the influence of fluid sensitive dispersion and attenuation on avo analysis summary analysis of seismic data suggests that hydrocarbon deposits are often associated with higher than usual values of attenuation but this is generally ignored during amplitude versus offset avo analysis the effect can be modelled with equivalent medium theory based on the squirt flow concept but the excess attenuation is associated with strong velocity dispersion consequently when we study reflections from the interface between such an equivalent medium and an elastic overburden we find that the reflection coefficient varies with frequency the impact of this variation depends on the avo behaviour at the interface class i reflections tend to be shifted to higher frequency while class iii reflections have their lower frequencies amplified we calculate synthetic seismograms for typical models using the reflectivity method for materials with frequency dependent velocities and attenuations and find that these effects are predicted to be detectable on stacked data two field data sets show frequency anomalies similar to those predicted by the analysis and we suggest that our modelling provides a plausible explanation of the observations

fracture characterization using frequency dependent shear wave anisotropy analysis of microseismic data summary the presence of fractures in hydrocarbon reservoirs can enhance porosity and permeability and consequently increase production the use of seismic anisotropy to characterize fracture systems has gained much interest in the last two decades however estimating fracture sizes from observations of seismic anisotropy has not been possible recent work has shown that frequency dependent anisotropy fda is very sensitive to the length scale of the causative mechanism for the anisotropy in this study we observe fda in a microseismic data set acquired from a carbonate gas field in oman the frequency dependent shear wave anisotropy observations are modelled using a poroelastic model which considers fluid communication between grain size pore spaces and larger scale fractures a grid search is performed over fracture parameters radius density and strike to find the model that best fits the real data the results show that fracture size varies from the microscale within the shale cap rocks to the metre scale within the gas reservoir to the centimetre scale within the non producing part of the carbonate formation the lateral variation in fracture density agrees with previous conclusions from ordinary shear wave splitting sws analysis cumulatively the results show the potential for characterizing fracture systems using observations of fda

factors affecting the durability of selected weak and clay bearing rocks from turkey with particular emphasis on the influence of the number of drying and wetting cycles weathering can induce a rapid change of rock material from initial rock like properties to soil like properties the resistance of a rock to short term weathering is described through a durability parameter called the slake durability index as durability is an important engineering parameter particularly for weak and clay bearing rocks it was assessed by a number of tests the main purpose of this study is to assess the influence of the number of drying and wetting cycles and controls of mineralogical composition and strength on durability for this purpose 141 samples of different types of weak and clay bearing rocks were selected from different parts of turkey and relationships between the above mentioned rock characteristics were statistically investigated the samples were subjected to multiple cycle slake durability testing x ray diffraction xrd analysis and uniaxial compression testing in addition to assess the influence of mineralogical composition on durability the mineral contents of the original material and the material passing from the drum of the slake durability apparatus after each cycle were also determined by xrd the results indicate that the type and amount of clay minerals are the main factors influencing the variations of the slake durability index in all samples the durability of the clay bearing rocks studied correlates best with the amount of expandable clay minerals a strong relationship between the uniaxial compressive strength and the fourth cycle slake durability index is found only for the marls among the rock types studied assessment of gradation results of the spoil pile materials consisting of clay bearing rocks also reveals that the increase in percentage of fines in old piles is indicative of material degradation as is evident by multiple cycle slaking it is emphasized that two cycle conventional slake durability testing did not appear to offer an acceptable indication of the durability of weak and clay bearing rocks when compared with multiple cyclic wetting and drying comments on the performance of the test are made that aim to make the testing process and interpretation of the results more reliable

mechanical properties of a weak pyroclastic rock and their relationship with microstructure the geotechnical behaviour of very weak pyroclastic rocks controls both the failure mechanisms at the margins of rock mesas where historic hill towns are often sited as well as the stability of o

engineering geological and geoenvironmental evaluation of unesco world heritage site of meymand rock hewn village iran meymand a historic 2000 year old village is an important heritage site in iran that was included on the world heritage list in 2015 by unesco the village is located in a volcanic terrain and its structures such as houses a mosque a public bath and a fire temple have been carved in to the pyroclastic rocks of the masahim volcano in the present study the engineering geological and geoenvironmental aspects of the meymand village were investigated including the geomorphology and landscape of the village the technical classification of the pyroclastic rocks and their geomechanical properties and the geoenvironmental characteristics and problems of the village the engineering geological characteristics of the meymand site were also compared with those of similar sites of the cappadocia region in turkey and the kandovan village in iran which were widely studied by earlier researchers the results of the present study indicated that the erosion of massive volcanic rocks free from systematic structural discontinuity has formed the unique landscape of the village which is different from similar other sites according to technical classification the meymand pyroclastic rock is a lithic tuff of a low degree of welding that has very weak strength and low durability accelerated weathering tests that artificially simulated the meymand site conditions suggested that the meymand tuff is prone to atmospheric conditions as its strength and deformability are drastically reduced when it becomes wet or saturated laboratory tests and field evidence show that the meymand village is under threat of erosion due to natural and anthropogenic agents that gradually destroy the landscape and structures of this significant world heritage site therefore conservation projects should be planned and applied that ensure the preservation of the village

neogene ignimbrites of the nevsehir plateau central turkey stratigraphy distribution and source constraints abstract in anatolia turkey extensive calc alkaline volcanism has developed along discontinuous provinces from neogene to quaternary times as a consequence of plate convergence and continental collision in the nevsehir plateau which is located in the central anatolian volcanic province volcanism consists of numerous monogenetic centres several large stratovolcanoes and an extensive mainly neogene rhyolitic ignimbrite field vent and caldera locations for the neogene ignimbrites were not well known based on previous studies in the neogene ignimbrite sequence of the nevsehir plateau we have identified an old group of ignimbrites kavak ignimbrites followed by five major ignimbrite units zelve sarimaden tepe cemilkoy gordeles kizilkaya and two smaller less extensive ones tahar sofular other ignimbrite units at the margin of the plateau occur as outliers of larger ignimbrites whose main distributions are beyond the plateau excellent exposure and physical continuity of the units over large areas have allowed establishment of the stratigraphic succession of the ignimbrites as from bottom to top kavak zelve sarimaden tepe cemilkoy tahar gordeles sofular kizilkaya our stratigraphic scheme refines previous ones by the identification of the zelve ignimbrite and the correlation of the previously defined akkoy ignimbrite with the sarimaden tepe ignimbrite correlations of distant ignimbrite remnants have been achieved by using a combination a field criteria 1 sedimentological characterisitics 2 phenocryst assemblage 3 pumice vesiculation texture 4 presence and characteristics of associated plinian fallout deposits and 5 lithic types the correlations significantly enlarge the estimates of the original extent and volume of most ignimbrites volumes range between 80 km 3 and 300 km 3 for the major ignimbrites corresponding to 2500 10 000 km 3 in areal extent the major ignimbrites of the nevsehir plateau have an inferred source area in the derinkuyu tectonic basin which extends mainly between nevsehir and the melendiz dag volcanic complex the kavak ignimbrites and the zelve ignimbrite have inferred sources located between nevsehir and derinkuyu coincident with a negative gravity anomaly the younger ignimbrites sarimaden tepe cemilkoy gordeles kizilkaya have inferred sources clustered to the south between the erdas dag and the melendiz dag volcanic complex we found evidence of collapse structures on the northern and southern flanks of the erdas dag volcanic massif and of a large updoming structure in the sahinkalesi tepe massif the present day derinkuyu tectonic basin is mostly covered with quaternary sediments and volcanics the fault system which bounds the basin to the east provides evidence that the ignimbrite volcanism and inferred caldera formation took place in a locally extensional environment while the basin was already subsiding drilling and geophysical prospecting are necessary to decipher in detail the presently unknown internal structure of the basin and the inferred probably coalesced or nested calderas within it

