fractal structure of spatial distribution of microfracturing in rock summary a constant stress fracture experiment of oshima granite was carried out at the confining pressure of 40mpa hypocentres of 2064 acoustic emissions were located during the experiment using the correlation integral we found that the spatial distribution of hypocentres of acoustic emission is a fractal and that the fractal dimension decreases with the evolution of rock fracturing the spatial distribution of earthquake s hypocentres reveals fractals ranging from regional to worldwide distribution if we extrapolate from laboratory measurements it is possible to predict the occurrence of large earthquakes by the decrease in the fractal dimension

northeast oriented transpression structure in the northern new madrid seismic zone extension of a shear zone across the reelfoot fault stepover arm high resolution seismic reflection profiles recently acquired 12 km northeast of the new madrid seismic zone s reelfoot thrust and along the central axis of the reelfoot rift imaged steeply dipping n30 e striking faults that have uplifted and arched post paleozoic sediments in a manner consistent with a dextral strike slip component of displacement the subparallel fault strands have been traced 1 4 km between reflection profiles in order to evaluate the structure s potential regional scale the strike was projected northeast 22 km to its intersection with a nearby industry profile at the intersection this lower resolution profile exhibits a discrete 0 75 km wide structure with style and offset similar to the high resolution lines the high resolution images indicate the deformation extends above paleozoic bedrock affecting the late cretaceous and eocene mississippi embayment sediments as well as the base of the quaternary the paleozoic and cretaceous horizons show as much as 75 and 50 m of relief respectively with the middle eocene and basal quaternary disrupted 25 and 15 m respectively geologic and geophysical logs from a borehole adjacent to the seismic lines constrain the depth velocity and stratigraphic interpretations we interpret the faults as a minimum 34 km northeast extension of the axial fault zone from a throughgoing intersection with the left stepover reelfoot thrust

near surface structural model for deformation associated with the february 7 1812 new madrid missouri earthquake the february 7 1812 new madrid missouri earthquake m moment magnitude 8 was the third and final large magnitude event to rock the northern mississippi embayment during the winter of 1811 1812 although ground shaking was so strong that it rang church bells stopped clocks buckled pavement and rocked buildings up and down the eastern seaboard little coseismic surface deformation exists today in the new madrid area the fault s that ruptured during this event have remained enigmatic we have integrated geomorphic data documenting differential surficial deformation supplemented by historical accounts of surficial deformation and earthquake induced mississippi river waterfalls and rapids with the interpretation of existing and recently acquired seismic reflection data to develop a tectonic model of the near surface structures in the new madrid missouri area this model consists of two primary components a north northwest trending thrust fault and a series of northeast trending strike slip tear faults we conclude that the reelfoot fault is a thrust fault that is at least 30 km long we also infer that tear faults in the near surface partitioned the hanging wall into subparallel blocks that have undergone differential displacement during episodes of faulting the northeast trending tear faults bound an area documented to have been uplifted at least 0 5 m during the february 7 1812 earthquake these faults also appear to bound changes in the surface density of epicenters that are within the modern seismicity which is occurring in the stepover zone of the left stepping right lateral strike slip fault system of the modern new madrid seismic zone

slow deformation and lower seismic hazard at the new madrid seismic zone global positioning system gps measurements across the new madrid seismic zone nmsz in the central united states show little if any motion these data are consistent with platewide continuous gps data away from the nmsz which show no motion within uncertainties both these data and the frequency magnitude relation for seismicity imply that had the largest shocks in the series of earthquakes that occurred in 1811 and 1812 been magnitude 8 their recurrence interval should well exceed 2500 years longer than has been assumed alternatively the largest 1811 and 1812 earthquakes and those in the paleoseismic record may have been much smaller than typically assumed hence the hazard posed by great earthquakes in the nmsz appears to be overestimated

