frictional discharge at fault asperities origin of fractal seismo electromagnetic radiation abstract to investigate the relation between the rock friction and the fractal electromagnetic radiation before the main shock of earthquakes we conducted a friction experiment simulating the motion of an asperity on a fault plane and observed photon emissions due to electric discharge by dielectric breakdown of ambient gases from friction contacts between rock minerals this indicates that frictional discharges plasma generations could occur locally at microscopic asperities on fault surfaces from concepts on the fractal size distribution and temporal evolution of fault asperities the frictional discharge occurring at asperities on the fault plane can be one of origins of the fractal electromagnetic radiation benioff electromagnetic radiation prior to earthquakes

ionospheric disturbances of the 2007 bengkulu and the 2005 nias earthquakes sumatra observed with a regional gps network 1 we studied ionospheric disturbances associated with the two large earthquakes in sumatra indonesia namely the 2007 bengkulu and the 2005 nias earthquakes by measuring the total electron contents tec using a regional network of global positioning system gps receivers we first focus on coseismic ionospheric disturbances cids of the bengkulu earthquake mw 8 5 they appeared 11 16 min after the earthquake and propagated northward as fast as 0 7 km s consistent with the sound speed at the ionospheric f layer height resonant oscillation of tec with a frequency of 5 mhz continued for at least 30 min after the earthquake the largest aftershock mw 7 9 also showed clear cids similar to the main shock a cid propagating with the rayleigh wave velocity was not observed possibly because the station distribution did not favor the radiation pattern of the surface waves this earthquake which occurred during a period of quiet geomagnetic activity also showed clear preseismic tec anomalies similar to those before the 2011 tohoku oki earthquake the positive and negative anomalies started 30 60 min before the earthquake to the north and the south of the fault region respectively on the other hand we did not find any long term tec anomalies within 4 5d ays before the earthquake co and preseismic ionospheric anomalies of the 2005 nias earthquake mw 8 6 were however masked by strong plasma bubble signatures and we could not even discuss the presence or absence of cids and preseismic tec changes for this earthquake

distribution and characteristics of natural gas hydrates in the shenhu sea area south china sea abstract structure type gas composition and cage occupancy are important gas hydrate characteristics which play an important role in calculating gas hydrate stability and estimating the amount of global hydrate bound methane china conducted the fourth gas hydrate drilling campaign gmgs4 in the shenhu sea area ssa of the south china sea in 2016 during which comprehensive logging while drilling lwd data and natural gas hydrate samples were obtained the lwd data shows high electrical resistivity and high sound velocity at various depth indicating the occurrence of gas hydrate in this area coexistence of structure i si and structure ii sii gas hydrates in the south china sea was confirmed for the first time by using raman spectra analysis the methane cage occupancies of large cages and small cages in si hydrate are 0 95 and 0 96 respectively the hydration number of si hydrate is 6 03 gas composition analysis shows that methane 98 7 is the dominate gas with small amount of heavier hydrocarbon gases ethane 0 006 0 976 propane 0 033 0 216 isobutane 0 004 0 047 and other non hydrocarbon gases carbon dioxide

in situ benthic fluxes from an intermittently active mud volcano at the costa rica convergent margin along the erosive convergent margin off costa rica a large number of mound shaped structures exist built by mud diapirism or mud volcanism one of these mound 12 an intermittently active mud volcano currently emits large amounts of aqueous dissolved species and water chemosynthetic vent communities authigenic carbonates and methane plumes in the water column are manifestations of that activity benthic flux measurements were obtained by a video guided benthic chamber lander bcl deployed at a vent site located in the most active part of mound 12 the lander was equipped with 4 independent chambers covering adjacent areas of the seafloor benthic fluxes were recorded by repeated sampling of the enclosed bottom waters while the underlying surface sediments were recovered with the lander after a deployment time of one day one of the chambers was placed directly in the centre of an active vent marked by the occurrence of a bacterial mat while the other chambers were located at the fringe of the same vent system at a lateral distance of only 40 cm a transport reaction model was developed and applied to describe the concentration profiles in the pore water of the recovered surface sediments and the temporal evolution of the enclosed bottom water repeated model runs revealed that the best fit to the pore water and benthic chamber data is obtained with a flow velocity of 10 cm yr 1 at the centre of the vent the flux rates to the bottom water are strongly modified by the benthic turnover benthic filter the methane flux from below at the bacterial mat site is as high as 1032 mol cm 2 yr 1 out of which 588 mol cm 2 yr 1 is oxidised in the surface sediments by microbial consortia using sulphate as terminal electron acceptor and 440 mol cm 2 yr 1 are seeping into the overlaying bottom water sulphide is transported to the surface by ascending fluids 238 mol cm 2 yr 1 and is formed within the surface sediment by the anaerobic oxidation of methane aom 588 mol cm 2 yr 1 however sulphide is not released into the bottom water but completely oxidized by oxygen and nitrate at the sediment water interface the oxygen and nitrate fluxes into the sediment are high 781 and 700 mol cm 2 yr 1 respectively and are mainly driven by the microbial oxidation of sulphide benthic fluxes were much lower in the other chambers placed in the fringe of the vent system thus methane and oxygen fluxes of only 28 and 89 mol cm 2 yr 1 respectively were recorded in one of these chambers our study shows that the aerobic oxidation of methane is much less efficient than the anaerobic oxidation of methane so that methane which is not oxidized within the sediment by aom is almost completely released into the bottom water hence anaerobic rather than aerobic methane oxidation plays the major role in the regulation of benthic methane fluxes moreover we demonstrate that methane and oxygen fluxes at cold vent sites may vary up to 3 orders of magnitude over a lateral distance of only 40 cm indicating an extreme focussing of fluid flow and methane release at the seafloor

a statistical investigation of preearthquake ionospheric anomaly 1 empirical evidence of the preearthquake ionospheric anomalies peias is reported by statistically investigating the relationship between variations of the plasma frequency at the ionospheric f2 peak fof2 and 184 earthquakes with magnitude m 5 0 during 1994 1999 in the taiwan area the peia defined as the abnormal decrease more than about 25 in the ionospheric fof2 during the afternoon period 1200 1800 lt significantly occurs within 5 days before the earthquakes moreover the odds of earthquakes with peia increase with the earthquake magnitude but decrease with the distance from the epicenter to the ionosonde station these results indicate that the peia is energy related

evidence of electro seismic phenomena abstract ground based observations of electromagnetic precursors to large earthquakes have been reported in japan iran chile greece and the soviet union ionospheric disturbances measured by soviet satellites have been claimed to be seismic precursors in addition observations of very low frequency anomalies measured by geos satellites have been reported by french researchers to confirm reports of electromagnetic precursors to earthquakes a series of low frequency broadband radio frequency receivers were deployed along the san andreas fault system this system of monitors has recorded electromagnetic anomalies occurring just before earthquakes between 1983 and 1986 these anomalies are of two types and are presumably caused by separate effects both of which may be related to stress induced changes in the crust just before fault rupture the first of these types of anomalies appears to be an interruption in the propagation of radio waves radio depressions lasting for many hours before an earthquake the second type is similar to those in previously published reports and consists of short duration broadband radio emissions given the results reported by other researchers and the results from our own experiments we believe that electromagnetic data may be useful as a tool for predicting earthquakes

grain boundary graphite in rocks and implications for high electrical conductivity in the lower crust the origin of zones of high electrical conductivity in the lower continental crust is a long standing mystery possible explanations include the presence of brines1 2 partial melt3 serpentine4 and graphite5 when discussing the occurrence of graphite in the crust many petrologists have considered phase relations as they would have existed at the peak of metamorphism or during igneous emplacement6 10 here we show that a fine film of graphite is present on the grain boundaries in three rocks from the laramie anorthosite complex in two of these rocks graphite was stable during igneous crystallization but in the other it was not we maintain that in all of the rocks the grain boundary graphite precipitated from a co2 rich fluid during cooling the chemical processes that produced the grain boundary graphite in these rocks are likely to operate in many lower crustal rocks we therefore contend that because the films we observe are capable of producing the high conductivity that is seen in the lower crust grain boundary graphite should be considered as a possible cause for some conductivity anomalies