the effect of welding degree on geotechnical properties of an ignimbrite flow unit the bitlis castle case eastern turkey ignimbrites are associated with nearly most of the world s volcanoes and are defined as a deposit from pyroclastic density currents they consist predominantly of pumiceous lapilli and blocks and glass shards which shows evidence of having been emplaced as a concentrated hot and dry particulate flow these rocks are widely used as building stone especially in ancient buildings bitlis valley is covered by ignimbritic products derived from nemrut stratovolcano one of the significant volcanic centers in eastern anatolia the bitlis ignimbrite is separated into lower level ll middle level ml and upper level ul according to color welding degree and structural features all three levels were used extensively in many parts of the bitlis castle as masonry materials studies were carried out on mineralogical and geochemical composition and on physical and mechanical properties of the ignimbrites in addition a freeze thaw cycle test was executed there are no considerable differences in mineralogical composition among the levels of ignimbrite all levels contain plagioclase sanidine pyroxene and opaque mineral in addition anorthoclase and quartz are seen in general the ll of ignimbrite shows relic perlitic and eutaxitic texture whereas eutaxitic and vesicular texture are commonly developed in the ml and ul respectively lower middle and upper level ignimbrite samples display similar and limited compositional spread in terms of major oxide elements they have trachyte composition building stones can be classified according to mineralogy mechanical and physical properties and processing types mechanical and physical properties are very important with respect to stone quality durability the mechanical and physical properties of the ignimbrites are controlled by the welding degree it was found that increasing welding degree from ul to ll correlates with increasing density compressive strength and slake durability index and with decreasing porosity the bitlis ignimbrites have turned out as susceptible to freeze thaw cycles

comment on the 3d shear experiment over the natih field in oman the effects of fracture filling fluids on shear propagation by c m van der kolk w s guest and j h h m potters we find errors in theory and application in the paper by van der kolk et al geophysical prospecting 49 179 197 2001 that invalidate their arguments for the cause of the reduction in the velocity of the vertically propagating slower split shear wave in the gas cap over the natih field in oman we suggest that existing theories are adequate and can explain the anomaly

structural geological problems in gumusler archeological site and monastery there are many underground settlings opened in historical times in cappadocia region and the gumusler monastery is one of these the monastery is a rock monastery church located in approximately 8 km northeast of nigde the most important characteristics of the monastery dated in 11th century ac are that it is an important settlement and touristic area that contains the most preserved frescoes in cappadocia region for this purpose were determined the geological features of the observed units in the areas where the monastery is located and the surroundings were determined engineering geological problems are mentioned for the negative effects of the discontinuities especially in the monastery part during field studies stones with different color and textural characteristics were taken into account and sampling was carried out from four different levels on representative samples laboratory studies were conducted for determining the mineralogical chemical and petrographic and geomechanical properties underground cavities in the region were opened in the lower part of the kizilkaya ignimbrite which has relatively more rock fragments higher amount of rock fragments in the lower part makes this level easier to cave in low welding rate of the rock is believed to be the cause of having relatively low values of engineering properties of the lower levels of examined ignimbrites ignimbrites in these levels are more sensitive against atmospheric conditions than those in the upper levels this study is the first study to determine engineering geology problems in the gumusler archeological area and provide data to planned conservation measures

microearthquake characteristics and crustal vp vs structure at the mid atlantic ridge 35 n we report on the results of a microearthquake experiment conducted at the along axis bathymetric high of the slow spreading ridge segment near 35 n on the mid atlantic ridge mar of a total of 255 microearthquakes recorded during the 43 day experiment 31 were located near the oceanographer transform at the northern end of the segment 79 occurred at the nontransform offset at the southern end of the segment and 145 were at the segment center at the segment center earthquake epicenters lay within the median valley inner floor and formed a 12 km long trend paralleling a steep scarp bounding the western wall of the inner valley focal depths were 3 4 km below the seafloor most 80 of the focal mechanisms for 32 segment center earthquakes are consistent with normal faulting on faults approximately parallel to the axial trend from a joint inversion for hypocenters and p and s wave velocity structures we determined a horizontally averaged v p v s ratio that decreases from 2 9 in the shallowmost 300 m to 1 7 at 2 km depth and we interpret this decrease as indicating a decreasing contribution of thin cracks to fracture porosity with depth the maximum depth of seismicity 4 km is anomalously shallow compared with other mar segments at which microearthquake experiments have been carried out cross axis relief is also anomalously low for this segment s center and on the basis of this and other mar microearthquake experiments there appears to be a correlation between cross axis relief and maximum depth of seismicity from the correlation of cross axis relief and inferred crustal thickness we suggest a relationship between thick crust high crustal temperatures and low cross axis relief in qualitative agreement with thermomechanical models for the depth of the axial valley

the 3d shear experiment over the natih field in oman reservoir geology data acquisition and anisotropy analysis this paper describes a large scale reservoir characterization experiment carried out in oman in 1991 which comprised the acquisition processing and interpretation of a 28 4 km 2 3d multicomponent seismic experiment over the natih field the objective of the survey was to obtain information on the fracture network present in the natih carbonates from shear wave anisotropy shear wave anisotropy in excess of 20 time splitting was encountered over a large part of the survey the seismic results are confirmed by geological and well data but provide additional qualitative information on fracturing where this was not available before regions of stronger and weaker shear wave anisotropy appear to be fault bounded the average well flow rates which are fracture dominated within such blocks correlate with the average anisotropy of the blocks the further observation that the anisotropy is largest in the fracture gas cap of the reservoir suggests that shear waves can provide a direct hydrocarbon indicator for fractured rock

quantitative determination of hydraulic properties of fractured rock using seismic techniques there have been significant advances over the last ten years in the use of the seismic anisotropy concept to characterize subsurface fracture systems measurements of seismic anisotropy are now used to deduce quantitative information about the fracture orientation and the spatial distribution of fracture intensity analysis of the data is based upon various equivalent medium theories that describe the elastic response of a rock containing cracks or fractures in the long wavelength limit conventional models assume scale frequency independence and hence cannot distinguish between micro cracks and macrofractures the latter however control the fluid flow in many oil gas reservoirs as the fracture size and spacing hence fracture storability are essential parameters for reservoir engineers recently a new equivalent medium theory for modelling of wave propagation in media with multi scale fractures has been presented the model predicts velocity dispersion and attenuation due to a squirt flow mechanism at two different scales the grain scale micro cracks and equant matrix porosity and formation scale fractures application of this model to field data shows that fracture density and fracture size can be inverted successfully from the frequency dependence of the time delay between split shear waves the derived fracture length matches independent observations from borehole data this paper presents the results of the latest development in the seismic characterization of natural fractures with an emphasis on the quantitative determination of fracture sizes

