on the viscosity of natural hyper saline solutions and its importance the dead sea brines summary the relationship between the density temperature and viscosity of hypersaline solutions both natural and synthetic is explored an empirical equation of the density viscosity relationship as a function of temperature was developed for the dead sea brine and its dilutions the viscosity levels of the dead sea brine density of 1 24 103 kg m3 viscosity of 3 6 mpa s at 20 c and of the more extremely saline natural brine density of 1 37 103 kg m3 were found to be 3 and 10 times greater than that of fresh water respectively the combined effect of the above changes in viscosity and density on the hydraulic conductivity is reduction by a factor of 3 7 the chemical composition significantly affects the viscosity of brines with similar densities whereby solutions with a higher mg na ratio have higher viscosity this explains the extremely high viscosity of the dead sea and related mg rich brines in comparison with the much lower values of nacl and kcl brines with similar density possible impacts of the results include reduced settling velocity of grains in hypersaline viscous brines and changing hydraulic dynamics at the freshwater saltwater and the vicinity of sinkholes

an appraisal of aftershocks behavior for large earthquakes in persia abstract this study focuses on the distribution of aftershocks in both location and magnitude for recent earthquakes in iran 43 earthquakes are investigated using data from the global international seismological center isc seismic catalogue and from the regional earthquake catalogue of the institute of geophysics university of tehran igut between 1961 2006 and 2006 2012 respectively we only consider the earthquakes with magnitude greater than 5 0 the majority of these events are intracontinental occurring over four seismotectonic provinces across iran processing aftershock sequences reported by both catalogues with cut off magnitude of 2 5 and a sequence duration of 70 days leads us to define a spatial horizontal area a occupied with the aftershocks as a function of mainshock magnitude m for persian earthquakes isc log10 a 0 45ms 0 23 igut log10 a 0 25mn 1 7 also we found a range for the difference between the magnitudes of the strongest aftershock and of the mainshock in each sequence which varies from 0 9 isc to 1 27 igut finally the spacial distribution of the aftershocks corresponds reasonably well to the causative fault planes of earthquakes

the long term stability of a possible aqueous ammonium sulfate ocean inside titan we model the thermal evolution of a subsurface ocean of aqueous ammonium sulfate inside titan using a parameterized convection scheme the cooling and crystallization of such an ocean depends on its heat flux balance and is governed by the pressure dependent melting temperatures at the top and bottom of the ocean using recent observations and previous experimental data we present a nominal model which predicts the thickness of the ocean throughout the evolution of titan after 4 5 ga we expect an aqueous ammonium sulfate ocean 56 km thick overlain by a thick 176 km heterogeneous crust of methane clathrate ice i and ammonium sulfate underplating of the crust by ice i will give rise to compositional diapirs that are capable of rising through the crust and providing a mechanism for cryovolcanism at the surface we have conducted a parameter space survey to account for possible variations in the nominal model and find that for a wide range of plausible conditions an ocean of aqueous ammonium sulfate can survive to the present day which is consistent with the recent observations of titan s spin state from cassini radar data lorenz r d stiles b w kirk r l allison m d del marmo p p iess l lunine j i ostro s j hensley s 2008 science 319 1649 1651

microseismicity and seismotectonics of the south caspian lowlands ne iran this paper is concerned with the microseismicity and seismotectonics of the eastern south caspian sea region where the east alborz mountains descend to meet the south caspian lowlands of ne iran to better understand the present day tectonics and seismicity of this region which includes the cities of gorgan and gonbad e qabus combined population 500 000 we installed a temporary local seismic network across the area for 6 months between 2009 and 2010 we analysed the seismicity and focal mechanisms together with data from the permanent networks of the institute of geophysics university of tehran igut and the international institute of earthquake engineering and seismology iiees based in tehran microseismicity is focused primarily on the shahrud fault system which bounds the east alborz range to the south relatively few earthquakes are associated with the khazar thrust fault which bounds the north side of the range a cluster of shallow microseismicity 15 km depth occurs 40 km north of the khazar fault within the south caspian lowlands scl an area typically thought to be non deforming this area coincides with the location of three relatively deep thrust earthquakes m w 5 3 5 5 which occurred in 1999 2004 and 2005 inversion of teleseismic body waveforms allows us to constrain the depth of these earthquakes at 26 29 km although significant sedimentation throughout the scl obscures any expression of recent fault activity at the surface focal mechanisms of well located events from the shallow cluster of micro seismicity show a significant component of left lateral strike slip motion assuming slip occurs on ne sw fault planes typical of active faults in the region as well as a small normal component inversion of traveltimes for well located events in our network yields a velocity structure for the region and a moho depth of 41 km the pattern of deep thrust and shallow normal seismicity could be explained by bending of the rigid south caspian crust as it underthrusts the east alborz mountains and central iran late quaternary reorganization of drainage systems in the scl may be the result of shallow normal fault activity within the scl