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

stable isotope analyses of tooth enamel carbonate of large herbivores from the tugen hills deposits palaeoenvironmental context of the earliest kenyan hominids abstract understanding shifts in past climatic and environmental conditions are crucial for throwing light on human evolution available reconstructions of the palaeoecology of faunal and floral assemblages indicate that the earliest kenyan hominids including orrorin tugenensis are associated with forest landscapes in this study we present stable isotope data of tooth enamel carbonate of large herbivores associated with these hominids in order further to evaluate their environmental context fossil teeth were sampled in the lukeino formation 6 1 5 7 ma late miocene and the mabaget formation 5 3 4 5 ma early pliocene at the foot of the tugen hills great rift valley despite chemical changes in fossil enamel preservation of the palaeoenvironmental signals is supported by the difference in 18 o between hippos and terrestrial fauna moreover the giraffid specimen from the mabaget formation exhibits one of the highest 18 o values as expected for a drought tolerant animal the 13 c of large herbivores indicates that the earliest kenyan hominids inhabited a mixed c 3 c 4 environment as did ardipithecus ethiopia and sahelanthropus chad two early putative hominids the tugen hills might have been a wooded grassland with patches of woodland there is no record of closed canopy forest at the time of deposition we emphasize differences in food habits among herbivore groups deinotheres nearly all elephantids and the giraffid individual had a c 3 diet which reflected browsing behaviour the intake of c 4 plants prevailed for equids and gomphotheres and was consistent with grazing habits most hippos and suids were mixed c 3 c 4 feeders and consequently were generalist herbivores bovids and rhinos had a diet ranging from c 3 to c 4 plants variations in 13 c and 18 o among faunal assemblages suggest changes in local climate and vegetation moister conditions likely occurred in the early pliocene and the latest miocene ca 5 7 ma than before the c 3 plant biomass would have increased in the latest miocene there were probably denser stands of trees within the depositional environment during the early pliocene than in the late miocene which is consistent with palaeontological studies

investigations of tectonomagnetic phenomena in china abstract the tangshan earthquake m 7 8 28 july 1976 occurred in north china where there is relatively dense network of geomagnetic observations before the earthquake there were anomalies of 8 10 nt in the total intensity of the geomagnetic field at ninghe and dongtietou sites 50 90 km from the epicenter and also in the beijing survey area anomalous changes in the vertical component of the geomagnetic field before the earthquake amounted to 12 nt at tangshan site and 10 nt at changli station which was 80 km from the epicenter there were also anomalous short period geomagnetic variations before and after the earthquake to investigate tectonomagnetic effects we measured the magnetic field at 17 sites near an underground nuclear test in 1983 in west china the total field changed by 2 nt at the time of the explosion and there were changes of 1 2 nt before and after the explosion we have also measured the magnetic field around the miyun reservoir during 1983 1987 and observed a correlation between geomagnetic changes and variations of water level in the reservoir

exploring the relationship between soil degassing and seismic activity by continuous radon monitoring in the longitudinal valley of eastern taiwan abstract donghua dh continuous soil gas monitoring station is located on the suture zone in eastern taiwan the variations in radon concentration are synchronized to variations in carbon dioxide co 2 which is considered as the companion gas for radon rn results reveal that semi diurnal variation of soil gas probably generated by the solar tide effect achieve values of 500 bq m 3 for rn and 0 4 for co 2 the variations exceeding the threshold by statistical analysis can be used to identify events associated with geodynamic processes such as earthquakes a significant increase in soil gas concentrations was recorded 2 months before the rueisuei earthquake m l 6 4 october 31 2013 and recurrent anomalies were observed 3 weeks before the fanglin earthquake m l 5 9 may 21 2014 both earthquakes occurred in the longitudinal valley area of eastern taiwan this study suggests that longer periods of soil gas anomalies are positively correlated with impending earthquake of larger magnitude from the high precision gps data showed an appreciable decrease in extension rate was also observed approximately 4 months before the rueisuei earthquake it is worthy to have a continuous monitoring on multiple parameters soil radon carbon dioxide atmospheric pressure humidity temperature and precipitation at dh station

free gas and gas hydrates from the sea of marmara turkey chemical and structural characterization gas hydrates and gas bubbles were collected during the marnaut cruise may june 2007 in the sea of marmara along the north anatolian fault system turkey gas hydrates were sampled in the western part of the sea of marmara on the western high and three gas bubble samples were recovered on the western high the central high center part of the sea of marmara and in the cinarcik basin eastern part of the sea of marmara methane is the major component of hydrates 66 1 but heavier gases such as c2 c3 and i c4 are also present in relatively high concentration the methane contained within gas hydrate is clearly thermogenic as evidenced by a low c1 c2 c3 ratio of 3 3 and carbon and hydrogen isotopic data 13cch4 of 44 1 pdb and dch4 of 219 smow a similar signature is found for the associated gas bubbles c1 c2 c3 ratio of 24 4 13cch4 of 44 4 pdb which have the same composition as natural gas from k marmara af field gas bubbles from central high show also a thermogenic origin as evidenced by a c1 c2 c3 ratio of 137 and carbon and hydrogen isotopic data 13cch4 of 44 4 pdb and dch4 of 210 smow whereas those from the cinarcik basin have a primarily microbial origin c1 c2 c3 ratio of 16 600 13cch4 of 64 1 pdb uv raman spectroscopy reveals structure ii for gas hydrates with ch4 trapped in the small 512 and large 51264 cages and with c2h6 c3h8 and i c4h10 trapped in the large cages hydrate composition is in good agreement with equilibrium calculations which confirm the genetic link between the gas hydrate and gas bubbles at western high and the k marmara af offshore gas field located north of the western high we calculate the characteristics of the hydrate stability zone at western high and in the cinarcik basin using the csm gem computer program the base of the structure ii hydrate stability field is at about 100 m depth below the seafloor at the western high site whereas in the cinarcik basin p t conditions at the seafloor correspond to the uppermost range for structure i hydrate formation from microbial gas

anomalous pre seismic transmission of vhf band radio waves resulting from large earthquakes and its statistical relationship to magnitude of impending earthquakes summary to confirm the relationship between anomalous transmission of vhf band radio waves and impending earthquakes we designed a new data collection system and have documented the anomalous vhf band radio wave propagation beyond the line of sight prior to earthquakes since 2002 december in hokkaido northern japan anomalous vhf band radio waves were recorded before two large earthquakes the tokachi oki earthquake mj 8 0 mj magnitude defined by the japan meteorological agency on 2003 september 26 and the southern rumoi sub prefecture earthquake mj 6 1 on 2004 december 14 radio waves transmitted from a given fm radio station are considered to be scattered such that they could be received by an observation station beyond the line of sight a linear relationship was established between the logarithm of the total duration time of anomalous transmissions te and the magnitude m or maximum seismic intensity i of the impending earthquake for m4 m5 class earthquakes that occurred at depths of 48 54 km beneath the hidaka mountains in hokkaido in 2004 june and 2005 august similar linear relationships are also valid for earthquakes that occurred at different depths the relationship was shifted to longer te for shallower earthquakes and to shorter te for deeper ones numerous parameters seem to affect te including hypocenter depths and surface conditions of epicentral area i e sea or land this relationship is important because it means that pre seismic anomalous transmission of vhf band waves may be useful in predicting the size of an impending earthquake

gas hydrate characterization and grain scale imaging of recovered cores from the mount elbert gas hydrate stratigraphic test well alaska north slope abstract using cryogenic scanning electron microscopy csem powder x ray diffraction and gas chromatography methods we investigated the physical states grain characteristics gas composition and methane isotopic composition of two gas hydrate bearing sections of core recovered from the bpxa doe usgs mount elbert gas hydrate stratigraphic test well situated on the alaska north slope the well was continuously cored from 606 5 m to 760 1 m depth and sections investigated here were retrieved from 619 9 m and 661 0 m depth x ray analysis and imaging of the sediment phase in both sections shows it consists of a predominantly fine grained and well sorted quartz sand with lesser amounts of feldspar muscovite and minor clays cryogenic sem shows the gas hydrate phase forming primarily as a pore filling material between the sediment grains at approximately 70 75 saturation and more sporadically as thin veins typically several tens of microns in diameter pore throat diameters vary but commonly range 20 120 microns gas chromatography analyses of the hydrate forming gas show that it is comprised of mainly methane 99 9 indicating that the gas hydrate is structure i here we report on the distribution and articulation of the gas hydrate phase within the cores the grain morphology of the hydrate the composition of the sediment host and the composition of the hydrate forming gas

theory of electrokinetic effects occurring at the final stage in the preparation of a tectonic earthquake crustal deformation processes occur with relative rapidity when short term precursors appear at the final preparatory stage of a tectonic earthquake this paper contains calculations of crustal bulk strain before an earthquake based on the model of a rigid inclusion the data give initial conditions for the problem of fluid percolation in a two phase medium accompanied by electrokinetic effects the solution provides a description of systems of currents arising in the vicinity of the source region an analysis of this theoretical evidence yields information on the behaviour of short term precursors in telluric currents and the geomagnetic field

variation of the electrical resistivity of large rock samples with stress many experimental and theoretical efforts have been devoted to the study of the electrical properties of rocks e g brace et al 1965 madden 1982 parkhomenko 1982 yamazaki 1966 special attention has been paid to possible relationships between variations of mechanical stresses inside the rock and variations of its electrical properties in reference to a possible technique of predicting earthquakes raleigh et al 1977 these studies were generally performed on small decimeter sized samples but the complexity of the physical processes involved and the heterogeneity of rocks in the field make it necessary to try to get results from larger blocks with dimensions of several decimeters sobolev et al 1983 or of meters this study it also appears quite desirable to look for information on the electrical properties of rocks at different scales from a centimeter to a kilometer say to see if some scaling laws could be experimentally established these scaling laws would allow inference of electrical properties at a given scale from the knowledge of the electrical properties at a smaller scale madden 1976 scaling law methods seem to be promising in seismogenesis studies e g allegre et al 1984 turcotte 1986