hydroacoustic detection of volcanic activity on the gorda ridge february march 1996 abstract beginning at 0700 gmt on 28 february 1996 intense seismicity was detected in the northeast pacific ocean using the t phase monitoring system developed by noaa pmel to access the u s navy s sound surveillance system sosus in the north pacific the event was preliminarily located on the northernmost segment of the gorda ridge near 42 67 n and 126 8 w in the vicinity of the ridge segment high narrowgate the nature of the seismicity was similar to that observed in june 1993 at the coaxial segment of the juan de fuca ridge which was later documented to be a lateral magma injection with subsequent eruption due to several gaps in the data the detection information was not as comprehensive as during the coaxial event but an initial migration of epicenters from the narrowgate area down rift is inferred based on arrival bearings from a single array there is evidence for an additional diking event on the second and third day of activity there is also indication of a concentration of epicenters located near 42 6 n as occurred during the coaxial episode at what was later determined to be an eruption site examination of t wave rise times generally supports this interpretation based on the nature and duration of the activity a response effort was initiated which later confirmed hot water plumes and fresh lava flows at the site based on both hydroacoustic information and field observations it is proposed that the episode began with a lateral dike injection possibly with eruptive activity in the summit region followed by multiple magma pulses and eventual focusing of the seismic activity and extrusion near 42 6 n

comparison of mid oceanic earthquake epicentral differences of travel time centroid locations and those determined by autonomous underwater hydrophone arrays 1 mid oceanic interplate earthquakes are difficult to locate accurately because they normally occur far away from land based seismic stations use of water borne t waves recorded by autonomous underwater hydrophone auh arrays records an order of magnitude more highly accurate regional low seismicity along the north mid atlantic ridge than the international seismic centre isc even though the physical meaning of an auh locations is still not well known auh s small location errors are important for better constraining mid oceanic earthquakes comparison of such auh locations with those in isc and harvard centroid moment tensor cmt location catalog and relocated ones based on the high resolution bathymetry and teleseismic p phases is made in this study auh locations are used as a reference to compare the teleseismically determined locations for large earthquakes with known focal mechanisms we find that relocated locations agree with auh ones better than with isc we also note that the centroid vectors from relocated epicenters are usually larger than auh centroid vectors the relocated epicenters and auh locations lie in similar azimuthal directions to the associated cmt epicenters the larger relocated and auh centroid vectors than the error ellipses of auh cmt and relocated ones combined might be explained by the fault rupture process for smaller events relocated location confidence ellipses are usually large enough to cover auh locations and their error ellipses overall the highly accurate auh locations can be used to confirm the mid oceanic earthquake hypocenters and seismicity characteristics and for detail studies of the low level seismicity associated with the plate motions

dehumidification property of eskisehir derbent ciftligi white tuffs in turkey in anatolia throughout the centuries caverns in tuffs have been used for food storage the aim of this study is to investigate experimentally the dehumidification property of tuffs and to confirm whether tuffs play any part in the humidity of the ecosystem in storage according to tests carried out on the eskisehir derbent ciftligi white tuffs and six different rock types from turkey it was found that the atmospheric moisture absorption ability of tuffs is relatively higher than those of other tested rocks this suggests that the dehumidification property is a unique characteristic of tuffs it may allow for the tuff walls to work as an air dehumidifier for storing food

frequency dependent anisotropy due to meso scale fractures in the presence of equant porosity fractured rock is often modelled under the assumption of perfect fluid pressure equalization between the fractures and equant porosity this is consistent with laboratory estimates of the characteristic squirt flow frequency however these laboratory measurements are carried out on rock samples which do not contain large fractures we consider coupled fluid motion on two scales the grain scale which controls behaviour in laboratory experiments and the fracture scale our approach reproduces generally accepted results in the low and high frequency limits even under the assumption of a high squirt flow frequency we find that frequency dependent anisotropy can occur in the seismic frequency band when larger fractures are present shear wave splitting becomes dependent on frequency with the size of the fractures playing a controlling role in the relationship strong anisotropic attenuation can occur in the seismic frequency band the magnitude of the frequency dependence is influenced strongly by the extent of equant porosity with these results it becomes possible in principle to distinguish between fracture and microcrack induced anisotropy or more ambitiously to measure a characteristic fracture length from seismic data

engineering geological properties and durability assessment of the cappadocian tuff abstract some of the unique landforms the so called fairy chimneys which were formed within the cappadocian tuff of central turkey were used as dwellings in the past and contain culturally valuable wall paintings however these structures are undergoing chemical and physical deterioration due to atmospheric effects for conservation studies an understanding of the engineering geological properties of the tuff is essential in this study emphasis is placed on both material and mass properties of the tuff these properties are evaluated for the assessment of rock durability this study shows that the cappadocian tuff is almost fresh with local discoloration is moderately weak to very weak and has low unit weight very high porosity and high deformability discontinuity surveys revealed two dominant joint sets which not only controlled the formation but also control the structural stability of the fairy chimneys various methods used for the durability assessment of the cappadocian tuff indicate poor to very poor durability due consideration must be given to strength reduction due to moisture poor to very poor durability and the adverse effects of joints on the structural stability of the fairy chimneys

geotechnical and geoenvironmental characteristics of man made underground structures in cappadocia turkey underground cities and semi underground settlements most of which are 1500 years at least exist in the cappadocia region of turkey these man made rock structures are carved in soft tuffs and the best examples of long term performance of man made structures in the field of rock engineering the tuffs also have good thermal isolation properties to be used as housing and storage of foods in this article the authors are only concerned with physical and short term mechanical characteristics due to the wide spectrum of the theme and the in situ characterization of the cappadocia tuffs and the results of investigations are presented in addition a critical overview on possible engineering geological problems at cappadocia with mechanical aspects of historical and modern rock structures and their implications in rock engineering is made from the experimental results in the field it is evident that the engineering characteristics of these rocks do not show significant changes in vertical and horizontal directions however they are prone to atmospheric conditions in addition temperature and humidity measurements at different floors of the underground cities and various parts of semi underground settlements indicated that variations in climatic conditions of the openings are very small when compared to those outside the ground surface

engineering geological characterization of coal mine waste material and an evaluation in the context of back analysis of spoil pile instabilities in a strip mine sw turkey abstract coal mine waste material which usually consists of a mixture of coarse grained particles to rock fragments grading to fine grained particles causes geotechnical and environmental problems on disposal a study of the geotechnical aspects of the problem is therefore important in rational planning for the disposal reclamation treatment and use of such material spoil pile instability has been a continuing problem in the eskihisar strip coal mine of southwestern turkey particularly shallow seated circular failures appearing along the haul road and instabilities covering large agricultural areas outside the dumping yard increase the importance of spoil pile stability the fact that the height of spoil piles dumped by trucks on both sides of the haul road will increase much more in the future has focused the attention of the miners to this problem this study outlines the geotechnical characteristics of waste material from the tertiary coal bearing rocks derived from field and laboratory investigations and describes the causes and mechanism of spoil instabilities which threaten the safety of the haul road and the agricultural areas in the vicinity of the pit gradation results suggest that fines and coarser material were approximately equally represented in the spoil the percentage of fines is indicative of material degradation as evidenced by slaking tests site observations and numerous back analysis of investigated failures reveal that the failures do not penetrate the foundation material and only occur along circular surfaces through the spoil material it is also noted that surface water infiltration reducing the effective shear strength of the spoil material contributes to failures shear test results indicate that the spoil is a nearly cohesionless material with a residual internal friction angle of about 33 which confirms the values derived from standard penetration tests it is also noted from back analyses that the spoil material exhibits a shear strength at or approaching the residual value at the time of failure the use of shear strength parameters defined by the linear mohr coulomb envelope yields results that are comparable with those obtained when the non linear failure envelope is used provided that such strength parameters were defined at the operating normal stress levels on the failure surfaces

