lapse time dependence of coda q anisotropic multiple scattering models and application to the pyrenees abstract the coda quality factor of short period s waves q c excited by local earthquakes in the pyrenees has been measured as a function of the length of the coda window l w for different choices of the onset time of the coda t w in the 2 16 hz frequency band we observe a transient regime characterized by an increase of q c with l w followed by a stabilization around a plateau the value of which depends on the central frequency of the signal using monte carlo simulations of wave transport in a variety of random media 1200 models we demonstrate that the lapse time dependence of q c in the pyrenees may be modeled by multiple anisotropic scattering of seismic waves without invoking any depth dependence of the attenuation properties in the crust in our model anisotropic scattering is quantified by the ratio between the transport mean free path and the mean path l l at 6 hz the data require an anisotropy factor l l 5 a transport mean free path l 400 km and an intrinsic quality factor q i 800 from the frequency dependent plateau of q c at large lapse time we infer an intrinsic quality factor of the form q i 400 f 0 4 in the pyrenees we also show how the rapid increase of the lapse time dependence of q c with frequency may be exploited to put constraints on the power spectrum of heterogeneities in the crust

global positioning system measurements of present day crustal movements in the arabia africa eurasia plate collision zone we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1994 at 54 sites extending east west from the caucasus mountains of southern russia georgia and armenia to the aegean coast of turkey and north south from the southern edge of the eurasian plate pontus block to the northern edge of the arabian platform viewed from a eurasia fixed reference frame sites on the northern arabian platform move n38 13 w at 20 3 mm yr roughly consistent with the velocity implied by nuvel 1a circuit closure n23 7 w at 24 2 mm yr the motion of arabia appears to be transferred directly to the region of turkey north of the suture however eastern turkey is characterized by distributed deformation while central western turkey is characterized by coherent plate motion involving westward displacement and counterclockwise rotation of the anatolian plate internal deformation within the central part of the anatolian plate is less than 2 mm yr the anatolian plate is decoupled from eurasia along the right lateral strike slip north anatolian fault naf this different response in eastern and western turkey to the collision of arabia may result from the different boundary conditions the hellenic arc forming a free boundary to the west and the asian continent and oceanic lithosphere of the black and caspian seas forming a resistant boundary to the north and east we derive a best fitting euler vector for anatolia eurasia motion of 29 2 0 8 n 32 9 0 4 1 3 0 1 m y the mapped surface trace of the naf corresponds well to a small circle about this pole the new euler vector implies an upper bound for naf slip rate of 30 2 mm yr i e assuming all relative motion is accommodated along the naf using the nuvel 1a euler vector for arabia eurasia and the gps euler vector for anatolia eurasia we determine an arabia anatolia euler vector of 31 2 n 45 2 e 0 9 0 1 m y and an upper bound on the east anatolian fault slip rate of 15 3 mm yr the aegean trough region of western turkey deviates significantly from coherent plate rotation in addition to rotating with anatolia this region shows roughly n s extension at a rate of 14 5 mm yr taken together with satellite laser ranging results along the hellenic arc the contemporary pattern of deformation indicates increasing motions toward the arc suggesting that the westward displacement and counterclockwise rotation of anatolia is driven both by pushing from the arabian plate and by pulling or basal drag associated with the foundering african plate along the hellenic subduction zone

geometrical spreading and attenuation of lg waves a comparison between western anatolia turkey and southern spain abstract we compared the attenuation and geometrical spreading coefficient of lg waves for crustal paths in western anatolia and southern spain at source receiver distances between 80 and 400 km we used the coda normalization method which is based on the elimination of the source and site effects from observed spectra of lg waves q for lg waves in the crust was determined as a function of frequency in the range 1 5 10 0 hz for western anatolia and in the range 1 5 12 hz for southern spain we found that qlg shows a strong frequency dependence in both regions in western anatolia the frequency dependence of qlg is qlg f 82 f1 0 and the geometrical spreading coefficient ranges from 0 6 to 0 9 we found qlg 83 f0 88 and a geometrical spreading coefficient close to 0 5 in southern spain comparing our results with coda q values obtained in both regions qlg qc are similar qlg is close to qi in all frequency bands we interpret the geometrical spreading coefficient higher than 0 5 for western anatolia as due to a strong layered and heterogeneous crustal structure

evidence of high lateral variations of coda q from local earthquakes in western iberia and its sw offshore area abstract we compute coda wave attenuation for the western iberia and for the first time for its sw offshore area western iberia has been well covered by the growing number of permanent seismic stations during the last decade providing a large dataset using this dataset along with offshore seismograms of local earthquakes recorded by temporary ocean bottom seismometers and adopting the single backscattering model we estimate the coda q at five frequency bands centred at 1 2 4 8 and 16 hz then we calculate coda q average values on a geographical grid 0 5 x0 5 resolution using regionalization and inversion techniques we observe that the coda q at 10 hz varies from 1057 in the nw continental iberia to 448 in the south western offshore area where there is no crust additionally we find that the area with similar low coda q value is located in the se iberia betic range therefore our coda q grid results exhibit higher values over the older and stable crust and lower values in the offshore margin or active tectonic regions this suggests that the regional variation in coda q is less sensitive to crustal thickness than to the tectonic activity in each area and crustal age furthermore we discuss our coda q results through a comparison with those from other regions in the world where coda q has been determined with the same parameters our work highlights the importance of coda q studies as an effective tool to investigate detailed regional differences in seismic attenuation that may be relevant for earthquake seismic hazard and risk assessment studies

spatial distribution of coda q in south korea analyzing spectral attenuation of coda waves we first mapped coda q values in the crust over the whole of south korea during the period from 1995 to 2004 we selected 574 north south component seismograms with epicentral distances less than 100 km from 328 earthquakes with magnitudes between 1 4 and 5 2 we estimated coda q values using the single isotropic scattering model at center fre quencies of 1 5 3 6 9 12 15 and 18 hz and found significant spatial variation over all frequency ranges and strong frequency dependence of coda q in the region the estimated coda q value at 1 hz q0 and the g value ranges are 80 300 and 0 4 1 1 respectively the values have strong correlation with the regional geology in the korean peninsula low q0 values are mainly obtained in the regions com prising sedimentary strata in southeastern south korea whereas granite regions in the northern part of south korea show high q 0 the q 0 values in the study area agree well with those of the eastern china and kyushu western japan furthermore our g values are also in good agreement with those of japan online material locations of seismometers list of event station pairs and linear regression of qc measurements

mgs radio science electron density profiles interannual variability and implications for the martian neutral atmosphere density of 7 3 8 5 10 4 cm 3 is also measured during solar moderate conditions at mars strong wave number 2 3 oscillations in peak heights are consistently observed as a function of longitude over the 2 martian years these observed ionospheric features are remarkably similar during aphelion conditions 1 martian year apart this year to year repeatability in the thermosphere ionosphere structure is consistent with that observed in multiyear aphelion temperature data of the mars lower atmosphere clancy et al 2000 smith 2004 coupled mars general circulation model mgcm and mars thermospheric general circulation model mtgcm codes are run for mars aphelion conditions yielding mean and longitude variable ionospheric peak heights that reasonably match rs observations a tidal decomposition of mtgcm thermospheric densities shows that observed ionospheric wave number 3 features are linked to a nonmigrating tidal mode with semidiurnal period s 2 and zonal wave number 1 s 1 characteristics the height of this photochemically determined ionospheric peak should be monitored regularly index terms 5435 planetology solid surface planets ionospheres 2459 5409 planetology solid surface planets atmospheres structure and dynamics 6225 planetology solar system objects mars keywords ionosphere mars thermosphere