geochemistry origin and deep water exploration potential of natural gases in the pearl river mouth and qiongdongnan basins south china sea more than 10 gas pools have been discovered since 1983 in the shallow water region of the pearl river mouth prm basin and the qiongdongnan qdn basin offshore south china sea gases produced from the qdn basin are characterized by high contents of benzene and toluene and relatively heavy 13c2 values 25 to 27 the associated condensates have a high abundance of bicadinanes and oleanane providing a good correlation with the coal bearing sequence of the oligocene yacheng formation in the basin in contrast the gases from the prm basin contain lower amounts of benzene and toluene and lighter 13c2 values 24 to 34 widely variable concentrations of bicadinane and oleanane were identifiied from the associated condensates which can be mostly correlated with the lower oligocene enping formation source rocks formed in a swamp to shallow lake environment oil cracked gases sourced from the eocene oil prone source rock may also provide some contribution to the prm basin gases the available geochemical data indicate that both the yacheng and enping formations contain mainly type iii and ii2 kerogens with dominant gas potential regional geological information indicates that the deep water regions of the two basins share the same hydrocarbon source sags with the shallow water areas and they developed massive sandstone reservoirs during the oligocene and miocene fluid flow modeling results show that the deep water regions were on the pathway of lateral migrating gases and the interpreted reservoirs in these zones have developed abundant seismic bright spots which may reflect the presence of gas the deep water regions of the offshore south china sea are believed to have great gas exploration potential

seismoionospheric gps total electron content anomalies observed before the 12 may 2008 mw7 9 wenchuan earthquake 1 the global ionospheric map gim is used to observe variations in the total electron content tec of the global positioning system gps associated with 35 m 6 0 earthquakes that occurred in china during the 10 year period of 1 may 1998 to 30 april 2008 the statistical result indicates that the gps tec above the epicenter often pronouncedly decreases on day 3 5 before 17 m 6 3 earthquakes the gps tec of the gim and electron density profiles probed by six microsatellites of formosat3 cosmic f3 c are further employed to simultaneously observe seismoionospheric anomalies during an mw7 9 earthquake near wenchuan china on 12 may 2008 it is found that gps tec above the forthcoming epicenter anomalously decreases in the afternoon period of day 6 4 and in the late evening period of day 3 before the earthquake but enhances in the afternoon of day 3 before the earthquake the spatial distributions of the anomalous and extreme reductions and enhancements indicate that the earthquake preparation area is about 1650 km and 2850 km from the epicenter in the latitudinal and longitudinal directions respectively the f3 c results further show that the ionospheric f2 peak electron density nmf2 and height hmf2 significantly decreases approximately 40 and descends about 50 80 km respectively when the gps tec anomalously reduces

mixed gas hydrate structures at the chapopote knoll southern gulf of mexico abstract in underwater hydrocarbon seepage environments gas hydrates are considered to play a significant role as shallow gas reservoirs and buffers for light hydrocarbon expulsion here we report on mixed hydrate structures from the chapopote knoll in the southern gulf of mexico and discuss several options on how a mixture of structure i si and structure ii sii gas hydrate may occur in nature locally resolving microscopic methods are needed to characterize the coexistence of different hydrate structures at geological hydrate deposits we used raman spectroscopy x ray diffraction and gas chromatography for our investigations gas hydrates were found within the matrix and pores of the asphalts extruded at the seafloor two of the three hydrate pieces investigated comprised only si formed mostly from methane in contrast one piece comprised an intimate mixture of both si and sii with sii representing ca 25 wt and si ca 75 wt of the hydrate present the two structures were closely associated within individual grain agglomerates the crystallites of sii were significantly larger than of si suggesting differences in the nucleation density or different crystallite ages the structural coexistence may be a result of one or more processes i de mixing into two hydrate structures during the growth from the gas phase which provides an additional degree of freedom for lowering the free energy in the system ii fractionated crystallization with a subsequently changing molecular composition iii crystallization from separated gas bubbles with different hydrocarbon compositions and water and iv partial transformation from sii to si after hydrate nucleation ceasing when a thermodynamically stable state was reached the presented work will affect future assessments of natural hydrate deposits at thermogenic hydrocarbon systems as it shows that both hydrate types i and ii can be present at a certain geological site and may provide a lingering strength to the system if conditions fall below the si stability limit this suggests that present worldwide hydrate occurrences are likely to be underestimated

methane formation at costa rica continental margin constraints for gas hydrate inventories and cross decollement fluid flow we present a numerical model study in order to quantify the effects of organic carbon poc degradation and fluid migration on methane and gas hydrate formation at odp site 1040 costa rica convergent margin various model runs show that poc degradation in upper plate sediments yields a potential for methane hydrate formation between 0 8 and 2 5 vol of pore space however observed chlorinity anomalies cannot be explained by the amount and the distribution pattern of gas hydrates moreover pore water profiles of ammonia do not match the observations setting up a moderate upward flow 0 03 cm yr 1 of methane enriched low chlorinity fluids induced by dewatering of oceanic plate sediments leads to a good approximation to measured pore water profiles thus enabling a precise estimate of poc degradation kinetics fluid flow has a strong impact on the location of the upper limit of the modeled gas hydrate occurrence zone ghoz and may increase the total amount of gas hydrate by more than 50 our best estimate of the amount of gas hydrate within the ghoz is on average 1 65 vol of pore space which corresponds to about 2 5 tg of methane per km trench within the frontal prism of slope sediments to comply with the fact that subducted pore waters are rich in sulfate and that there is striking evidence for fluid conduits at various depths we performed additional model runs where we simulated fluid flow by using a gauss type rate law allowing us to define distinct fluid sources we can demonstrate that combined methane production in the upper plate sediments and sulfate reduction at the top of the down going slab is sufficient to prevent the upward movement of the zone of anaerobic oxidation of methane aom to above the decollement at given upward advection rates steep pore water gradients along the plate boundary can be explained by lateral backflow within oceanic plate sediments on a long term in the order of at least some 100 000 years fluid flow along conduits is likely to occur at low rates with temporarily increased pulses all modeled runs are constrained by their compatibility to observed pore water profiles

chemical and structural characteristics of gas hydrates from the haima cold seeps in the qiongdongnan basin of the south china sea abstract crystalline structure cage occupancy and gas composition are important gas hydrate characteristics which can be used to calculate the gas hydrate s stability and to estimate the energy potential in may and october of 2015 a guangzhou marine geological survey team investigated two sites in the haima cold seeps in the qiongdongnan basin northern south china sea they recovered massive gas hydrate samples by conventional gravity coring after the shenhu sea area and dongsha sea area the qiongdongnan basin became a new area on the northern slope of the south china sea where gas hydrates have been found in order to reveal the structural and geochemical characteristics of the natural gas hydrates samples were analyzed by micro raman spectroscopy and x ray diffraction under ambient pressure and low temperature conditions the results indicate that the gas hydrate samples from the haima cold seeps are typical structure i hydrates with a hydration number of 6 12 6 19 in addition trace amounts of h2s trapped in the hydrate were identified based on its characteristic vibrational signature the gas composition and 13c ch4 of the hydrate bound gas samples were analyzed for gas source correlation all of the gas samples are dominated by methane with small amounts of ethane and propane and had relatively light 13c ch4 indicating that all of the hydrate bound gases are mixtures of biogenic and thermogenic gas the thermogenic gas is inferred to be mainly derived from the coal layers of the late miocene pliocene yacheng formation in the northern lingshui sag

monitoring resistivity change in parkfield california 1988 1995 continuous electric field measurements from 1988 1995 with a telluric array straddling the san andreas fault in parkfield california have been analyzed for changes in electrical resistivity associated with the four largest mb 4 0 local earthquakes and three larger but more distant california earthquakes 1989 loma prieta 1992 landers 1994 northridge treatment of the propagation of errors through the analysis process yields formal estimates of the uncertainties in the results and thus a definition of anomalous variations based on statistical confidence statistically significant variations of the telluric coefficients were associated with none of the four local earthquakes and none of the california earthquakes an obvious but mistaken conclusion from this disappointing result is that resistivity changes do not occur prior to earthquakes previous observations in both the field and laboratory have shown that they do occur a more likely explanation of the current result is that the telluric array is not sufficiently sensitive to resistivity changes associated with such small earthquakes the next parkfield earthquake while overdue should be of sufficient magnitude to test this explanation results from this experiment have shown the need for continuous redundant measurements in precursory monitoring studies

gas hydrate distributions in sediments of pockmarks from the nigerian margin results and interpretation from shallow drilling a joint research expedition between the french ifremer and the german marum was conducted in 2011 using the r v pourquoi pas to study gas hydrate distributions in a pockmark field 1141 1199 meters below sea surface at the continental margin of nigeria the sea floor drill rig mebo of marum was used to recover sediments as deep as 56 74 meters below seafloor the presence of gas hydrates in specific core sections was deduced from temperature anomalies recorded during continuous records of infrared thermal scanning and anomalies in pore water chloride concentrations in situ sediment temperature measurements showed elevated geothermal gradients of up to 258 c km in the center of the so called pockmark a which is up to 4 6 times higher than that in the background sediment 72 c km the gas hydrate distribution and thermal regime in the pockmark are largely controlled by the intensity periodicity and direction of fluid flow the joint interaction between fluid flow gas hydrate formation and dissolution and the thermal regime governs pockmark formation and evolution on the nigerian continental margin

