a tree ring based reconstruction of summer relative humidity variability in eastern mongolian plateau and its associations with the pacific and indian oceans a regional chronology rc based on tree ring width data at two sites was developed for the southern hulun buir sandy land a marginal area of the eastern mongolian plateau china this chronology significantly and positively correlated with the relative humidity from the previous december to september except in may the highest correlation of the rc with the mean june august relative humidity suggested that the growth of pinus sylvestris var mongolica strongly reflects seasonal moisture conditions consequently the variation in the mean june august relative humidity was reconstructed for the reliable time period of 1835 2013 41 6 of the variance occurred during the calibration period of 1953 2012 similar patterns of drought and pluvial fluctuations were found in other tree ring based moisture reconstructions our reconstruction implied that the characteristics of regional hydroclimatic variations such as the drought and low humidity of the late 1990s to 2000s were not unusual from the long term perspective as suggested by the hydrological records obtained from tree ring material spectrum analyses results and significant spatial correlations of our relative humidity reconstruction with the sea surface temperature sst in the eastern equatorial pacific ocean and tropical indian ocean implied close linkages between moisture in the eastern mongolian plateau and remote oceans when the sst related to the el nino southern oscillation was high low the intensity of the indian summer monsoon at the northern extremities weakened strengthened thus moisture decreased i e the relative humidity was low in north china and in our study area the low land sea thermal contrast between asia and the indian ocean due to the enhanced ssts in the tropical indian ocean also influenced the strength of the moisture transfer via the indian summer monsoon thereby reducing the moisture variations in the eastern mongolian plateau

frequency dependent body wave attenuation characteristics in the kumaun himalaya abstract we have analyzed a data set consisting of 23 well located local earthquakes to study the seismic attenuation characteristics of the kumaun himalaya region these events were recorded at 9 digital seismic stations in this region during 2004 2008 the frequency dependent attenuation of p and s waves are estimated using the extended coda normalization method for the frequency range of 1 5 3 6 8 and 12 hz the values of q p and q s show a ubiquitous observation of frequency dependence for the studied frequencies we obtained q p 22 5 f 1 35 0 04 and q s 104 10 f 1 3 0 03 by fitting a power law frequency dependence model with the estimated values over the whole region both q values indicate a strong attenuation in the crust of kumaun himalaya the ratio of q s q p 1 obtained for the entire analyzed frequency range may suggest that the crust is characterized by a high degree of heterogeneity

attenuation of high frequency seismic waves in eastern iran we investigated the frequency dependent attenuation of the crust in eastern iran by analysis data from 132 local earthquakes having focal depths in the range of 5 25 km we estimated the quality factor of coda waves q c and body waves q p and q s in the frequency band of 1 5 24 hz by applying the single backscattering theory of s coda envelopes and the extended coda normalization method respectively considering records from recent earthquakes rigan m w 6 5 2010 12 20 goharan m w 6 2 2013 5 11 and sirch m w 5 5 2013 1 21 the estimated values of q c q p and q s vary from 151 49 63 6 and 93 14 at 1 5 hz to 1 994 124 945 84 and 1 520 123 at 24 hz respectively the average frequency dependent relationships q q o f n estimated for the region are q c 108 10 f 0 96 0 01 q p 50 5 f 1 01 0 04 and q s 75 6 f 1 03 0 06 these results evidenced a frequency dependence of the quality factors q c q p and q s as commonly observed in tectonically active zones characterized by a high degree of heterogeneity and the low value of q indicated an attenuative crust beneath the entire region

comparison of different site response estimation techniques using aftershocks of the 1999 izmit earthquake on 17 august 1999 the m w 7 4 izmit earthquake occurred in northwestern turkey a temporary seismic network was installed to improve the geometry of a previously installed network in this study 262 aftershocks of the izmit earthquake with magnitude m l ranging between 0 4 and 4 5 were analyzed using digital recordings from 17 stations of these networks s wave and p wave spectral records corrected for path attenuation function were inverted by means of the generalized inversion technique git the git site responses were compared with those calculated by horizontal to vertical h v ratios applied to both earthquake data and to pre event noise in most cases the h v of the earthquake data provided site responses with shapes consistent with those obtained using git however the level of amplification was occasionally found to be different in general these discrepancies can be explained either by the amplification affecting the vertical component of the ground motion that we detected by git or by the waves having a propagation in almost the vertical direction using the h v ratio applied to noise for most cases we obtained not only the peaks for the fundamental resonance frequencies but site responses with shapes similar to those obtained by git the detected level of amplifications using the h v ratio showed a tendency not to exceed those calculated by the inversion finally amplifications up to a factor 5 are found for stations placed over complex topography for these sites amplifications are not always correctly identified by the h v technique using either earthquakes or noise