comments on monitoring soil erosion in cappadocia region selime aksaray turkey by yilmaz et al environ earth sci 2012 66 75 81 yilmaz et al 2012 presented a monitoring survey on soil erosion carried out around fairy chimneys of cappadocia region of turkey they scanned the study area by geodetic robotic total station at five different times and calculated the volume differences in order to find out the total erosion during that given time interval they finally analyzed the relationship between erosion and meteorological data and proposed that climatic conditions especially rainfall are an important eroding agent in the formation of this landscape whereas we welcome quantitative erosion surveys that are practically nonexistent in turkey the geological and geomorphological descriptions of the study area and scientific background contain vital mistakes that are totally unacceptable herein some important ones are commented upon although the aim of yilmaz et al s work is presented as the study of the role of erosion of the surrounding soil in the formation of fairy chimneys it is clear from their figs 1 and 4 where they show a photograph of the study area that their work does not deal with any soil formation but rather is an outcrop of eroding ignimbrite therefore the title of their work is misleading to say the least and do not represent their survey topic on the other hand even if we assume that the scanned area was covered by soil which we insist is not the case we are than entitled to question the use of such a method to measure the fairy chimneys erosion rates where no soil is involved during their formation during the description of their study area the authors state the region was formed sixty billion years ago it is common knowledge that the age of the earth is 4 54 0 05 billion years based on evidence from radiometric dating of meteorite material which is similar to the ages of the oldest known terrestrial and lunar rocks dalrymple 2001 we believe that the authors and the reviewers did not see this obvious mistake however even if we assume that they meant sixty million instead of sixty billion they are still very far away from the calculated age of the rocks in the area the reality is that the volcanism in cappadocia situated in central anatolian volcanic province cavp dates back to late miocene around 10 my my million years to holocene le pennec et al 2005 aydar et al 2012 fig 1 the authors scientific inconsistencies do not end on the formation age of the study area as they claim that all rocks forming fairy chimneys were produced by soft layers of lava and ash erupted from erciyes hasan and gullu volcanoes actually these three stratovolcanoes are mainly quaternary in age around 2 5 my aydar et al 1995 aydar and gourgaud 1998 kurkcuoglu et al 1998 en et al 2003 while the youngest ignimbrite layer kizilkaya ignimbrite that is known to form basin wide mesas in the region is 5 2 my of age le pennec et al 1994 aydar et al 2012 hence was emplaced well before the eruption of these volcanoes the stratigraphical framework of the region is very well established by several works where ar ar and u pb zircon ages between 10 and 5 2 my are proposed for the formation of the ignimbrites that are susceptible to form fairy chimneys pasquare 1968 innocenti et al 1975 a ciner geological engineering department hacettepe university ankara turkey e mail aciner hacettepe edu tr

rock rupture phenomenon and pillar failure in tuffs in the cappadocia region turkey the aim of this study is to investigate the relation between the critical failure stresses for rupture and pillar instabilities observed in tuffs in cappadocia region and stresses triggering the early crack propagation stages such as crack initiation systematic cracking and crack coalescence thresholds determined from brazilian and uniaxial compression tests on rock samples obtained from these instabilities these failures in the region have been occurring as a result of strength reduction of rocks through time and long term strengths of these rocks are achieved by own weight of the rock mass in this study these failures were evaluated in order to estimate long term failure strength of rocks by classical short term laboratory tests for this purpose some cases on rock rupture phenomenon and a pillar failure case were picked from different parts of the region during the selection of these instabilities the ones with relatively regular geometries were preferred rock block samples were collected from each case and uniaxial compressive and indirect tensile brazilian tests were carried out on dry and saturated specimens in these tests axial deformations and acoustic emission ae activity were also recorded in order to identify thresholds of the crack propagation and deformation stages of rock samples the simplified back analysis of each case was conducted and the tensile stresses on rupture surfaces and uniaxial compressive stress on pillar were calculated then stress levels at the thresholds of crack propagation and deformation stages determined by laboratory tests and stress levels determined by back analyses were compared finally it is concluded that crack initiation and or systematic cracking thresholds may be a good indicator to determine lower bound of the in situ strength of these tuffs and can be used as an estimator of their long term strengths

modelling frequency dependent seismic anisotropy in fluid saturated rock with aligned fractures implication of fracture size estimation from anisotropic measurements measurements of seismic anisotropy in fractured rock are used at present to deduce information about the fracture orientation and the spatial distribution of fracture intensity analysis of the data is based upon equivalent medium theories that describe the elastic response of a rock containing cracks or fractures in the long wavelength limit conventional models assume frequency independence and cannot distinguish between microcracks and macrofractures the latter however control the fluid flow in many subsurface reservoirs therefore the fracture size is essential information for reservoir engineers in this study we apply a new equivalent medium theory that models frequency dependent anisotropy and is sensitive to the length scale of fractures the model considers velocity dispersion and attenuation due to a squirt flow mechanism at two different scales the grain scale microcracks and equant matrix porosity and formation scale fractures the theory is first tested and calibrated against published laboratory data then we present the analysis and modelling of frequency dependent shear wave splitting in multicomponent vsp data from a tight gas reservoir we invert for fracture density and fracture size from the frequency dependence of the time delay between split shear waves the derived fracture length matches independent observations from borehole data

field based experimental determination of the weathering rates of the cappadocian tuffs abstract since the last eruption in the cappadocia region that resulted in the formation of irregular hard thick lava layers on top of the cappadocian tuffs atmospheric processes have preferentially sculptured the tuffs the erosion processes have resulted in some beautiful topographical landscape features the so called fairy chimneys however erosion which is an important factor in the formation of fairy chimneys in the early stages has a negative effect on their future over time the number of visitors to this region has also increased and therefore in addition to natural erosion the effects of localized erosion resulting from tourism at the site have increased in the last few decades the physical mineralogical and mechanical properties of the cappadocian tuffs have been widely investigated in previous studies but their weathering characteristics particularly weathering rate were not determined in these studies determination of the weathering rate of these rocks is mandatory especially for conservation projects which should be urgently applied in order to protect this heritage in this study a comprehensive research program was carried out on the weathering properties of the cappadocian tuffs and the weathering rate was determined in field and laboratory investigations to this purpose a detailed field investigation was performed besides field observations the mineralogical physical and mechanical properties of tuffs were also determined in addition to durability evaluation by the slake durability index test wetting drying and freezing thawing tests were also performed for weathering rate assessment of the cappadocian tuffs in order to account for overburden load on some specific parts of pillars these wetting drying and freezing thawing tests were performed under loads the results obtained from field observations of old man made structures and from laboratory studies show that the weathering rate varies between 0 03 and 0 59 mm year for the esbelli tuff and 0 4 and 2 5 mm year for softer part of the kavak member