geochemistry origin and accumulation of natural gases in the deepwater area of the qiongdongnan basin south china sea abstract the qiongdongnan basin south china sea has received huge thickness 12 km of tertiary quaternary sediments in the deepwater area to which great attention has been paid due to the recent discoveries of the ss22 1 and the ss17 2 commercial gas fields in the pliocene upper miocene submarine canyon system with water depth over 1300 m in this study the geochemistry origin and accumulation models of these gases were investigated the results reveal that the gases are predominated by hydrocarbon gases 98 99 by volume with the ratio of c 1 c 1 5 ranging from 0 92 to 0 94 and they are characterized by relatively heavy 13 c 1 36 8 to 39 4 and d ch4 values 144 to 147 similar to the thermogenic gases discovered in the shallow water area of the basin the c 5 7 light hydrocarbons associated with these gases are dominated by isoparaffins 35 65 implying an origin from higher plants for the associated condensates carbon isotopic compositions and high abundance of oleanane and presence of bicadinanes show close affinity with those from the yc13 1 gas field in the shallow water area all these geochemical characteristics correlate well with those found in the shales of the oligocene yacheng formation in the qiongdongnan basin the yacheng formation in the deepwater area has toc values in the range of 0 4 21 and contains type ii b iii gas prone kerogens indicating an excellent gas source rock the kinetic modeling results show that the 13 c 1 values of the gas generated from the yacheng source rock since 3 or 4 ma are well matched with those of the reservoir gases indicating that the gas pool is young and likely formed after 4 ma the geologic and geochemical data show that the mud diapirs and faults provide the main pathways for the upward migration of gases from the deep gas kitchen into the shallow normally pressured reservoirs and that the deep overpressure is the key driving force for the vertical and lateral migration of gas this gas migration pattern implies that the south low uplift and the no 2 fault zone near the deepwater area are also favorable for gas accumulation because they are located in the pathway of gas migration and therefore more attention should be paid to them in the future

electric potential changes prior to shear fracture in dry and saturated rocks electric potential changes before shear rupture were measured using darley dale sandstone quartz rich and icelandic basalt quartz free on both dry specimens and in the presence of pore fluid we find that electric potential changed markedly just prior to dynamic rupture in dry and saturated sandstones and saturated basalt but we did not detect precursory signals in dry basalt the absence of signals in dry basalt provides strong evidence that the piezoelectric effect and electrokinetic effect are dominant sources for precursory signals moreover we find that the amplitude of the precursory signals due to electrokinetic effect in saturated sandstone were as large as the coseismic signals we propose that this signal is caused by accelerating evolution of dilatancy as cracks grow in the rock before rupture resulting in water flow into the dilatant region with an electric current produced concurrently

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

precursory effects in the subionospheric vlf signals for the kobe earthquake abstract the subionospheric vlf omega signal transmitted from tsushima japan geographic coordinates 34 37 n 129 27 e was continuously received at inubo 35 42 n 140 52 e this data was analyzed during an 8 month period centered on the great hyogo ken nambu kobe earthquake m g 7 2 on 17 january 1995 the epicenter located inside of fresnel zone of the vlf path to clarify the possible effect we developed the special tt terminator time method of data processing which was useful for our short vlf path distance 1000 km we discovered a statistically significant change of tt characteristics which began a few days before the main shock and probably continued a few weeks after it as a transient oscillation with period 10 days by simple modelling it was shown that tt changes could be caused by the decrease of the vlf reflection height by 2 km the possible underlying mechanisms of the effect are not defined however an increase of the regular electric field due to radon exhalation before the earthquake or an intensification of planetary waves by seismically influenced atmospheric turbulence might be considered

temporal and spatial precursors in the ionospheric global positioning system gps total electron content observed before the 26 december 2004 m9 3 sumatra andaman earthquake 1 we report seismo ionospheric precursors of anomalous decreases in the total electron content tec appearing day 5 prior to an m9 3 earthquake the largest one in the last five decades which occurred in sumatra andaman indonesia on 26 december 2004 sequences of global ionosphere maps of the tec derived from worldwide ground based receivers of the global positioning system gps are used to statistically study the temporal and spatial precursors of the earthquake it was found that the temporal precursor of the gps tec around the epicenter was significantly reduced during the afternoon period on d 5 before the earthquake the spatial precursors prominently persistently and simultaneously appear around the epicenter and its conjugate areas of the sumatra andaman earthquake

time resolved study of charge generation and propagation in igneous rocks electrical resistivity changes ground potentials electromagnetic em and luminous signals preceding or accompanying earthquakes have been reported many times in addition to ground uplift and tilt and other parameters however no concept exists that would tie these diverse phenomena together into a physically coherent model using low to medium velocity impacts to measure electrical signals with microsecond time resolution it is observed that when gabbro and diorite cores are impacted at relatively low velocities 100 m s highly mobile charge carriers are generated in a small volume near the impact point they spread through the rocks causing electric potentials exceeding 400 mv em and light emission as the charge cloud spreads the rock becomes momentarily conductive when a granite block is impacted at higher velocity 1 5 km s the propagation of the p and s waves is registered through the transient piezoelectric response of quartz after the sound waves have passed the surface of the granite block becomes positively charged suggesting the same charge carriers as observed during the low velocity impact experiments expanding from within the bulk during the next 2 3 ms the surface potential oscillates indicating pulses of electrons injected from ground and contact electrodes the observations are consistent with positive holes e g defect electrons in the o2 sublattice traveling via the o 2p dominated valence band of the silicate minerals the positive holes propagate as charge clouds rather than as classical em waves before activation they lay dormant in form of electrically inactive positive hole pairs php chemically equivalent to peroxy links o3x oo xo3 with x si4 al3 etc phps are introduced into the minerals by way of hydroxyl o3x oh which all nominally anhydrous minerals incorporate when crystallizing in h2o laden environments the fact that positive holes can be activated by low energy impacts and their attendant sound waves suggests that they can also be activated in the crust by microfractures during the dilatancy phase depending on where in the stressed rock volume the charge carriers are activated they will form rapidly moving or fluctuating charge clouds that can account for earthquake related electrical signals and em emission wherever such charge clouds intersect the surface high fields are expected causing electric discharges and earthquake lights

earthquake prediction a critical review summary earthquake prediction research has been conducted for over 100 years with no obvious successes claims of breakthroughs have failed to withstand scrutiny extensive searches have failed to find reliable precursors theoretical work suggests that faulting is a non linear process which is highly sensitive to unmeasurably fine details of the state of the earth in a large volume not just in the immediate vicinity of the hypocentre any small earthquake thus has some probability of cascading into a large event reliable issuing of alarms of imminent large earthquakes appears to be effectively impossible key word earthquake prediction

variations of ionospheric total electron content during the chi chi earthquake on 20 september1999 ut 21 septemberin local time lt a large earthquake mw 7 7 struck central taiwan nearthe small town of chi chi the greatest plasma frequency in the ionosphere fof2 observed by the chung li ionosonde 25 0 n 121 2 e reveals three clear precur sors at 1 3 and 4 days prior to the earthquake this paper examines the ionospheric total electron content tec ob served by a network of the global positioning system gps receivers in taiwan area it is found that variations in fof2 and overhead tec recorded at chung li have a similar ten dency combining the data of the network of 13 gps re ceivers time and spatial variations of tec prior to the chi chi earthquake are examined results show that the equa torial anomaly crest moves equatorward and its tec value significantly decreases 1 3 and 4 days before the earth quake a comparison between the disturbed and reference previous 15 day median days confirms that tec decreases significantly around the epicenter in the afternoons of these days finally possible mechanisms are proposed and dis cussed

characterization of natural gas hydrate recovered from pearl river mouth basin in south china sea abstract china carried out a drilling campaign in the eastern part of the pearl river mouth prm basin and successfully obtained natural gas hydrate samples in 2013 laboratory based studies for the characteristics of gas hydrate were carried out on one of the hydrate bearing sediment sample the gas hydrate sample shows nodular occurrence with host matrix predominantly composed of silty sand and clay on the basis of the raman spectroscopic and x ray diffraction results the gas hydrate demonstrates a typical structure i si with cage occupancy of methane is more than 99 5 in large cage and 91 4 in small cage respectively corresponding to a hydration numbers of 5 90 by thermodynamic calculation the molecular compositions of hydrate bound gas suggest that the guest molecules are predominantly methane 99 9 with trace amount of ethane 0 04 and propane 0 01 the isotopic analysis indicates that the methane of hydrate bound gas of the studied drilling well in prm basin is a typical microbial origin