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

s wave attenuation in the sea of marmara turkey abstract this paper presents the estimates of frequency dependent attenuation of s waves for five different regions of the crust in the sea of marmara the estimation method for the s wave attenuation is based on the rate of decay of the s wave to coda wave amplitude ratio with distance qs 1 the epicentral distances of the selected earthquakes are between 15 and 70 km and the duration magnitudes are between 2 4 and 3 9 the quality factors qs are calculated at frequencies 1 5 3 6 and 12 hz and a lapse time 50 s the frequency dependency of average qs values calculated at these frequencies for five regions is 40 5f1 03 0 06 the estimated qs values for five regions ranging from 13 1f1 22 0 05 to 94 3f0 83 0 04 indicate the regional differences in the rheology and tectonic activity of the crust

drastic desalination of small lakes in east siberia russia in the early twentieth century inferred from sedimentological geochemical and palynological composition of small lakes reconstruction of temporal and spatial climate development on a seasonal basis during the last few centuries may help us better understand modern day interplay between natural and anthropogenic climate variability the objective of this paper is to reconstruct hydrology and landscape changes of east siberia during the termination of the little ice age and the subsequent recent warming we analysed sediment samples from the saltwater sulfatnoe lake bolshoye alginskoe and freshwater shuchie lake using high resolution x ray fluorescence spectroscopy at 1 mm scan resolution fourier transform infrared techniques and pollen analyses the depth age models of the cores were constructed by 210pb activity using the constant rate of supply model the lake sediment cover of these lakes began to form from ca 1870 three significant periods 1870 1895 1895 1925 and from 1925 to the present were defined in hydrology and chemical regime of these lakes for the past 140 years lake levels were extremely low and high saturated with salts during the final period of the little ice age lake levels began to slowly rise from 1870 to 1895 and vegetation was poor at that period intensive desalination of the lakes occurred in 1895 1925 and environment conditions were temperate and favourable for the majority of the taxa of the regional vegetation regional precipitation significantly increased and water saturation of the catchments was high from 1925 to the present the chemical precipitation of carbonate stopped completely in lake shichie and reduced considerably in lake sulfatnoe and b alginskoe strong increasing trend of weathering of the lake catchments began in 1970 and still continues

attenuation of high frequency body waves in the crust of western tibet abstract the attenuation characteristics of western tibet have been analyzed by estimating the seismic attenuation parameters q p 1 and q s 1 at five different central frequencies 1 5 3 6 12 and 18 hz the extended coda normalization method has been used on 469 three component local earthquakes which are recorded at y2 network of broadband stations deployed in western tibet during years 2007 2011 we have estimated the frequency dependent q p 1 and q s 1 values at each station the results indicate strong body wave attenuation in the medium below western tibet the highest attenuation is observed at wt19 and wt13 stations located near to the karakoram fault kkf and indus yarlung suture iys across the kkf we have subdivided the entire study area into two regions to explore the lateral variations of crustal attenuation properties the first part covers the northeastern of kkf referred as region 1 while the second part covers the southwestern of kkf referred as region 2 the frequency dependent relations are found as follows q p 1 19 4 4 4 10 3f 0 9 0 2 q s 1 13 3 2 1 10 3f 0 8 0 1 for region 1 and q p 1 18 4 1 8 10 3f 0 8 0 1 q s 1 13 2 2 2 10 3f 0 8 0 1 for region 2 both the regions show strong frequency dependent nature of q 1 values with no significant lateral variations it may suggest the presence of similar tectonic complexities and heterogeneities beneath both the regions we also find that all the estimated values of q p 1 q s 1 ratios are greater than unity at all the frequency range which are likely to be associated with both the intrinsic and scattering phenomenon in the crust of western tibet