attenuation and velocity structure from diffuse coda waves constraints from underground array data abstract an analysis of coda waves excited in the 0 2 20 hz frequency band and recorded by the underground array underseis central italy has been performed to constrain both seismic attenuation at regional scale and velocity structure in the mount gran sasso area attenuation was estimated with the mltwa method and shows a predominance of scattering phenomena over intrinsic absorption the values of q i and q s are compatible with other estimates obtained in similar tectonic environments array methods allowed for a detailed study of the propagation characteristics demonstrating that earthquake coda at frequencies greater than about 6 hz is composed of only body waves coherence and spectral characteristics of seismic waves measured along the coda of local and regional earthquakes indicate that the wavefield becomes fully diffuse only in the late coda the frequency dependent energy partitioning between horizontal and vertical components has been also estimated and compared with synthetic values computed in a layered half space under the diffuse field assumption this comparison confirms that for frequencies higher than 6 hz the coda appears as a sum of body waves coming from all directions while in the low frequency range 0 2 2 hz the observations can be well explained by a coda wavefield composed of an equipartition mixture of surface and body waves traveling in a multiple layered medium a monte carlo inversion has been performed to obtain a set of acceptable velocity models of the upper crust the present results show that a broadband coda wavefield recorded in an underground environment is useful to constrain both the regional attenuation and the velocity structure of the target area thereby complementing the results of classical array analysis of the wavefield

separation of intrinsic and scattering seismic attenuation in the southern apennine zone italy summary scattered waves observed at the seismographs of the national italy s seismic network have been used to investigate the intrinsic dissipation and scattering properties of the lithosphere under the southern apennines italy first we investigate the coda q properties then we apply the mltw analysis in the hypothesis of velocity and scattering coefficient constant with depth and finally we interpret these results with the aid of numerical simulations in a medium with depth dependent velocity and scattering coefficient results obtained in the hypothesis of a uniform model show that a low scattering q 1 and a relatively higher intrinsic q 1 characterize the lithosphere of the southern apennines numerical simulations of the seismogram energy envelopes were performed hypothesizing a strongly scattering crust and trasparent upper mantle both with reasonable intrinsic dissipation coefficients in these symplifying assumptions the theoretical curves calculated for the homogeneous model fit to the synthetic envelopes with scattering attenuation coefficients always greater than the synthetic values this results lead to the consideration that scattering q 1 obtained using mltw analysis under the assumption of uniform medium are overestimated the values of the scattering q 1 estimated for apennines at low frequency 1 2 hz in the hypothesis of uniform medium are of the same order of those obtained in several areas around the world the estimates obtained for frequencies ranging from 2 to 12 hz are very low if compared with those obtained in the same hypothesis for other areas around the world coda q 1 closely resembles intrinsic q 1

high frequency attenuation in the lake van region eastern turkey we provide a complete description of the characteristics of excitation and attenuation of the ground motion in the lake van region eastern turkey using a data set that includes three component seismograms from the 23 october 2011 m w 7 1 van earthquake as well as its aftershocks regional attenuation and source scaling are parameterized to describe the observed ground motions as a function of distance frequency and magnitude peak ground velocities are measured in selected narrow frequency bands from 0 25 to 12 5 hz observed peaks are regressed to define a piecewise linear regional attenuation function a set of excitation terms and a set of site response terms results are modeled through random vibration theory see cartwright and longuet higgins 1956 in the log log space the regional crustal attenuation is modeled with a bilinear geometrical spreading graphic 1 characterized by a crossover distance at 40 km graphic 2 fits our results at short distances r is better at larger distances 40 r 200 km a frequency dependent quality factor q f 100 f f ref 0 43 in which f ref 1 0 hz is coupled to the geometrical spreading because of the inherent trade off of the excitation attenuation parameters and their specific values strongly depend on the choice made for the stress drop of the smaller earthquakes after choosing a brune stress drop brune 4 mpa at m w 3 5 we were able to define 1 an effective high frequency distance and magnitude independent roll off spectral parameter eff 0 03 s and 2 a size dependent stress drop parameter which increases with moment magnitude from brune 4 mpa at m w 3 5 to brune 20 mpa at m w 7 1 the set of parameters mentioned here may be used in order to predict the earthquake induced ground motions expected from future earthquakes in the region surrounding lake van 1 embed inline graphic 1 gif 2 embed inline graphic 2 gif 3 embed inline graphic 3 gif

seismicity within the actively deforming eastern sierras pampeanas argentina summary the eastern sierras pampeanas of central argentina have been interpreted by previous studies to represent the easternmost expression of continental deformation resulting from the flat slab subduction of the nazca plate beneath the south american plate yet the seismic activity and deformation of this area as well as its relationship to subduction more than 700 km to the west are poorly understood using seismic data recorded by the eastern sierras pampeanas broadband seismic array between 2008 august and 2009 august we identified and located 445 local crustal earthquakes most with magnitudes of 2 5 or less we employed a double difference location method to clarify the hypocentral distribution of local seismicity and to define zones of both clustered and diffuse seismicity the relocated events define active structures in the region including a horizontal zone of seismicity between 15 and 25 km depth a prominent west dipping structure beneath the central ranges and a vertical structure along the eastern margin of the study area overall seismicity in this region during the study period is constrained to the upper 25 km of the crust and is mostly concentrated along minor structures and not along the major range bounding faults focal mechanism solutions from the nine clearest events show mainly normal deformation with an oblique component and e w oriented p axes that likely result from shortening along structures with oblique orientations to the direction of plate convergence this is the first seismic study to document that the eastern sierras pampeanas are actively deforming in response to compression from the convergent margin

site dependent coda q at mono craters california abstract the coda q of the early coda of shear waves was determined from a network of seismic stations deployed in the mono craters area during the summer of 1982 coda amplitudes determined from a moving window analysis were fit to single scattering theory with an l1 norm for center frequencies from 1 5 to 12 0 hz we find that station to station variations in coda q observed for frequencies between 6 and 12 hz are well correlated with near site geology coda q for stations on crystalline rocks is larger and more frequency dependent than for stations sited on bishop tuff adjacent to mono craters coda q from sites on bishop tuff away from mono craters is still lower and less frequency dependent these observations suggest that site effects dominate the early coda in the mono craters region and that the single scattering model is inappropriate the mechanisms generating these site effects are inferred to be 1 multiple scattering from resonant structures such as sedimentary basins volcanic edifices variable basement topography and surface topography and 2 near site attenuation

the energy partitioning and the diffusive character of the seismic coda following recent theoretical developments of the radiative transfer the ory of elastic waves we propose to use the ratio r of energies of curl and divergence part of the ground displacement to distinguish between the different possible domi nant scattering regimes in the lithosphere a consequence of the diffusion regime is the partitioning of the energy between different vibrational modes which is inde pendent of time it results in the stabilization of r this behavior is not expected if low order diffraction such as single scattering is dominant we apply our technique to seismograms recorded by a small aperture seismic array operated during june august 1997 in guerrero mexico we estimate the energy ratio r in the coda of 13 earthquakes recorded by the array we find it to be very stable in the coda window while the energy level itself changes by several orders of magnitude the value of r is 7 1 independent of the earthquake location and the magnitude the observed stabilization of r is a strong indication of the diffusive regime of the seismic coda