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

seismic electromagnetic signals sems explained by a simulation experiment using electromagnetic waves abstract the propagation characteristics of seismic electromagnetic signals sems both at an ultra low frequency ulf and at a very low frequency vlf are discussed based on a model experiment of propagation of electromagnetic em waves in the earth s crust and atmospheric waveguide a granite slab and two aluminium plates simulated the earth s crust ionosphere and underground conductive layer respectively the greek archipelago was modeled using a geographical map with the ocean covered by aluminium foil the intensity of em waves transmitted from a model hypocenter was mapped to investigate the influence of the ocean the propagation of vlf waves over the long distance was obtained while that of ulf indicated the exponential decay from the epicenter this experiment considered waveguides might explain the ocean s effect on the selectivity and the long distance propagation of sems presumably including seismic electric signals ses in the van method

electro magnetic earthquake bursts and critical rupture of peroxy bond networks in rocks abstract we propose a mechanism for the low frequency electromagnetic emissions and other electromagnetic and electric phenomena which have been associated with earthquakes the mechanism combines the critical earthquake concept and the concept of crust acting as a charging electric battery under increasing stress the electric charges are released by activation of dormant charge carriers in the oxygen anion sublattice called peroxy bonds or positive hole pairs php where a php represents an o 3 x oo yo 3 with x y si 4 al 3 i e o in a matrix of o 2 of silicates we propose that php are activated by plastic deformations during the slow cooperative build up of stress and the increasingly correlated damage culminating in a large critical earthquake recent laboratory experiments indeed show that stressed rocks form electric batteries which can release their charge when a conducting path closes the equivalent electric circuit we conjecture that the intermittent and erratic occurrences of em signals are a consequence of the progressive build up of the battery charges in the earth crust and of their release when crack networks percolate through the stressed rock volumes providing a conductive pathway for the battery currents to discharge em signals are thus expected close to the rupture either slightly before or after that is when percolation is most favored the proposed mechanism should be relevant for the broader understanding of fractoemissions

gas hydrate of lake baikal discovery and varieties abstract this paper summarizes the results of recent gas hydrate studies in lake baikal the only fresh water lake in the world containing gas hydrates in its sedimentary infill we provide a historical overview of the different investigations and discoveries and highlight some recent breakthroughs in our understanding of the baikal hydrate system so far 21 sites of gas hydrate occurrence have been discovered gas hydrates are of structures i and ii which are of thermogenic microbial and mixed origin at the 15 sites gas hydrates were found in mud volcanoes and the rest six near gas discharges additionally depending on type of discharge and gas hydrate structure they were visually different investigations using mir submersibles allowed finding of gas hydrates at the bottom surface of lake baikal at the three sites

electrical conductivity of brine saturated fractured rock a theoretical analysis shows that electrical conductivity along fractures in a saturated porous rock is a function of many factors fluid and rock conductivities initial fracture aperture and contact area fracture surface geometry asperity height distribution and tip curvature elastic moduli of the rock and confining pressure or normal stress acting across the fracture the conductivity in the fracture plane decreases approximately in proportion to log pressure but the conductivity is influenced by the increased contact area and hence flow path tortuosity along the fracture surface at elevated pressures electrical conductivity in fractures is more affected by flow path tortuosity than is permeability the dependence on pressure was tested using laboratory measurements of conductivity through split cores containing ground saw cut surfaces in a variety of rocks under confining pressures to 200 mpa the conductivity decreased approximately in proportion to log pressure there was little effect of

electrical conductivity of olivine a dunite and the mantle laboratory studies of the electrical conductivity of rocks and minerals are vital to the interpretation of electromagnetic soundings of the earth s mantle to date the most reliable data have been collected from single crystals we have extended these studies with electrical conductivity measurements on a dunite from north carolina in the temperature range of 600 1200 c and under controlled oxygen fugacity observations of conductivity as a function of oxygen fugacity and temperature demonstrate that conduction in the dunite is indistinguishable from conduction in single olivine crystals thus the common practice of exaggerating the single crystal conductivities to account for conduction by grain boundary phases in the mantle is unnecessary because the dunite conductivity is consistent with that published for single crystals under similar conditions we have made a combined analysis of these data conductivity as a function of temperature between 600 and 1450 c displays three conduction mechanisms whose activation energies may be recovered by nonlinear least squares fitting yielding activation energies of 0 21 2 56 10 19 j 0 13 1 60 ev below 720 c 2 56 0 02 10 19 j 1 60 0 01 ev between 720 c and 1500 c and 11 46 0 90 10 19 j 7 16 0 56 ev above 1500 c the behavior of conductivity as a function of oxygen fugacity is well explained by a model in which an o2 independent population of charge carriers is supplemented at high oxygen fugacities with a population that is proportional to o20 3 this parametrization produces a clear correlation of the o2 dependent term with iron content which is otherwise obscured by variations in conductivity among olivines

ionosphere plasma bubbles and density variations induced by pre earthquake rock currents and associated surface charges 1 recent ionospheric observations indicate that the total electron content tec may anomalously decrease or increase up to 5 20 before the occurrence of big earthquakes the ionospheric density variations can be caused by earth surface charges currents produced from electric currents associated with the stressed rock we formulate a coupling model for the stressed rock earth surface charges atmosphere ionosphere system the stressed rock acts as the dynamo to provide the currents for the coupling system the electric fields and currents in the atmosphere and the lower boundary of ionosphere are obtained by solving the current continuity equation j 0 where j is the current density a three dimensional ionosphere simulation code is then used to study the ionospheric dynamics based on the obtained electric fields and currents the simulation results show that a current density jrock 0 2 10 a m2 in an earthquake fault zone is required to cause daytime tec variations of 2 25 the simulation results also show that a current density jrock 0 01 1 a m2 can lead to nighttime tec variations of 1 30 as well as the formation of a nighttime plasma bubble equatorial spread f extending over the whole magnetic flux tube containing the earthquake epicenter we suggest that observations of daytime and nighttime tec variations and a nighttime plasma bubble within the affected region can be used as precursors for earthquake prediction

electrical conductivity temperatures and fluids in the lower crust we have compiled both laboratory and worldwide field data on electrical conductivity to help understand the physical implications of deep crustal electrical profiles regional heat flow was used to assign temperatures to each layer in regional electrical conductivity models we avoided those data where purely conductive heat flow suggested temperatures more than about 1000 sup 0 c substantially higher than solidus temperatures and outside the range of validity of heat flow models the resulting plots of log conductivity sigma versus 1 t demonstrate that even low conductivity layers lcl have conductivities several orders of magnitude higher than dry laboratory samples and that the data can be represented by straight line fits in addition tectonically active regions show systematically higher conductivities than do shield areas because volatiles are usually lost in laboratory measurements and their absence is a principal difference between laboratory and field conditions these materials probably account for the relatively higher conductivities of rocks in situ in the crust free water in amounts of 0 01 0 1 in fracture porosity could explain crustal conductivities other possibilities are graphite hydrated minerals in rare instances and sulfur in combination with other volatiles as most of the temperatures are less than 700 sup 0 c partial melting seems likely onlymore in regions of highest heat flow where the conductive temperature profiles are inappropriate another result is that at a given temperature crustal high conductivity layes hcl are more conductive by another order of magnitude and show more scatter than do lcl s less

electric potential changes associated with slip failure of granite preseismic and coseismic signals electric potential changes were measured for stick slip events in granite samples with a three block direct shear arrangement at 8 mpa normal stress two electrodes were mounted on the left and right hand blocks and the electric potential difference between each electrode and the ground was measured with a high input impedance recording system of frequency range from dc to 100 hz as well as coseismic electric signals of about 1 5 v which appeared the moment of the dynamic slip event preseismic signals were detected just before the slip event the coseismic signal rises stepwise with opposite polarities at the two electrodes and exponentially decays with a time constant of e s where e is the permittivity and s is the conductivity of the rock sample we conducted a simple test of rapid stress drop without slipping and observed almost the same electric signal as the coseismic signal this suggests that the electric signal is generated by the piezoelectric effect we proposed a generation model based on the piezoelectric effect and the resultant relaxation process and obtained a theoretical frequency response which is in agreement with experimental data the preseismic signal appears about 2 3 s before the dynamic event with an amplitude of about 50 mv the local strains along two sliding surfaces were also measured to monitor the growth of the rupture nucleation zone when the growth of the rupture nucleation zone occurred on the left sliding surface a clear preseismic signal was detected at the electrode mounted on the left granite block when the growth occurred on the right hand surface a signal was detected at the electrode on the right block this shows that the preseismic electric signal is caused by stress change in the rupture nucleation zone these preseismic and coseismic signals were also detected with an antenna which was placed away from the sample surface

epicenter location by abnormal ulf electromagnetic emissions 1 the epicenter location before earthquake is very important we investigated the characteristics of the ulf electromagnetic emissions which were observed by an east west chain at kashi anxi and beijing stations before the ml 7 1 hetian earthquake xingjiang china on november 19 1996 we define the polarization angle as the angle between the east direction of the geomagnetic field and the major axis of the polarization ellipse which is obtained by the filtered data of two horizontal components the source of ulf electromagnetic emissions before earthquake is probably coming from the direction perpendicularly to the polarization major axis of earthquake related emissions we located the source as the cross of two source directions that were obtained at kashi and anxi station on november 18 1996 the estimated source is consistent with the epicenter of the hetian event