quaternary faulting in the southern mississippi embayment and implications for tectonics and seismicity in an intraplate setting the recently recognized saline river fault zone in the southwestern mississippi embayment strike 135 is characterized by moderate historic seismicity we document paleoseismicity possibly strong on the saline river fault zone that is outside the known region of neotectonism in the northern embayment six surface faults were excavated within the saline river fault zone and all faults displace marine eocene units and fluvial pliocene pleistocene units five show post wisconsin loess movement thermoluminescence tl age 23 6 3 ka and three deform middle to late holocene eolian silt tl age 5 1 0 6 ka and 3 6 0 5 ka as fault tip flexures along the principal excavated fault fault plane braiding and plunging drag folding suggest a strong component of left slip and subsidiary faults show both normal and reverse displacement 1m of pliocene pleistocene wisconsin and holocene units we interpret these faults as components of a left slip flower structure a shallow seismic reflection profile acquired across the principal fault and a subsidiary fault shows eocene stratigraphy separated in a reverse sense below 120 m depth and separated in a normal sense above 120 m supporting a strike slip interpretation in addition the only focal plane mechanism available in the area indicates left slip with a small reverse component we conclude that the saline river fault zone is a paleozoic mesozoic basement fault zone reactivated as a left slip system in a quaternary east west compressive stress field field evidence suggests that earthquakes with several meters of strike slip may be characteristic and the width of a liquefaction field on the saline river fault zone suggests an event of magnitude 5 5 6 considering a similarity of strike and sense of holocene movements of the meers fault of southern oklahoma and of the saline river fault zone there may be additional active fault zones that pose seismic hazards concealed by sediments in southern north america

space geodetic evidence for rapid strain rates in the new madrid seismic zone of central usa a series of large earthquakes centred on the town of new madrid in the mississippi valley in the winter of 1811 12 still reverberates in the world of seismology the controversy relates to their origin over 2 000 km from the nearest plate boundary and their relevance to earthquake hazard today the population of new madrid in the early nineteenth century was tiny a similar event today would have much more serious consequences new evidence based on gps data points to the existence of rapid strain rates in the area comparable in magnitude to those across active plate boundaries and consistent with known active faults in the region in the winter of 1811 1812 near the town of new madrid in the central united states and more than 2 000 km from the nearest plate boundary three earthquakes within three months shook the entire eastern half of the country and liquefied the ground over distances far greater than any historic earthquake in north america1 2 the origin and modern significance of these earthquakes however is highly contentious3 geological evidence demonstrates that liquefaction due to strong ground shaking similar in scale to that generated by the new madrid earthquakes has occurred at least three and possibly four times in the past 2 000 years refs 4 6 consistent with recurrence statistics derived from regional seismicity7 here we show direct evidence for rapid strain rates in the area determined from a continuously operated global positioning system gps network rates of strain are of the order of 10 7 per year comparable in magnitude to those across active plate boundaries and are consistent with known active faults within the region these results have significant implications for the definition of seismic hazard and for processes that drive intraplate seismicity

continuity of the reelfoot fault across the cottonwood grove and ridgely faults of the new madrid seismic zone previous investigators have argued that the northwest striking reelfoot fault of northwest tennessee and southeastern missouri is segmented one segment boundary is at the intersection of the northeast striking cottonwood grove and ridgely strike slip faults with the reelfoot fault we use seismic reflection and geologic mapping to locate and determine the history of the reelfoot south fault across this boundary zone one reflection profile revealed a southwest dipping 81 reelfoot south reverse fault that displaces the top of the paleozoic 65 m cretaceous 40 m paleocene 31 m eocene wilcox group 20 m and eocene memphis sand 16 m a second reflection profile reveals a north dipping 84 reverse fault 4 3 km south of the reelfoot south fault which defines the southwest margin of the tiptonville dome a geologic profile of the base of the 3 1 ma upland complex mississippi river terrace alluvium within the mississippi river bluffs reveals 6 m of displacement across the reelfoot south fault similarly quaternary stream terrace distribution suggests 6 m of reelfoot south hanging wall tiptonville dome uplift that is probably holocene fault strike trends show the reelfoot fault and its hanging wall tiptonville dome are not laterally offset across the cottonwood grove and ridgely faults the reelfoot south fault northwest and southeast of the cottonwood grove and ridgely faults has very similar vertical displacement on common stratigraphic marker horizons in the upper 900 m these data indicate the reelfoot fault tiptonville dome has acted as one continuous fault zone across the cottonwood grove and ridgely faults since late cretaceous