lapse time dependence of coda q in the source region of the 1999 chamoli earthquake abstract in the present study the attenuation of seismic wave energy in and around the source area of the chamoli earthquake of 29 march 1999 is estimated using aftershock data most of the analyzed events are from the vicinity of the main central thrust mct which is a well defined tectonic discontinuity in the himalayas the method of a single backscattering model is employed to calculate frequency dependent values of coda q q c a total of 30 aftershock events are used for q c estimation at central frequencies 1 5 3 6 9 12 18 and 24 hz through five lapse time windows from 10 to 50 sec starting at double the travel time of the s wave the observed q c is strongly dependent on frequency which indicates that the region is seismically and tectonically active with high heterogeneities the variation of q c has also been estimated at different lapse times to observe its effect with depth the variation of q c with frequency and lapse time shows that the lithosphere becomes more homogeneous with depth q c values for higher frequencies increase very fast with depth within about the top 63 km of the lithosphere and then become more or less constant beyond this depth this indicates that turbidity at higher frequency decays very fast with depth and the mantle may be transparent to high frequency waves the variation of q c at 1 5 hz with lapse time matches quite well with those predicted by gusev 1995 however the frequency parameter n in the relation q c q 0 f n where q 0 q c at 1 hz does not follow the expected pattern given in his model this could be due to faster depth decay of turbidity as mentioned previously

electron densities in the ionosphere of mars a comparison of marsis and radio occultation measurements radio occultation electron densities measurements from the mariner 9 and viking spacecraft which orbited mars in the 1970s have recently become available in a digital format these data are highl

a post pioneer venus reassessment of the martian dayside ionosphere as observed by radio occultation methods the dayside altitude profiles of the electron density obtained with the radio occultation experiments on mariners 4 6 7 and 9 and the viking 1 and 2 spacecraft are collectively reanalyzed to determine the global characteristics of the dayside ionosphere of mars these analyses concentrate on the comparison of the properties of both the electron density peaks and the topside profiles with the behavior expected for a chapman layer and that observed at venus with the pioneer venus orbiter radio occultation experiment as at venus the peak densities at mars behave much like chapman layer peaks with only slight departure from a cos dependence where is the solar zenith angle in contrast the peak heights depart from ideal chapman layer behavior at venus but not at mars because the dayside neutral atmosphere at venus depends on solar zenith angle the global dust storm during the mariner 9 main mission appears to have elevated the martian ionosphere as a whole by 20 30 km without otherwise notably altering its density profile these results generally corroborate the findings of earlier studies an examination of the solar zenith angle dependence of density levels on the topsides of profiles obtained both at mars and at venus near solar minimum provides a new perspective on the solar zenith angle variation of the scale heights of the two ionospheres the key contribution of this study is the improved picture of the solar zenith angle dependences of both the peaks and scale heights of the ionosphere of mars and their comparison with venus at solar minimum in particular this study illustrates that under the similar conditions where incident solar wind dynamic pressure exceeds peak ionospheric thermal pressure the martian dayside ionosphere peaks at higher altitudes in the flanks and has a greater scale height overall thus even magnetically unshielded martian and venusian ionospheres would present slightly different obstacles to the solar wind

new insights into martian dust distribution and water ice cloud microphysics 1 in this paper we use a direct method which combines microphysics and photometric simulations of the martian atmosphere this approach allows us to reproduce vertical profiles of the light scattered by the haze at the limb of mars subsequent results are compared to a multiple color image provided by the viking orbiter camera the free parameters of our study are related to vertical transport and dust size distribution a sensitivity study has been conducted encompassing a relevant range of parameters in order to obtain the most satisfying multispectral modeled profile with respect to the one inferred from data except for an unlikely distribution of submicron particles reff 0 2 m no consistent fit can be obtained this implies that size distributions of dust suggested by previous studies are not in agreement with the present analysis this apparent discrepancy can be resolved by adding a separate peak of submicron particles to the size distribution previously extracted from viking lander images only in that case can spectral and vertical structures of haze be successfully matched while a bimodal distribution would change the current picture of martian dust such distribution is a common representation of soil derived aerosol size function in earth deserts we also attempted to derive information from the cloud shown in the viking limb image our estimates suggest that cloud particle effective radius is around 1 2 1 8 m while the cloud visible opacity is 0 02

q c of three component seismograms of volcanic microearthquakes at campi flegrei volcanic area southern italy digital recordings of three component microearthquake codas from shallow seismic events in the volcanic region of campi flegrei southern italy were used with an automatic technique to calculate the attenuation factorq c codaq in the hypothesis of singles tos backscattering results show the same value ofq for each of the three components this result is interpreted as due to isotropics wave radiation pattern a check of the coda method was performed using a single station method based on simple assumptions on the direct sh wave spectrum single stationq was averaged over the stations and over the earthquakes results show that the two methods lead to comparable results a frequency dependence quite different from that evaluated in active tectonic regions was found for coda attenuation comparable to other volcanic areas throughout the world this is interpreted as due to the presence of magma that affects anelasticity and scattering

estimation of coda wave attenuation in the east anatolia fault zone turkey in this study the attenuation of coda waves qc f has been estimated for different lapse times and frequencies in the east anatolian fault zone eafz in turkey using a single back scattering model of s coda envelopes the data include 255 earthquakes recorded by ten stations the frequency dependent qc values are estimated at central frequencies of 1 5 3 6 8 12 and 18 hz using 20 30 40 s lapse time windows along this fault zone the frequency dependent qc obtained for all data and lapse time is qc 57 5f0 82 the entire study area is divided into six subregions according to the magnitude of the earthquakes and the location of the fault segments the estimated average frequency dependent relation for all lapse times are q text c left text i right 3 4 3f 0 9 3 for bingol karliova erzincan triple junction q text c left text ii right 56 3f 0 71 for bingol lake hazar segment q text c left text iii right 68 5f 0 75 for lake hazar sincik segment q text c left text iv right 72 5f 0 78 hazar sincik and celikhan golbasi faults q text c left text v right 59 7f 0 87 for kahramanmaras triple junction and q text c left text vi right 67 4f 0 94 for amanos range and karasu basin the lowest qc is determined between bingol and malatya the highest qc value is along amanos range in addition qc values are calculated for each regions at different lapse times the average qc value of the study region varies from 53 11 at 1 5 hz to 498 41 at 18 hz for 20 s lapse time window as its variation is from 116 11 at 1 5 hz to 749 75 at 18 hz of central frequency for 40 s lapse time window the increase of qc with lapse times changes from one subregion to another along the fault zone the rate of increment is significantly higher in bingol karliova erzincan triple junction than in the other subregions this rapid increase of low qc values in the junction reaches the general attenuation characteristics of the fault at 40 s lapse time finally the low q0 and high n values can be attributed to the energy loss as a result of the heterogeneity and activity along the fault zone the increase of qc with frequency lapse time may be related to heterogeneity decreases with depth the rapid increase of qc with depth in bingol karliova erzincan triple junction may be interpreted that the effect of the northern anatolian fault zone is effective in the upper crust is not so deep compared to eafz

