coda q c attenuation and source parameter analysis in friuli ne italy and its vicinity the digital data acquired by 16 short period seismic stations of the friuli venezia giulia seismic network for 56 earthquakes of magnitude 2 3 4 7 which occurred in and near ne italy have been used to estimate the coda attenuation q c and seismic source parameters the entire area under study has been divided into five smaller regions following a criterion of homogeneity in the geological characteristics and the constrains imposed by the distribution of available events standard iaspei routines for coda q c determination have been used for the analysis of attenuation in the different regions showing a marked anomaly in the values measured across the ne border between friuli and austria for q 0 value a large variation exists in the coda attenuation q c for different regions indicating the presence of great heterogeneities in the crust and upper mantle of the region the mean value of q c f increases from 154 203 at 1 5 hz to 1947 2907 at 48 hz frequency band with large standard deviation estimates using the same earthquake data the seismic moment m 0 source radius r and stress drop for 54 earthquakes have been estimated from p and s wave spectra using the brune s seismic source model the earthquakes with higher stress drop greater than 1 kbar occur at depths ranging from 8 to 14 km

attenuation of coda waves in western anatolia abstract by analyzing the decay of coda wave amplitude we have determined coda q qc in western anatolia turkey using the single isotropic scattering model we analyzed 116 earthquakes which registered at the gebze station by using five narrow frequency bands centered at 1 5 3 6 8 and 10 hz coda q values were obtained using different lapse times between 30 and 190 s in steps of 10 s coda qc for western anatolia depends on frequency and lapse time for a lapse time of 30 s the frequency dependence of qc is q c 50 7 1 01 and for a lapse time of 190 s it is q c 183 2 0 76 in this region the exponential value of the qc frequency dependence is practically constant between 0 7 and 1 0 the obtained coda qc values were compared with those estimated in other regions the coda qc values for lapse times between 60 and 100 s for western anatolia and southern spain are practically the same indicating similar coda wave attenuation patterns in both regions of the mediterranean basin

estimation of coda wave attenuation for nw himalayan region using local earthquakes abstract the attenuation of seismic wave energy in nw himalayas has been estimated using local earthquakes most of the analyzed events are from the vicinity of the main boundary thrust mbt and the main central thrust mct which are well defined tectonic discontinuities in the himalayas the time domain coda decay method of a single back scattering model is employed to calculate frequency dependent values of coda q qc a total of 36 local earthquakes of magnitude range 2 1 4 8 have been used for q c estimation at central frequencies 1 5 3 0 6 0 9 0 12 0 and 18 0 hz through eight lapse time windows from 25 to 60 s starting at double the time of the primary s wave from the origin time the estimated average frequency dependence quality factor gives the relation q c 158 f 1 05 while the average q c values vary from 210 at 1 5 hz to 2861 at 18 hz central frequencies the observed coda quality factor is strongly dependent on frequency which indicates that the region is seismic and tectonically active with high heterogeneities the variation of the quality factor q c has been estimated at different lapse times to observe its effect with depth the estimated average frequency dependent relations of q c vary from 85 f 1 16 to 216 f 0 91 at 25 to 60 s lapse window length respectively for 25 s lapse time window the average q c value of the region varies from 131 36 at 1 5 hz to 2298 397 at 18 hz while for 60 s lapse time window its variation is from 285 95 at 1 5 hz to 2868 336 at 18 hz of central frequency the variation of q c with frequency and lapse time shows that the upper crustal layers are seismically more active compared to the lower lithosphere the decreasing value of the frequency parameter with increasing lapse time shows that the lithosphere acquires homogeneity with depth

coda q distribution in the canary islands abstract the canary archipelago near the african plate between 27 and 30 n and 13 and 19 w is included in the oldest region 135 m y of the eastern atlantic ocean the tectonic seismicity is moderate with low magnitudes and it is almost totally related to an active fault located between the islands of tenerife and gran canaria the purpose of this paper is to provide a clear idea of the anelasticity of coda waves in the region in order to compute master dispersion curves as a function of the quality factor q we have applied inversion methods to obtain analytical magnification curves for all the seismographic stations used fp t data corresponding to the coda wave dispersion of 52 local and regional seismic events recorded at 6 seismographic stations have been obtained the fit of the data to the master curves determined yields estimates of coda q values and their frequency dependence most of the q0 values determined at 1 hz vary between 100 and 300 showing a strong frequency dependence in the range 0 2 2 hz the characteristic v value degree of frequency dependence of q in the region given by the law q q0 fv is v 0 9 by applying regionalization techniques an iso q0 map for a reference frequency of 1 hz has been obtained for the canary archipelago this map shows important lateral variations in q0 reflecting the tectonics and the volcanism of the region the lowest q0 values are found along the trend of the fault and beneath the islands

attenuation of coda waves in new england abstract seismic wave attenuation was measured in new england from the time domain decay of coda wave amplitudes on narrow bandpass filtered seismograms of local earthquakes the frequency band of interest was 0 75 to 10 hz q c f was found to increase with frequency across this band but there was also a difference between the q c f values for short t t 100 sec lapse times of coda wave propagation for the short lapse time data corresponding to wave paths primarily in the upper crust q c f increases from 400 at 3 hz to 1300 at 10 hz for the large lapse time data corresponding to wave paths in the lower crust and upper mantle q c f was found to vary from 660 at 1 hz to 1500 at 10 hz if we interpret this dataset in terms of a model incorporating both scattering and anelastic attenuation we find that the mean free path of seismic waves over this frequency band is 80 km for short lapse times and 400 km for long lapse times if we assume that scattering is entirely responsible for the observed attenuation we find that the minimum mean free path for short lapse times is about 75 km over all frequencies whereas for long lapse times the minimum mean free path decreases from 400 km at 0 75 hz to 90 km at 10 hz