dawn arrives at ceres exploration of a small volatile rich world on 6 march 2015 dawn arrived at ceres to find a dark desiccated surface punctuated by small bright areas parts of ceres surface are heavily cratered but the largest expected craters are absent ceres appears gravitationally relaxed at only the longest wavelengths implying a mechanically strong lithosphere with a weaker deep interior ceres dry exterior displays hydroxylated silicates including ammoniated clays of endogenous origin the possibility of abundant volatiles at depth is supported by geomorphologic features such as flat crater floors with pits lobate flows of materials and a singular mountain that appears to be an extrusive cryovolcanic dome on one occasion ceres temporarily interacted with the solar wind producing a bow shock accelerating electrons to energies of tens of kilovolts

mud flow levitation on mars insights from laboratory simulations sediment mobilisation occurring at depth and ultimately manifesting at the surface is a process which may have operated on mars however the propagation behaviour of this mixture of water and sediments hereafter simply referred to as mud over the martian surface remains uncertain although most of the martian surface is below freezing today locally warmer surface temperatures do occur and our current knowledge suggests that similar conditions prevailed in the recent past here we present the results of experiments performed inside a low pressure chamber to investigate mud propagation over a warm 295 k unconsolidated sand surface under martian atmospheric pressure conditions 7 mbar results show that the mud boils while flowing over the warm surface the gas released during this process can displace the underlying sand particles and hence erode part of the substrate this entrenched flow can act as a platform for further mud propagation over the surface the escaping gas causes intermittent levitation of the mud resulting in enhanced flow rates the mud flow morphologies produced by these phenomena differ from those produced when mud flows over a frozen martian surface as well as from their terrestrial counterparts the intense boiling removes the latent heat both from the mud and the subsurface meaning that the mud flow would eventually start to freeze and hence changing again the way it propagates the diverse morphology expressed by our experimental mudflows implies that caution should be exercised when interpreting flow features on the surface of mars and other celestial bodies

teleseismic interpretation of the 1968 dasht e bayaz ne iran earthquake the 1968 dasht e bayaz earthquake is the oldest destructive earthquake in north east iran recorded by the wwssn network at teleseismic distances these records are well distributed in azimuth and allow a detailed study of the rupture process of the main shock we invert the wwssn long period body waves of the dasht e bayaz earthquake and its principal aftershock which occurred about 20 hours later to their sources to study the complexity of the sources the results of our analysis suggest that the main shock consists of three major subevents while the principal aftershock is a single event mechanisms of the subevents of the main shock are mainly strike slip and consistent with the observed fault movement the principal aftershock has a dip slip mechanism the sum of the seismic moments of the main shock is m0 4 5 1026 dyn cm the moment of the largest subevent of the main shock is m0 2 4 1026 dyn cm and its stress drop is about 200 bar this shows that the main shock has a high stress drop nature the largest subevent with shallow depth and large lateral displacement mostly caused the great destruction during the source process of the main shock the moment of the principal aftershock is m0 1 9 1025 dyn cm and its stress drop is about 40 bar mechanism of the earthquakes suggest that there is a shortening in north east iran mostly due to the north east compressional stress in the iranian plateau

microseismicity and seismotectonics of the firuzkuh and astaneh faults east alborz iran abstract in 2007 and 2008 we installed two local seismological networks of 10 stations around the two active faults of firuzkuh and astaneh which are part of the sharud fault system located in central alborz 150 km east of tehran iran these networks were deployed for about 7 months each and recorded 785 and 1194 earthquakes respectively we analyzed the seismicity and focal mechanisms together with data from the permanent network of the institute of geophysics university of tehran the tectonics of this area shows a pull apart relay bashm and chashm faults between the 2 left lateral strike slip faults of firuzkuh and astaneh firstly we computed the velocity structure which minimizes the travel time residuals and obtained a sedimentary cover of 4 km overlying an 8 km thick upper crust with a moho located at a depth of 33 5 km secondly we located the seismicity which is distributed mainly on the astaneh fault and chashm fault seismicity is also associated with the north semnan fault located farther south cross sections show that the north semnan fault is dipping north and both the chashm and astaneh faults are vertical the garmsar bashm and north alborz faults seem to be less active focal mechanisms associated with the chashm and astaneh faults show mainly strike slip motion left lateral on a ne sw trending active plane with no difference between the 2 faults suggesting they behave similarly

multiple parent bodies of ordinary chondrites abstract thermal histories of chondrite parent bodies are calculated from an initial state with material in a powder like form taking into account the effect of consolidation state on thermal conductivity the very low thermal conductivity of the starting materials makes it possible for a small body with a radius of less than 100 km to be heated by several hundred degrees even if long lived radioactive elements in chondritic abundances are the only source of heat the maximum temperature is determined primarily by the temperature at which sintering of the constituent materials occurs the thermal state of the interior of a chondrite parent body after sintering has begun is nearly isothermal near the surface however where the material is unconsolidated and the thermal conductivity is much lower the thermal gradient is quite large this result contradicts the conventional onion shell model of chondrite parent bodies but because the internal temperature is almost constant through the whole body it supports a multiple parent bodies model according to which each petrologic type of chondrite comes from a different parent body