electrical conductivity of dry lower crustal rocks this study provides values of electrical conductivity of possible lower crustal materials to assist interpretation of lower crustal magnetotelluric soundings we present mean values of conductivity measurements collected from the literature for dry mafic and silicic rocks in the temperature range of 500 c to 1000 c we observe statistically significant differences between rock types mafic rocks are better conductors than granites by about half an order of magnitude and within the mafic group aphanitic fine grained rocks have higher conductivity than phaneritic coarse grained ones best fitting curves of log conductivity versus temperature are presented for each rock type to show mean log conductivity values together with standard deviations so that most probable temperature ranges can be inferred from conductivity because the laboratory rocks are dry their conductivities are lower at a given temperature than they would be if fluids or volatiles were present hence any temperatures inferred from

electromagnetic precursors to earthquakes in the ulf band a review of observations and mechanisms despite over 2 decades of international and national monitoring of electrical signals with the hope of detecting precursors to earthquakes the scientific community is no closer to understanding why precursors are observed only in some cases laboratory measurements have demonstrated conclusively that self potentials develop owing to fluid flow and that both resistivity and magnetization change when rocks are stressed however field experiments have had much less success many purported observations of low frequency electrical precursors are much larger than expectations based on laboratory results in some cases no precursors occurred prior to earthquakes or precursory signals were reported with no corresponding coseismic signals nonetheless the field experiments are in approximate agreement with laboratory measurements maximum resistivity changes of a few percent have been observed prior to some earthquakes in china but the mechanism causing those changes is still unknown anomalous electric and magnetic fields associated with fluid flow prior to earthquakes may have been observed finally piezomagnetic signals associated with stress release in earthquakes have been documented in measurements of magnetic fields

piezoelectric effects in quartz rich rocks abstract piezoelectricity a polarization of charge produced by an applied stress occurs in many minerals it is particularly strong in quartz aggregates of piezoelectric grains are themselves piezoelectric if the grains are suitably aligned such aggregates may be said to have a piezoelectric fabric thus quartz rich rocks may possess a piezoelectric fabric and this paper discusses the various possible fabrics to test whether a piezoelectric fabric might be detected in a quartz rich rock apparatus was built that hydraulically applied a sinusoidal stress to cubic specimens the three resulting orthogonal polarizations of charge were measured via a charge amplifier a specimen of pure quartz was used to verify the experimental method and to ensure that absolute piezoelectric moduli were being measured rocks with and without preferred orientation were tested of the latter types those containing little or no free quartz marble basalt did not exhibit measurable piezoelectric effects however all quartz rich rocks quartzites granites gneisses mylonites did show piezoelectric effects when stressed these effects were in two categories 1 1 effects due to piezoelectric fabrics called true piezoelectric effects 2 2 effects due to random distributions of the piezoelectric vectors called statistical effects to distinguish between these two effects three criteria were used firstly the measured effects were compared with the expected statistical effect for a rock of that grain size and composition secondly where possible multiple specimens were cut from the one rock sample all specimens with the same orientation specimens from a rock with a piezoelectric fabric should show similar results thirdly the optically observed c axis distribution and orientation was compared with the piezoelectrically predicted fabric and orientation this paper shows that while most rocks gave results consistent with statistical effects from a non polar or random distribution some rocks exhibited a true piezoelectric effect due to fabric this effect may be used with some imprecision to locate the a axes and c axes of quartz in the aggregate the polarities of the a axes are also obtained

subionospheric vlf signal perturbations possibly related to earthquakes a likely vlf subionospheric signal effect related to seismic activity was first reported by hayakawa et al 1996a b in association with the great kobe earthquake we have analyzed similar data during periods around 10 other great earthquakes magnitude m 6 in order to understand the main features of such an effect the following characteristics emerged from our analysis the effect appears as a transient oscillation with a 5 to 10 day period which is initiated a few days before a large earthquake and decays over a few days to weeks after it it is mainly related to crustal earthquakes it appears when resonant atmospheric oscillations with periods in a range of 5 11 days exist before the earthquake the seismic influence on the vlf signal is probably explained by the generation of long period gravity waves during the earthquake process and their intensification at heights of 70 90 km

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

particle precipitation prior to large earthquakes of both the sumatra and philippine regions a statistical analysis abstract a study of statistical correlation between low l shell electrons precipitating into the atmosphere and strong earthquakes is presented more than 11 years of the medium energy protons electrons detector data from the noaa 15 sun synchronous polar orbiting satellite were analysed electron fluxes were analysed using a set of adiabatic coordinates from this significant electron counting rate fluctuations were evidenced during geomagnetic quiet periods electron counting rates were compared to earthquakes by defining a seismic event l shell obtained radially projecting the epicentre geographical positions to a given altitude towards the zenith counting rates were grouped in every satellite semi orbit together with strong seismic events and these were chosen with the l shell coordinates close to each other noaa 15 electron data from july 1998 to december 2011 were compared for nearly 1800 earthquakes with magnitudes larger than or equal to 6 occurring worldwide when considering 30 100 kev precipitating electrons detected by the vertical noaa 15 telescope and earthquake epicentre projections at altitudes greater that 1300 km a significant correlation appeared where a 2 3 h electron precipitation was detected prior to large events in the sumatra and philippine regions this was in physical agreement with different correlation times obtained from past studies that considered particles with greater energies the discussion below of satellite orbits and detectors is useful for future satellite missions for earthquake mitigation

microstructures of structure i and ii gas hydrates from the gulf of mexico gas hydrate samples from various locations in the gulf of mexico gom differ considerably in their microstructure distinct microstructure characteristics coincide with discrete crystallographic structures gas compositions and calculated thermodynamic stabilities the crystallographic structures were established by x ray diffraction using both conventional x ray sources and high energy synchrotron radiation the microstructures were examined by cryo stage field emission scanning electron microscopy fe sem good sample preservation was warranted by the low ice fractions shown from quantitative phase analyses gas hydrate structure ii samples from the green canyon in the northern gom had methane concentrations of 70 80 and up to 30 of c2 c5 of measured hydrocarbons hydrocarbons in the crystallographic structure i hydrate from the chapopote asphalt volcano in the southern gom was comprised of more than 98 methane fairly different microstructures were identified for those different hydrates pores measuring 200 400 nm in diameter were present in structure i gas hydrate samples no such pores but dense crystal surfaces instead were discovered in structure ii gas hydrate the stability of the hydrate samples is discussed regarding gas composition crystallographic structure and microstructure electron microscopic observations showed evidence of gas hydrate and liquid oil co occurrence on a micrometer scale that demonstrates that oil has direct contact to gas hydrates when it diffuses through a hydrate matrix

is an unusual large enhancement of ionospheric electron density linked with the 2008 great wenchuan earthquake 1 on 12 may 2008 at 0628 ut a major earthquake ms 8 0 struck wenchuan county 31 0 n 103 4 e in southwest china the maximum ionospheric electron density at f2 peak nmf2 recorded an unusual large enhancement during the afternoon sunset sector by the chinese ionosondes over wuhan 30 5 n 114 4 e and xiamen 24 4 n 123 9 e which are close to the earthquake epicenter an averaged increase at these two stations is about 2 times on a geomagnetic quiet day 9 may kp 2 3 days prior to the earthquake relative to the median value of 1 12 may whereas the increase was much less significant over yamagawa 31 2 n 130 6 e and okinawa 26 7 n 128 2 e in japan combining the data from the network of 58 global positioning system receivers around china and the global ionospheric map the variations of the total electron content reveal the region where enhancement persisted for a long period to be within longitudes 90 130 e our results suggest that this abnormal enhancement is most possibly a seismo ionospheric signature

lipid biomarker patterns of authigenic carbonates reveal fluid composition and seepage intensity at haima cold seeps south china sea abstract authigenic carbonates retrieved from sites rov1 and rov2 of the haima hydrocarbon seeps of the south china sea at approximately 1390 m water depth were studied using lipid biomarker analyses abundant molecular fossils of anaerobic methane oxidizing archaea anme and sulfate reducing bacteria srb with strong 13c depletions 13c values as low as 126 in combination with low 13ccarbonate values 42 7 to 36 8 provide evidence that anaerobic oxidation of methane aom was the major process driving the precipitation of the studied seep carbonates the extremely low 13c values of archaeal biomarkers confirm that biogenic methane was the main carbon source but the seepage of accessory crude oil is also suggested by the presence of unresolved complex mixtures in the hydrocarbon fractions a suite of 13c depleted biomarkers indicate the predominance of anme 1 dss consortia at both sites which indicates that the studied carbonates formed during low to medium methane flux somewhat higher contents of archaeal biomarkers and their stronger 13c depletion at site rov2 probably reflect at least temporarily higher seepage intensities than at site rov1 abundant bacterial dialkyl glycerol diethers dages revealing a large offset of their 13c values compared to srb derived terminally branched fatty acids were possibly produced by distinct srb species other than members of the dss cluster the encountered hopanoids are attributed to aerobic methanotrophic bacteria based on their moderate 13c depletion the application of molecular fossils in combination with their compound specific isotope signatures is an efficient tool to reconstruct the composition of seepage fluids and seepage intensities