attenuation of coda waves in the saurashtra region gujarat india the attenuation characteristics based on coda waves of two areas jamnagar and junagarh of saurashtra gujarat india have been investigated in the present study the frequency dependent relationships have been developed for both the areas using single back scattering model the broadband waveforms of the vertical components of 33 earthquakes mw 1 5 3 5 recorded at six stations of the jamnagar area and broadband waveforms of 68 earthquakes mw 1 6 5 recorded at five stations of the junagarh area have been used for the analysis the estimated relations for the junagarh area are qc 158 5 f 0 99 0 04 lapse time 20 s qc 170 4 4 f 0 97 0 02 lapse time 30 s and qc 229 6 6 f 0 94 0 03 lapse time 40 s and for the jamnagar area are qc 178 3 f 0 95 0 05 lapse time 20 s qc 224 6 f 0 98 0 06 lapse time 30 s and qc 282 7 f 0 91 0 03 lapse time 40 s these are the first estimates for the areas under consideration the junagarh area appears to be more attenuative as compared to the jamnagar area the increase in qc values with lapse time found here for both the areas show the depth dependence of qc as longer lapse time windows will sample larger area the rate of decay of attenuation q 1 with frequency for the relations obtained here is found to be comparable with those of other regions of the world though the absolute values differ a comparison of the coda q estimated for the saurashtra region with those of the nearby kachchh region shows that the saurashtra region is less heterogeneous the obtained relations are expected to be useful for the estimation of source parameters of the earthquakes in the saurashtra region of gujarat where no such relations were available earlier these relations are also important for the simulation of earthquake strong ground motions in the region

near surface attenuation and site effects from comparison of surface and deep borehole recordings abstract near surface attenuation and site effects are investigated using the seismograms of 17 local earthquakes recorded at depths of 0 0 3 1 5 2 5 and 2 9 km in the cajon pass borehole southern california the borehole penetrates 500 m of miocene sandstone and then crystalline granitic basement rock previous estimates of site response have been limited to shallower holes where the surface reflection interferes with the upgoing direct wave and the deepest sensor is not below the severe near surface effects in bedrock spectral ratios of the direct p and s waves for each earthquake between the different recording levels are well modeled with frequency independent q and amplification at the borehole q p 27 8 and q s 21 7 in the upper 2 9 km increasing from q p 26 and q s 15 in the upper 300 m to q p 133 and q s 47 between 1 5 and 3 km one event was also recorded at a surface granite site less than 1 5 km from the wellhead comparison of the 2 9 km recording with that at this granite site gives q p 50 and q s 23 the similarity of these values with those of previous studies at a wide range of sites suggests that q is very low in the near surface independent of rock type near surface amplification appears considerably more site dependent at the wellhead the amplifications at 1 hz of the direct p and s waves are 12 7 and 13 7 respectively these values include the free surface effect and are in reasonable agreement with the impedance contrast from the borehole logs at the granite site amplification of both p and s waves is less than four direct wave amplification at the wellhead is therefore at least three times that of the granite site the spectra of the direct and coda waves of the one earthquake recorded at both the wellhead and granite sites are compared with the corresponding 2 9 km recording coda wave amplification is in good agreement with the direct wave at the rock site but at the borehole the coda wave amplification factor overestimates the direct wave amplification by a factor of 3

estimates of q in central asia as a function of frequency and depth using the coda of locally recorded earthquakes digital recordings of microearthquake codas from shallow and intermediate depth earthquakes in the hindu kush region of afghanistan were used to determine the attenuation factors of the s wave coda qc and primary s waves q an anomalously rapid decay of the coda shortly after the s wave arrival observed also in a study of coda in central asia by rautian and khalturin 1978 seems to be due primarily to depth dependent variations in qc in particular we deduce the average qc in the crust and uppermost mantle 100 km depth is approximately four times lower than the deeper mantle 400 km depth over a wide frequency range 0 4 to 24 hz further while qc generally increases with frequency at any depth the degree of frequency dependence of qc depends on depth except at the highest frequency studied here 48 hz the magnitude of qc at a particular frequency increases with depth while its frequency dependence decreases for similar depths determinations of q and qc agree suggesting a common wave composition and attenuation mechanism for s waves and codas comparison of these determinations of qc in afghanistan with those in other parts of the world shows that the degree of frequency dependence of qc correlates with the expected regional heterogeneity such a correlation supports the prejudice that qc is primarily influenced by scattering and suggests that tectonic processes such as folding and faulting are instrumental in creating scattering environments

coda waves a review the analysis and interpretation of coda waves have received increasing attention since the early seventies in the past few years interest in this subject has spread worldwide and the study of high frequency seismic coda waves has become a very important seismological topic as a conclusion of the studies accomplished in this time coda waves are considered the result of scattering processes caused by heterogeneities acting on seismic waves p ands waves play a particularly important role in this interaction the process introduces an attenuation which added to the intrinsic absorption gives the observed apparent attenuation therefore coda waves constitute a thumbprint left by the heterogeneities on the seismograms coda waves offer decisive information about the mechanism of how scattering and attenuation take place this review describes coda waves in detail and summarizes the work done in this subject to 1986 the relation between coda waves and attenuation in the context of research on seismic scattering problems is stressed particular attention has been given to the application of coda waves to estimate source and medium parameters the state of the art of the temporal variations of coda wave shape and the possible use of these variations as an earthquake precursor also are presented care has been taken to introduce the statistical models used to deal with the heterogeneities responsible for scattering

a frequency dependent relation of coda q c for koyna warna region india attenuation properties of the lithosphere around the koyna warna seismic zone is studied by estimating the coda q c from 30 local earthquakes of magnitude varying from 1 5 to 3 8 an average lapse time of 65 sec used in the single scattering model sampled a circular area with an average radius of 114 km the estimated q c values show a frequency dependent relation q c 169 f0 77 and range from 169 at i hz to 1565 at 18 hz a comparison of worldwide q studies reveals that for a large frequency range the q for active regions is low as compared to that for stable regions however south carolina and norway are exceptions in that their q is low in the low frequency range while new england and north iberia are exceptions as they have a q value similar to that for active regions like spain turkey italy and garhwal himalaya stih in the higher frequency range in contrast to this the q for the koyna warna area which belongs to a stable region is low in the entire frequency range as compared to the stable regions and similar to the active stih regions

attenuation of high frequency p and s waves in the gujarat region india the local earthquake waveforms recorded on broadband seismograph network of institute of seismological research in gujarat india have been analyzed to understand the attenuation of high frequency 2 25 hz p and s waves in the region the frequency dependent relationships for quality factors for p qp and s qs waves have been obtained using the spectral ratio method for three regions namely kachchh saurashtra and mainland gujarat the earthquakes recorded at nine stations of kachchh five stations of saurashtra and one station in mainland gujarat have been used for this analysis the estimated relations for average qp and qs are qp 105 2 f0 82 0 01 qs 74 2 f1 06 0 01 for kachchh region qp 148 2 f0 92 0 01 qs 149 14 f1 43 0 05 for saurashtra region and qp 163 7 f0 77 0 03 qs 118 34 f0 65 0 14 for mainland gujarat region the low q 0 5 as obtained from present analysis indicate the predominant seismic activities in the region the lowest q values obtained for the kachchh region implies that the area is relatively more attenuative and heterogeneous than other two regions a comparison between qs estimated in this study and coda q qc previously reported by others for kachchh region shows that qc qs for the frequency range of interest showing the enrichment of coda waves and the importance of scattering attenuation to the attenuation of s waves in the kachchh region infested with faults and fractures the qs qp ratio is found to be less than 1 for kachchh and mainland gujarat regions and close to unity for saurashtra region this reflects the difference in the geological composition of rocks in the regions the frequency dependent relations developed in this study could be used for the estimation of earthquake source parameters as well as for simulating the strong earthquake ground motions in the region

