mechanical interactions between rigid particles in a deforming ductile matrix analogue experiments in simple shear flow abstract the mechanical interaction between two or more particles is investigated in newtonian simple shear flow the experimental models allow observation of both the particle rotation and the deformation pattern around the particles the finite and instantaneous strain patterns around rigid particles are strongly heterogeneous and asymmetric with high finite strain zones aligned to the direction of maximum finite stretch these correspond to local flow with low vorticity number heterogeneous strain patterns around rigid particles spread over a distance of 1 2 times the particle length and this distance increases with increasing bulk strain where rigid particles are more concentrated these patterns coalesce and the overall pattern is then strongly controlled by the particles and cannot be simply related to the external boundary conditions in rocks the characteristic asymmetric strain pattern around rigid isolated particles is a reliable shear criterion which becomes unreliable with high concentrations of rigid particles particle rotation is significantly disturbed when the distance between adjacent particles of equal size is shorter than their length that is only in very concentrated suspensions of rigid particles in a composite shape fabric the development of the sub fabric corresponding to the smaller minerals will be more disturbed

short term and intermediate term geochemical precursors detection of precursory phenomena in observation data is essential to earthquake prediction studies continuous monitoring of radon concentration in groundwater in japan in one case showed a short term anomaly related to a nearby earthquake with the exception of the 1978 izu oshimakinkai earthquake m7 0 however no abnormal change has been noted this may be due partially to difficulty in detecting insignificant precursory signals from observation data which ordinarily contains a noise induced fluctuations and partially to lack of understanding of the mechanism controlling the appearance of precursory phenomena in order to increase our knowledge of the variation pattern of precursory changes in radon concentration of groundwater hydrologic precursors with significant features are examined in this paper complexity of appearance of precursory phenomena and problems in assignment of the specific earthquake are discussed

coseismic changes in groundwater temperature of the usu volcanic region observations of groundwater temperature to an accuracy of 0 001 c or better have been made at about 30 wells in various areas of impending earthquakes in japan the main aim of the observations was to monitor the crustal strain and or the movement of groundwater which relate to earthquake occurrence one thermometer was installed at a depth of 200 m in an active volcanic area usu where an upward movement of the magma is occurring we report here that there was a generally increasing temperature trend at this location 0 3 c in the half year of observation decreases in the rate of increase preceded intense local earthquake activity temperature jumps were accompanied by large local earthquakes with magnitudes up to 4 2 and the polarity of the steps corresponded to the location of hypocentres this is probably the first microtemperature measurement made in the proximity of seismic activity

comparison of postseismic groundwater temperature changes with earthquake induced volumetric strain release yudani hot spring japan we observed temporal variations of the groundwater temperature during two observation periods may 1983 july 1984 september 1991 august 1995 at yudani hot spring in tottori prefecture japan the groundwater temperature is affected by tides atmospheric pressure changes and earthquakes assuming that volumetric strain change is the cause of these temperature changes we calculated the respective strain sensitivities of the groundwater temperature as a result the sensitivities estimated from theoretical volumetric strain changes by earthquake fault models are more than 1 000 times larger than those from tides and atmospheric pressure we infer that the actual volumetric strain changes near yudani hot spring due to the earthquakes are larger than theoretical strain changes calculated by earthquake fault models

using robust satellite technique rst to determine thermal anomalies before a strong earthquake a case study of the saravan earthquake april 16th 2013 mw 7 8 iran abstract employing an efficient and robust prediction system along with early warnings is useful to reduce the effects of devastating earthquakes thermal anomaly as an earthquake precursory is widely confirmed in this study to characterize the thermal anomalies within a 10 year specific observation interval of land surface temperature lst satellite data products obtained from modis aqua march 16th to may 16th every year from 2004 to 2013 were analyzed using robust satellite technique rst method the saravan earthquake april 16th 2013 mw 7 8 iran were used for validation phase and the year 2012 as a relatively seismically unperturbed year no earthquakes with mw 3 5 regarding target time and region was taken for confutation phase for the first time to reduce the effects of the topography with respect to vegetation cover using unsupervised classification the study area was divided into the low and high elevation regions the results of the present study showed the significant sequences of lst anomalies sslas from several days before and immediately after the saravan earthquake appeared in the north south and center of the study area however no anomalies were observed in a seismically unperturbed year 2012 therefore the results confirmed the existence of space time thermal anomalies related to destructive earthquakes and revealed that the rst method is a reliable approach to detect disturbances of the earth s thermal emission