40ar 39ar ages and paleomagnetism of sao miguel lavas azores we present new 40 ar 39 ar ages and paleomagnetic data for sao miguel island azores paleomagnetic samples were obtained for 34 flows and one dike successful mean paleomagnetic directions were obtained for 28 of these 35 sites 40 ar 39 ar age determinations on 12 flows from the nordeste complex were attempted successfully ages obtained are between 0 78 ma and 0 88 ma in contrast to published k ar ages of 1 ma to 4 ma our radiometric ages are consistent with the reverse polarity paleomagnetic field directions and indicate that the entire exposed part of the nordeste complex is of a late matuyama age the duration of volcanism across sao miguel is significantly less than previously believed which has important implications for regional melt generation processes and temporal sampling of the geomagnetic field observed stable isotope and trace element trends across the island can be explained at least in part by communication between different magma source regions at depth the 40 ar 39 ar ages indicate that our normal polarity paleomagnetic data sample at least 0 1 myr 0 0 1 ma and up to 0 78 myr 0 0 78 ma of paleosecular variation and our reverse polarity data sample approximately 0 1 myr 0 78 0 88 ma of paleosecular variation our results demonstrate that precise radiometric dating of numerous flows sampled is essential to accurate inferences of long term geomagnetic field behavior negative inclination anomalies are observed for both the normal and reverse polarity time averaged field within the data uncertainties normal and reverse polarity field directions are antipodal but the reverse polarity field shows a significant deviation from a geocentric axial dipole direction 1998 elsevier science b v all rights reserved

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

coda q in southwestern british columbia canada abstract coda decay rates of 122 locally recorded earthquakes are used to infer frequency dependent coda q values at 21 short period stations in southwestern british columbia canada using the single scattering model coda q values q c are derived for a range of sampling volumes corresponding to maximum lapse times of 36 59 sec and maximum sampling depths of 70 110 km maps of q 0 q c inferred at 1 hz for different sampling volumes show a consistent trend of increasing q 0 to the northeast away from the subduction zone and into the coast belt batholith and decreasing q 0 toward the southeastern most stations near the vedder fault at the southern terminus of the coast belt q 0 increases gradually with sampling volume at all stations the dependence of q c on frequencies between 2 and 16 hz for different stations varies but on average ranges from 280 at 2 hz to 850 at 16 hz for sampling volumes that extend to depths of 90 km an average of all data for the same sampling volume size gives a relationship of q c 110 f 0 72 for frequencies in the 2 to 16 hz range which suggests significant differences in lithospheric coda attenuation properties in comparison with northwestern washington state where q c 63 f 0 97 changes in coda q correlate with the volume of brittle and fractured continental and subducting oceanic lithosphere sampled

elastic character of seismic coda envelopes within east indian shield seismic codas are usually characterized by the values of coda q qc however interpretation of this quantity is often tricky because of its frequency dependence and acute sensitivity to subjective theoretical assumptions and processing parameters here a simpler and physically more consistent parameterization of coda envelopes is proposed by noting that their temporal decay rates are often nearly frequency independent this weak frequency dependence shows that codas mostly consist of elastic reverberations and scattering on larger scale structures and the subwavelength scale scattering and q type wave attenuation are weak a recent study of the eastern indian shield by singh et al in this journal gives an illustration of such elastic coda from that study the inferred qc steeply increases with frequency lapse times window lengths and distances from the seismic station however we show that all of these dependencies of qc represent a common artifact of the acquisition geometry and inversion procedure in an alternate interpretation we explain the same coda envelopes by two frequency independent properties of the earth s subsurface geometrical attenuation denoted c earth and effective q denoted qc earth based on these parameters the model becomes independent of theoretical assumptions and comparable to other areas and the acquisition inversion artifact is reduced the estimated c earth is above 0 01 s 1 which is also found in other areas of active tectonics the effective attenuation is weak qc earth 5700 likely below the measurable level which is typical for stable tectonic areas the data indicate near surface resonances beneath the recording station effects of these resonances on coda envelopes also exceed those of q type attenuation thus in the eastern indian shield and likely many other areas coda envelopes are principally controlled by elastic structures such as crustal and near surface layering and not necessarily by the s wave q and uniformly distributed random small scale scattering as commonly thought

attenuation of lg waves in the new madrid seismic zone of the central united states using the coda normalization method abstract unique properties of coda waves are employed to evaluate the frequency dependent quality factor of lg waves using the coda normalization method in the new madrid seismic zone of the central united states instrument and site responses are eliminated and source functions are isolated to construct the inversion problem for this purpose we used 121 seismograms from 37 events with moment magnitudes m ranging from 2 5 to 5 2 and hypocentral distances from 120 to 440 km recorded by 11 broadband stations a singular value decomposition svd algorithm is used to extract q values from the data while the geometric spreading exponent is assumed to be a constant inversion results are then fitted with a power law equation from 3 to 12 hz to derive the frequency dependent quality factor function the final results of the analysis are q v lg f 410 38 f 0 49 0 05 for the vertical component and q h lg f 390 26 f 0 56 0 04 for the horizontal component where the term after sign represents one standard error for stations within the mississippi embayment with an average sediment depth of 1 km around the memphis metropolitan area estimation of quality factor using the coda normalization method is not well constrained at low frequencies f

depth dependent seismic scattering attenuation in the nuevo cuyo region southern central andes 1 in the present work we separated intrinsic from scattering attenuation coefficients both for the crust and the upper mantle in the tectonically highly active areas of the southern central andes nuevo cuyo region analyzing two groups of earthquakes well separated in depth this region is characterized by the presence of flat subduction we apply mltwa multiple lapse time window analysis coda normalization and q coda techniques to measure the scattering and intrinsic attenuation coefficient and the total q for s waves we find that intrinsic attenuation does not decrease with depth whereas scattering attenuation is higher in the crust than in the upper mantle and that intrinsic attenuation predominates over scattering attenuation we interpret this observation in terms of the release of water and other fluids into the overlying lithosphere due to the dynamics of the subduction process in agreement with most of the prevalent geodynamic models

neotectonic activity along the shanxi rift system china abstract the shanxi rift system is one of the most outstanding pliocene quaternary continental rift systems and strong earthquake belts in china it extends as a series of en echelon left stepping asymmetrical half graben basins on the shanxi highlands over a distance of more than 1200 km it describes a sinous s shaped curve with a nne trending transtensional segment in the middle and ne ene trending extensional domains on both terminal segments the latter are characterized by apparently synchronous high angle normal faulting accommodating large vertical and relatively smaller lateral strains 3 5 8 5 which produces the modern basin and range structure the rift system has been intermittently active since the pliocene geomorphological neotectonic and seismic studies indicate that the rift system is at present still developing as demonstrated by the occurrence of strong destructive historical earthquakes of magnitudes 7 8 and the large slip rates on the nne trending transtensional faults in the middle segment the slip rates of these faults reached 4 9 6 4 mm per year during the holocene geophysical studies show that the rifting occurred in a thickened crust and no compelling evidence exists for the major thermal event in the mantle uniquely associated with the rifting the development of the shanxi rift system is consistent with the regional brittle strain pattern of a right lateral shear belt and a regional stress field of ene wsw compression and nnw sse extension of the north china subplate this structural setting corroborates the hypothesis that the deformation is in response to the escape tectonics caused by the himalayan indenter from the southwest and at the same time by the counter clockwise rotation of the intervening crustal blocks this provides the mode of formation of the shanxi rift system