low coda qc in the epicentral region of the 2001 bhuj earthquake of mw 7 7 on 26 january 2001 03 46 55 ut a devastating intraplate earthquake of m w 7 7 occurred in a region about 5 km nw of bhachau gujarat 23 42 n 70 23 e the epicentral distribution of aftershocks defines a marked concentration along an e w trending and southerly dipping 45 zone covering an area of 60 40 km2 the presence of high seismicity including two earthquakes of magnitudes exceeding 7 7 in the 200 years is presumed to have caused a higher level of shallow crustal heterogeneity in the kutch area a site lying in the seismic zone v zone of the highest seismicity for potentially m8 earthquakes on the seismic zoning map of india attenuation property of the medium around the epicentral area of the bhuj earthquake covering a circular area of 61 500 km2 with a radius of 140 km is studied by estimating the coda q c from 200 local earthquakes of magnitudes varying from 3 0 4 6 the estimated q 0 values at locations in the aftershock zone high seismicity are found to be low in comparison to areas at a distance from it this can be attributed to the fact that seismic waves are highly scattered for paths through the seismically active and fractured zone but they are well behaved outside the aftershock zone distribution of q 0 values suggests that the local variation in q 0 values is probably controlled by local geology the estimated q 0 values at different stations suggest a low value of q 102 0 80 f 0 98 0 02 indicating an attenuative crust beneath the entire region the frequency dependent relation indicates a relatively low q c at lower frequencies 1 3 hz that can be attributed to the loss of energy due to scattering attenuation associated with heterogeneities and or intrinsic attenuation due to fluid movement in the fault zone and fluid filled cracks the large q c at higher frequencies may be related to the propagation of backscattered body waves through deeper parts of the lithosphere where less heterogeneity is expected based on the attenuation curve estimated for q 0 102 the ground acceleration at 240 km distance is 13 of 1 g i e 0 13 g agreeing well with the ground acceleration recorded by an accelerograph at ahmedabad 0 11 g hence it is inferred that the q 0 value obtained from this study seems to be apt for prediction of ground motion for the region

coda q for the state of washington abstract frequency dependent coda q values for subregions of the state of washington have been determined using a time domain coda decay method a total of 95 earthquakes digitally recorded on a regional seismograph network of over 100 short period stations were selected to obtain 206 on scale high signal to noise ratio traces for analysis grouping the data by structural regions of the state showed only small variations in coda q by region other than in a very localized area at mount st helens at mount st helens coda q was significantly lower than for all other areas an average of all of the data except that from the local mount st helens area results in a q relationship of q c 63 f 0 97 for the frequency band 2 to 16 hz there is little variation of this coda q relationship when using sources down to 50 km depth and thereby uniformly sampling the top 50 to 100 km of the crust and upper mantle

qlg distribution in the basin and range province of the western united states q values for the direct l g phase were estimated for event station q lg paths that lie entirely within the western united states particularly in the southern great basin and surrounding areas the qo at 1 hz values were estimated by qlg fitting synthetic spectra to observed lg spectra using a genetic algorithm technique we have created a tomographic image of the variations of qo for a part of the southwestern united states the image shows that qo varies between about 234 and 312 at 1 hz with an average of 267 the lowest qo occurs in the northwest part of the basin and range province where extensional deformation has occurred since the mesozoic qo values start to increase toward the colorado plateau to the east and continue to gradually increase northward and decrease southward we also find rela tively high frequency dependence to the values with a 1d mean of g 0 57 qlg

the effect of air pollution on stone decay the decay of the drachenfels trachyte in industrial urban and rural environments a case study of the cologne altenberg and xanten cathedrals severe stone deterioration is evident at the cologne cathedral in particular the drachenfels trachyte which was the building material of the medieval construction period shows significant structural deterioration as well as massive formation of gypsum crusts the present article investigates crust formation on limestone sandstone and volcanic rock from the cologne cathedral as well as from the xanten and altenberg cathedrals these three buildings showing varying degrees of deterioration are located in different areas and exposed to varying industrial urban and rural pollution thin laminar and black framboidal crusts form on calcareous as well as silicate stone the lack of a significant intrinsic calcium and sulfur source for the formation of the gypsum crusts on the drachenfels trachyte indicates major extrinsic environmental impact a sufficient offer of sox from pollutant fluxes as well as external calcium sources e g pollution mortars neighboring calcite stones chemical analyses reveal strong gypsum enrichment within the crusts as well as higher concentrations of lead and other pollutants arsenic antimony bismuth tin etc which generally can be linked to traffic and industry the formation of weathering crusts in an industrial environment is clearly distinguishable from that in rural areas scanning electron microscopy observations confirm that the total amount of pollution is less at the altenberg cathedral than at the cologne and xanten cathedrals xrf analyses show that the formation of gypsum occurs in lower amounts at altenberg this correlates well with the measured so2 content and the intensity of the decay at the different locations furthermore the different types of crusts e g framboidal and laminar can be differentiated and assigned to the different locations the black weathering crusts on the silicate drachenfels trachyte contribute to the degradation of the historic building material they enhance mechanical moisture related deterioration processes and the decay by chemical corrosion of rock forming minerals although so2 concentrations in air have shown a strong decrease over the past 30 years degradation in connection with weathering crusts is still observed this indicates that not only contemporary or recent emissions but also past pollutant concentrations have to be considered

attenuation of coda waves in the dead sea region abstract coda waves of local small earthquakes in the dead sea region part of the jordan rift structure show frequency invariant codas that is q c q 0 f f 0 n with q 0 65 5 f 0 1 hz and n 1 05 0 04 for hypocentral distances between 10 and 55 km and lapse times less than 60 sec this justifies for example the use of part of the coda for relative site response studies lacking direct q measurements q c might be considered as a first approximation of q for the region for short hypocentral distances r q c with lapse time t has been observed

