toward the rift center which results in a narrowing of the active rift environments with time

regional stress field as determined from electromagnetic radiation in a tunnel abstract the paper presents the results of electromagnetic radiation emr measurements in the feuerberg tunnel in southwest germany emr is associated with small scale fracturing processes the measured numbers of emr impulses are shown to be proportional to shear stresses from the correlation of emr and shear stresses along the long axis of the tunnel orientations and magnitudes of the horizontal principal stresses are determined the major horizontal principal stress is 3 6 0 3 mpa and has an azimuth of 143 6 the minor principal horizontal stress is 2 1 0 3 mpa zones in the tunnel are located where low shear stresses occur because vertical overburden and horizontal stresses are equal in these zones also minimum radiation was detected a possible stress accumulation close to a fault is suggested by higher emr values in a part of the tunnel orientations and magnitudes of the horizontal principal stresses which are derived from the measurements of emr correlate well with conventional stress measurements it is suggested that the cross section measuring method described in the study is used to determine regional stress fields as well as to investigate endangered zones with high stresses in underground facilities which may be critical with regard to stability

the relationship between plate curvature and elastic plate thickness a study of the peru chile trench the age of the nazca plate where it enters the peru and northern chile trenches varies from 30 ma in the north to 45 ma in the south as its dip beneath the south american continent steepens from 13 to 30 if the elastic thickness te of oceanic lithosphere depends only on its age and therefore thermal state we would expect that te determined from fitting the flexure of the lithosphere over the outer rise as revealed in the depth geoid and gravity anomalies would increase from the peru trench in the north to the northern chile trench further south we find that the opposite is true the lithosphere appears suffer outboard of the peru trench than it does offshore chile to explain deflections of the lithosphere seaward of peru the isotherm controlling the elastic ductile transition must be near 800 c providing the thermal structure of the plate is that predicted by the standard thermal plate model because the decrease in plate stiffness to the south is correlated with an increase of plate curvature over the outer rise and outer trench wall we interpret our result in terms of inelastic yielding of the oceanic lithosphere when bent to high strains the magnitude of the reduction in strength however suggests that the standard oceanic yield strength envelope underestimates the amount of failure for lithosphere bent to high strains unless the stress field off northern chile is characterized by 100 mpa level tension the more highly bent segment of subducting lithosphere at this trench also dips at a steeper angle at greater depth beneath the continent but detailed analysis of plate geometry does not support a relationship between slab dip as determined by earthquake hypocenters and elastic behavior over the outer rise

study of directivity effect on electromagnetic emissions in the hf band as earthquake precursors preliminary results on field observations abstract this work focuses on the use of electromagnetic emissions em in the hf band as a warning event for earthquakes em at hf components 41 mhz and 46 mhz were monitored and recorded from eight field stations in greece and correlated with seismological events directivity effect raised since em emissions at specific station locations were correlated to earthquake events from prescribed regions em recordings during 1999 were used and by visual inspection were associated to most of the earthquake events greater than 5r using these observations a novel algorithm based on the ratio of short term to long term signal average together with a prediction rules set derived from 1999 s em emissions study were developed to combine results from several field stations performance of the system was promising but was dependent on the geographic area of interest overall performance for earthquakes events of magnitude greater than 5 7 r was 75 of seismic events were correctly predicted by em activity while 25 were not predicted

theory of time dependent rupture in the earth at a velocity x which is a well defined function of k this propagation is stable and quasi static and is referred to as subcritical crack growth we shall use the terms stable quasistatic and subcritical to mean propagation at velocities much less than the sonic velocities of the medium this behavior results from stress induced corrosion at the crack tip the principal corrodent for the present application being h20 this behavior has been firmly established in the laboratory for mode i tensile cracks in a wide variety of materials ineluding silicates and silicate glasses see cholz 1968a 1972a martin 1972 wiederhorn and bolz 1970 atkinson 1979 lawn and wilshaw 1975 knott 1973 the form of the relationship between k and x does not vary significantly with the material only the parameters in the law vary as an example we show in figure 1 data on subcritical crack growth in quartz after atkinson 1979 the empirical relationship is found to take the form