body wave crustal attenuation characteristics in the garhwal himalaya india we estimate frequency dependent attenuation of p and s waves in garhwal himalaya using the extended coda normalization method for the central frequencies 1 5 2 3 4 6 8 10 12 and 16 hz with earthquake hypocentral distance ranging from 27 to 200 km forty well located local earthquake waveforms were used to study the seismic attenuation characteristics of the garhwal himalaya india as recorded by eight stations operated by wadia institute of himalayan geology dehradun india from 2007 to 2012 we find frequency dependent p and s wave quality factors as defined by the relations q p 56 8f 0 91 0 002 and q s 151 8f 0 84 0 002 by fitting a power law frequency dependence model for the estimated values over the whole region both the q p and q s values indicate strong attenuation in the crust of garhwal himalaya the ratio of q s q p 1 obtained for the entire analyzed frequency range suggests that the scattering loss is due to a random and high degree of heterogeneities in the earth medium playing an important role in seismic wave attenuation in the himalayan crust

k ar ages of granitoids unravel the stages of neo tethyan convergence in the eastern pontides and central anatolia turkey k ar dating of mineral separates extracted from various granitoid rock units of the eastern pontides and central anatolia turkey has provided some new insights unravelling various stages of the neo tethyan convergence system which evolved with northward subduction between the eurasian plate ep to the north and the tauride anatolide platform tap to the south along the izmir ankara erzincan suture iaes zone arc related granitoid rocks are only encountered in the eastern pontides and yield k ar cooling ages of both early cretaceous 138 5 2 2 ma early arc and late cretaceous ranging from 75 7 0 0 to 66 5 1 5 ma mature arc respectively the multi sourced granitoids of the eastern pontides with a predominant mantle component and k ar ages between 40 and 50 ma are considered to be a part of post collisional slab break off magmatism accompanied by tectonic denudation of pre late cretaceous granitoid rocks following juxtaposition of the ep and the tap around 55 50 ma in the eastern pontides the k ar cooling ages of collision related s i and a type granitoids in central anatolia reflect good synchronism between 80 and 65 ma suggesting a coeval genesis in a unique geodynamic setting but with derivation from various sources namely purely crustal purely mantle and or of mixed origin this sort of simultaneous generation model for these s i a type intrusives seems to be consistent with a post collisional lithospheric detachment related geodynamic setting i type granodioritic to tonalitic intrusives with k ar cooling ages ranging from 40 to 48 ma in east central anatolia are interpreted to have been derived from a post collisional within plate extension related geodynamic setting following the amalgamation of the ep and the tap in east central anatolia

effect of a sedimentary basin on estimations of qc and qlg abstract the effect which a sedimentary basin granada basin southern spain exercises on the estimated q c and q lg attenuation values within a determined frequency range are described it has been shown that for the values of q c there is a decrease in the number of fits with a correlation coefficient 0 8 in the 1 5 hz frequency band in comparison with the other frequency bands on the other hand an overestimation of the values of the coda q is observed between a station located on the sediment in the interior of the basin and the stations situated on the borders of the basin the values of the attenuation for lg waves in the paths which cross the granada basin show a series of peaks centred in the 1 3 hz frequency band which overestimate the values of q lg with respect to other frequency bands all these phenomena indicate that the presence of a low velocity sedimentary basin modifies the processes of generation of coda waves and the propagation of lg waves

spatial distribution of scattering loss and intrinsic absorption of short period s waves in the lithosphere of japan on the basis of the multiple lapse time window analysis of hi net data summary propagation of short period s waves through the crust is strongly controlled by scattering loss and intrinsic absorption scattering loss controls the shape of the seismic envelope and the spatial distribution of the energy while intrinsic absorption produces an exponential decay as a function of time which is independent of the coordinates since both parameters have a different effect it is possible to compute them by means of the multiple lapse time window analysis mltwa in this paper high resolution maps of japan for both seismic s wave attenuation parameters are obtained by using the mltwa with data provided by the hi net seismic network the maps show strong regional variation of the parameters the variations depend mainly on the tectonic setting of each region and volcanism mechanisms in the scattering loss maps in the 1 2 hz map there is a very different behaviour between the northeast stronger scattering loss and the southwest much weaker scattering loss in the northeast of japan areas with strong scattering loss correspond mainly to the location of the volcanic arcs in southwest japan chugoku region and the west side of kii peninsula show strong scattering levels for the 4 8 hz and higher frequency bands in hokkaido strong scattering loss and intrinsic absorption can be observed for the lower frequency bands in the sendai plain we find strong scattering loss for all the frequency bands under all these areas low velocity anomalies have been detected in previous works in tohoku area the east side shows lower intrinsic attenuation than the west side this characteristic seems to extend to the southern part of hokkaido and to central japan in kanto area the values of intrinsic absorption are lower than in the surrounding areas but in the region around the itoigawa shizuoka tectonic line and in its western side strong absorption areas are observed the behaviour of each area for intrinsic absorption is similar to the behaviour observed in the q 1c maps the mltwa is based on the hypothesis of multiple isotropic scattering in a medium with the homogeneous distribution of scattering mean free path and intrinsic absorption although these hypotheses are very simple the results are very informative on the characteristics of each region and show the usefulness of studying the properties of scattered seismic waves in the understanding of the properties of the crust

attenuation of short period seismic waves at mt vesuvius italy we analysed short period seismograms from about 250 very local events recorded by a network of high dynamic range short period seismic stations deployed on mt vesuvius to estimate the site corrected short period seismic attenuation we calculated qc 1 the inverse of the quality factor for coda waves for short lapse times 12 s and qp 1 and qs 1 the inverse of the direct body wave quality factors for p and s waves follow ing shallow ray paths we used the single scattering assumption to fit the amplitude envelopes of the coda at different frequency bands obtaining a qc 1 slowly varying with frequency similar to values measured for other volcanoes at the same lapse time site corrected qp 1 and qs 1 were estimated using the frequency decay method for both p and s waves in two frequency bands 1 6 hz and 15 24 hz results show that qp 1 is 0 028 in both frequency bands and qs 1 is 0 015 and 0 017 at low and high frequencies respectively almost independent of the frequency and that the value of qp 1 is about twice that of qs 1 as measured worldwide a check was made by measuring the broadening of the first p wave pulse with station source distance finding qp 1 0 024 using the independent estimates of qc 1 and qs 1 we separated the intrinsic from the scattering quality factor at mt vesuvius obtaining a high scattering and a low intrinsi c q 1 as already observed for other volcanoes this result confirms the hypothesis of the predominant role of the scattering phenomena with respect to the intrinsic dissipation in the seismogram formation for volcanic earthquakes