bright carbonate surfaces on ceres as remnants of salt rich water fountains abstract vinalia and cerealia faculae are bright and salt rich localized areas in occator crater on ceres the predominance of the near infrared signature of sodium carbonate on these surfaces suggests their original material was a brine here we analyze dawn framing camera s images and characterize the surfaces as composed of a central structure either a possible depression vinalia or a central dome cerealia and a discontinuous mantling we consider three materials enabling the ascent and formation of the faculae ice ascent with sublimation and carbonate particle lofting pure gas emission entraining carbonate particles and brine extrusion we find that a mechanism explaining the entire range of morphologies topographies as well as the common composition of the deposits is brine fountaining this process consists of briny liquid extrusion followed by flash freezing of carbonate and ice particles particle fallback and sublimation subsequent increase in briny liquid viscosity leads to doming dawn observations did not detect currently active water plumes indicating the frequency of such extrusions is longer than years

palynological records of holocene monsoon change from the gulf of tonkin beibuwan northwestern south china sea article i nfo article history received 2 september 2008 palynological records in cores c4 and b106 from the gulf of tonkin reveal signals of paleo monsoon and paleoenvironmental change during the late pleistocene and holocene before 13 4 cal kyr bp the gulf of tonkin was exposed to the atmosphere and covered by grassland starting at 11 7 cal kyr bp the gulf of tonkin was inundated by brackish water indicated by the appearance of the brackish algae cleisto sphaeridium sentusidinium and spiniferites a decrease of herb content and an increase of pinus after hainan island was completely separated from the leizhou peninsula by qiongzhou strait at 8 5 cal kyr bp a continuous marine sedimentary environment was found the current patterns were similar to those of the present with a general trend of current homogenization reflected by gradually decreasing quantities of quercus pollen and a narrowing gap between the palynological concentrations of the southern and northern parts of the region the data suggest that three short periods of strengthened winter monsoons and currents were centered at 6 0 cal kyr bp 2 7 cal kyr bp and 0 2 cal kyr bp and that two short periods of strengthened summer monsoons and currents were centered at 7 5 cal kyr bp and 3 4 cal kyr bp

strike slip kinematics in central and eastern iran estimating fault slip rates averaged over the holocene 1 according to gps measurements the right lateral shear between central iran and afghan blocks amounts to 16 mm yr a model based on very long term estimates of fault rates suggests the current shear originated about 5 ma ago and has been accommodated by strike slip faulting limited to the western 2 mm yr gowk nayband fault and eastern 14 mm yr sistan system fault edges of the lut block we have used high resolution spot5 pixel size 2 5 m images to measure recent cumulative offsets and estimate slip rates over shorter time periods that average several seismic cycles only recent offsets a few tens of meters have been found along the anar fault inside the central iran plateau and along the sistan faults east of the lut the offset morphologies postdate the last incision of the network and are most probably of holocene age 12 2 ka the corresponding slip rates range between 0 5 0 75 mm yr 1 75 2 5 mm yr 1 5 mm yr 1 2 5 mm yr for the anar east neh west neh and asagie fault respectively these estimates suggest the gps shear rate across the lut may not extrapolate over the holocene they also indicate strike slip faulting is not confined to the lut edges but also occurs in central iran suggesting the ongoing strike slip tectonics might have originated between 8 and 22 ma ago earlier than considered previously and consistent with observations in ne iran

slurry extrusion on ceres from a convective mud bearing mantle ceres is a 940 km diameter dwarf planet that is predominantly composed of silicates and water ice in ceres partially differentiated interior extrusive processes have led to the emplacement on its surface of domes with heights of kilometres here we report the analysis of a gravity anomaly detected by the dawn spacecraft which is associated with the geologically recent dome ahuna mons by modelling the anomaly with a mass concentration method we determine that the subsurface structure includes a regional mantle uplift which we interpret as a plume this structure is the probable source of fluids forming ahuna mons and together with constraints from the dome s morphology indicates a rheological regime corresponding to a slurry of brine and solid particles we propose that the properties of such a solid liquid mixture can explain the viscous relaxation and the mineralogy of the dome the presence of a plume and of slurry material indicate recent convection in a mud bearing mantle the inferred slurry extrusion on ceres differs from the water dominated cryovolcanism of icy satellites and so reveals compositional and rheological diversity in extrusive phenomena on planetary surfaces ahuna mons dome on ceres formed by extrusion of a mixture of brine and solids sourced from a muddy mantle plume according to numerical modelling of slurry rheology and a gravity anomaly found by the dawn mission