coda q in the charlevoix quebec region lapse time dependence and spatial and temporal comparisons coda q is determined in the seismically active charlevoix region quebec using 34 earthquakes recorded on the six station charlevoix local telemetered network for comparison an average value of coda q for southeastern canada is determined from 32 events that occur over a much larger region at lapse times of 20 to 40 sec coda q at 1 hz q at charlevoix and for southeastern canada is 91 4 and 125 10 respectively at a 40 to 80 sec lapse time it is 200 3 and 305 15 respectively the lower q value at charlevoix in comparison with other parts of southeastern canada is in agreement with jin and aki s 1988 finding that q is lower in the vicinity of large earthquakes no statistically significant temporal change in coda q at charlevoix is observed over the 11 yr of data studied a variation of as little as 15 would be statistically apparent ongoing monitoring of coda q in the area is planned using the local network in order to investigate any temporal changes prior to future large earthquakes coda q is found to increase with lapse time lapse time is defined as time elapsed after the origin time this dependence could be due to any of the following nonzero source receiver distance nonisotropic scattering scattering from below the crust multiple scattering or increase of q with depth or with distance from both source and receiver

weathering of carbonate materials in ancient maya constructions rio bec and dzibanche limestone and stucco deterioration patterns carbonate materials limestone and lime stuccos were widely used in ancient maya construction deterioration of these materials presents a major problem for the conservation of maya architectural heritage however the mechanisms of deterioration and their interaction with the diverse inner structures of these materials are still insufficiently understood we performed micromorphological and mineralogical research of the limestone alteration in the buildings of rio bec and stuccos in dzibanche two late classic maya sites in the southern yucatan peninsula dissolution and recrystallization of calcite were found to be universal and the most important weathering process in both materials dissolution is selective affecting mostly micrite larger crystals especially rhombohedral calcitic pseudomorphs developed after dolomite are more stable selective dissolution of micritic cement of limestones and stuccoes enhances physical breakdown by producing numerous pores and loosening bounds between coarser inclusions this process clearly controls the deterioration grade of different limestones those with more intensive fragmentation and powdering have higher contents of micrite secondary carbonates are represented mostly by acicular calcite filling fissures and forming coatings on the outer surface clear spatial relation to fungi and roots and their similarity to well known soil neoformations indicate biogenic origin of these neoformations in most cases they contribute to macroscopic powdering being loose however in the cracks of some limestones they form dense infillings which could plug the fractures and prevent further advance of weathering to the core of the stone neoformed sulfates and iron oxides are fewer but also participate in the deterioration

coda q in the kachchh basin western india using aftershocks of the bhuj earthquake of january 26 2001 q c estimates of kachchh basin in western india have been obtained in a high frequency range from 1 5 to 24 0 hz using the aftershock data of bhuj earthquake of january 26 2001 recorded within an epicentral distance of 80 km the decay of coda waves of 30 sec window from 186 seismograms has been analysed in four lapse time windows adopting the single backscattering model the study shows that q c is a function of frequency and increases as frequency increases the frequency dependent q c relations obtained for four lapse time windows are q c 82 f1 17 20 50 sec q c 106 f1 11 30 60 sec q c 126f1 03 40 70 sec and q c 122f1 02 50 80 sec these empirical relations represent the average attenuation properties of a zone covering the surface area of about 11 000 20 000 28 000 and 38 000 square km and a depth extent of about 60 80 95 110 km respectively with increasing window length the degree of frequency dependence n decreases marginally from 1 17 to 1 02 whereas q0 increases significantly from 82 to 122 at lower frequencies up to 6 hz q c 1 of kachchh basin is in agreement with other regions of the world whereas at higher frequencies from 12 to 24 hz it is found to be low

coda q estimates in the mount cameroon volcanic region west africa abstract coda q qc has been determined in the mount cameroon volcanic region west africa from the decay of the amplitudes of coda waves on narrow band pass filtered seismograms of local microearthquakes in the frequency range 1 5 to 24 hz qc averages about 121 and 1745 at 1 5 hz and 24 hz respectively and has a frequency dependence of the form qc 65f for each frequency band the coda q values averaged over all the earthquakes show an insensitivity to the compoment of the ground motion considering a model incorporating both scattering and intrinsic attenuation and assuming that the attenuation is entirely due to the scattering loss a frequency independent minimum mean free path of about 38 km was found

studies of the seismic coda using an earthquake cluster as a deeply buried seismograph array loosely speaking the principle of green s function reciprocity means that the source and receiver positions in a seismic experiment can be exchanged without affecting the observed seismograms consequently the seismograms observed at a single observation location o and caused by a cluster of microearthquakes at locations ei are identical to the time series that would be measured by an array of stress meters emplaced at positions ei recording waves generated by a source acting at o by applying array analysis techniques like slant stacking and frequency wave number analysis to these seismograms we can determine the directions and velocities of the component waves as they travel in the earthquake focal region rather than at the surface we have developed a computationally rapid plane wave decomposition which we have applied to single station recordings of aftershocks of the 1984 morgan hill california earthquake the analysis is applied to data from three seismic stations having considerably different site geologies one is a relatively hard rock station situated on franciscan metamorphics one is within the calaveras fault zone and one is on semiconsolidated sand and gravels we define the early coda to be the part of the coda initiating immediately after the direct s wave and ending at twice the s wave lapse time the character of the s wave and early coda varies from being impulsive at the first station to highly reverberative at the last we examine waves in sequential time windows starting at the s wave and continuing through the early part of the coda at all seismic stations the early coda is dominated by a persistent signal that must be caused by multiple scattering probably within 2 km of each seismic station despite clear station to station differences in the character of the early coda coda q values measured in the late coda greater than twice the s lapse time agree well among stations implying that the mechanisms causing the varying behavior of the early coda do not control the coda decay rate at the stations we have considered coda q values measured on horizontal components of motion agree within a factor of 2 with those measured on vertical components we have not been able to determine the composition of the late coda because of a low signal to noise ratio our analysis technique however is quite appropriate for such a task