an attenuation study of body waves in the south central region of the gulf of california mexico abstract we studied the seismic attenuation of body waves in the south central region of the gulf of california goc with records from the network of autonomously recording seismographs of baja california nars baja from the centro de investigacion cientifica y de educacion superior de ensenada s broadband seismological network of the goc resban and from the ocean bottom seismographs obs deployed as part of the sea of cortez ocean bottom array experiment scooba we examine 27 well located earthquakes reported in sumy et al 2013 that occurred from october 2005 to october 2006 with magnitudes m w between 3 5 and 4 8 we estimated s wave site effects by calculating horizontal to vertical spectral ratios and determined attenuation functions with a nonparametric model by inverting the observed spectral amplitudes of 21 frequencies between 0 13 and 12 59 hz for the scooba obs stations and 19 frequencies between 0 16 and 7 94 hz for nars baja and resban stations we calculated the geometrical spreading and the attenuation 1 q factors for two distance intervals 10 120 and 120 220 km respectively for each frequency considered the estimates of q obtained with the scooba obs records for the interval 10 120 km indicate that the p waves attenuate more than s waves q p 34 1 2 f 0 82 0 10 q s 59 1 1 f 0 90 0 03 for frequencies between 0 6 and 12 6 hz whereas for the 120 220 km interval where ray paths travel deeper s waves attenuate more than p waves q p 117 1 3 f 0 44 0 19 q s 51 1 2 f 1 12 0 11 the estimates of q obtained using nars baja and resban records within 10 120 km indicate that p waves attenuate more than s waves q p 69 1 2 f 0 87 0 16 q s 176 1 4 f 0 61 0 26 at frequencies between 0 3 and 6 3 hz whereas at the 120 220 km distance interval s waves attenuate slightly more than p waves q p 39 1 1 f 0 64 0 06 q s 48 1 1 f 0 37 0 07 at high frequencies f 3 hz these results based on a unique obs dataset provide an indirect mean to constrain future models of the thermal structure beneath the goc

h2o in rhyolitic glasses and melts measurement speciation solubility and diffusion dissolved h2o in silicate melts and glasses plays a crucial role in volcanic eruptions on terrestrial planets and affects glass properties and magma evolution in this paper major progress on several aspects of the h2o melt or glass system is reviewed consistency among a variety of data is investigated discrepancies are evaluated and confusion is clarified on the infrared measurement of total h2o and species concentrations calibration for a variety of glasses has been carried out at room temperature the measurements for h2o in rhyolitic glasses have undergone the most scrutiny resulting in the realization that absorptivities for the near infrared bands depend on total h2o content although the variation of the absorptivities does not seem to significantly affect the determination of total h2o it does affect the determination of molecular h2o and oh species concentrations calibration of the infrared technique for h2o in rhyolitic glasses still needs much improvement especially at high total h2o furthermore it is now almost certain that the molar absorptivities also depend on the measurement temperature in in situ studies hence it will be necessary to carry out calibrations in situ at high temperatures on h2o speciation results from two experimental approaches the quench technique and the in situ technique are very different leading to controversy in our understanding of true speciation a solution is presented to reconcile this controversy it is almost certain that the quench technique does not suffer from a quench problem but interpretation of in situ results suffered from ignoring the dependence of the molar absorptivities on measurement temperature accurate calibration at high temperatures is necessary for the quantitative application of the in situ technique to h2o speciation in silicate melts and glasses on h2o solubility in silicate melts recent experimental work has significantly expanded the t p range of solubility measurements and recent solubility models fill a gap for predicting solubility for a wide range of melt compositions i present a solubility model for rhyolitic and quasi rhyolitic melts over a wide range of t and p 500 1350 c 0 8 kbar by incorporating the role of speciation the solubility model is able to recover the experimental solubility data and has extrapolative value although the partial molar volume of h2o derived from the solubility model differs from that derived from density measurements on h2o diffusion recent studies on h2o diffusion in a quasi rhyolitic melt at 800 1200 c 0 5 5 kbar and up to 7 total h2o not only provide important new diffusion data but are also challenging earlier understanding of h2o diffusion based on data in rhyolitic glasses at 400 550 c 1 bar and 0 2 1 8 total h2o a comparison between the earlier model and recent data is made the recent high temperature diffusivities at total h2o 2 can be predicted by the earlier model however at higher total h2o the earlier model fails new work is under way to understand the diffusion mechanisms at high h2o contents

seismicity and volcanism of jan mayen island the small arctic jan mayen island site of the world s northernmost active volcano beerenberg is part of the mid atlantic ridge system and located along the jan mayen fracture zone jmfz recent data from the local seismic network and fault plane solutions from the global network indicate that the island is located at a ridge crest intersection which might explain the origin of the island and the associated volcanism moreover the new data suggest a series of offset segments of the mohn s ridge overlapping in an en echelon pattern in january 1985 a flank eruption was for the first time observed with the local seismic network volcanic tremors and low frequency events were observed on 5 january at 2230 h and 10 hours later the first large earthquake occurred no visual confirmation of the eruption was made until 6 january at 1630 h the seismic observations rule out the possibility that the large earthquake caused the eruption it seems more likely that the changes in local stress conditions triggered the earthquake and that the eruption started before the first large earthquake recent observations show that the local network provides an efficient tool for monitoring and warning of volcanic activity however since there was no change in the local seismicity in the days or months before the 1985 eruption it seems to be difficult to make long term predictions of beerenberg flank eruptions without using other techniques such as observations of tilt

coda q in different tectonic areas influence of processing parameters abstract published results of coda q show a large variation in values these variations are often claimed to be related to different tectonics whereas they might just be related to using different assumptions in the processing leading to different input parameters for the analysis in this study the effect of using different processing parameters is investigated and significant differences particularly at low frequencies are observed we find a new set of optimal parameters which we recommend using in future studies using a short lapse time of 30 s and optimal parameters data from both similar and very different tectonic regions are used to calculate coda q using the same program and the same parameters the regions considered are eastern anatolia the azores jan mayen northwestern and central argentina the shanxi rift system in china and southwestern norway we obtain the following relations eastern anatolia q 88 f 0 66 azores q 86 f 0 70 jan mayen q 90 f 0 72 northwestern and central argentina q 89 f 0 94 shanxi rift system q 99 f 0 89 and southwestern norway q 124 f 0 91 the results show that coda q is very similar for regions of similar tectonics and significantly different for regions with varying tectonics using alternative more common parameters gives different q but the regional differences remain so which parameters to use to get correct coda q values is still uncertain however coda q can clearly distinguish different tectonic areas provided identical processing parameters are used even if they are not optimal