adjoint tomography of the southern california crust using an inversion strategy based on adjoint methods we developed a three dimensional seismological model of the southern california crust the resulting model involved 16 tomographic iterations which required 6800 wavefield simulations and a total of 0 8 million central processing unit hours the new crustal model reveals strong heterogeneity including local changes of 30 with respect to the initial three dimensional model provided by the southern california earthquake center the model illuminates shallow features such as sedimentary basins and compositional contrasts across faults it also reveals crustal features at depth that aid in the tectonic reconstruction of southern california such as subduction captured oceanic crustal fragments the new model enables more realistic and accurate assessments of seismic hazard

crustal attenuation characteristics in northwestern turkey in the range from 1 to 10 hz we have analyzed the aftershocks m l 4 5 following the 1999 izmit earthquake m w 7 4 to infer the frequency dependent attenuation characteristics of both p and s waves in the frequency range from 1 to 10 hz and in the distance range from 10 to 140 km a linear predictive model is assumed to describe the spectral amplitudes in terms of attenuation and source contributions the results show that both p and s waves undergo a strong attenuation along ray paths shorter than 40 km while the secondary arrivals significantly contribute to the spectral amplitudes over the distance range from 40 to 60 km as also confirmed by the computation of synthetic seismograms for longer ray paths the decrease in attenuation suggests an increase in the propagation efficiency with depth finally the spectral attenuation curves are flattened or sloped upward at low frequencies in the range from 100 to 140 km due to the contemporary arrivals of direct waves and postcritical reflections from the moho in terms of geometrical spreading and anelastic attenuation the attenuation in the range from 10 to 40 km is well described by a spreading coefficient n 1 for both p and s waves and the quality factors can be approximated by qs f 17 f 0 80 for 1 f 10 hz and qp f 56 f 0 25 for 2 5 f 10 hz for ray paths in the range from 60 to 80 km the attenuation weakens but the interaction between seismic waves and propagation medium is more complex the multilapse time window analysis mltwa is applied to quantify the amount of scattering loss and intrinsic absorption for s waves the seismic albedo b decreases from 0 5 at 1 hz to 0 3 at 10 hz while the total quality factor qt increases from about 56 to 408 the multiple lapse time window analysis mltwa results provide only an average estimate of the attenuation properties in the range from 10 to 80 km in fact by neglecting the variation of attenuation with depth the mltwa results underestimate attenuation for distances less than 40 km and do not capture the significant features caused by the integrated energy of the secondary arrivals observed in the range from 40 to 60 km

distribution of seismic velocities and attenuation in the crust beneath the north anatolian fault turkey from local earthquake tomography we investigate the crustal structure beneath the western part of the north anatolian fault zone nafz an area where at least five damaging earthquakes occurred during the twentieth century this study is based on local earthquake tomography using the data from aftershocks of the izmit event 17 august 1999 m 7 4 recorded by stations of permanent and temporary networks we derive the distribution of v p v s and the v p v s ratio based on the iterative inversion for both v p v s and v p v p v s using the lotos code innovatively in this study we perform an inversion for frequency dependent s wave attenuation 1 q s the reliability of the results is assessed through synthetic tests the distributions of the resulting seismic parameters v p v s v p v s and q s highlight important geodynamical features in the study area the low velocity and high attenuation patterns mostly correlate with the fracturing zones of the nafz low velocities are also observed beneath the main sedimentary basins e g adapazari duzce and kuzuluk high velocity and low attenuation patterns correlate with blocks presumed to be rigid kocaeli armutlu and almacik blocks the rupture traces of the largest earthquakes in this area pass generally in the transition areas between high and low velocities while moderate and weak seismicity is mostly concentrated in low velocity areas based on these results we propose and discuss the role that the almacik block could have played in producing the largest earthquakes in the study area in the twentieth century