a possible brine reservoir beneath occator crater thermal and compositional evolution and formation of the cerealia dome and vinalia faculae abstract the dawn spacecraft has imaged several putative cryovolcanic features on ceres and several lines of evidence point to past cryovolcanic activity at occator crater it is therefore possible that cryovolcanism played a key role in delivering sodium carbonate and chloride enriched brines to ceres surface in recent geological times the detection of a 200 km 200 km negative bouguer anomaly beneath occator suggests the presence of a low density region beneath the crater if this region is a residual partially crystallized cryomagma chamber excess pressures caused by its gradual freezing or stresses produced by the occator forming impact could have facilitated the delivery of cryolavas to the surface in the geologically recent past here the progressive solidification of a cryomagma chamber beneath occator and implications for the delivery of cryolavas to the surface has been explored models for the behavior of cryolavas at ceres surface and for the formation of the cerealia dome and vinalia faculae are also presented minimal crystallization of a subsurface fluid reservoir located at the crust mantle boundary could have driven cryolavas enriched in chloride salts and nh3 to ceres surface however cryolavas enriched in sodium carbonates would have had to have existed at shallower levels in the crust in order to be delivered to the surface via pressure driven ascent depending on the size of the reservoir cryolavas could have been driven to ceres surface for tens to hundreds of millions of years after cooling of the cryomagma chamber commenced the mineralogy at occator is suggestive of subsurface cryomagma reservoirs enriched in sodium carbonate and chloride salts aqueous solutions enriched in chloride salts and or ammonia would have arrived at the surface at warm enough temperatures to erupt if transported in propagating fractures that traveled at least 10 5 m s additionally if the cerealia dome was formed from viscous cryolava extrusions bulk kinematic lava viscosities may have been between 106 108 m2 s at the onset of relaxation plausible relaxation times to form the dome which are linked to bulk cryolava rheology are found to have ranged from 2 5 to 273 days moreover the low volatile content necessary to drive explosive eruptions on ceres supports the possibility that cerealia and vinalia faculae were emplaced as a consequence of ballistic eruptions the enigmatic geology of occator crater is consistent with a diversity of exchange processes operating on ceres in the geologically recent past further the processes that have occurred at occator could shed light on the changing geology associated with a relic ocean world future studies of occator and ceres should be undertaken with these results in mind

maximum magnitudes in aftershock sequences in taiwan abstract in this work bath s law the b value in gutenberg richter law g r law in the form of the 1 relationship and both the a and b values in the g r law were introduced in order to estimate maximum aftershock magnitudes of earthquake sequences in the taiwan region the averaged difference of magnitude between the mainshock and the maximum aftershock is 1 20 and is consistent with bath s law however with a large uncertainty the large uncertainty implies that the difference may result from a variable controlled by other factors such as the aftershocks number of an earthquake sequence and magnitude threshold for mainshock with 1 since 86 of the earthquake sequences with a m 6 0 mainshock follow this relationship the upper bound of the maximum magnitude can be estimated for an earthquake sequence with a large mainshock the a and b values in the g r law was also considered by evaluating maximum aftershock magnitudes as there are low residuals between the model and the observations the results suggest that the g r law is a good index for maximum aftershock magnitude determinations in order to evaluate the temporal decays of maximum aftershock magnitudes modified omori s law was introduced using the approaches mentioned above the maximum magnitudes and the temporal evolution of an earthquake sequence could be modeled among them the model of the g r law has the best fit with observations for most of earthquake sequences it shows its feasibility the results of this work may benefit seismic hazards mitigation in the form of rapid re evaluations for short term seismic hazards immediately following devastating earthquakes

geochemistry thermal evolution and cryovolcanism on ceres with a muddy ice mantle we present a model of the internal evolution of ceres consistent with pre dawn observations and preliminary data returned by dawn we assume that ceres accreted ice and both micron and millimeter sized rock particles and that micron sized fines stayed suspended in liquid during differentiation we conclude that aqueously altered grains were emplaced on ceres s surface during the first tens of megayears of its evolution our geochemical simulations suggest that ceres s unusual surface mineralogy is consistent with aqueous alteration of cm material possibly by nh3 bearing fluid thermal evolution simulations including insulating fines yield present day liquid at depth if ceres has a small core or no core at all otherwise they yield temperatures at the core mantle boundary of 240 250 k just warm enough for chloride brines to persist and be freezing today we hypothesize that ongoing freezing may overpressurize liquid or briny reservoirs driving cryovolcanic outflow whose surface expression may have been observed by dawn at ceres s bright spots these outflows may contribute to the water vapor being produced at ceres

compositional diapirism as the origin of the low albedo terrain and vaporization at midlatitude on ceres recent observations of ceres made using the heterodyne instrument for the far infrared on board the european space agency s herschel space observatory have shown that water vapor is emanated from the low albedo midlatitude regions based on the supposition that some dark spots on europa may be caused by diapirism we explored whether ceres environment also can induce compositional diapirism and whether an upwelling diapir could explain the origin and distribution of the dark spots and vaporization of ceres if the density of the rock that constitutes ceres is around 2700 kg m 3 the undifferentiated crust is stable over geological time periods at less than 180 k at a surface temperature of 170 k a diapir can reach the surface if the crust is a few tens of kilometers thick alternatively if the surface temperature is 150 k a large contrast in viscosity would prevent diapirs from reaching the surface the relatively moderate surface temperature in the midlatitude regions of ceres may be the reason for the formation of dark terrains occurring only in such areas our finite difference calculations do not show that diapirism melts the surface ice because the temperature gradient changes very little however if the observed vapor emission is caused by the sublimation of fresh ice compositional diapirism could be the mechanism that transports the fresh ice to the surface in addition to other mechanisms such as cryovolcanism diapirism is a valid hypothesis for explaining the dark terrain and vapor emissions of ceres