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

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

coda q in the northern cascadia subduction zone using seismograms recorded at 66 canadian seismic stations coda q was estimated from earthquakes in southwestern british columbia and northern washington state employing the single backscattering approximation a total of 580 earthquakes with magnitudes ranging from 1 2 to 6 4 depths from 0 to 67 km and epicentral distances of 5 110 km were selected to obtain 3022 high signal to noise ratio traces for analysis an average of all the data yields a relationship for coda q of q c 72 f 0 91 there is little variation of this coda q relationship when using either crustal or in slab sources which represent uniform sampling of the crust and upper mantle crustal earthquakes result in a relationship of q c 73 f 0 89 and for in slab events q c can be expressed as q c 69 f 0 94 in general q q c at 1 hz increases from the west coast of vancouver island to the east southeast within the coast belt stations on west central vancouver island closest to the landward projection of the nootka fault zone and the location of the only two known large crustal earthquakes 1918 m 7 and 1946 m 7 3 on vancouver island have the lowest q values in our study area suggesting a contrast in q between the north and south of the island online material figure showing principal tectonic units and station locations and tables of average q and alpha values with estimated uncertainties

energy flux model of seismic coda separation of scattering and intrinsic attenuation a new model of seismic coda is presented based on the balance between the energy scattered from the direct wave and the energy in the seismic coda this energy flux model results in a simple formula for the amplitude and time decay of the seismic coda that explicitly differentiates between the scattering and intrinsic anelastic attenuation of the medium this formula is valid for both weak and strong scattering and implicitly includes multiple scattering the model is tested using synthetic seismograms produced in finite difference simulations of wave propagation through media with random spatial variations in seismic velocity some of the simulations also included intrinsic dissipation the energy flux model explains the coda decay and amplitude observed in the synthetics for random media with a wide range of scattering q in contrast the single scattering model commonly used in the analysis of microearthquake coda does not account for the gradual coda decay observed in the simulations for media with moderate or strong scattering attenuation scattering q less than or equal to 150 the simulations demonstrate that large differences in scattering attenuation cause only small changes in the coda decay rate as predicted by the energy flux model the coda decay rate is sensitive however more to the intrinsic q of the medium the ratio of the coda amplitude to the energy in the direct arrival is a measure of the scattering attenuation thus analysis of the decay rate and amplitude of the coda can in principle produce separate estimates for the scattering and intrinsic q values of the crust we analyze the coda from two earthquakes near anza california intrinsic q values determined from these seismograms using the energy flux model are comparable to coda q values found from the single scattering theory the results demonstrate that coda q values are at best measures of the intrinsic attenuation of the lithosphere and are unrelated to the scatteing q less

residence time of diffuse waves in the crust as a physical interpretation of coda q application to seismograms recorded in mexico summary we consider a simple model for elastic wave propagation in the earth s litho sphere consisting of a heterogeneous and scattering crust overlying a homogeneous mantle that is we neglect backscattering from the upper mantle this rough condition is not strictly valid everywhere but this model allows us to investigate the effects of variations of diffracting properties between crust and mantle on the coda decay the free parameters describing the wave propagation are the mean free path of the waves and the intrinsic absorption in the crust in the framework of the radiative transfer theory we treat accurately jumps in s wave speed and the mean free path at the moho without intrinsic absorption this configuration yields a synthetic coda decay 1 texp 2 ft qc a form similar to that proposed by aki chouet 1975 to parametrize the observations the exponential decay in our purely elastic model is due to the partial leakage of diffuse energy into the mantle in order to test the applicability of our model we have determined the coda q parameter qc in the 1 15 hz frequency band from data recorded at four stations in mexico in the low frequency regime around 1 hz we suggest that the energy leakage significantly affects coda q whilst at higher frequencies around 10 hz the anelastic attenuation dominates a weak intrinsic absorption expressed by a frequency independent parameter qi of about 1000 accounts satisfactorily for the observed qc values in the whole frequency range our very simple model has only two free parameters and offers an attractive alternative physical interpretation of coda q in mexico this model is sufficient to interpret the coda observations according to our model in regions where the mean free path is much larger than the crustal thickness weakly heterogeneous crust the leakage effect should be small and the observed qc will mainly be due to the intrinsic absorption on the other hand when the mean free path is of the order of the crustal thickness strongly heterogeneous crust we predict a strong sensitivity of the decay rate of the coda to the crustal thickness this dependence may be important for the interpretation of the regional variations of coda q we propose introducing a new parameter d the residence time of diffuse energy in the crust which is physically more meaningful than a quality factor to quantify the leakage effect

separation of intrinsic and scattering attenuation using single event source in south korea abstract simultaneous use of numerous events in the multiple lapse time window analysis mltwa method is the most effective way to obtain and values such simultaneous use of numerous events normally shows a large observational scatter which may be caused by different radiation pattern and focal depth of each earthquake and regional alteration of the local structure to avoid these scattering factors the current study attempted to use single event source as the input data in mltwa for south korea the direct simulation monte carlo dsmc method was used to simulate the observations which showed realistic results when the number of recorded stations was eight or more the obtained values of seismic albedo b 0 were less than 0 5 which were in accordance with the same in the previous results three envelopes constructed by combination of three regional values of at 1 hz produced regional variations of which the ones at high frequencies of and at low frequencies of were remarkable this result showing the local variation indicated an advantage of the study using single source event over the previous studies in south korea that involved extensively distributed data because dsmc was known to be applicable to 3d structure due to its simple algorithm the current study also tried to correct radiation pattern of the observations by inserting focal mechanism algorithm to the code of the dsmc method such insertion however generated extremely low values of because the geometrically shrunk receiver could not capture most of the scattered particles this receiver problem is most likely to be a major obstacle of the 3d study of dsmc in addition the significant depth effect of q 1 was identified for the prior mltwa studies resulting from different measurement range and focal depth

effect of crustal magnetic fields on the near terminator ionosphere at mars comparison of in situ magnetic field measurements with the data of radio science experiments on board mars global surveyor 1 electron density profiles of the ionosphere of mars derived from radio occultation data obtained by the radio science mars global surveyor mgs experiment have been compared with the crustal magnetic fields measured by the mgs magnetometer electron reflectometer mag er experiment in the northern hemisphere the crustal fields are rather weak and usually do not prevent direct interaction between the solar wind sw and the martian ionosphere atmosphere exceptions do occur in the isolated mini magnetospheres formed by the crustal anomalies much stronger crustal fields are located in limited regions in the southern hemisphere and lead to the formation of large scale mini magnetospheres a study of the electron density profiles obtained when the mini magnetosphere regions are near the terminator has been conducted using the magnetic field measurements at altitudes 170 180 km and 400 km the magnitude of the electron density peak and the effective scale height of the electron density for two altitude ranges 145 165 km and 165 185 km have been derived for each of the 326 selected profiles studied in each hemisphere the longitudinal variations of these derived parameters have been studied a significant difference between the large scale mini magnetospheres and regions outside of them has been found the neutral atmosphere is cooler inside the large scale mini magnetospheres the variations of the magnitude of the electron density peak indicate that the electrons are usually hotter inside a large scale mini magnetosphere than outside it appears that the mini magnetospheres formed by strong crustal magnetic fields prevent additional heating of the neutral atmosphere due to direct interaction of the sw and also confine the hotter electrons created by photo ionization

coda q estimates in the hong kong region abstract complementing a series of recent seismic hazard studies for hong kong we have estimated the q factor using 25 local earthquakes within 200 km of hong kong digitally recorded from january 1998 to july 2000 by eight short period stations of the hong kong observatory seismic monitoring network by analyzing the coda wave at frequencies 2 20 hz we obtained a q f relation of q 256 f 0 7 the values of q 0 q at 1 hz determined for three distance ranges r are 224 for r 50 km 342 for 50 r r 200 km the results are consistent with the spatial variations of the q factor in the wider region of south china the results fill an important gap in knowledge about the q factor and associated crustal attenuation conditions in the pearl river delta region including hong kong and provide useful insight into the influence of epicentral distance range in coda q measurements allowing better understanding of the degree of complexity in the crustal structure of the region