stability of source mechanisms inverted from p wave amplitude microseismic monitoring data acquired at the surface we study the stability of source mechanisms inverted from data acquired at surface and near surface monitoring arrays the study is focused on p wave data acquired on vertical components as this is the most common type of acquisition we apply ray modelling on three models a fully homogeneous isotropic model a laterally homogeneous isotropic model and a laterally homogeneous anisotropic model to simulate three commonly used models in inversion we use geometries of real arrays one consisting in surface receivers and one consisting in buried geophones at the nearsurface stability was tested for two of the frequently observed source mechanisms strike slip and dip slip and was evaluated by comparing the parameters of correct and inverted mechanisms we assume these double couple source mechanisms and use quantitatively the inversion allowing non double couple components to measure stability of the inversion to test the robustness we inverted synthetic amplitudes computed for a laterally homogeneous isotropic model and contaminated with noise using a fully homogeneous model in the inversion analogously amplitudes computed in a laterally homogeneous anisotropic model were inverted in all three models we show that a star like surface acquisition array provides very stable inversion up to a very high level of noise in data furthermore we reveal that strike slip inversion is more stable than dip slip inversion for the receiver geometries considered here we show that noise and an incorrect velocity model may result in narrow bands of source mechanisms in hudson s plots

the ml scale in southern california measurements 9 941 of peak amplitudes on wood anderson instruments or simulated wood anderson instruments in the southern california seismographic network for 972 earthquakes primarily located in southern california were studied with the aim of determining a new distance correction curve for use in determining the local magnitude m l events in the mammoth lakes area were found to give an unusual attenuation pattern and were excluded from the analysis as were readings from any one earthquake at distances beyond the first occurrence of amplitudes less than 0 3 mm the remaining 7 355 amplitudes from 814 earthquakes yielded the following equation for m l distance correction log a 0 log a 0 1 110log r 100 0 00189 r 100 3 0 where r is hypocentral distance in kilometers a new set of station corrections was also determined from the analysis the standard deviation of the m l residuals obtained by using this curve and the station corrections was 0 21 the data used to derive the equation came from earthquakes with hypocentral distances ranging from about 10 to 700 km and focal depths down to 20 km with most depths less than 10 km the log a 0 values from this equation are similar to the standard values listed in richter 1958 for 50 200 km the effect at close distances is consistent with that found in several other studies and is simply due to a difference in the observed 1 r geometrical spreading for body waves and the 1 r 2 spreading assumed by gutenberg and richter in the construction of the log a 0 table m l s computed from our curve and those reported in the caltech catalog show a systematic dependence on magnitude small earthquakes have larger magnitudes than in the catalog and large earthquakes have smaller magnitudes by as much as 0 6 units to a large extent these systematic differences are due to the nonuniform distribution of data in magnitude distance space small earthquakes are preferentially recorded at close distances relative to large earthquakes for large earthquakes however the difference in the two magnitudes is not solely due to the new correction for attenuation magnitudes computed using richter s log a 0 curve are also low relative to the catalog values the differences in that case may be due to subjective judgment on the part of those determining the catalog magnitudes the use of data other than the caltech wood anderson seismographs the use of different station corrections or the use of teleseismic magnitude determinations whatever their cause the departures at large magnitude may explain a 1 0 0 7 proportionality found by luco 1982 between m l s determined from real wood anderson records and those from records synthesized from strong motion instruments if it were not for the biases in reported magnitudes luco s finding would imply a magnitude dependent shape in the attenuation curves we studied residuals in three magnitude classes 2 0 m l 3 5 3 5 m l 5 5 and 5 5 m l 7 0 and found no support for such a magnitude dependence based on our results we propose that local magnitude scales be defined such that m l 3 correspond to 10 mm of motion on a wood anderson instrument at 17 km hypocentral distance rather than 1 mm of motion at 100 km this is consistent with the original definition of magnitude in southern california and will allow more meaningful comparison of earthquakes in regions having very different attenuation of waves within the first 100 km

rapid full wave centroid moment tensor cmt inversion in a three dimensional earth structure model for earthquakes in southern california summary a central problem of seismology is the inversion of regional waveform data for models of earthquake sources in regions such as southern california preliminary 3 d earth structure models are already available and efficient numerical methods have been developed for 3 d anelastic wave propagation simulations we describe an automated procedure that utilizes these capabilities to derive centroid moment tensors cmts the procedure relies on the use of receiver side green s tensors rgts which comprise the spatial temporal displacements produced by the three orthogonal unit impulsive point forces acting at the receivers we have constructed a rgt database for 219 broad band stations in southern california using a tomographically improved version of the 3 d scec community velocity model version 4 0 cvm4 and a staggered grid finite difference code finite difference synthetic seismograms for any earthquake in our modelling volume can be simply calculated by extracting a small source centred volume from the rgt database and applying the reciprocity principle the partial derivatives needed for the cmt inversion can be generated in the same way we have developed an automated algorithm that combines a grid search for suitable focal mechanisms and hypocentre locations with a gauss newton optimization that further refines the grid search results using this algorithm we have determined cmt solutions for 165 small to medium sized earthquakes in southern california preliminary comparison with the cmt solutions provided by the southern california seismic network scsn shows that our solutions generally provide better fit to the observed waveforms when applied to a large number of earthquakes our algorithm may provide a more robust cmt catalogue for earthquakes in southern california