fluid dependent shear wave splitting in fractured media azimuthal anisotropy in rocks can result from the presence of one or more sets of partially aligned fractures with orientations determined by the stress history of the rock a shear wave propagating in an azimuthally anisotropic medium splits into two components with different polarizations if the source polarization is not aligned with the principal axes of the medium for vertical propagation of shear waves in a horizontally layered medium containing vertical fractures the shear wave splitting depends on the shear compliance of the fractures but is independent of their normal compliance if the fractures are not perfectly vertical the shear wave splitting also depends on the normal compliance of the fractures the normal compliance of a fluid filled fracture decreases with increasing fluid bulk modulus for dipping fractures this results in a decrease in shear wave splitting and an increase in shear wave velocity with increasing fluid bulk modulus the sensitivity of the shear wave splitting to fluid bulk modulus depends on the interconnectivity of the fracture network the permeability of the background medium and on whether the fracture is fully or partially saturated

experimental verification of the fracture density and shear wave splitting relationship using synthetic silica cemented sandstones with a controlled fracture geometry we present laboratory ultrasonic measurements of shear wave splitting from two synthetic silica cemented sandstones the manufacturing process which enabled silica cementation of quartz sand grains was found to produce realistic sandstones of average porosity 29 7 0 5 and average permeability 29 4 11 3 md one sample was made with a regular distribution of aligned penny shaped voids to simulate meso scale fractures in reservoir rocks while the other was left blank ultrasonic shear waves were measured with a propagation direction of 90 to the coincident bedding plane and fracture normal in the water saturated blank sample shear wave splitting the percentage velocity difference between the fast and slow shear waves of 0 5 was measured due to the bedding planes or layering introduced during sample preparation in the fractured sample shear wave splitting corrected for layering anisotropy of 2 72 0 58 for water 2 80 0 58 for air and 3 21 0 58 for glycerin saturation at a net pressure of 40 mpa was measured analysis of x ray ct scan images was used to determine a fracture density of 0 0298 0 077 in the fractured sample this supports theoretical predictions that shear wave splitting sws can be used as a good estimate for fracture density in porous rocks i e sws 100 f where f is fracture density regardless of pore fluid type for wave propagation at 90 to the fracture normal

a shear experiment over the natih field in oman pilot seismic and borehole data an experimental multicomponent three dimensional 3d seismic survey has been carried out over the natih field in oman this paper describes the small scale two dimensional experiment carried out beforehand and how the results obtained from this pilot were used to assess the feasibility of a nine component three dimensional 9c3d operation as well as to determine the field parameters for the field scale 3d survey it also describes the two vsps and a wireline shear log acquired in conjunction with the pilot experiment and the importance of such borehole data for establishing the correct time to depth relationship for the seismic data and for providing an independent check on the seismic interpretation the observation of cusps in the offset vsp indicated the strong anisotropy of the fiqa shales overlying the natih reservoir

rock physics developments in seismic exploration a personal 50 year perspective i present an historical overview of the major developments in rock physics over the past half century key developments are described for both modeling and laboratory experiments and how they have been applied in seismic exploration reservoir characterization and monitoring in particular i chronicle the development of laboratory methods for determining the velocity and attenuation of elastic waves in rock samples at sonic and ultrasonic frequencies this is followed by a description of the validity of theories originally developed by gassmann and biot in the 1950s and employed for describing the propagation of elastic waves in fluid saturated porous media i outline problems and solutions in the use of ultrasonic measurements to predict velocities and attenuation at seismic frequencies field and laboratory studies are described in which a range of frequencies seismic through sonic and ultrasonic was covered and successfully modeled i describe procedures developed during the 1950s and 1960s for interpreting laboratory measurements in terms of pore structure and degree of saturation based on self consistent and scattering theories laboratory equipment used for determining the elastic properties of anisotropic materials is described along with a discussion of the results obtained including the correlation between both fluid permeability and prediction of in situ state of stress with the degree of shear wave splitting finally i discuss the application of rock physics developments to reservoir characterization and monitoring in particular to time lapse seismic monitoring

the 3d shear experiment over the natih field in oman the effect of fracture filling fluids on shear propagation this is the final paper in a series on the 3d multicomponent seismic experiment in oman in this experiment a 3d data set was acquired using three component geophones and with three source orientations the data set will subsequently be referred to as the natih 9c3d data set we present for the first time evidence demonstrating that shear waves are sensitive to fluid type in fractured media two observations are examined from the natih 9c3d data where regions of gas are characterized by slow shear wave velocities one is that the shear wave splitting map of the natih reservoir exhibits much larger splitting values over the gas cap on the reservoir this increase in splitting results from a decrease in the slow shear wave velocity which senses both the fractures and the fracture filling fluid using a new effective medium model it was possible to generate a splitting map for the reservoir that is corrected for this fluid effect secondly an anomaly was encountered on the shear wave data directly above the reservoir the thick fiqa shale overburden exhibits a low shear wave velocity anomaly that is accompanied by higher shear reflectivity and lower frequency content no such effects are evident in the conventional p wave data this feature is interpreted as a gas chimney above the reservoir a conclusion supported by both effective medium modelling and the geology with this new effective medium model we show that introduction of gas into vertically fractured rock appears to decrease the velocity of shear waves s2 polarized perpendicular to the fracture orientation whilst leaving the vertical compressional wave velocity largely unaffected this conclusion has direct implications for seismic methods in exploration appraisal and development of fractured reservoirs and suggests that here we should be utilizing s wave data as well as the conventional p wave data as a direct hydrocarbon indicator

rockfall hazard assessment in a cultural and natural heritage ortahisar castle cappadocia turkey the cappadocia region is one of the most important tourism centers of turkey owing to its natural beauty and historical heritage the natural landscapes predominantly contribute to the tourism capacity of the region this is controlled directly by the characteristic lithological units and surface processes however rockfall events which are sometimes observed in the region are typical natural hazards conditioned by discontinuities steep topography and human activities the ortahisar castle is one of the natural monuments and also one of the historical places of this region this castle is located on a steep hill formed by jointed ignimbrite and its height and settlement area are approximately 50m and 500m2 respectively however some blocks on the castle have begun to exhibit serious rockfall potential rock hewn structures carved by man for various purposes contribute to increase in rockfall hazard for this reason the castle was closed to touristic visits the purpose of this study was to evaluate this hazard potential and perform a series of rockfall analyses and discuss the results besides location and dimension of fallen blocks were determined at the final stage of the fieldwork location and size of detached blocks having potential to fall were described during the analysis stage runout distance bounce height kinetic energy and velocity of the detached blocks were determined by using rocfall v 4 software the results obtained from rockfall analyses were used to map the areas under rockfall threat in the close vicinity of the castle and the potential risk was interpreted