high pressure creep of serpentine interseismic deformation and initiation of subduction the supposed low viscosity of serpentine may strongly influence subduction zone dynamics at all time scales but until now its role could not be quantified because measurements relevant to intermediate depth settings were lacking deformation experiments on the serpentine antigorite at high pressures and temperatures 1 to 4 gigapascals 200 to 500 c showed that the viscosity of serpentine is much lower than that of the major mantle forming minerals regardless of the temperature low viscosity serpentinized mantle at the slab surface can localize deformation impede stress buildup and limit the downdip propagation of large earthquakes at subduction zones antigorite enables viscous relaxation with characteristic times comparable to those of long term postseismic deformations after large earthquakes and slow earthquakes antigorite viscosity is sufficiently low to make serpentinized faults in the oceanic lithosphere a site for subduction initiation

the origin of lunar mascon basins high resolution gravity data from the gravity recovery and interior laboratory spacecraft have clarified the origin of lunar mass concentrations mascons free air gravity anomalies over lunar impact basins display bull s eye patterns consisting of a central positive mascon anomaly a surrounding negative collar and a positive outer annulus we show that this pattern results from impact basin excavation and collapse followed by isostatic adjustment and cooling and contraction of a voluminous melt pool we used a hydrocode to simulate the impact and a self consistent finite element model to simulate the subsequent viscoelastic relaxation and cooling the primary parameters controlling the modeled gravity signatures of mascon basins are the impactor energy the lunar thermal gradient at the time of impact the crustal thickness and the extent of volcanic fill

spectral analysis of ahuna mons from dawn mission s visible infrared spectrometer ahuna mons is the highest mountain on ceres a unique complex in terms of size shape and morphology ahuna is bordered by flanks of the talus around its summit recent work by ruesch et al 2016 based on dawn s framing camera images shed light on the possible origin of ahuna mons according to ruesch et al 2016 ahuna mons is formed by a volcanic process involving the ascent of cryomagma and extrusion onto the surface followed by dome development and subsequent spreading here we analyzed in detail the composition of ahuna mons using data acquired by the visible and infrared spectrometer aboard dawn the spectral analysis reveals a relatively high abundance of carbonates and a non homogeneous variation in carbonates composition and abundance along ahuna s flanks associated with a lower amount of the ceres s ubiquitous nh4 phyllosilicates over a large portion of the flanks the grain size is coarser on the flanks than in the surrounding regions suggesting the presence of fresher material also compatible with a larger abundance of carbonates thermal variations are seen in ahuna supporting the evidence of different compactness of the surface regolith in specific locations results of the spectral analysis are consistent with a possible cryovolcanic origin which exposed fresher material that slid down on the flanks

the 2004 may 28 baladeh earthquake mw 6 2 in the alborz iran overthrusting the south caspian basin margin partitioning of oblique convergence and the seismic hazard of tehran we use teleseismic waveform analysis and locally recorded aftershock data to investigate the source processes of the 2004 baladeh earthquake which is the only substantial earthquake to have occurred in the central alborz mountains of iran in the modern instrumental era the earthquake involved slip at 10 30 km depth with a south dipping aftershock zone also restricted to the range 10 30 km which is unusually deep for iran these observations are consistent with co seismic slip on a south dipping thrust that projects to the surface at the sharp topographic front on the north side of the alborz this line is often called the khazar fault and is assumed to be a south dipping thrust which bounds the north side of the alborz range and the south side of the south caspian basin though its actual structure and significance are not well understood the lack of shallower aftershocks may be due to the thick pile of saturated overpressured sediments in the south caspian basin that are being overthrust by the alborz a well determined earthquake slip vector in a direction different from the overall shortening direction across the range determined by gps confirms a spatial separation partitioning of left lateral strike slip and thrust faulting in the alborz these strike slip and thrust fault systems do not intersect within the seismogenic layer on the north side though they may do so on the south the earthquake affected the capital tehran and reveals a seismic threat posed by earthquakes north of the alborz located on south dipping thrusts as well as by earthquakes on the south side of the range closer to the city

active tectonics and late cenozoic strain distribution in central and eastern iran 1 right lateral shear between central iran and afghanistan is accommodated on n s right lateral strike slip faults surrounding the aseismic dasht e lut north of 34 n the right lateral shear is accommodated on left lateral faults that rotate clockwise about vertical axes little is known of the late tertiary and younger offsets and slip rates on the active fault systems results that are important for understanding the regional tectonics we use observations from satellite imagery to identify displaced geological and geomorphological markers which we use in conjunction with the overall morphology and orientation of the active fault systems to estimate the total cumulative right lateral shear estimates of cumulative fault movements from offset features and inferred vertical axis rotation of fault bounded blocks suggest that the late cenozoic strain is concentrated toward the eastern margin of iran along the sistan shear zone where bedrock offsets of at least 70 km are observed across the active faults the geomorphology of the deh shir anar and great kavir strike slip faults in central iran suggest that although little shortening is accommodated across this region they might still be active and hence capable of producing earthquakes present day activity on these faults in central iran would not be expected from distributions of instrumental and historical earthquakes although speculative the late tertiary strain distribution described in this paper is consistent with what we know of the present day rates of shear in eastern iran and provides a framework to which later more detailed work can be added