assessing the potential of thermal infrared satellite surveys for monitoring seismically active areas the case of kocaeli izmit earthquake august 17 1999 abstract space time anomalies of earth s emitted radiation in the thermal infrared spectral range tir measured from satellite months to weeks before the occurrence of earthquakes have been interpreted by several authors as pre seismic signals the claimed connection of tir emission with seismic activity has been considered up to now with some caution by the scientific community mainly for the insufficiency of the validation data sets and the scarce importance attached by those authors to other causes e g meteorological that rather than seismic activity could be responsible for the observed tir signal fluctuations in this paper a robust satellite data analysis technique is described which permits us to identify anomalous space time tir signal transients even in very variable observational satellite view angle land topography and coverage etc and natural e g meteorological conditions a statistically well founded definition of tir anomaly is given and proposed as a suitable tool for satellite tir surveys in seismically active regions eight years of meteosat tir observations have been analyzed in order to characterize the tir signal behavior at each specific observation time and location space time tir signal transients have then been analyzed both in the presence validation and in the absence of confutation seismic events looking for possible space time relationships the devastating earthquake which occurred in turkey izmit august 17 m s 7 8 in 1999 has been considered as a test case for validation relatively unperturbed periods no earthquakes with m 5 were taken for confutation purposes quite intense s n 3 5 and rare spatially extensive and time persistent tir signal transients were identified appearing eight days before the izmit main shock in greece moving to turkey on august 13 and disappearing moving back to greece some days after possible implications of such results together with present limitations of the proposed technique will also be discussed in the light of the improved performances expected by its extension to other existing or future satellite packages

physical properties of the variations of the electric field of the earth preceding earthquakes ii determination of epicenter and magnitude abstract as reported in the preceding paper a transient change of the electric field of the earth seismic electric signal hereafter called ses appears many hours before an earthquake eq by measuring this change in a given direction and dividing it with a suitable relative effective resistivity one obtains a quantity that reflects the current density in this direction measurements in two directions e w and n s give the relative signal intensity jrel at the station under consideration by measuring jrel at a number of stations and considering that it attenuates according to a 1 r law the epicenter can be determined with an accuracy usually around 100 km once the epicenter has been determined the product jrel r can be evaluated so that the magnitude m can be estimated by resorting to an empirical log jrel r versus m plot the uncertainty of m is around 0 5 units following sobolev 1975 and for the statistics to be beyond any doubt predictions were officially documented before the eq occurrence for 23 earthquakes with a magnitude equal or greater than ms 5 0 two events were missed the present method is compared to other electrical methods used in china japan and soviet union a number of problems concerning the origin of the effect its directivity and the attenuation with distance remain open for further studies

magnitude of velocity anomalies prior to earthquakes a model is presented which allows us to reexamine the interpretation of velocity anomalies observed before some earthquakes occur this model extends the well known dilatancy models by accounting for two scales of heterogeneities the variations in pore crack compressibility at a microscopic scale and the variations in the spatial fluid distribution for partially saturated rocks at a much larger scale this model is relevant for cracked rocks which are partially saturated such a situation is likely to develop in impending earthquake source areas although previous models have considered cracked rocks and partially saturated rocks none of the above heterogeneity induced effects has been considered previously so that the previous predictions are in fact shown to be inappropriate at earthquake or exploration seismic frequencies 1 100 hz saturation inhomogeneity can play a prominent role and this results in velocity dispersion so that high frequency predictions may not be valid and low frequency velocities should be calculated in order to do that we assume that crustal rocks are described by a saturated matrix in which spherical undersaturated pockets are embedded the matrix is itself made of a rock containing an isotropic distribution of cracks then low and high frequency velocities are calculated coupling the biot gassmann domenico theory with the effective medium approach differential self consistent method if the diffusion dilatancy model of scholz et al 1973 is superimposed on our theoretical velocity curves it appears that the low frequency predicted velocity anomaly is quite high when saturation heterogeneities are ignored it is however quite small if this effect is taken into account this result can explain the lack of observations of precursory changes of seismic velocities before many events