age constraints on the tectonic evolution and provenance of the pie de palo complex cuyania composite terrane and the famatinian orogeny in the sierra de pie de palo san juan argentina abstract new u pb age determinations confirm earlier interpretations that the strongly deformed and metamorphosed mafic and intermediate igneous rocks of the pie de palo complex represent a mesoproterozoic fragment of suprasubduction zone oceanic crust a gabbroic pegmatite interpreted to have formed during arc rifting or subsequent back arc spreading yielded a u pb age of 1204 5 3 4 7 ma highly tectonized ultramafic mafic cumulates occurring at the structural base of the pie de palo complex and previously interpreted to represent remnants of a primitive arc phase prior to rifting and back arc spreading could not be dated but should be older than 1204 ma if these inferences are correct tabular sill like bodies of leucogabbro diorite and calc alkaline tonalite granodiorite sills yielded ages of 1174 43 and 1169 8 7 ma respectively they may represent a younger more evolved arc phase established after arc rifting or a younger tectonically unrelated mesoproterozoic arc shrimp analysis of metamorphic zircon rims with low th u ratios in vvl 110 gave a 206pb 238u age of 455 10 ma similar to lower intercept dates determined by discordia lines combined these data indicate that the bulk of the amphibolite facies metamorphism present in the pie de palo complex was generated during the famatinian orogeny analysis of six single detrital zircon grains in a metasedimentary quartzofeldspathic garnet mica schist tectonically interleaved with the igneous rocks of the pie de palo complex and tentatively correlated with the difunta correa metasedimentary sequence of other workers yielded three age populations 1150 1160 ma 1050 1080 ma and 665 ma indicating that these sedimentary rocks were deposited during the late neoproterozoic or early paleozoic in addition they confirm structural evidence that intercalation of rocks of the pie de palo complex with isolated slivers of these sedimentary rocks is due to tectonic imbrications these ages are also consistent with a laurentian provenance and earlier interpretations that these rocks once represented a sedimentary cover to the pie de palo complex the zircon population of 1050 1080 ma could be derived from grenville age felsic plutons identified elsewhere in the pie de palo complex by other workers however no evidence has been found in our samples for a grenville age orogenic event invoked previously to explain accretion of the oceanic pie de palo complex to laurentia prior to the late neoproterozoic early cambrian rifting and drift of cuyania

morphological analysis of active mount nemrut stratovolcano eastern turkey evidences and possible impact areas of future eruption abstract mount nemrut an active stratovolcano in eastern turkey is a great danger for its vicinity the volcano possesses a summit caldera which cuts the volcano into two stages i e pre and post caldera wisps of smoke and hot springs are to be found within the caldera although the last recorded volcanic activity is known to have been in 1441 we consider here that the last eruption of nemrut occurred more recently probably just before 1597 the present active tectonic regime historical eruptions occurrence of mantle derived magmatic gases and the fumarole and hot spring activities on the caldera floor make nemrut volcano a real danger for its vicinity according to the volcanological past of nemrut the styles of expected eruptions are well focused on two types 1 occurrence of water within the caldera leads to phreatomagmatic highly energetic eruptions subsequently followed by lava extrusions and 2 effusions extrusions non explosive or weakly energetic eruptions on the flanks from fissures to predict the impact area of future eruptions a series of morphological analyses based on field observations digital elevation model and satellite images were realized twenty two valleys main transport pathways were classified according to their importance and the physical parameters related to the valleys were determined the slope values in each point of the flanks and the heim parameters h l were calculated in the light of morphological analysis the possible impact areas around the volcano and danger zones were proposed the possible transport pathways of the products of expected volcanic events are unified in three main directions bitlis guroymak tatvan and ahlat cities the about 135 000 inhabitants of which could be threatened by future eruptions of this poorly known and unsurveyed volcano

estimation of coda wave attenuation in the central and eastern alborz iran the quality factor of coda q c waves has been estimated by using single backscattering and single isotropic scattering models the earthquakes used were recorded by three permanent and one temporary network located in the central and eastern alborz iran the database was composed of 746 local earthquakes with local magnitude from 1 1 to 5 7 the estimated q c has been found to be similar for lapse times greater than twice the s wave travel time 2 t s for both methods the estimated q c for central frequencies 1 0 hz shows less frequency dependency compared with the higher frequencies by using a q f n relation the average frequency dependence of q c for the whole area has been estimated as 59 f 1 03 69 f 0 97 78 f 0 97 105 f 0 93 123 f 0 89 159 f 0 79 and 203 f 0 68 for central lapse times 30 40 50 65 85 110 and 155 s respectively we found the value of q decreases at an average depth of 78 km which may be the result of high dissipating media at this depth the average q c values estimated for central and eastern alborz and their frequency dependent relationships are similar to those of tectonically active regions

variation of coda wave attenuation in the alborz region and central iran summary more than 340 earthquakes recorded by the institute of geophysics university of tehran igut short period stations from 1996 to 2004 were analysed to estimate the s coda attenuation in the alborz region the northern part of the alpine himalayan orogen in western asia and in central iran which is the foreland of this orogen the coda quality factor qc was estimated using the single backscattering model in frequency bands of 1 25 hz in this research lateral and depth variation of qc in the alborz region and central iran are studied it is observed that in the alborz region there is absence of significant lateral variation in qc the average frequency relation for this region is qc 79 2f1 07 0 08 two anomalous high attenuation areas in central iran are recognized around the stations las and raz the average frequency relation for central iran excluding the values of these two stations is qc 94 2f0 97 0 12 to investigate the attenuation variation with depth qc value was calculated for 14 lapse times 25 30 35 90s for two data sets having epicentral distance range r 100 km data set 1 and 100 r 200 km data set 2 in each area it is observed that qc increases with depth however the rate of increase of qc with depth is not uniform in our study area beneath central iran the rate of increase of qc is greater at depths less than 100 km compared to that at larger depths indicating the existence of a high attenuation anomalous structure under the lithosphere of central iran in addition below 180 km the qc value does not vary much with depth under both study areas indicating the presence of a transparent mantle under them

volcanic history and 40ar 39ar and 14c geochronology of terceira island azores portugal abstract seven new 40ar 39ar and 23 new radiocarbon ages of eruptive units in support of new geologic mapping improve the known chronology of middle to late pleistocene and holocene volcanic activity on the island of terceira azores and define an east to west progression in stratovolcano growth the argon ages indicate that cinco picos volcano the oldest on terceira completed its main subaerial cone building activity by about 370 380 ka collapse of the upper part of the stratovolcanic edifice to form a 7 9 km caldera occurred some time after 370 ka postcaldera eruptions of basalt from cinder cones on and near the caldera floor and trachytic pyroclastic flow and pumice fall deposits from younger volcanoes west of cinco picos have refilled much of the caldera the southern portion of guilherme moniz volcano in the central part of the island began erupting prior to 270 ka and produced trachyte domes flows and minor pyroclastic deposits until at least 111 ka the northern part of guilherme moniz caldera is less well exposed than the southern part but reflects a similar age range the northwest portion of the caldera was formed sometime after 44 ka several well studied ignimbrites that blanket much of the island likely erupted from guilherme moniz volcano the pico alto volcanic center a tightly spaced cluster of trachyte domes and short flows is a younger part of guilherme moniz volcano stratigraphic studies and our new radiocarbon ages suggest that most of the pico alto eruptions occurred during the period from about 9000 to 1000 years bp santa barbara volcano is the youngest stratovolcano on terceira began erupting prior to 29 ka and has been active historically