microseismicity and seismotectonics of the north tabriz fault iran abstract we present the results of a microearthquake study conducted in 2004 with 31 portable stations around the city of tabriz which is crossed by an active fault and has experienced several destructive earthquakes in the recent history from april 24 until july 24 we recorded 80 earthquakes by more than 4 stations we complement these data with earthquakes recorded by the 8 permanent seismological stations of the tabriz network operated by institute of geophysics of the university of tehran from august 1995 until march 2008 among a total of 6377 events only 394 earthquakes were recorded by more than 5 stations and located with statistical uncertainties erz and erh less than 5 km and a gap less than 270 most of these earthquakes are located along the tabriz fault at a depth ranging from the surface to 20 km comparable to other studies conducted in central alborz we computed 22 focal mechanisms most of which show right lateral strike slip motion along east southeast planes consistent with the geologic evidence for quaternary slip we do not see any peculiar pattern near the tabriz pull apart basin or at both ends of the north tabriz fault where it terminates in ew trending reverse faults this suggests that the fault is simpler more mature at depth than at the surface

the 1997 may 10 zirkuh qa enat earthquake mw 7 2 faulting along the sistan suture zone of eastern iran summary the destructive zirkuh e qa enat earthquake of 1997 may 10 mw 7 2 ms 7 3 mb 6 3 produced 125 km of nnw sse right lateral strike slip surface faulting on the abiz fault in the sistan suture zone of eastern iran the longest known surface rupture associated with an iranian earthquake analysis of the body wave seismograms from the main shock shows that rupture occurred in four main subevents propagating in a sequence from north to south although predominantly strike slip the orientation of the faulting in each subevent varies with appreciable reverse components in the north central part and at the southern end of the abiz fault this change in fault style along the abiz fault inferred from the seismograms is also seen in the coseismic surface ruptures and the geomorphology average coseismic surface displacements were approximately 2 m implying a static stress drop of only 5 bar 0 5 mpa the 1997 surface ruptures followed clear traces of late quaternary slip on the abiz fault and for its northern 50 km re ruptured fault segments that had slipped in previous earthquakes of ms 6 0 6 6 in 1936 and 1979 the 1997 earthquake ruptured the northern end of the n s right lateral strike slip system of the sistan suture zone ending where it abuts a system of e w left lateral strike slip faults which have also slipped in large earthquakes during the last 30 years the earthquakes on this conjugate system of strike slip faults form a sequence that may have been triggered by the enhancement of stress on one fault as a result of slip on a neighbouring fault together these faults achieve n s right lateral shear of deforming iran against stable western afghanistan by n s slip on the right lateral faults and clockwise rotation of the e w left lateral faults

constraints on ceres internal structure and evolution from its shape and gravity measured by the dawn spacecraft ceres is the largest body in the asteroid belt with a radius of approximately 470 km in part due to its large mass ceres more closely approaches hydrostatic equilibrium than major asteroids pre dawn mission shape observations of ceres revealed a shape consistent with a hydrostatic ellipsoid of revolution the dawn spacecraft framing camera has been imaging ceres since march 2015 which has led to high resolution shape models of the dwarf planet while the gravity field has been globally determined to a spherical harmonic degree 14 equivalent to a spatial wavelength of 211 km and locally to 18 a wavelength of 164 km we use these shape and gravity models to constrain ceres internal structure we find a negative correlation and admittance between topography and gravity at degree 2 and order 2 low admittances between spherical harmonic degrees 3 and 16 are well explained by airy isostatic compensation mechanism different models of isostasy give crustal densities between 1 200 and 1 400 kg m3 with our preferred model giving a crustal density of 1 287 70 87 kg m3 the mantle density is constrained to be 2 434 5 8 kg m3 we compute isostatic gravity anomaly and find evidence for mascon like structures in the two biggest basins the topographic power spectrum of ceres and its latitude dependence suggest that viscous relaxation occurred at the long wavelengths 246 km our density constraints combined with finite element modeling of viscous relaxation suggests that the rheology and density of the shallow surface are most consistent with a rock ice salt and clathrate mixture

building mountains on ceres the large domes found on the dwarf planet ceres may not result from cryovolcanism but from solid state flow analogous to salt doming on earth according to numerical simulations of gravitational loading