the solubility of halite as a function of temperature in the highly saline dead sea brine system the dead sea brine is characterized by high ionic strength 9 10 m and a ca cl composition the lake is currently saturated with respect to aragonite gypsum and halite harned s rule is applied to calculate the saturation index of halite in the dead sea brine system this system includes brines at ionic strengths in the range of 9 l 6 1 derived from evaporating dead sea brine to facilitate the calculation we determined new interaction coefficients experimentally these were found to be a function of the ionic strength of the solution as well as of the temperature 25 c anaa mgc12 0 002611 0 00905 anac1 caci 0 001501 0 00650 3 5 c anac l m cl 0 002831 0 01972 anacl caci 0 002071 0 01851 50 c anaci m l 0 002261 0 01416 anaci cacl 0 001561 0 01315 the new parameters are used to predict the effect of temperature on halite precipitation in the lake from both the evaporating surface layer and the entire upper water body the calculated weight of halite expected to precipitate before the onset of carnallite precipitation is on the order of lo o t at the present rate of evaporation at least 120 yr will pass before that point is reached

the mechanism of deformation and fracture in potash rock specimens of potash rock from the rocanville mine of the potash corporation of saskatchewan were subjected to uniaxial compression tests and to time dependent creep tests under static uniaxial loading during the first cycle of loading the main sources of the measured strain are compaction and dilation at grain boundaries and consolidation of the clay phase the crystals of halite and sylvite deform elastically at low stress and in a brittle manner at high stress there is little if any evidence for constant volume plastic deformation at any level of uniaxial stress the stress strain curve can be divided into three parts each representing a different dominant deformational process a low stress quasi elastic an intermediate stress ductile and a high stress brittle mechanism the three parts are separated by the yield point 1 8 mpa and the crack initiation point 10 13 mpa the strength of the rocanville potash specimens ranged between 15 and 18 mpa the deformation of potash rock is strongly time

the sulfur system in anoxic subsurface brines and its implication in brine evolutionary pathways the ca chloride brines in the dead sea area abstract important elements in the evolutionary history of saline groundwater might be overlooked when they involve both sulfate removal through reduction and input of sulfate via dissolution these two simultaneous and apparently contrasting processes can result in a negligible net effect on the sulfate concentration isotopic composition of sulfur in sulfate and sulfide can be applied to identify the bacterial sulfate reduction bsr though the extent of the process is difficult to quantify saturation with respect to gypsum may suggest that gypsum dissolution also occurs however a more definite identification of these processes and their quantification can be achieved through the use of ammonium concentration in the anoxic brines this approach assumes that the ammonium is derived only from the oxidation of organic matter through bsr and it requires that the c n ratio in the oxidized organic matter be known a minimum estimate for the sulfate reduction can be obtained when the redfield c n ratio 106 16 is assumed several calculation methods are presented to identify the extent of sulfate reduction prior to concomitant with or following gypsum dissolution that are based on combining sulfur isotopic compositions rayleigh distillation equation and calculated gypsum saturation indices the required assumptions are presented and their validation is discussed the subsurface hypersaline ca chloride brines in the vicinity of the dead sea are taken as a case study here sulfur isotope compositions of sulfate and sulfide and high ammonium concentrations indicate bsr occurs in the subsurface the sulfur isotopic composition of the sulfate makes it possible to distinguish between two major groups of brine and their recent evolutionary histories 1 the qedem shalem thermal brines 34 s so4 21 24 which emerge as springs along the shores and are slightly undersaturated with respect to gypsum 2 dsif tappuah brines 34 s so4 30 60 which are found in shallow boreholes and are saturated to oversaturated with respect to gypsum calculations based on their ammonium content suggest that both groups of brine require apparent unreasonably high oversaturations with respect to gypsum prior to the onset of the reduction this implies that the groundwater systems were open with respect to sulfate and that the sulfate reservoir was replenished continuously or intermittently during the bsr the dsif tappuah brines continue to dissolve gypsum during their bsr the dissolving sulfate is derived from relatively isotopically enriched gypsums 34 s so4 20 such as found in the lisan formation these brines approach the steady state isotopic composition 34 s ss dictated by the combination of the 34 s of the dissolving gypsum and the fractionation factor accompanying bsr the sulfur isotopic composition of the qedem shalem brines implies that most of their ammonium content is derived from an earlier phase of bsr and that the last phase of bsr takes place during the brines rapid ascent to the surface prior to this stage they evolved through either 1 dissolution of gypsum with 34 s so4 20 which occurred after the main bsr in the subsurface 2 a previous phase in which the brines were part of a lake and later percolated to the subsurface as such their isotopic composition and ammonium content were determined by the combined effect of freshwater sulfate input to the lake and bsr in the stratified lake