q determined from local earthquakes in the south carolina coastal plain abstract coda q or qc is determined from the rate of coda decay in the coastal plain near charleston south carolina the mean of qc calculated from individual estmates is near 190 at 1 hz and increases to over 1650 at 10 hz a possible temporal change in qc is identified high values being associated with increased seismic activity during late 1977 temporal changes have been observed elsewhere and laboratory measurements of q under different stress states correlate high q with high stress a spatial variation in qc is identified increasing from west qc at 10 hz equal to 850 to east qc at 10 hz greater than 2100 across the coastal plain the demarcation of high to highest zones of qc is coincident with the western boundary of the innermost isoseismal of the charleston 1886 earthquake it is hypothesized that the 1886 earthquake was mislocated originally because of this spatial variation in energy attenuation that was unrecognized at that time

on concepts and methods for the estimation of dissolutional denudation rates in karst areas abstract the paper discusses methods and principles used to estimate dissolutional denudation rates in karst areas surface lowering can be measured directly by micro erosion meters or calculated from the mass loss in rock tablets exposed to dissolution in different environments indirect approaches are based on the measurements of solute load leaving the catchment area geomorphological investigations and methods of cosmogenic nuclides particularly 36 cl calculations based on the solute load measurements generally give higher denudation rates than direct measurements on the surface of limestone terrains this can be explained by the fact that only about 30 of water s dissolution potential is used on the exposed surfaces and the rest is done deeper in the fracture system the role of endokarst dissolution is demonstrated with a denudation model of rock column where dissolution rate depends solely on the distance from the surface the denudation rates of a uniform rock column approach maximal when the thickness of the removed rock is about twice an e folding length for the dissolution rates the model also gives possible mechanisms for differential denudation in regions with different infiltration intensity and fracture density

crustal structure from deep seismic soundings along the koyna ii kelsi loni profile in the deccan trap area india abstract the crustal depth section obtained from deep seismic soundings along the koyna ii kelsi loni profile which lies near latitude 18 n roughly in the east west direction in that part of the deccan trap maharashtra state india shows a number of reflection segments below the deccan traps down to the moho discontinuity a deep fault below the deccan traps 13 km east of mahad divides the entire cross section including the moho boundary into two crustal blocks the reflection segments show updip towards the west coast in the western block the moho discontinuity which is at a depth of 39 km near the deep fault starts rising towards the coast reaching a depth of 31 5 km at the west coast the eastern block is thrown up by 1 5 km with respect to the western block along the deep fault a structural contour map of the moho discontinuity for the koyna reservoir area has been prepared from the present results and the crustal information obtained along the koyna i profile kaila et al 1979a shows that the deep fault in the koyna area is aligned in the nnw sse direction refraction seismic data analysis by the wave front method reveals that the thickness of the deccan trap increases towards the west coast the deccan trap is 600 700 m thick in the eastern region between nira sp 130 and loni sp 200 and attains a thickness of 1500 m at 10 km east of the west coast the longitudinal wave velocity in the deccan traps along the profile varies from 4 8 to 5 0 km sec and in the crystalline basement from 6 0 to 6 15 km sec a tentative isopach contour map of the deccan traps and a tentative structural contour map of the pre deccan trap contact have been prepared for the koyna reservoir area from the results along the koyna ii and koyna i profiles a flexure aligned in a nnw sse direction in the pre deccan trap contact which is an expression of the deep fault into the basement has been clearly brought out the flexure coincides in general with the orientation of the deccan volcanic scarp in this area

coda q estimates in the andaman islands using local earthquakes the attenuation property of andaman island has been investigated analyzing coda waves from 57 local earthquakes in the magnitude range of 2 0 4 9 using the single backscattering model these earthquakes waveforms recorded on five broadband seismographs sited over the island from north to south during nov 2003 to march 2004 have been used to calculate the frequency dependent coda q q c applying the time domain coda decay method the coda q computed at central frequencies from 0 5 12 hz and five lapse time windows from 40 to 80 s progressively increases from 105 f 0 88 in the north andaman to 135 f 0 79 in the south andaman with an average of 119 f 0 80 the average q c values vary from 75 42 at 0 5 hz to 697 54 at 12 hz central frequency for 40 s lapse time window while for 80 s lapse time window its variation is from 117 38 at 0 5 hz to 1256 115 at 12 hz the q c estimated at different lapse times manifests a significant variation from 122f 0 75 to 174f 0 73 corresponding to lapse time window lengths of 40 and 80 s respectively the variation of q c with frequency lapse time and also with the location of seismograph reflects the marked structural and compositional inhomogeneity with depth along the andaman islands these observations are well correlated with the seismicity pattern and distinct high angle subduction beneath the island

seismic q for the lithosphere of the montenegro region yugoslavia frequency depth and time windowing effects abstract the availability of accelerometric data for the montenegro earthquake of 15th april 1979 makes it possible to investigate seismic q of the lithosphere in that region in particular its dependence on frequency on the depth reached by seismic waves and on the length of time windows in which signals are processed two different spectral methods s phase energy ratio and coda envelope decay are applied respectively to direct and scattered shear waves similar results are obtained using different portions of the recordings i e coda waves for the envelope decay fit and the s wave train with a significant duration of 10 s for the energy ratios the same apparent q q 40 f where f is the frequency expressed in hz that is found for other neighbouring central mediterranean regions e g ancona on the central italian adriatic coast valnerina in the central apennines irpinia in the southern apennines is also found for the southern yugoslavian coast in the band 1 25 hz up to a maximum range of 120 km from the focus this strong frequency dependence is probably connected with the type of small scale heterogeneity and the same geological age and level of tectonic activity peculiar to all these seismotectonic areas in order to compare the apparent q of the whole s wave train 10 s long with the intrinsic apparent q of the single direct s wave usually 1 s or less the maximum entropy method is applied in the energy spectrum computation for shorter wave trains the use of shorter time windows does not reveal any significant variation in the tendency of q to increase linearly with frequency as the length of the time window containing the sample of the s waves decreases this seems to indicate that scattering dependent q is generally inseparable from intrinsic q in the lithosphere when estimates based on variations with distance of the seismic signal spectrum are used while the type of linear growth with frequency does not seem to undergo any variations it remains of the q qf type the data show there are a considerable decrease in the coefficient of proportionality q with decreasing duration of the window of s waves analysed probably as a result of variations in seismic attenuation with depth