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

electromagnetic signals associated with stick slip of quartz free rocks abstract we recorded clear transients in the electric and magnetic fields upon sudden slip in stick slip experiments on dry cylindrically shaped quartz free rock specimens of basalt and peridotite with a 30 saw cut representing a fault at confining pressures of up to 120 mpa the amplitudes of the measured electric field signals were always higher at the electrode pair oriented parallel to the strike of the fault than at the pair oriented perpendicular this anisotropy suggests a preferred electric polarization normal to the slip surface the transients in the electric and magnetic fields were observed only when the fault slip occurred by stick slip mode not by a stable mode of the sliding and the amplitudes of the electric field signals increased with increasing stress drop it is suggested that the generation process of the electromagnetic signals is closely related to the characteristic behavior of the fault at the time of the initiation of slip during stick slip events probably with respect to the intensity of the signals we propose that one or both of the following two processes characteristic of the fault at the time of the initiation of slip during stick slip events are essential for the generation of detectable electromagnetic signals rapid slip along the simulated fault and separation of the rock masses across the fault

electromagnetic elf radiation from earthquake regions as observed by low altitude satellites seismo electromagnetic sem waves observed by low altitude satellites passing over seismic regions were studied the data of the cosmos 1809 satellite were analysed over the earthquake region in armenia during the period from january 20 to february 17 1989 intense em radiation at frequencies below 450 hz was observed at the l shells of the earthquake during 12 orbits out of the 13 that passed within 6 in longitude from the epicenter and during 1 out of 6 in the range of 6 8 longitude away from this region the other orbits which passed 10 12 from the epicentre showed no effect to complete this study we used the emissions observed by another low altitude satellite aureol 3 it is shown that during the event the seismic region is permanently radiating the intensity and the envelope shape of the wave depend on its time relatively to the time of the earthquake their frequency spectra are compared to the average spectrum recorded in the same geomagnetic regions similar wave intensities and spectral distributions were observed on the two satellites during the seismic periods

emission of electromagnetic radiation preceding the ito seismic swarm of 1989 there have been several reports1 8 of electromagnetic radiation being detected in air and or underground before large earthquakes or volcanic eruptions unfortunately such measurements are often plagued by contamination from other sources of noise we have developed an electrode system that is effective at filtering out urban and atmospheric background noise here we report the detection of anomalous electromagnetic signals several hours before the occurrence of large earthquakes near ito city japan about 150 km from the location of the electrodes we have also detected anomalous signals about one day before an undersea volcanic eruption that constituted part of the same seismic swarm near ito although the mechanism responsible for such signals is still unclear these results indicate that their monitoring could be valuable for the prediction of seismic activity

coupled pyrite concentration and sulfur isotopic insight into the paleo sulfate methane transition zone smtz in the northern south china sea abstract the sulfate methane transition zone smtz is an important diagenetic redox boundary within marine sediments where the anaerobic oxidation of methane aom coupled with bacterial sulfate reduction can promote sulfur isotopic enrichments in several solid phase minerals including pyrite fes2 authigenic pyrite can form in concentrated abundances within the smtz and as such can be used as a proxy to identify paleo smtzs this study uses enrichments in 34s and anomalously high abundances of authigenic pyrites in 287 samples from the northern south china sea scs to determine the paleo smtz the pyrite samples were collected from sediment cores acquired at three sites each of which are known to be located in natural gas hydrate bearing regions we assess the relative abundances of authigenic pyrites the types of pyrite morphologies recovered in the cored sediments and the sulfur isotopic values of recovered pyrite samples using two methods 1 handpicked sample analysis using a binocular microscope and 2 the chromium reduction method our results show that pyrite concentrations and sulfur isotopic compositions exhibit synchronous fluctuations particularly from 6 8 m below seafloor mbsf to 8 4 mbsf at all three study sites there is a significant increase in the occurrence of rod like pyrite morphology within this key interval we define the position of the paleo smtz by the presence of anomalously high accumulations of pyrites at greater than 5 0 wt using the handpicking method or greater than 0 5 wt via the chromium reduction method along with positive 34s excursions greater than 10 0 vcdt we discovered a regional paleo smtz that is shallower than the modern smtz suggesting a previous period of elevated methane flux from depth possibly related to widespread gas hydrate dissociation

impact of anaerobic oxidation of methane on the geochemical cycle of redox sensitive elements at cold seep sites of the northern south china sea abstract cold hydrocarbon seepage is a frequently observed phenomenon along continental margins worldwide however little is known about the impact of seeping fluids on the geochemical cycle of redox sensitive elements pore waters from four gravity cores d 8 d 5 d 7 and d f collected from cold seep sites of the northern south china sea were analyzed for so42 mg2 ca2 sr2 dissolved inorganic carbon dic 13cdic dissolved fe mn and trace elements e g mo u the sulfate concentration depth profiles 13cdic values and dic ca2 mg2 so42 ratios suggest that organoclastic sulfate reduction osr is the dominant process in d 8 core besides osr anaerobic oxidation of methane aom is partially responsible for depletion of sulfate at d 5 and d 7 cores the sulfate consumption at d f core is predominantly caused by aom the depth of sulfate methane interface smi and methane diffusive flux of d f core are calculated to be 7 m and 0 035 mol m 2 yr 1 respectively the relatively shallow smi and high methane flux at d f core suggest the activity of gas seepage in this region the concentrations of dissolved uranium u were inferred to decrease significantly within the iron reduction zone it seems that aom has limited influence on the u geochemical cycling in contrast a good correlation between the consumption of sulfate and the removal of molybdenum mo suggests that aom has a significantly influence on the geochemical cycle of mo at cold seeps accordingly cold seep environments may serve as an important potential sink in the marine geochemical cycle of mo

subsurface fluid flow at an active cold seep area in the qiongdongnan basin northern south china sea abstract the active haima cold seep sites were discovered by the remotely operated vehicle on the western part of the northern slope of south china sea in 2015 and 2016 however the subsurface structures in the seep area are not well studied which prevents the further understanding of the evolution of fluid venting system in the active cold seep area in 2017 a high resolution 2d seismic line transecting the two main seep sites was acquired and processed in this study the subsurface structures were well resolved on the seismic profile the new observations include the widespread subsurface fluid flow features i e chimney structures and pockmarks and the pervasively distributed magmatic activities seismic indicators for hydrothermal vents were also observed on the seismic section this new discovery confirms the contribution of magmatic activities to the evolution of subsurface fluid flow in the study area minor faults under the recognizable resolution of seismic profile which can act as conduits for the subsurface fluid flow were also identified in the fine grained sediment sequences overall these results provide new insights into the evolution of subsurface fluid flow in the study area

streaming potential properties of westerly granite with applications this paper reports on laboratory measurements of the streaming potential properties of common minerals and in particular of westerly granite data are presented for these solids in contact with simple electrolytic solutions and in one case for temperature variation in the range 5 70 c for 1 1 electrolytes the ratio of the streaming potential coupling coefficient to fluid resistivity was approximately 4 mv atm m and for 2 1 electrolytes 2 mv atm m the effect of temperature was small 0 05 mv c temperature increase and indicates that the zeta potential was independent of temperature preliminary experimental results using mixed electrolytic solutions nacl cacl2 and two phase fluid flow are also described two phase flow can enhance streaming potentials by as much as a factor of 3 or 4 the laboratory data are used to interpret streaming potentials in geological problems such as earthquake prediction geothermal prospecting using the self potential method and surface conductivity contribution to the electrical resistivity of rocks

on the origin and evolution of electrical signals during frictional stick slip in sheared granular material electromagnetic signals have been reported in association with geophysical phenomena including earthquakes landslides and volcanic events mechanisms that suggested to explain seismoelectrical signals include triboelectricity piezoelectricity streaming potentials and the migration of electron holes yet the origin of such phenomena remains poorly understood we present results from laboratory experiments regarding the relationship between electrical and mechanical signals for frictional stick slip events in sheared soda lime glass bead layers the results are interpreted in the context of lattice defect migration and granular force chain mechanics during stick slip events we observe two distinct behaviors delineated by the attainment of a frictional stick slip steady state during initial shear loading layers charge during stick slip events and the potential of the system rises after steady state stick slip behavior is attained the system begins to discharge coseismic signals are characterized by potential drops superimposed on a longer term trend we suggest that the observed signal is a convolution of two effects charging of the forcing blocks and signals associated with the stress state of the material the long term charging of the blocks is accomplished by grain boundary movement during the initial establishment of force chain networks short term signals associated with stick slip events may originate from produced electron holes applied to tectonic faults our results suggest that electrical signals generated during frictional failure may provide a way to monitor stress and the onset of earthquake rupture potential changes could produce detectable signals that may forecast the early stages of failure providing a modest warning of the event