relics of evaporated sea water in deep basins of the eastern mediterranean abstract reexamination of data on hypersaline bottom brines from the deep anoxic tyro and bannock basins in the eastern mediterranean reveals that despite their similar chlorinity 6 0 mole kg h 2 o their chemical composition is significantly different the brine in the tyro basin has a na chloride composition na cl 1 with conspicuously low ratios of conservative elements to chloride br cl 2 4 10 4 li cl 1 4 10 5 b cl 1 6 10 4 indicating dissolution of halite in contrast brines from the bannock basin are characterized by an mg chloride signature na cl 0 78 with relatively high ratios of conservative elements to chloride br cl 1 7 10 3 li cl 5 2 10 5 b cl 8 4 10 4 the contents of na mg k li cl br and b in the deep bannock brines brine ii are identical to those in evaporated sea water of a degree of evaporation of 12 13 whereas ca is enriched and so 4 is depleted in contrast to previous studies it is suggested that brine ii from the bannock basin is a relic of ancient evaporated sea water that was slightly modified by sulphate reduction and gypsum dissolution the interstitial ancient evaporated sea water was liberated and accumulated on the sea floor probably during the formation of the deep basins in the bannock area

time variable deformation in the new madrid seismic zone new geodetic measurements show that the new madrid is currently deforming too slowly if at all to account for large earthquakes in the region over the past 5000 years this result together with increasing evidence for temporal clustering and spatial migration of earthquake sequences in continental interiors indicates that either tectonic loading rates or fault properties vary over a few thousand years

strontium isotopic chemical and sedimentological evidence for the evolution of lake lisan and the dead sea precise strontium isotope ratios combined with chemical analyses and sedimentological information are used to monitor the water sources and the evolution of the dead sea and its late pleistocene precursor lake lisan 70 18 kyr b p the materials analyzed include bulk aragonite water leached soluble salts and residual aragonite and gypsum from the lisan formation in the perazim valley near the sw shore of the dead sea the residual aragonite and the associated soluble salts display systematic fluctuations in 17sr86sr ratios between 0 70803 and 0 70806 and from 0 70805 to 0 70807 respectively in individual soluble salt residual aragonite pairs the soluble salt displays a higher 87sr86sr ratio gypsum samples yield 17sr86sr ratios similar to the soluble salts from adjacent layers in the section this shows that in individual samples the source of sr in aragonite was distinct from that in soluble salts and the gypsum the sterility of the lisan sediments their strictly nonbioturbated fine lamination and their high content of chloride salts indicate that lake lisan was a saline or even hypersaline water body in the absence of alternative sources of hco3 and s042 the abundance of primary aragonite and gypsum in the lisan column reflects an import of very large volumes of freshwater into the otherwise saline lake resulting in a density stratification of this water body the history of the upper water layer and that of the lower brine is reflected in the chemical and strontium isotope composition of the aragonite and in that of the associated soluble salts and in the gypsum samples respectively whereas the bicarbonate and much of the ca2 required for aragonite crystallization were supplied by the freshwater the complementary ca2 and sr 2 were added by the lower brine the upper water layer of lake lisan acted as a so42 capacitor during the lake s rise periods it was removed therefrom as prominent gypsum beds upon climatic induced drier period mixing or even complete overturn of the lake the evolution of lake lisan took place between two distinct modes the first was characterized by an extensive supply of freshwater and resulted in a rise of the lake s level a density layered structure and precipitation of aragonite the second mode was marked by a diminishing freshwater input resulting in mixing or complete overturn of its water and precipitation of gypsum these two modes reflect the climatic evolution of the region in the late pleistocene which fluctuated between drier and wetter periods the transition to the holocene is accompanied by the dry up of lake lisan and its contraction to the present dead sea