accommodation of late cenozoic oblique shortening in the alborz range northern iran abstract the alborz range northern iran deforms by strain partitioning of oblique shortening onto range parallel left lateral strike slip and thrust faults deformation is due to the north south arabia eurasia convergence and westward motion of the adjacent south caspian relative to iran roughly north south shortening occurs on thrusts that dip inwards from the range margins precambrian basement is not exposed because of detachment along upper proterozoic evaporites and the thickness of overlying strata 10 km other detachments occur within phanerozoic sediments active left lateral strike slip faults trend ene in the east of the range wnw in the west the eastern mosha fault has a left lateral offset of 30 35 km shortening across the range is 30 km 25 30 at the longitude of tehran this is hard to reconcile with the crustal thickness of 35 km which is similar to adjacent basins percentage shortening across the alborz is similar to the adjacent kopet dagh but because the latter is twice as wide finite shortening is roughly half the difference may be accommodated by subduction of the adjacent south caspian basin northwards under the middle caspian south caspian sediments began folding in the pliocene the present kinematics of the alborz may have begun at this time including a reversal from range parallel right lateral to left lateral strike slip faulting but the regional stratigraphy indicates uplift as early as the mid tertiary

melting behavior of fluid inclusions in laboratory grown halite crystals in the systems naclh2o naclkclh2o naclmgcl2h2o and naclcacl2h2o abstract the chemical composition of aqueous fluid inclusions in crystals of halite can be accurately determined from observed melting behaviors of ice hydrohalite and sylvite some fluid inclusion melting behaviors observed in laboratory grown halite crystals systems nacl h 2 o nacl kcl h 2 o nacl mgcl 2 h 2 o and nacl cacl 2 h 2 o differ from predicted stable equilibrium relations in the nacl h 2 o and nacl kcl h 2 o systems observed first melt temperatures are up to 15 c below the equilibrium eutectic temperatures of 21 2 and 22 9 c respectively the final melting temperature of ice in the presence of hydrohalite and the final melting temperature of hydrohalite are reproducible and match predicted melting temperatures the limit of detection of sylvite daughter crystals in the nacl kcl h 2 o system is approximately 5 wt 1 molal kcl final melting temperatures of sylvite match published equilibrium data to within 0 3 c in the nacl kcl h 2 o system at halite saturation m kcl can be determined from the final sylvite dissolution temperature or from the final melting temperature of hydrohalite fluid inclusions in the nacl mgcl 2 h 2 o and nacl cacl 2 h 2 o systems that form stable salt hydrates mgcl 2 12h 2 o and cacl 2 6h 2 o during freezing first melt within 3 c of predicted eutectic temperatures 37 and 52 c however fluid inclusions with mgcl 2 or cacl 2 may also start melting at temperatures as low as 80 c such low first melt temperatures indicate the presence of metastable salt hydrates presumably mgcl 2 8h 2 o mgcl 2 6h 2 o or cacl 2 4h 2 o the formation of metastable phases during freezing of fluid inclusions can lead to misinterpretation of the chemical composition of fluid inclusions in natural samples this is especially true for fluid inclusions with first melt temperatures below 37 c which may be erroneously interpreted as being rich in cacl 2 the final melting of ice in the presence of hydrohalite may vary by more than 15 c in fluid inclusions of different size but identical bulk composition and occurs at lower temperatures than predicted in fluid inclusions from the nacl mgcl 2 h 2 o and nacl cacl 2 h 2 o systems however the final melting temperature of ice in inclusions which fail to nucleate hydrohalite and the final melting temperature of hydrohalite are reproducible to within 0 1 c and can be used to determine mgcl 2 and cacl 2 molalities

true polar wander of ceres due to heterogeneous crustal density ceres is the largest body in the main asteroid belt it was recently explored by the dawn mission to uncover strong similarities with other icy bodies the morphological features observed on the surface of ceres indicate a relatively wide range of water ice concentrations leading us to investigate the magnitude and distribution of crustal density heterogeneities and to consider whether they could have caused a reorientation of ceres here we present three independent and corroborating lines of evidence for the true polar wander of ceres thanks to the global gravity inversion approach applied to the shape and gravity data of ceres we find crustal density heterogeneities up to approximately 0 3 g cm 3 with a prominent positive density anomaly aligned with the equator in the region of ahuna mons the topography shows the remnants of an equatorial ridge compatible with the position of the palaeo equator and indicates that ceres reoriented by approximately 36 with the palaeo pole following an indirect path to the current pole of ceres the tectonic patterns generated by the true polar wander are in close agreement with the location and orientation of the samhain catenae and uhola catenae crustal fractures these results highlight the complex interior structure and richness of processes taking place in ceres scale icy bodies the dwarf planet ceres may have reoriented in the past due to a heterogeneously dense crust a scenario consistent with gravity and topographic data and the distribution of crustal fractures

experimental evidence for lava like mud flows under martian surface conditions large outflow channels on ancient terrains of mars have been interpreted as the products of catastrophic flood events the rapid burial of water rich sediments after such flooding could have led to sedimentary volcanism in which mixtures of sediment and water mud erupt to the surface tens of thousands of volcano like landforms populate the northern lowlands and other local sedimentary depocentres on mars however it is difficult to determine whether the edifices are related to igneous or mud extrusions partly because the behaviour of extruded mud under martian surface conditions is poorly constrained here we investigate the mechanisms of mud propagation on mars using experiments performed inside a low pressure chamber at cold temperatures we found that low viscosity mud under martian conditions propagates differently from that on earth because of a rapid freezing and the formation of an icy crust instead the experimental mud flows propagate like terrestrial pahoehoe lava flows with liquid mud spilling from ruptures in the frozen crust and then refreezing to form a new flow lobe we suggest that mud volcanism can explain the formation of some lava like flow morphologies on mars and that similar processes may apply to cryovolcanic extrusions on icy bodies in the solar system