attenuation characteristics of coda waves in mainland gujarat india abstract the attenuation characteristics based on coda waves of mainland gujarat india have been investigated in the present study the broadband waveforms of 53 local earthquakes mw 1 1 3 3 having focal depths in the 6 0 33 6 km range recorded at five stations of mainland gujarat region has been used for the analysis the frequency dependent relationships q q0fn for coda q qc and dependency of coda q on lapse time windows have been determined for the said region the average lapse time dependent coda q relations estimated for the region are qc 87 13 f 1 01 0 06 lapse time 30 s qc 112 20 f 0 94 0 08 lapse time 40 s and qc 120 22 f 0 76 0 07 lapse time 50 s the increase in qc values with lapse time shows the depth dependence of qc as longer lapse time windows will sample larger area the observed quality factor is strongly dependent on frequency and lapse time which indicates that the upper lithosphere is more heterogeneous and seismotectonically active while the lower lithosphere is homogeneous and relatively less active a comparison of the coda q estimated for mainland gujarat region with those of nearby kachchh and saurashtra regions shows that mainland gujarat region is more heterogeneous the rate of decay of attenuation q 1 with frequency for the relations obtained here is found to be comparable with those of other regions of the world though the absolute values differ the obtained relations are expected to be useful for the estimation of source parameters of the earthquakes in the mainland gujarat region where no such relations were available earlier these relations are also important for the simulation of earthquake strong ground motions in the region

effect of fluid salinity on subcritical crack propagation in calcite abstract the slow propagation of cracks also called subcritical crack growth is a mechanism of fracturing responsible for a ductile deformation of rocks under crustal conditions in the present study the double torsion technique was used to measure the effect of fluid chemistry on the slow propagation of cracks in calcite single crystals at room temperature time lapse images and measurements of force and load point displacement allowed accurate characterization of crack velocities in a range of 10 8 to 10 4 m s velocity curves as a function of energy release rates were obtained for different fluid compositions varying nh 4 cl and nacl concentrations our results show the presence of a threshold in fluid composition separating two regimes weakening conditions where the crack propagation is favored and strengthening conditions where crack propagation slows down we suggest that electrostatic surface forces that modify the repulsion forces between the two surfaces of the crack may be responsible for this behavior

attenuation of seismic waves in the trinidad and tobago area abstract the attenuation of seismic waves from earthquakes located within the area bounded by 9 12 n and 60 63 w was estimated from short period seismograms coda q q c determinations were made for each of the six seismograph stations within the area while spectral q values from p phases q were estimated for station trn the s s single scattering model was assumed for coda generation and the 2 source model was assumed for the spectral q determinations the q c values show a strong frequency dependence in the frequency range 1 5 12 hz the value of q at 1 hz q o was found to lie within the range 107 132 while the rate of frequency dependence n extends from 0 80 to 1 06 for shallow events for intermediate depth events q o varies from 101 to 173 and n from 0 80 to 1 02 the q values obtained show a spatial variation within the region the highest attenuation was obtained on land trinidad

coda q distribution in the iberian peninsula summary several attenuation studies have established a frequency dependence law of the anelastic attenuation factor q in the form q qo f fo v for the approximate 1 10 hz frequency range we propose a method that leads to the determination of q which is a function of the reference frequency fo and the real exponent v with a single station to carry out the problem we determine a set of master curves as a function of y we discuss the method and the different features of the master curves when it is applied to the complicated regions of the iberian peninsula and to several instruments with different responses using this new method and the seismographic stations available in the iberian peninsula we have mapped iso qo lines at a reference frequency of 1 hz applying inversion methods the q values determined for iberia vary between about 100 and about 600 values close to 100 correspond to the southern part of iberia in general q values increase from south to north with values about 600 near the nw part of iberia the pyrenees mountains and adjacent areas present q values between about 200 and about 350 these results suggest a strong qo lateral variation in iberia a considerable frequency dependence of coda q has also been determined the v values vary between 0 3 and 0 8 the q values obtained in the iberian peninsula show very good agreement with several q values obtained in other regions of the world comparison between the iso q lines and other geophysical parameters like regional variations of p velocities heat flow isoseismal intensity distribution and crustal thickness indicates that lower q values are associated with higher isoseismal intensity attenuation higher heat flow lower p velocities and thinner crust

attenuation of coda waves in the garhwal himalaya india abstract q c estimates have been obtained by analysing coda waves of seven local earthquakes recorded in the garhwal himalaya the earthquakes have their epicentral distances within 100 km focal depths up to 20 km with 2 4 m l 4 9 q c values have been computed at central frequencies of 1 5 3 0 6 0 12 0 and 18 0 hz for different earthquake stations falling in the lapse time window of 30 60 s using a single backscattering model the mean value of q c shows a dependence on frequency varying from 206 at 1 5 hz to 2090 at 18 hz the frequency dependence average q c relationship q c q 0 f n has been obtained for the region as q c 126 f 0 95 which indicates that attenuation at higher frequencies is less pronounced q c values estimated for the region represent the average attenuation properties for a surface area of about 20 000 km 2 in a circular shape with a radius of about 80 km assuming single backscattering

stability of coda q in the region of parkfield california view from the u s geological survey parkfield dense seismograph array many investigators have proposed that changes in the rate at which the coda decays may be an intermediate term precursor to moderate to large earthquakes parkfield california on the san andreas fault is a promising location for studying premonitory changes in coda q qc because a large earthquake is likely to occur there we have investigated qc using recordings from the u s geological survey parkfield dense seismograph array which is a digital array with 14 triaxial sensors and an aperture of about 1 km for each earthquake we can measure qc from up to 42 recordings their average is more stable than the measurement from a single station using clustered seismicity we have developed criteria for selecting events and reducing scatter in the measurement the qc value determined from a seismogram depends on the position and length of the analysis window thus qc should always be measured from the same length window starting at the same lapse time regardless of the source location in addition the band limited signal to noise ratio at the end of the analysis window is important qc determined in two frequency bands 4 8 hz and 8 16 hz from a tight cluster of 26 events which occurred between december 1989 and january 1994 has not changed despite m 4 7 and m 4 6 events in october 1992 and november 1993 qc measured from local events 60 km in three frequency bands shows larger scatter but has also not changed during this period for monitoring qc observations should include array averaged measurements from a single lapse time because qc measurements made using an analysis window that starts at a constant multiple of the s wave lapse time depend on epicentral distance a procedure combining the evaluation of the time and distance dependences of qc also gives stable observations