refinement of thrust faulting models for the central new madrid seismic zone abstract we present the results of the joint relocation of events recorded during 1989 1992 by the panda network in the central new madrid seismic zone the near surface material in the study area is a gently dipping layer of poorly consolidated sediments with low p wave velocity and high v p v s estimated values 1 8 km s 1 and 3 the sediments are underlain by high velocity paleozoic rocks under the network the difference in sediment thickness is only 0 6 km but because of the low velocities the location of the events using layered models is affected by errors application of the joint hypocentral determination jhd technique to a subset of 580 events shows that the single event locations may be in error by as much as 1 km in depth depending on where the events are located analysis of synthetic data generated for a realistic 3 d velocity model supports the jhd results the analysis of synthetic data also suggests that a v p v s 2 3 is more appropriate for the post paleozoic mississippi embayment sediments based on the jhd locations we present a new interpretation of the seismicity with two en echelon sw dipping thrust faults connected by a west dipping thrust fault these faults appear associated with the reelfoot scarp and its northern extension the kentucky bend scarp

study of rock fracture by permeability method the permeability of sandstone was measured in triaxial tests within the range of confining pressures used here permeability as a function of differential stress was found to decrease until a minimum value was reached at about 60 70 of the fracture strength i e at a stress that lies between the crack initiation stress and the stress corresponding to the volumetric strain reversal thereafter permeability started to rise and at about 85 90 of the fracture strength its rate of increase was greater the permeability method was not sensitive enough to mark the point of crack initiation and the onset of crack coalescence however differential stress versus volumetric strain curves were in general similar to differential stress versus permeability curves thus the permeability method can be successfully used to study the fracture mechanism of rocks

seismology tectonic strain in plate interiors arising from r smalley jr m a ellis j paul r b van arsdale nature 435 1088 1090 2005 r smalley et al reply it is not fully understood how or why the inner areas of tectonic plates deform leading to large although infrequent earthquakes smalley et al 1 offer a potential breakthrough by suggesting that surface deformation in the central united states accumulates at rates comparable to those across plate boundaries however we find no statistically significant deformation in three independent analyses of the data set used by smalley et al and conclude therefore that only the upper bounds of magnitude and repeat time for large earthquakes can be inferred at present

displacement history and slip rate on the reelfoot fault of the new madrid seismic zone abstract a displacement history and slip rates were determined for the reelfoot fault in the new madrid seismic zone from a seismic reflection profile and trench data based on calculations from the seismic reflection line the average slip rate over the last 80 million years is 0 0009 mm year 1 slip rate during the late cretaceous was 0 0007 mm year 1 0 002 mm year 1 during the paleocene midway group 0 001 mm year 1 during paleocene eocene wilcox formation time 0 0003 mm year 1 during the post wilcox pre holocene period and a holocene slip rate of 1 8 mm year 1 based on trench data slip rate on the reelfoot fault has been 4 4 mm year 1 over the last 2400 years and a maximum of 6 2 mm year 1 during the two most recent earthquake cycles between ad 900 and ad 1812 the holocene slip rate is at least four orders of magnitude higher than the average late cretaceous and cenozoic slip rates for the reelfoot fault it would appear that there has been a quaternary change in the stress field in the central united states or the reelfoot fault is experiencing a short lived burst of seismic activity