fluid dependent shear wave splitting in a poroelastic medium with conjugate fracture sets the dependence of shear wave splitting in fractured reservoirs on the properties of the filling fluid may provide a useful attribute for identifying reservoir fluids if the direction of wave propagation is not perpendicular or parallel to the plane of fracturing the wave polarized in the plane perpendicular to the fractures is a quasi shear mode and therefore the shear wave splitting will be sensitive to the fluid bulk modulus the magnitude of this sensitivity depends upon the extent to which fluid pressure can equilibrate between pores and fractures during the period of the deformation in this paper we use the anisotropic gassmann equations and existing formulations for the excess compliance due to fracturing to estimate the splitting of vertically propagating shear waves as a function of the fluid modulus for a porous medium with a single set of dipping fractures and with two conjugate fracture sets dipping with opposite dips to the vertical this is achieved using two alternative approaches in the first approach it is assumed that the deformation taking place is quasi static that is the frequency of the elastic disturbance is low enough to allow enough time for fluid to flow between both the fractures and the pore space throughout the medium in the second approach we assume that the frequency is low enough to allow fluid flow between a fracture set and the surrounding pore space but high enough so that there is not enough time during the period of the elastic disturbance for fluid flow between different fracture sets to occur it is found that the second approach yields a much stronger dependence of shear wave splitting on the fluid modulus than the first approach this is a consequence of the fact that at higher wave frequencies there is not enough time for fluid pressure to equilibrate and therefore the elastic properties of the fluid have a greater effect on the magnitude of the shear wave splitting

determination of the principal directions of azimuthal anisotropy from p wave seismic data in an azimuthally anisotropic medium the principal directions of azimuthal anisotropy are the directions along which the quasi p and the quasi s waves propagate as pure p and s modes when azimuthal anisotropy is induced by oriented vertical fractures imposed on an azimuthally isotropic background two of these principal directions correspond to the directions parallel and perpendicular to the fractures s waves propagating through an azimuthally anisotropic medium are sensitive to the direction of their propagation with respect to the principal directions as a result primary or mode converted multicomponent s wave data are used to obtain the principal directions apart from high acquisition cost processing and interpretation of multicomponent data require a technology that the seismic industry has not fully developed anisotropy detection from conventional p wave data on the other hand has been limited to a few qualitative studies of the amplitude variation with offset avo for different azimutha

pressure dependent seismic response of fractured rock effects of external stress and pore pressure variations on the seismic signature of fractured rocks remain of interest to geoscientists and practicing geophysicists commonly the effects are modeled theoretically assuming fracture faces to be rough surfaces contacting each other via the surface asperities the model proposed here differs from other models of this kind in that 1 fracture roughness is described by a single parameter and 2 a controlled degree of hydraulic connectivity between fractures and equant pores is introduced this adds to the model s convenience and makes it applicable to a wide variety of reservoirs the model predictions of seismic velocities in fractured rock at variable stress are consistent with experimental data for fixed effective stress the model predictions coincide with those obtained using the model with ellipsoidal fractures of certain average aspect ratio and the same fracture porosity apart from known effects the model introduced predicts an amplification of th

elastic wave propagation in media with parallel fractures and aligned cracks a model of parallel slip interfaces simulates the behaviour of a fracture system composed of large closely spaced aligned joints the model admits any fracture system anisotropy triclinic the most general monoclinic orthorhombic or transversely isotropic and this is specified by the form of the 3 3 fracture system compliance matrix the fracture system may be embedded in an anisotropic elastic background with no restrictions on the type of anisotropy to compute the long wavelength equivalent moduli of the fractured medium requires at most the inversion of two 3 3 matrices when the fractures are assumed on average to have rotational symmetry transversely isotropic fracture system behaviour and the background is assumed isotropic the resulting equivalent medium is transversely isotropic and the effect of the additional compliance of the fracture system may be specified by two parameters in addition to the two isotropic parameters of the isotropic background dilute systems of flat aligned microcracks in an isotropic background yield an equivalent medium of the same form as that of the isotropic medium with large joints i e there are two additional parameters due to the presence of the microcracks which play roles in the stress strain relations of the equivalent medium identical to those played by the parameters due to the presence of large joints thus knowledge of the total of four parameters describing the anisotropy of such a fractured medium tells nothing of the size or concentration of the aligned fractures but does contain information as to the overall excess compliance due to the fracture system and its orientation as the aligned microcracks which were assumed to be ellipsoidal with very small aspect ratio are allowed to become non fiat i e have a growing aspect ratio the moduli of the equivalent medium begin to diverge from the standard form of the moduli for flat cracks the divergence is faster for higher crack densities but only becomes significant for microcracks of aspect ratios approaching 0 3

assessment of environmental and engineering geological problems for the possible re use of an abandoned rock hewn settlement in urgup cappadocia turkey the cappadocia region of central anatolia having a very distinct culture is one of the attractive touristic sites of turkey due to its spectacular and unique landforms and historical heritages in this region the structures carved into thick to massive tuffs survived and kept their original integrity for a number of centuries environmental and anthropological factors at the cappadocia region have been the main reasons for extensive subsurface and multi purpose use in the past and present in addition thermal insulation properties of the tuffs make these rocks suitable for use in underground openings the kayakapi neighborhood located in the town of urgup is one of the famous historical sites this site is situated within the goreme national park and the rock sites of cappadocia which was inscribed on the world heritage list in 1985 in order to develop the tourism potential of this abandoned site while preserving its cultural and natural values a natural environmental conservation and revitalization project was initiated as an integral part of this project in this study environmental and engineering geological problems including rock fall potential and stability of about 1 200 rock hewn structures were investigated and an inventory was prepared for the possible re use of the underground openings and other structures at the site and remedial measures were recommended the assessments based on observations and experimental studies indicated that the tuffs do not show significant changes both perpendicular and parallel to layering and discontinuities and rock weathering seem to be more important factors controlling the stability of rock hewn structures the major stability problems threatening the re use of the openings are structurally controlled block instabilities overbreaks and erosion and shearing of the pillars made of tuff on the other hand the area at the entrance of the site requires some protection measures such as the construction of a retaining wall systematic bolting of rock slabs and removal of some blocks having rock fall potential the inventory for the openings suggests that there are a number of openings that can be re used after necessary remedial measures

experimental observation of water saturation effects on shear wave splitting in synthetic rock with fractures aligned at oblique angles fractured rocks are known to exhibit seismic anisotropy and shear wave splitting sws sws is commonly used for fractured rock characterization and has been shown to be sensitive to fluid type the presence of partial liquid gas saturation is also known to affect the elastic properties of rocks the combined effect of both fractures and partial liquid gas saturation is still unknown using synthetic silica cemented sandstones with aligned penny shaped voids we conducted laboratory ultrasonic experiments to investigate the effect fractures aligned at an oblique angle to wave propagation would have on sws under partial liquid gas saturation conditions the result for the fractured rock shows a saturation dependence which can be explained by combining a fractured rock model and a partial saturation model at high to full water saturation values sws decreases as a result of the fluid bulk modulus effect on the quasi shear wave this bulk modulus effect is frequency dependent as a result of wave induced fluid flow mechanisms which would in turn lead to frequency dependent sws this result suggests the possible use of sws for discriminating between full liquid saturation and partial liquid gas saturation