coda wave seismic structure beneath the indian ocean region and its implications to seismotectonics and structural heterogeneity abstract the indian ocean region is one of the challenging areas for seismological research because of its complex seismotectonic settings and intricate structural heterogeneity prevails beneath the indian ocean region in order to address the problem we attempted to determine the attenuation structure for the indian ocean region using coda wave generation by single backscattering model in this study the central frequency of interest has been considered between 1 5 and 12 0 hz with lapse time window ltw of 20 30 40 50 and 60 s measured from the origin time of the earthquake we obtained the attenuation relation for different seismotectonic zones associated with varying estimate of attenuation parameters spreading zone qc spz 171f1 10 subduction zone qc sz 220f0 961 triple point junction qc tpj 156f1 15 prominent faults of indian ocean region qc pfioz 197f0 99 and volcanic and hotspot qc vz hs 209f0 97 we estimated average frequency dependent attenuation parameters of q0 that varies as 156 32 q0 220 33 with corresponding variability in frequency parameter as 0 96 0 05 1 15 0 09 at 40 s ltw for the entire indian ocean region suggesting that the entire indian ocean is seismo tectonically highly active and is attributed to the nature and extent of attenuation due to varying amount of structural heterogeneity in different tectonic zones characterized by the occurrence of earthquakes of varying strengths in the seismically active tectonic zones of the region we found that the triple junction rtj is associated with low qc and high attenuation because of deposition of a variety of sediments at the rtj which is in unison to the geological mapping of the region we observed that our estimated attenuation model is comparable that of the aleutian islands the adak seismic zone at low frequency 5 hz and to the philippine sea subduction zone petukhin at higher frequency range 5 hz which is very much correlative to seismo tectonic settings we infer that our assimilated attenuation model has potential to provide information on intricate seismotectonics and seismogenesis for computing earthquake source parameters and earthquake hazards that may be useful for assimilating detailed seismic velocity structure beneath the indian ocean region

depth dependent seismic attenuation in the granada zone southern spain abstract coda q estimates for the granada basin southern spain are obtained by analyzing earthquakes occurring within or close to the borders of this area the data set is composed of 54 earthquakes with local magnitudes ranging between 2 2 and 4 0 and with epicentral distances to the nearest station smaller than 10 km a single scattering process is assumed coda q values obtained show a clear dependence on frequency according to the relationship q q o f n where n ranges from 0 81 to 0 89 after removing the main site effects and discussing the possible multiple scattering influence the lapse time dependence is interpreted as due to attenuation variations with depth this result agrees with the variation of coda q obtained by using different sets of events with increasing hypocentral depth ranges

attenuation of high frequency shear waves in the crust measurements from new york state south africa and southern california we compare the attenuation of high frequency 3 30 hz shear waves for crustal paths in new york state south africa and southern california over source receiver distances of about 10 400 km the data consist of digital recordings of s waves 5 100 km and lg waves 100 400 km produced by earthquakes we use a coda normalization method to remove the effects of site amplification and source excitation from the amplitudes of the s and lg waves over the entire distance range studied 10 400 km the amplitude decay of 3 hz shear wave energy is considerably less for the tectonicaily stable areas of new york and south africa than for the tectonicaily active region of southern california high frequency 30 hz s wave attenuation is significantly less for new york and south africa than for southern california for distances between 15 and 90 km we parameterize the decay with distance r of coda normalized shear wave amplitudes with a frequency independent q and geometrical spreading exponent where geometrical spreading is proportional to r for new york state the s wave amplitude decay 3 30 hz is well described by a frequency independent q of 2100 330 490 and of 1 3 0 1 the decay of lg wave amplitudes from 3 to 15 hz in the new york state region is fit with a frequency independent q of 1600 280 330 of 0 70 0 2 the s wave amplitudes 3 30hz in south africa yield a q of 1500 190 380 and of 1 3 0 1 fixing the geometrical spreading at r 0 5 produces an lg wave q estimate at 3 hz in south africa of 360 50 80 this lg wave q is low considering that south africa is a cratonic tectonicaily stable area the s wave amplitudes from southern california are described with a frequency independent q of 800 150 240 and a large geometrical spreading exponent of of 1 9 0 2 we find an lg wave q at 3 hz of 260 30 for southern california after constraining the geometrical spreading at r 0 5

application of the telegraph model to coda q variations in southern california we examine waveforms and data used to construct coda magnitude in southern california to estimate the spatial variation of coda q and its dependence on frequency our analysis combined with independent borehole data suggests that coda is mainly generated by multiple scattering in the upper few kilometers of the crust where large impedance contrasts occur because of surface layering or fracturing the ubiquitous observation that coda q increases with frequency is explained as arising from multiple reverberations in the upper crust we suggest that the telegraph model that has been successfully used to describe reflection seismogram multiples in the exploration industry may also apply to earthquakes under this model the apparent increase of q with frequency is due to trapping of high frequency energy in the upper crust this behavior is expected if the associated reflector series has an exponential autocorrelation function a feature of the telegraph model at lower frequencies trapping is less efficient the combined effects give rise to an apparent absorption band that we suppose is superimposed on frequency independent intrinsic attenuation maximum apparent attenuation occurs at wavelengths equal to the dimensions of the regions of upper crust that contain the scattering layers at lower frequencies trapping is less effective and attenuation decreases as the longer wavelength waves sample the deeper crust and upper mantle where because of overburden pressures acoustic impedance contrasts are less extreme by taking spectral ratios of coda waves to direct s we estimate that intrinsic q is high 3000 and that coda may be modeled as multiple scattered s waves in a region of anisotropic scattering the exponential decay of the coda is a result of the perfectly reflecting surface of the earth with backscattering from random near surface layers causing progressive leakage and loss of energy downward into the more transparent lower crust and mantle

regional tectonic framework structure and evolution of the western marginal basins of india abstract the kutch saurashtra cambay and narmada basins are pericontinental rift basins in the western margin of the indian craton these basins were formed by rifting along precambrian tectonic trends interplay of three major precambrian tectonic trends of western india dharwar nnw sse aravalli delhi ne sw and satpura ene wsw controlled the tectonic style of the basins the geological history of the basins indicates that these basins were formed by sequential reactivation of primordial faults the kutch basin opened up first in the early jurassic rifting was initiated in late triassic along the delhi trend followed by the cambay basin in the early cretaceous along the dharwar trend and the narmada basin in late cretaceous time along the satpura trend the evolution of the basins took place in four stages these stages are synchronous with the important events in the evolution of the indian sub continent its breakup from gondwanaland in the late triassic early jurassic its northward drifting during the jurassic cretaceous and collision with the asian continent in the early tertiary the most important tectonic events occurred in late cretaceous time the present style of the continental margins of india evolved during early tertiary time the saurashtra arch the extension of the aravalli range across the western continental shelf subsided along the eastern margin fault of the cambay basin during the early cretaceous it formed an extensive depositional platform continuous with the kutch shelf for the accumulation of thick deltaic sediments a part of the saurashtra arch was uplifted as a horst during the main tectonic phase in the late cretaceous the present high thermal regime of the cambay bombay high region is suggestive of a renewed rifting phase