dilation in granite during servo controlled triaxial strength tests abstract we investigated the stress strain response of three different intact granitic rocks to do this a press with servo controlled loading was modified to control the confining pressure in triaxial tests and to measure the volume of hydraulic fluid displaced from hoek s triaxial cell so that this volume could be related to volumetric strain in the rock sample a series of unconfined and confined compressive tests were performed on the rock samples and results were plotted analysed and interpreted regarding the most relevant parameters including elastic strength and post failure parameters with special attention paid to the dilation angle our main conclusions refer to the capability to investigate consistent post failure rock properties by means of servo controlled loading set ups which we plan to improve in the future the dilation angle of granite was captured with all the tested granites showing similar behaviour trends that fit reasonably well with recently developed theories on plastic shear strain and confinement stress dependent dilation and that are analogous to those observed for other hard rocks

northeastern extension of the new madrid north fault new madrid seismic zone central united states abstract analysis of electric and geologic logs of 517 shallow wells 91 m 300 ft deep in southeastern missouri has revealed a subsurface structural high herein called the charleston uplift trending n46 e from near new madrid missouri to cairo illinois that juxtaposes paleocene flour island formation against eocene claiborne group the charleston uplift is 30 km 19 miles long 7 2 km 4 5 miles wide and has a relief of 36 m 120 ft at the unconformity surface between the paleogene and quaternary sections two seismic reflection soundings one conducted north of the uplift and the second conducted within the uplift indicate 60 m 198 ft of apparent structural relief on the underlying top of the paleozoic 47 m 155 ft on the top of the late cretaceous and 19 m 63 ft on a tertiary reflector the charleston uplift is interpreted to be the northeastern extension of the new madrid north fault of the new madrid seismic zone and locally the western margin fault zone of the reelfoot rift although no surface faulting has been mapped along the charleston uplift the uplift appears to have influenced the holocene course of the mississippi river and displaced the paleocene quaternary unconformity thus indicating quaternary displacement of the charleston uplift across southeastern missouri which may continue beneath the ohio river valley into adjacent illinois and kentucky thus the charleston uplift strongly suggests quaternary structural continuity between the reelfoot rift and rough creek graben of kentucky although currently seismically quiet the 12 february 2012 m 3 9 earthquake and probably the 31 october 1895 m 6 6 charleston earthquake occurred on this structure thereby illustrating the seismic potential of this structure and extending the new madrid north fault system at least 30 km 19 miles

the origin of crowley s ridge northeastern arkansas erosional remnant or tectonic uplift the geomorphology of crowley s ridge apparent quaternary reactivation of the ridge bounding faults and orientation of the faults to the present stress field suggest that the faults bounding crowley s ridge and the western margin of the reelfoot rift may be seismogenic fifteen high resolution seismic reflection lines were acquired across and adjacent to the margins of crowley s ridge to test the hypothesis that corwley s ridge is fault bounded eleven of the reflection lines were 24 channel mini sosie data with 1 sec record length and four lines were 24 channel shotgun source data with 0 25 sec record length nine lines traversed the margins and adjacent areas of the northern segment of the ridge near jonesboro arkansas and the other six were located south of jonesboro on the southern segment the reflection data show that paleozoic through eocene wilcox sections have been uplifted beneath crowley s ridge from 60 to 30 m across ridge bounding faults however eocene or pliocene pleistocene near surface strata appear to be displaced a maximum of 7 5 m based on reflection and geomorphologic data we believe that reactivation of the bounding faults of crowley s ridge occurred concurrently with and strongly influenced wisconsin denudation of the mississippi valley

solubilities of gypsum and halite in the dead sea and in its mixtures with seawater1 the solubilities of gypsum cas04 2h 0 and halite nacl in aqueous solutions with ionic strengths between 3 and 13 were studied under ambient conditions mixtures of mediterranean seawater and dead sea brines evaporated to various degrees served as experimental solutions the practical solubility constant of gypsum k mca x vlso eq was found to be related to the ionic strength i of the solution by the empirical expression lox 5 498 0 3769z this relationship was then applied to calculate the degree of saturation with respect to gypsum dsg of the present dead sea water column calculations indicate that the entire dead sea water column ionic strength 9 10 is saturated or even slightly oversaturated with respect to both minerals studied