reply to comment by b e prokhorov and o v zolotov on an improved coupling model for the lithosphere atmosphere ionosphere system the currents flowing between the earth and ionosphere are numerically calculated we solve the current continuity equation by two methods the first method is to solve in j 0 kuo et al 2011 where is atmospheric conductivity and is the electric potential and the second method is to solve the current potential in j 2 0by assuming j a curl free current density kuo et al 2014 two solutions of j 0for current flow in the atmosphere between earth surface and ionosphere are compared in this reply the differences of two results are 4 which may be partly caused by the numerical errors in the presence of large variations in the profile the current potential can provide a good approximation for upward currents that flow into the ionosphere in addition we compare two models for the current flow from lithosphere to atmosphere a two charge layers embedded in the lithosphere and b a dynamo in the lithosphere the presence of a dynamo in the lithosphere for model b can lead to the presence of current and electric field in the atmosphere and hence in the ionosphere in model a the electrostatic charge layers in the lithosphere cannot lead to the presence of electric field in the atmosphere

characteristics of electromagnetic noise in the ioannina region greece a possible origin for so called seismic electric signal ses the study of electromagnetic noise in the ioannina region nw greece shows the existence of long transient electric signals duration 10 s without measurable correlated magnetic signals as is the case for seismic electric signal ses observed in the van network of short term earthquake prediction our signals have an artificial origin and are emitted by different kinds of transmitters implanted in the ioannina region this origin can be clearly ascertained from simultaneous observation at stations in direct sight of the transmitters of four electromagnetic components two electric and two magnetic in a broad band of frequencies 10 3 10 hz relying on these observations it is proposed that the april 18 and 19 1995 electric signals interpreted by the van group as ses precursors to the may 13 kozani earthquake are due to some transmitter located far to the north of the ioa station of the van network the transmitters of this area would be of digital type as is increasingly common in radio telecommunication networks we believe that careful studies of electromagnetic noise in a broad range of frequencies should precede lengthy discussions of the statistical significance of recorded signals

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

plausibility of long distance electrotelluric precursors to earthquakes a systematic analysis of the plausibility of different classes of models which could account for low frequency precursory electrotelluric signals observable at large distances from a large earthquake is carried out first we consider linear models for which either a stationary electrical field is generated by a current dipole in the source volume or a static deformation field results from a precursory strain in the source volume linearly inducing a streaming potential effect near the electrode in the former case only the conjunction of very favorable circumstances may lead to an electrical field larger than 10 mv km at more than 100 km with the constraint that no anomaly exceeds a few volts per kilometer in the source area it indeed requires a powerful electrical dipole current 104 a length 1 km which might be produced by a streaming potential effect associated with the connection of nonhydrostatic fluid reservoirs pore pressure difference up to 100 mpa a two dimensional channeling of the electrical currents from the source to the electrode area which would result from high conductivity horizontal layers and finally a local amplification factor of typically 100 near the electrodes which might be produced by a narrowing of the conductive channel for an elastic long distance interaction an electric field of 10 mv km at a distance 10 times the source length 100 km away from a m 6 earthquake requires a precursory deformation larger than the coseismic deformation if no strong local amplification is considered alternatively nonlinear models are proposed and discussed assuming that the crust is stuffed with small scale local instabilities fractures and nonhydrostatic fluid reservoirs among which a number are close to their instability threshold these instabilities may follow their own evolutionary process inducing sporadic fluid flow and hence streaming potential effect in the vicinity of the electrodes without any relation to a remote tectonic activity however these instabilities may be sensitive to very small changes in the stress field and hence be triggered by the elastic precursory deformation of a remote seismic source this requires that the precursory deformation near the instability is at least larger than the tidal strain 10 7 this necessary condition is met at a distance of up to 10 times the source dimension when the precursory strain source is only 10 of the coseismic deformation provided that the strain source is double the size of the seismic fault itself this model could account for the absence of self potential anomalies related to the earthquake itself as a large proportion of the available instabilities could have been swept away by the precursory strain furthermore with such a model a precursory strain in the source area could induce a detectable change in the background seismic activity over a vast area which may give a new interpretation of the times of increased probability observations for short distances the triggering of fluid instabilities by strain perturbation and the associated streaming potential effect may well be a promising model for explaining low frequency electric and magnetic precursors

electric and magnetic field perturbations recorded by demeter satellite before seismic events of the 17th july 2006 m 7 7 earthquake in indonesia abstract seismo electromagnetic phenomena refers to the electric and magnetic field perturbations that may be caused due to geophysical activities like earthquakes and volcanic eruptions due to the existence of such phenomena before earthquakes they may be regarded as short term precursors to earthquakes keeping in mind the in situ measurements for detection of such phenomena the satellite based techniques are of great interest because they keep a constant track of the seismically active zones globally with the objective of detecting the electromagnetic emissions in the ionosphere the demeter satellite has been launched on 29th june 2004 from baikonour in order to study the ionospheric perturbations associated with seismic activities in this paper we discuss some interesting results of electromagnetic emissions that are observed before a series of recent indonesian earthquakes in the jawa region with a major shock measuring 7 7 magnitude on richter scale which occurred on 17 july 2006 the emissions have been observed in the ultra low frequency ulf extremely low frequency elf range of electromagnetic spectra

examination of core samples from the mount elbert gas hydrate stratigraphic test well alaska north slope effects of retrieval and preservation abstract collecting and preserving undamaged core samples containing gas hydrates from depth is difficult because of the pressure and temperature changes encountered upon retrieval hydrate bearing core samples were collected at the bpxa doe usgs mount elbert gas hydrate stratigraphic test well in february 2007 coring was performed while using a custom oil based drilling mud and the cores were retrieved by a wireline the samples were characterized and subsampled at the surface under ambient winter arctic conditions samples thought to be hydrate bearing were preserved either by immersion in liquid nitrogen ln or by storage under methane pressure at ambient arctic conditions and later depressurized and immersed in ln eleven core samples from hydrate bearing zones were scanned using x ray computed tomography to examine core structure and homogeneity features observed include radial fractures spalling type fractures and reduced density near the periphery these features were induced during sample collection handling and preservation isotopic analysis of the methane from hydrate in an initially ln preserved core and a pressure preserved core indicate that secondary hydrate formation occurred throughout the pressurized core whereas none occurred in the ln preserved core however no hydrate was found near the periphery of the ln preserved core to replicate some aspects of the preservation methods natural and laboratory made saturated porous media samples were frozen in a variety of ways with radial fractures observed in some ln frozen sands and needle like ice crystals forming in slowly frozen clay rich sediments suggestions for hydrate bearing core preservation are presented

investigation of ionospheric electron content variations before earthquakes in southern california 2003 2004 1 it has been proposed that earthquakes are preceded by electromagnetic signals detectable from ground and space based measurements ionospheric anomalies such as variations in the electron density a few days before earthquakes are one of the precursory signals proposed since global positioning system gps data can be used to measure the ionospheric total electron content tec the technique has received attention as a potential tool to detect ionospheric perturbations related to earthquakes here we analyze 2 years 2003 2004 of data from the southern california integrated gps network scign a dense network of 265 continuous gps stations centered on the los angeles basin for possible precursors this time period encompasses the december 2003 m6 6 san simeon and september 2004 m6 0 parkfield earthquakes we produce tec time series at all scign sites and apply three different statistical tests to detect anomalous tec signals preceding earthquakes we find anomalous tec signals but no statistically significant correlation in time or in space between these tec anomalies and the occurrence of earthquakes in southern california for the 2003 2004 period this result does not disprove the possibility of precursory phenomena but show the signal to noise ratio of a hypothetical tec precursor signature is too low to be detected by the analysis techniques employed here precursors may still be revealed for future large earthquakes in well instrumented areas such as california and japan if the tests can be developed into techniques that can better separate external influences from the actual tec signal

laboratory investigations of impact generated plasma the production of magnetic fields by hypervelocity meteoroid impact has been proposed to explain the presence of paleomagnetic fields in some lunar samples as well as on the lunar surface impact generated magnetic fields also may be significant for the paleomagnetic record on a variety of cratered surfaces in the solar system such as the moon mercury phobos and asteroids previous experiments with the two stage hydrogen light gas gun at the nasa ames vertical gun range demonstrated that hypervelocity impacts can produce impact generated magnetic fields by the expansion of an impact derived ionized vapor cloud impact generated plasma here we further characterize impact generated magnetic fields and plasma with hypervelocity impact experiments at the nasa ames vertical gun spherical projectiles 0 32 cm fe cu 0 64 cm al nylon with velocities from 5 2 to 6 0 km s were impacted at impact angles of 15 30 60 and 90 measured from horizontal into powdered dolomite silica sand and aluminum plate three sets of experiments using search coils as magnetic detectors characterized impact generated magnetic fields as functions of ambient field strength and orientation projectile target composition and impact angle experiments using langmuir probes indicated a charged particle density between 109 and 1011 ions el cm 3 and an electron temperature 4500 k of the impact generated plasma the inferred source of impact induced magnetic fields these new results demonstrate that impact generated magnetic fields at the laboratory scale exhibit spatial and temporal complexity dependent on impact angle velocity and projectile target composition thereby suggesting that crater related paleomagnetism associated with this mechanism should exhibit similar complexity with spatial wavelengths on the order of a fraction of the crater radius