pore fluid viscosity effects on p and s wave anisotropy in synthetic silica cemented sandstone with aligned fractures ultrasonic 500 khz p and s wave velocity and attenuation anisotropy were measured in the laboratory on synthetic octagonal shaped silica cemented sandstone samples with aligned penny shaped voids as a function of pore fluid viscosity one control blank sample was manufactured without fractures another sample with a known fracture density inline image measured from x ray ct images velocity and attenuation were measured in four directions relative to the bedding fabric introduced during packing of successive layers of sand grains during sample construction and the coincident penny shaped voids fractures both samples were measured when saturated with air water viscosity 1 cp and glycerin 100 cp to reveal poro visco elastic effects on velocity and attenuation and their anisotropy the blank sample was used to estimate the background anisotropy of the host rock in the fractured sample the bedding fabric was found to show transverse isotropy with shear wave splitting sws of 1 45 1 18 i e for s wave propagation along the bedding planes in the fractured rock maximum velocity and minimum attenuation of p waves was seen at 90 to the fracture normal after correction for the background anisotropy the fractured sample velocity anisotropy was expressed in terms of thomsen s weak anisotropy parameters a theory of frequency dependent seismic anisotropy in porous fractured media was able to predict the observed effect of viscosity and bulk modulus on and in water and glycerin saturated samples and the higher and values in air saturated samples theoretical predictions of fluid independent are also in agreement with the laboratory observations we also observed the predicted polarisation cross over in shear wave splitting for wave propagation at 45 to the fracture normal as fluid viscosity and bulk modulus increases

mechanism analysis of a landslide in highly weathered volcanic rocks of niushoushan hill in nanjing in this paper the landslide mechanism in highly weathered volcanic rocks is analyzed in niushoushan hill in nanjing this hill is mainly composed of volcanic tuff rocks the gradually weathered rocks reduce the hillslope stability and cause landslides during continuous rainfall the kaolin and montmorillonite clay minerals were tested using an x ray diffractometer the subsequent swelling disintegration and permeable tests indicated the location of soft zones and the poor hydraulic conductivity of the highly weathered tuff hwt the overflow from boreholes and joints exposes a confined aquifer that is caused by rainfall infiltration in the lower moderately weathered tuff mwt which crops out on the top of the hill and is bounded on the interface of the hwt and mwt the electrical resistivity tomography method was carried out for the considered slope to define the boundaries of the discontinuities as a supplement to drilling the displacements of the slope surface and the deep rocks were monitored and the results indicated that sliding had not stopped after a long period of continuous rainfall slope stability analysis considering a water head rise due to rainfall infiltration was carried out using the slide v6 0 computer package the simulation included steady state flow transient seepage associated with rainfall and slope stability variation caused by different infiltration conditions the results indicate that the hwt with low permeability can confine the activity of the lower aquifer and result in a rapid rise of pore pressure in response to rainfall which can lead to slope failure

use of avoa data to estimate fluid indicator in a vertically fractured medium microstructural attributes of cracks and fractures such as crack density aspect ratio and fluid infill determine the elastic properties of a medium containing a set of parallel vertical fractures although the tangential weakness t of the fractures does not vary with the fluid content the normal weakness n exhibits significant dependence on fluid infill based on linear slip theory we used the ratio g n t termed the fluid indicator as a quantitative measure of the fluid content in the fractures with g representing the square of the ratio of s and p wave velocity in the unfractured medium we used a born formalism to derive the sensitivity to fracture weakness of pp and ps reflection coefficients for an interface separating an unfractured medium from a vertically fractured medium our formulae reveal that the pp reflection coefficient does not depend on the 2d microcorrugation surface roughness with ridges and valleys parallel to the fracture strike whereas the ps reflection coefficien

fairy chimney erosion rates on cappadocia ignimbrites turkey insights from cosmogenic nuclides abstract cappadocia in the central anatolian plateau of turkey is famous for its unique landscape and unusual rock formations the development of this landscape dates back to late miocene epoch c 10 million years when volcanoes spread pyroclastic deposits over an area of about 20 000 km 2 the volcanism continued for several millions of years and laid down thick and colorful ignimbrite layers the evolution of the cappadocian landscape starts with nearly horizontal plateaus which are then dissected usually along cooling fractures to form mushroom like structures hoodoos locally known as fairy chimneys different layers of ignimbrites have different resistance to erosion softer layers necks are easier to erode compared to the harder ignimbrites caps when the chimneys are isolated the caps play an important role in slowing further erosion of softer layers when the caps finally drop or completely erode away the soft necks of the chimneys are quickly destroyed here for the first time we have determined the bedrock erosion rates at the three evolution stages of fairy chimneys using the cosmogenic chlorine 36 36 cl the pre chimney plateaus stage the chimney stage and the post chimney stage the data show that the plateaus erode at a very low rate between 0 58 0 02 cm ky and 0 93 0 05 cm ky when dissection of a plateau starts the erosion rate increases to about 4 5 0 6 cm ky the caps of chimneys have erosion rates between 3 21 0 36 cm ky and 3 39 0 36 cm ky once the chimneys disappear erosion rates increase significantly to 28 0 9 9 cm ky

capillary water absorption characteristics of some cappadocian ignimbrites and the role of capillarity on their deterioration cappadocia stands out as one of the most important regions in turkey for its natural historical and cultural heritages the region is under the influence of wetting and drying and freezing and thawing weathering processes which are largely controlled by the water content water migrates through rock pores via different processes such as capillary water absorption which is one of the most common ways observed in the cappadocia region in this study a research program consisting mainly of laboratory studies was carried out to investigate the capillary water absorption characteristics of ignimbrites which are the host rocks of many natural and historical heritage structures in cappadocia accordingly xrd analyses mercury porosimeter and capillary water absorption tests were performed the pore size distribution which is a function of welding degree controls the capillary water absorption process of ignimbrites particularly ignimbrites that have a uniform pore size distribution of around 5 10 m reveal higher capillary water absorption potential ignimbrites have a considerable and variable potential in terms of capillarity and the capillarity plays a major role on the deterioration and decomposition of many of the historical and natural heritage structures in the cappadocia region

experimental studies on ignimbrite and the effect of lichens and capillarity on the deterioration of seljuk gravestones abstract ignimbrites are used extensively in masonry and decorative cladding not only in historical structures but also in residential houses recently as well as monuments around ahlat bitlis turkey region because of their light weight softness and insulating properties the most famous architectural monument is the ahlat seljuk tombs in which ignimbrites were used for the structure these are thousand year old gravestones that have been subjected to significant degradation over time caused by many physical and chemical effects the aim of this study is revealing the mineralogical petrographical petrophysical and mechanical properties of fresh ignimbrites as well as determining the effect of lichens and capillarity on the deterioration of seljuk gravestones in accordance with laboratory studies and field observations a total of four different ignimbrite levels have been evaluated which are widespread in the region and named as n1 reddish brown n2 dark brown n3 yellowish gray and n4 black respectively among these ignimbrites the samples of n1 and n2 were employed in the construction of seljuk gravestones the lithic material content and welding degree are the main controlling factors of the engineering properties of ignimbrites laboratory test results indicate that high porosity of ignimbrites and transport of water mediated by capillarity accelerate the deterioration of ignimbrites furthermore lichens play a preventive role in the deterioration mechanism of ignimbrites rather than disintegrating the tombstones