the earthquake potential of the new madrid seismic zone the fault system responsible for new madrid seismicity has generated temporally clustered very large earthquakes in a d 900 100 years and a d 1450 150 years as well as in 1811 1812 given the uncertainties in dating liquefaction features the time between the past three new madrid events may be as short as 200 years and as long as 800 years with an average of 500 years this advance in understanding the late holocene history of the new madrid seismic zone and thus the contemporary tectonic behavior of the associated fault system was made through studies of hundreds of earthquake induced liquefaction features at more than 250 sites across the new madrid region we have found evidence that prehistoric sand blows like those that formed during the 1811 1812 earthquakes are probably com pound structures resulting from multiple earthquakes closely clustered in time or earthquake sequences from the spatial distribution and size of sand blows and their sedimentary units we infer the source zones and estimate the magnitudes of earth quakes within each sequence and thereby characterize the detailed behavior of the fault system it appears that fault rupture was complex and that the central branch of the seismic zone produced very large earthquakes during the a d 900 and a d 1450 events as well as in 1811 1812 on the basis of a minimum recurrence rate of 200 years we are now entering the period during which the next 1811 1812 type event could occur

conduct and interpretation of gas permeability measurements in rock salt abstract a series of gas permeability measurements have been conducted surrounding excavations in a bedded rock salt formation the resolution of the measurement system is on the order of 10 20 to 10 21 m2 depdending on the test zone pressure and to a lesser degree on the test duration two types of tests were conducted constant pressure flow tests for permeabilities above 10 18 m2 and pressure decay tests for smaller permeabilities the gas flow data are interpreted in terms of transient flow through a compressible porous medium a finite difference solution was used to develop estimates of permeability and porosity which match the measured data the gas permeability of the undisturbed rock salt 1 to 5 m from an excavation is very low corresponding to a gas permeability of less than 10 21 m2 between the undisturbed region and the excavation the interpreted permeabilities range from 10 16 to 10 20 m2 generally immediately above and below excavations relatively great permeabilities are measured in the interbed layers these measurements substantiate the existance and nature of a limited disturbed rock zone sorrounding excavations in a bedded rock salt formation

reconciling short recurrence intervals with minor deformation in the new madrid seismic zone at least three great earthquakes occurred in the new madrid seismic zone in 1811 and 1812 estimates of present day strain rates suggest that such events may have a repeat time of 1000 years or less paleoseismological data also indicate that earthquakes large enough to cause soil liquefaction have occurred several times in the past 5000 years however pervasive crustal deformation expected from such a high frequency of large earthquakes is not observed this suggests that the seismic zone is a young feature possibly as young as several tens of thousands of years old and no more than a few million years old

constraints on evaporation and dilution of terminal hypersaline lakes under negative water balance the dead sea israel abstract the response of hypersaline terminal lakes to negative water balance was investigated by studying brines evaporating to extreme salinities in sinkholes along the western coast of the dead sea and during on site evaporation experiments of the dead sea brine density and temperature were determined in the field and all samples were analyzed for their major and a few minor solutes the activity of h 2 o a h2o in the brines was calculated and the degree of evaporation de was established using sr 2 as a conservative solute the relations between density and water activity were obtained by polynomial regression and the relation between the lake s volume and level was established using hall s 1996 hypsographic model for the dead sea basin relating the results to the modern long term relative humidity rh over the basin shows that a the lowermost attainable level of a terminal lake undergoing evaporation with no inflow is dictated by the median rh this level represents equilibrium between the brine s a h2o and rh b small saline water bodies with high surface to volume ratios a v such as the hypersaline brines in the sinkholes are very sensitive to short term changes in rh in these the brines a h2o closely follows the seasonal changes c the level decline of the dead sea due to evaporation under present climatic conditions and assuming no inflow to the lake may continue down to 516 537 m below mean sea level bmsl corresponding to a water activity range of 0 46 0 39 in its brine in equilibrium with the overlying relative air humidity this suggests that the lake level cannot drop more than 100 m from its present level and d the maximum rh values that existed over the precursor lake of the dead sea lake lisan during geologically reconstructed minima levels can be similarly calculated