a statistical procedure for the analysis of seismotectonically induced hydrochemical signals a case study from the eastern carpathians romania changes in the stress field of an aquifer system induced by seismotectonic activity may change the mixing ratio of groundwaters with different compositions in a well leading to hydrochemical signals which in principle could be related to discrete earthquake events due to the complexity of the interactions and the multitude of involved factors the identification of such relationships is a difficult task in this study we present an empiric statistical approach suitable to analyse if there is an interdependency between changes in the chemical composition of monitoring wells and the regional seismotectonic activity of a considered area to allow a rigorous comparison with hydrochemistry the regional earthquake time series was aggregated into an univariate time series this was realized by expressing each earthquake in form of a parameter beq taking into consideration both energetic magnitude of a seismic event and spatial parameters position of epi hypocentrum relative to the monitoring site the earthquake and the hydrochemical time series were synchronised aggregating the e parameters into bearthquake activityq functions e which takes into account the time of sampling relative to the earthquakes which occurred in the considered area for the definition of the aggregation functions a variety of different beq parameters were considered the set of earthquake functions e was grouped by means of factor analysis to select a limited number of significant and representative earthquake functions e to be used further on in the relation analysis with the multivariate hydrochemical data set from the hydrochemical data a restricted number of hydrochemical factors were extracted factor scores allow to represent and analyse the variation of the hydrochemical factors as a function of time finally regression analysis was used to detect those hydrochemical factors which significantly correlate with the aggregated earthquake functions this methodological approach was tested with a hydrochemical data set collected from a deep well monitored for two years in the seismically active vrancea region romania three of the hydrochemical factors were found to correlate significantly with

groundwater microtemperature in earthquake regions microtemperature measurements of groundwater with a relative precision better than 1 1000 c have been made in several seismically active areas in japan the measured temperatures show clear coseismic signals as well as a correlation with atmospheric pressure simultaneous observations at various depths have shown that these temperature changes were not induced by simple groundwater level changes also distinctive signals occurred before several earthquakes and seem to be caused by a different mechanism than the coseismic signals the microtemperature at some observation sites shows excellent correlation with records of nearby sensitive borehole strainmeters simultaneous recording of microtemperature and strain has been initiated in some boreholes

rotation of rigid elliptical cylinders in viscous simple shear flow analogue experiments we used experiments to investigate the behaviour of rigid elliptical cylinders embedded in a viscous fluid of finite thickness and for very small ratios s between shear zone width z and the shortest principal axis e2 of the ellipse that constitutes the base of the elliptical cylinder 3 5 s z e2 1 2 former theoretical and experimental work on the rotation of rigid inclusions immersed in a viscous matrix considered infinite shear zone thickness and or a very large ratio between shear zone thickness and inclusion size s 1 and concluded that inclusions rotate continuously and synthetically with the applied bulk simple shear flow except for inclusions with infinite axial ratio our results depart greatly from the analytical predictions experiments were carried out at constant shear zone thickness but variable s and degree of coupling at the inclusion matrix interface the results show that 1 confined inclusion rotation always deviates from theoretical predictions for infinite shear zone thickness even for synthetic rotation 2 the deviation in the angular velocity and or in the sense of rotation increases as s approaches 1 and antithetic rotation is possible from a position with ellipse longest axis parallel to the shear plane and 3 a slipping inclusion matrix interface greatly enhances deviation from theoretical predictions with antithetic rotations to as much as 20

a robust satellite technique for monitoring seismically active areas the case of bhuj gujarat earthquake abstract a robust satellite data analysis technique rat has been recently proposed as a suitable tool for satellite tir surveys in seismically active regions and already successfully tested in different cases of earthquakes both high and medium low magnitudes in this paper the efficiency and the potentialities of the rat technique have been tested even when it is applied to a wide area with extremely variable topography land coverage and climatic characteristics the whole indian subcontinent bhuj gujarat s earthquake occurred on 26th january 2001 m s 7 9 has been considered as a test case in the validation phase while a relatively unperturbed period no earthquakes with m s 5 in the same region and in the same period has been analyzed for confutation purposes to this aim 6 years of meteosat 5 tir observations have been processed for the characterization of the tir signal behaviour at each specific observation time and location the anomalous tir values detected by rat have been evaluated in terms of time space persistence in order to establish the existence of actually significant anomalous transients the results indicate that the studied area was affected by significant positive thermal anomalies which were identified at different intensity levels not far from the gujarat coast since 15th january but with a clearer evidence on 22nd january and near the epicentral area mainly on 21st january on 25th january 1 day before gujarat s earthquake significant tir anomalies appear on the northern indian subcontinent showing a remarkable coincidence with the principal tectonic lineaments of the region thrust himalayan boundary on the other hand the results of the confutation analysis indicate that no meaningful tir anomalies appear in the absence of seismic events with m s 5