observations of fluid dependent shear wave splitting in synthetic porous rocks with aligned penny shaped fractures p and s wave velocity and attenuation coefficients accurate to 0 3 and 0 2 db cm respectively were measured in synthetic porous rocks with aligned penny shaped fractures using the laboratory ultrasonic pulse echo method shear wave splitting was observed by rotating the s wave transducer and noting the maximum and minimum velocities relative to the fracture direction a block of synthetic porous rock of fracture density 0 0201 0 0068 and fracture size 3 6 0 38 mm measured from image analysis of x ray ct scans was sub sampled into three 20 30 mm long 50 mm diameter core plugs oriented at 0 45 and 90 to the fracture normal transversely isotropic symmetry axis full waveform data were collected over the frequency range 500 1000 khz for both water and glycerin saturated cores to observe the effect of pore fluid viscosity at 1 cp and 100 cp respectively the shear wave splitting observed in the 90 core was 2 15 0 02 for water saturated and 2 39 0 02 for glycerin saturated in agreement with the theory that suggests that the percentage splitting should be 100 times the fracture density and independent of the saturating fluid in the 45 core by contrast splitting was 0 00 0 02 for water saturation and 0 77 0 02 for glycerin saturation this dependence on fracture orientation and pore fluid viscosity is consistent with the poro visco elastic theory for aligned meso scale fractures in porous rocks the results suggest the possible use of shear or converted wave data to discriminate between fluids on the basis of viscosity variations

volcanological constraints on the post emplacement zeolitisation of ignimbrites and geoarchaeological implications for etruscan tomb construction 6th 3rd century b c in the tufo rosso a scorie nere vico caldera central italy abstract we examine the role of physical volcanological processes including eruption style magmatic versus phreatomagmatic as well as transport and depositional processes pyroclastic fall versus pyroclastic flow in promoting the ideal hydrologic conditions necessary for large scale homogeneous post emplacement zeolitisation of ignimbrites associated with caldera forming eruptions we consider the tufo rosso a scorie nere trsn of vico caldera 151 ka in central italy the trsn exhibits pervasive homogenous alteration of high alkali tephriphonolitic and phonolitic glass to zeolite minerals chabazite and phillipsite in all regions of the study area and at all stratigraphic levels with the exception of the basal 1 m based on detailed lithological studies we propose that a large geothermal field around the vent area was destroyed during the closing stages of the sutri eruption subsequent incorporation and entrapment of superheated geothermal fluids into the ensuing pyroclastic flow during eruption column collapse greatly influenced the emplacement temperature and provided the necessary water required for post emplacement zeolitisation of the trsn we suggest that the absence of zeolitisation at the base of the ignimbrite is directly related to transport conditions reflecting cooler regions in the lower portions of the deposit where the flow came into contact with the underlying substrate we also consider the geoarchaeological implications of enhanced strength and cohesiveness provided by the zeolite rock framework on etruscan tomb location and burial architecture in the vico region the trsn contains literally hundreds of hypogeum style etruscan tombs at a number of sites across the study area this study focuses on two sites in particular the norchia necropoli and the san guiliano necropoli considering the enhanced mechanical properties of zeolitised ignimbrites we infer that physically the trsn would still have been a relatively soft rock suitable for the carving of tombs however we infer the increased strength and cohesiveness provided by the zeolite framework enhanced the conservation potential of these tombs preserving them for over two thousand years

modeling the effect of multiple sets of mesoscale fractures in porous rock on frequency dependent anisotropy this study models the seismic response of porous rock containing two fracture sets with different orientations sizes and connectivities modeling demonstrates frequency dependent anisotropy controlled by two characteristic frequencies that are defined by fluid mobility and the length scales of the fractures fracture related dispersion and attenuation typically occur over a wider frequency band than is seen in the case of a single fracture set when one set of fractures is modeled as being sealed the azimuthal variation of velocity and attenuation can be different with the azimuth of minimum attenuation coinciding with the strike direction of the open fracture set the results should support attempts to differentiate between open and closed fractures on the basis of seismic measurements

assessment of rock mass strength for underground excavations abstract when the stability of underground openings is assessed one must concern with local and global failure modes local failures may take place as long as rock blocks are kinematically movable into openings while global failure modes are associated with the stress state and the strength of rock mass surrounding openings this fact is always confused in underground rock engineering first the authors briefly describe several approaches how to assess the strength of rock masses together with some new proposals for underground excavations then the estimations by these methods are compared with each other as well as with experimental data finally the validity of these methods are discussed and some recommendations are made for practical applications

assessments on the stability of natural slopes prone to toe erosion and man made historical semi underground openings carved in soft tuffs at zelve open air museum cappadocia turkey abstract the zelve open air museum consisting of three valleys is one of the oldest historical semi underground settlements in the cappadocia region of turkey which was designated as a world heritage site in 1985 by unesco particularly in the first valley there are a lot of underground openings of different sizes carved in a soft tuff next to the valley cliffs used for cliff settlement in the past and several antique churches with some geo engineering problems in addition steep natural slopes in this valley are prone to toe erosion resulting in stability problems in this study it is aimed to investigate engineering characteristics of the surrounding tuff and factors affecting them and to assess the effect of rate of toe erosion on the stability of steep valley slopes and structural stability of some selected typical underground openings with large spans subjected to spalling for these purposes some observational experimental and numerical modelling studies were conducted experimental results indicate that strength and deformability properties of the weak tuff surrounding the openings drastically reduce when it becomes wet or saturated this situation suggests that possibility of occurrence of failures is expected to be higher in rainy seasons due to increase in water content of the tuff experimental results also suggest that spalling commonly observed in the valley is related with freezing thawing and wetting drying cycles in nature and that the process of freezing and thawing accelerates further the degradation of the rock the long term measurements at selected locations suggest that erosion in the tuff is important which increases particularly in winter and spring seasons and results in the loss of support accelerating the occurrence of further slope failures the 2 d numerical solutions indicate that no significant change in shear and tensile stresses in steep valley slopes prone to toe erosion would be expected after 100 years however the solutions obtained from the 500 and 1000 year scenarios suggest that failure zones due to the tensile stresses would develop in the form of slabs with thicknesses of 50 60 cm and 90 100 cm respectively which would break off from the slope and fall down the results from 3 d numerical solutions indicate that failure yield zone resulting from tensile stresses around the semi underground openings will develop parallel to the sidewalls these results confirm the observed spalling of the tuff in the form of slabs parallel to the walls of the openings

continental arc volcanism and tectonic setting in central anatolia turkey abstract the neogene and quaternary volcanism of central anatolia represents the central sector of the anatolian volcanic arc related to continental collision between the afro arabian and eurasian plates it is closely associated with a complex system of tectonic depressions related to brittle deformations of transtentional type and which commenced in the late miocene the volcanism here considered can be divided into three main periods of activity separated by important deformative and erosive events the first period is represented by a mostly andesitic effusive activity the second period is characterized by the emplacement of a thick ignimbritic sequence and shows an areal distribution up to 11 000 km 2 seven ignimbrite units have been recognized the three main units were found at a distance of more than 100 km from the presumed source area geological and sedimentological data lead us to recognize the melendiz dag volcanic complex and the ciftlik caldera as the probable ignimbrites source vent during the third period great andesitic basaltic stratovolcanoes and a number of prevalently acid monogenic centres developed the relationship between the volcanic activity is clearly conditioned by the main transcurrent fault systems present in central anatolia the neogene quaternary volcanic activity prevalently developed along the ene wsw karaman sivas lineament most of the great central volcanoes developed at the intersection between the ene wsw trends and the ecemis and tuz golu transcurrent faults the structural interpretation of the quaternary monogenic centres is more difficult probably they are related to the very recent n s fault swarms which cross the anatolides and the taurus range