the vanishing cryovolcanoes of ceres ahuna mons is a 4 km tall mountain on ceres interpreted as a geologically young cryovolcanic dome other possible cryovolcanic features are more ambiguous implying that cryovolcanism is only a recent phenomenon or that other cryovolcanic structures have been modified beyond easy identification we test the hypothesis that cerean cryovolcanic domes viscously relax precluding ancient domes from recognition we use numerical models to predict flow velocities of ahuna mons to be 10 500 m myr depending upon assumptions about ice content rheology grain size and thermal parameters slower flow rates in this range are sufficiently fast to induce extensive relaxation of cryovolcanic structures over 108 109 years but gradual enough for ahuna mons to remain identifiable today positive topographic features including a tholus underlying ahuna mons may represent relaxed cryovolcanic structures a composition for ahuna mons of 40 ice explains the observed distribution of cryovolcanic structures because viscous relaxation renders old cryovolcanoes unrecognizable

considerations for effusive cryovolcanism on europa the post galileo perspective 1 cryovolcanic resurfacing is a popular mechanism to explain relatively young surface units on icy satellites of jupiter saturn uranus and neptune prior to the galileo data acquired between 1996 and 2001 europa was thought to have undergone significant cryovolcanic resurfacing facilitated by a global ocean beneath the icy surface however close examination of galileo data at resolutions much better than those of voyager images show that many of the features previously thought to be cryovolcanic are commonly best explained by other formative mechanisms including tectonism and diapirism in this study i present an examination of the characteristics of a variety of europan surface features for which effusive cryovolcanism is a possible origin including apparently lobate flows certain elliptical to circular lenticulae and low lying smooth low albedo surfaces a review of cryovolcanic eruption theory together with galileo data analysis of europan surface geology and composition indicates that cryovolcanism is a viable though not unequivocal explanation for some of these features some constraints on cryomagma properties and lithospheric structure are offered for these cases the presence of small volume low viscosity effusions is supported by observations and modeling some positive relief lenticulae could represent more viscous effusions although diapirism may be a preferable explanation however strong evidence is lacking for cryovolcanic resurfacing on a large scale on the basis of our experience with galileo images of europa and ganymede voyager era inferences for widespread cryovolcanism on icy satellites may be overstated and will need to be carefully reexamined in the light of new data from upcoming spacecraft missions

the interior structure of ceres as revealed by surface topography abstract ceres the largest body in the asteroid belt 940 km diameter provides a unique opportunity to study the interior structure of a volatile rich dwarf planet variations in a planetary body s subsurface rheology and density affect the rate of topographic relaxation preferential attenuation of long wavelength topography 150 km on ceres suggests that the viscosity of its crust decreases with increasing depth we present finite element fe geodynamical simulations of ceres to identify the internal structures and compositions that best reproduce its topography as observed by the nasa dawn mission we infer that ceres has a mechanically strong crust with maximum effective viscosity 10 25 pa s combined with density constraints this rheology suggests a crustal composition of carbonates or phyllosilicates water ice and at least 30 volume percent vol low density high strength phases most consistent with salt and or clathrate hydrates the inference of these crustal materials supports the past existence of a global ocean consistent with the observed surface composition meanwhile we infer that the uppermost 60 km of the silicate rich mantle is mechanically weak with viscosity 21 pa s suggesting the presence of liquid pore fluids in this region and a low temperature history that avoided igneous differentiation due to late accretion or efficient heat loss through hydrothermal processes

the ceres gravity field spin pole rotation period and orbit from the dawn radiometric tracking and optical data abstract ceres gravity field and rotational parameters have been precisely measured using 1 5 years of radiometric doppler and range data and optical landmark tracking from the dawn spacecraft in orbit about the dwarf planet as was the case with dawn at vesta the gravity field orientation parameters landmark locations and ceres orbit are jointly estimated in a global solution even though dawn s radio science investigation at ceres was complicated by additional thrusting for attitude control the resulting spherical harmonic gravity field has a half wavelength resolution of up to 82 km degree 18 near the equator which is similar harmonic resolution to that of vesta the gravity field is consistent with airy isostatic compensation and this model assumption limits ceres crustal density to be between 1200 and 1600 kg m 3 for two layer and three layer models with mean crustal thickness between 27 and 43 km the compensation depth is determined using admittance between gravity and gravity from topography and is superior to admittance between gravity and topography the gravitational mass of ceres is determined to better than 0 002 gm ceres 62 62736 0 00040 km 3 s 2 the spin pole location is improved by 10 over previous results with right ascension 291 427 and declination 66 760 uncertainty less than 0 001 and the rotation rate is improved by 100 over previous determinations from hubble space telescope hst images ceres heliocentric orbit has also been improved with about 17 months of precision range measurements reducing ephemeris uncertainties to about 10 m during the dawn timeframe