time variable response characteristics of groundwater radon to earthquakes a clear coseismic anomaly of groundwater radon was observed for a magnitude 5 6 earthquake that occurred on may 11 1992 the coseismic radon anomaly was observed at a station which is located right on a major active fault in northeast japan and about 140 km away from the hypocenter this was the first time that an earthquake with m 6 had ever been accompanied by a clear radon anomaly at the station although we had observed 12 similar coseismic radon anomalies at the station during the observation period from 1984 to 1987 all of the earthquakes that were accompanied by radon anomalies in that period had been with magnitude 6 0 and over surprisingly the radon concentration has become more sensitive to show coseismic anomalies even for m 5 earthquakes since october 1992 this enhancement of sensitivity of the coseismic radon response may be attributed to the progress of micro crack formation in the fracture zone of the active fault which could be related to unusual stress accumulation in the region

extensional detachment at the inclusion matrix interface in a multiple inclusion system abstract this paper deals with a theoretical analysis of extensional fissures around spherical rigid inclusions hosted in a ductile matrix undergoing bulk shear the analysis shows that the mechanical interaction of inclusions is a function of the inclusion concentration a b 2 a and 2 b are the inclusion diameter and mean inter inclusion distance respectively and intensifies the tensile stress imparted by the flowing matrix on the inclusion matrix interface inclusion concentration a b thus appears to be a crucial parameter in perturbing the inclusion matrix coherence and leading to formation of extensional fissures around an inclusion we performed numerical simulations to delineate the fields for coherent and incoherent interfaces in the t o a b space where t o is the tensile strength of the interface normalized to where and are the viscosity of matrix and bulk shear rate respectively for a given a b the interface cannot remain coherent unless the tensile strength is greater than a critical value the critical t o increases almost linearly at a gentle gradient with increasing a b however for a b 0 7 this increases nonlinearly assuming a large value when the concentration is high a b 0 8 it is also revealed that under the same deformation conditions the instantaneous opening in fissures may vary depending upon the a b values

degassing of deep groundwater in fractured rock around boreholes and drifts deep groundwater contains dissolved gases that may come out of solution if the water pressure is lowered water pressures are often decreased down to atmospheric pressure when water is withdrawn from deep boreholes and drifts in the bedrock for example in investigations regarding nuclear waste disposal groundwater degassing may then contribute to the development of a local unsaturated zone around the borehole or drift which may affect inflow and as a consequence the outcome of hydraulic and tracer tests in fractured rock laboratory experiments with gas saturated water in rock fracture replicas have demonstrated that degassing causes considerable hydraulic conductivity reduction under certain conditions degassing has also been hypothesized to be the cause of observed flow reductions in the field however supporting field experiments have so far been lacking we report results that constitute the first field support of the development of an unsaturated zone and as a consequence hydraulic conductivity reduction due to groundwater degassing around a borehole the borehole tests were conducted approximately 450 m below the groundwater table at the aspo hard rock laboratory in southeastern sweden no hydraulic conductivity reductions were observed at gas contents of about 1 whereas a 50 reduction in hydraulic conductivity was observed at a gas content of 13 formal hypothesis testing based on all available field and laboratory degassing tests supports degassing as the actual cause of the observed hydraulic conductivity reduction at the higher gas content we also show analytically that hydraulic conductivity reductions due to degassing may occur at much lower gas contents around drifts than around boreholes

stress transfer and nonlinear stress accumulation at subduction type plate boundaries application to the aleutians a study of stress accumulation in seismic gaps and of stress transfer along linear plate boundaries is presented time dependent reloading of plate boundaries following seismic ruptures is modeled by a modified elsasser model of a coupled lithosphere asthenosphere plate system this model is applied to study a series of large earthquakes in the aleutian islands and the alaska peninsula in 1938 1965 it is found that the rat island earthquake and the 1948 earthquake in the central aleutians are likely to have been triggered by adjacent ruptures in the sense that their occurrence would have come at a later time had their neighboring segments not been ruptured stresses in the unalaska gap and the shumagin gap are at a relatively high level and these segments of the plate boundary may be expected to rupture in the near future in general in the ten years about 16 of the earthquake cycle for the aleutians following an earthquake the stress recovery in the rupture zone is highly nonlinear resulting in a much more rapid stress accumulation than the linear case even at a later stage of an earthquake cycle adjacent ruptures can cause an acceleration of loading rate in addition to the coseismic stress jump a good example is the influence of the 1964 alaska earthquake on the 1938 rupture zone a general conclusion of this work is that long term earthquake prediction models must take into account the nonlinear stress accumulation behavior in seismic gaps also we have shown the interaction of adjacent plate boundary segments which suggests that some large earthquakes may have been triggered by nearby ruptures