an intrusive origin of some ug 1 chromitite layers in the bushveld igneous complex south africa insights from field relationships abstract the ug 1 chromitite in the bushveld complex is a 1 m thick massive layer overlain by orthopyroxenite 4 9 m thick and underlain by anorthosite 1 5 2 0 m thick which is strongly interleaved with numerous thin layers of ug 1 chromitite mm to 10 s of cm thick the chromitite bearing anorthosite is further underlain by mottled anorthosite which is devoid of chromitites sometimes the massive ug 1 chromitite may be hosted entirely within orthopyroxenite in this study however the orthopyroxenite occurs intermediate to the massive ug 1 layer and the footwall interleaved anorthosite unit which has a 10 cm thick chromitite layer at the contact though the ug 1 chromitites display complex features in the field outcrops e g presence of numerous anorthosite autoliths bifurcations and dimpled contacts with anorthosite the ones discussed in this study are distinctive and diagnostic of the emplacement mechanism for this chromitite layer in this study of the ug 1 chromitite at the impala platinum mine the chromitite is seen to form a small pothole 1 5 m deep 3 6 m wide that cuts down into the underlying orthopyroxenite exposed only on the right side of the pothole and anorthosite layers a 15 cm thick ug 1 chromitite layer 85 modal chromites is observed to protrude or branch out of the pothole margin and laterally extend into the anorthosite with which it shows several crosscutting features examples include truncation of layering defined by interstitial pyroxene mottles within the footwall anorthosite against the protruding ug 1 layer and truncation of several thinner ug 1 layers in the hanging wall anorthosite against erosive outlines of this chromitite layer these observations strongly attest to the emplacement of the protruding ug 1 chromitite layer as a sill into the anorthosite the presence of thin anorthosite lenses with high aspect ratios within this ug 1 layer along with lateral variations in thickness of the layer its irregular contact with the host anorthosite and disturbances observed for the ug 1 layers in the footwall anorthosite adjacent to the erosive contact implies that the superheated melt parental to the chromitite chemically dissolved the anorthosite and made space for it to flow as a sill within the latter the probable mode of emplacement of the laterally protruding ug 1 layer would be through the opening of fractures related to the event of pothole formation where there is ponding of hot thick and dense melt above the anorthosite the melt subsequently filled the fractures and flowed laterally into the anorthosite thereby eroding it an open magmatic system ensured continuous addition of melts in the pothole and their supply into the sill this study thus emphasizes that some of the ug 1 chromitite layers within anorthosite can be emplaced as sills and not all need to form from discrete cyclical pulses of chromite saturated and plagioclase saturated melts being brought into the chamber

frequency dependent attenuation of coda waves in the crust in southwest anatolia turkey the attenuation of coda waves in the earth s crust in southwest sw anatolia is estimated by using the coda wave method which is based on the decrease of coda wave amplitude in time and distance a total of 159 earthquakes were recorded between 1997 and 2010 by 11 stations belonging to the koeri array the coda quality factor q c is determined from the properties of scattered coda waves in a heterogeneous medium firstly the quality factor q 0 the value of q c at 1 hz and its frequency dependency are determined from this method depending on the attenuation properties of scattered coda waves for frequencies of 1 5 3 0 6 0 8 0 12 and 20 hz secondly the attenuation coefficients are estimated the shape of the curve is controlled by the scattering and attenuation in the crustal volume sampled by the coda waves the average q c values vary from 110 15 to 1 436 202 for the frequencies above the q 0 and values vary from 63 7 to 95 10 and from 0 87 0 03 to 1 04 0 09 respectively for sw anatolia in this region the average coda q f relation is described by q c 78 9 f 0 98 0 07 and 0 012 km 1 the low q 0 and high are consistent with a region characterized by high tectonic activity the q c values were correlated with the tectonic pattern in sw anatolia

quantifying micron scale grain detachment during weathering experiments on limestone weathering in carbonate rocks is often assumed to be governed by chemical dissolution nevertheless chemical processes can be coupled to mechanical mechanisms with small grains undergoing partial dissolution along grain boundaries followed by detachment from the rock surface crucially this process can even extend down to the micron scale although chemo mechanical detachment could be critical for the understanding of carbonate weathering at the global scale the role it plays has not been directly quantified to calculate the contribution of grain detachment to surface retreat rates and to determine the impact of the flow regime we carried out a series of flow through weathering experiments on micritic limestone using atomic force microscopy we obtained high resolution in situ data of surface topography for reacting rock surfaces in all the experiments both grain detachment and chemical dissolution were observed under the laminar flow conditions we explored we found no clear correlation between flow rate and the size of detached grains or between the flow rate and the frequency of grain detachment events importantly our results establish that grain detachment contributes significantly to the overall surface retreat on average accelerating mass loss by 38 in addition to speeding up weathering this micron scale mechanism could also influence the evolution of porosity in aquifers and hydrocarbon reservoirs and provide a natural flux of colloids that could transport heavy metals or radionuclides in groundwater

pore scale heterogeneous reaction rates on a dissolving limestone surface abstract the rate at which limestone dissolves determines the resistance of buildings and monuments to weathering the efficiency of carbon capture in deep geological reservoirs and the processes by which soils rocks and landscapes form and evolve however the normalized rates of mineral dissolution measured in laboratory experiments are often found to be far greater than those measured in field settings here we use atomic force microscopy afm measurements to demonstrate experimentally that the rate of calcite dissolution within micron size pores at the surface of a limestone sample is much lower than the rate of dissolution in the surrounding calcite surface in addition we use numerical simulations to show that this difference cannot be explained using a simple diffusion surface reaction model we suggest that the observed heterogeneous reaction rates could instead be due to the elevated density of reactive high curvature features on the polished surface surrounding the pore these high curvature features can strongly affect local interfacial free energy making such surfaces more prone to dissolution as a result polished surfaces should be more reactive than pore surfaces that have effectively been smoothed during prolonged contact with natural fluids as rate experiments routinely use polished and powdered samples the results may help to explain the widely reported discrepancy between lab and field based dissolution rates