pre seismic responses of underground water level and temperature concerning a 4 8 magnitude earthquake in greece on october 20 1988 abstract it is widely known that level and temperature changes of the underground waters are associated with earthquake activity in this paper we present results obtained from a simple and indeed inexpensive underground water level and temperature monitoring network established for the first time in a seismic zone of greece sharp changes in the underground water level and temperature have been recorded mainly as pre seismic events of the earthquake of magnitude 4 8 which occurred in the area of the network on october 20 1988

geoelectric potential changes possible precursors to earthquakes in japan whether electromagnetic precursors to earthquakes eqs exist is an important question not only for eq prediction but also for understanding the physical processes of eq generation slow transient geoelectric potential changes have been observed before several recent eqs in japan in most cases they appeared 1 19 days before the eqs and their duration and intensity were several minutes to 1 h and 1 2 mv 100 m the changes appeared before five of all six eqs with magnitude 5 that occurred within 20 km of our stations during the observation period changes were also detected at greater epicentral distances up to 75 km before two other eqs including one eq of magnitude 4 7 which was preceded by a signal simultaneously recorded at three widely separated stations these geoelectric potential changes have been distinguished through the following criteria from a multitude of other changes which were noise of various origins i the selected changes were proportional in amplitude to the length of the recording station s short 100 m dipoles and were simultaneously detected also on long 1 10 km dipoles when the latter were in operation ii no such changes occurred during the observation period that were not followed by eqs although the eq precursory nature of these geoelectric potential changes is admittedly unproven it seems that the present results warrant continued serious research into the occurrence generation and transmission of these signals and their possible causal relationship to eqs

regional study of the anomalous change in apparent resistivity before the tangshan earthquake m 7 8 1976 in china electrical resistivity measurements have been conducted as a possible means for obtaining precursory earthquake information before five great earthquakes m 7 h 25 km in china the apparent resistivity a showed systematic variations within a region 200 km from the epicenters in particular 9 stations in the tangshan tianjin beijing region prior to the tangshan earthquake m 7 8 h 11 km 27 july 1976 showed a consistent decrease of apparent resistivity around the epicenter with a maximum resistivity change of 6 and a period of variation of 2 3 years simultaneous water table observations in this region showed a declining water table and ground surface observations indicated a slight 5 mm uplift in the epicenter region relative to its surroundings

physical properties of the variations of the electric field of the earth preceding earthquakes i abstract in an earlier paper we described the physical properties of the preseismic transient variations in the electrotelluric field the present letter clarifies a few points that were not properly emphasized in our previous publications furthermore recent results like that of the destructive kalamata earthquake on september 13 1986 indicate that the duration of a preseismic electric signal may reach considerably high values lasting up to several hours

tectonic leakage of fault bounded aquifers subject to non isothermal recharge a mechanism generating thermal precursors to seismic events abstract the thermal consequences of flow transients generated by deformation induced leakage at fault zones intersecting confined aquifers have been examined using a simple analytical model the recharge of the aquifer is assumed to take place by vertical infiltration through the confining layers the energy equation relevant in this case has been derived by evaluating enthalpy fluxes associated with lateral and vertical components of fluid flows as well as that due to volume changes in the permeable layer generated by deformation induced alterations in the hydraulic head results of numerical simulations indicate that thermal transients arise during the stress build up period when the infiltrating fluids mix with those in the aquifer but relatively rapid return to equilibrium conditions occur as soon as the leakage is cut off the model is thus capable of reproducing the characteristic features of thermal precursors found in observational records according to model results the growth of thermal perturbation as well as the time for attaining steady state conditions is proportional to the recharge rate the magnitude of the perturbation is related to the thermal gradients in the confining layers but permeability contrast between the confining layer and the aquifer also plays a significant role the model results also indicate that precursory signals are likely to be significant only in areas close to the fault plane where tectonic leakage has a direct influence on the hydraulic head of the aquifer if the fault plane is sensitive to deformation the tectonic leakage rate may undergo substantial changes in response to changing stress patterns and this in turn may easily lead to abrupt and substantial changes in the local thermal regime some of the transient thermal anomalies observed in records of temperatures in boreholes in tectonically active areas have characteristics similar to those predicted by the deformation induced leakage model examples are presented illustrating model fits to thermal transients identified as precursors to seismic events in firjusa turkmenistan didiweli georgia and izu peninsula japan the possibility of obtaining complementary information on processes responsible for fluid flow during pre seismic periods is pointed out it appears that the occurrence of thermal anomalies associated with small scale tectonic deformation may not be uncommon its detection depends on availability of suitable boreholes and of the facilities for monitoring of temperatures using high precision sensors over periods comparable to local recurrence periods of earthquakes