enhanced ground motions due to large amplitude critical moho reflections sms in the sea of marmara turkey 1 aftershocks of the 17 august 1999 mw 7 4 kocaeli earthquake were used to investigate the large amplitude sms arrivals in the sea of marmara we produced the event record sections from the transverse components of s and sms arrivals at a distance of 10 to 200 km for the data recorded towards the east and west in the sea of marmara for the data recorded towards the west we observed that the amplitude of sms phases enhances the ground motion by a factor of 2 to 3 the dipping moho and or anisotropy in the upper mantle or deep convex structure or deep lens are possible sources for the large amplitude sms phases since the study area has a potential of creating damaging earthquakes in the future the effect of large amplitude sms phases on the ground motion should be considered in the studies of the seismic hazard of the region

broad band modelling of regional seismograms the basin and range crustal structure three component broad band displacement seismograms with paths sampling the basin and range province are studied to constrain the crustal structure to find an average model that fits the data in both absolute time and waveform we generate broad band reflectivity synthetics and conduct sensitivity tests on different parts of a layered crustal model where only a few layers are involved generalized rays are used to help identify the various phases it proves useful to decompose a regional seismogram into segments so that the impact of model parameters on each segment can be clearly identified thus for mid crustal earthquakes it is established that the top crustal layer controls the rayleigh wave the airy phase in shape over the range from 300 to 600 km and the crustal layer just above the source depth controls its timing the p nl waves the p n and p l portion are controlled in broad band character by the mid crust while the top layer contributes to their long period motion these crustal parameters control the tangential motion similarly the sv wave the segment between the p nl wave and the rayleigh wave is mostly controlled by the shear velocity of the lower crust in judging the goodness of fit between the array observations and synthetic waveforms we allow individual data segments to shift relative to the 1 d synthetics by a few seconds to account for some lateral variation the amount of time shift is found by the cross correlation in displacement between the data segment and the synthetics applying these tests in a forward modelling approach we find that a simple two layer crustal model is effective in explaining this data set in this model the main crustal layer has p and s velocities of 6 1 km s 1 and 3 6 km s 1 similar to those found by langston helmberger 1974 a surface layer of thickness 2 5 to 3 5 km is required to fit the rayleigh waves the refined model can be used as a reference model for further studies in this region

apparent q for upper crustal rocks of the central rio grande rift spectra from 130 digitally recorded microearthquakes in the magnitude range 0 9 to 0 3 were used to compute apparent seismic quality factors q for upper crustal rocks within 45 km of socorro new mexico in this study apparent q was defined as a measure of seismic wave attenuation due to intrinsic absorption and scattering and was computed over the frequency range 0 50 hz most of the recorded energy was in the 3 30 hz band it was found that apparent q increases with event distance for the eight stations used in this study this increase was successfully modeled with a varying thickness low q low velocity layer lying above a relatively high q high velocity half space it was found that 1 near surface low q regions lying directly beneath the recording sites vary from 0 3 to 2 0 km in thickness and exhibit qp and qs values less than 50 2 the average qs for the upper crust in the central rio grande rift excluding the near surface low q region is 535 95 confidence interval 374 938 3 the observed qp qs ratio for events recorded at eight stations varied from 0 34 to 1 39 for earthquakes recorded at three stations the qp qs ratio decreased with increasing event distance more for two other stations no systematic increase or decrease in qp qs with distance was evident and for the remaining three stations events were too closely clustered to draw any conclusions these changes in the qp qs ratio with increasing event distance may reflect varying degrees of fluid saturation in upper crustal rocks 4 at least three anomalously low qs regions exist within 20 km southwest of socorro these abnormally low q regions may reflect small magmatic intrusions or high fracture densities at depth and may lie in close proximity to microearthquake swarms at depths of 7 2 10 3 km 63 references 10 figures 4 tables less

attenuation of high frequency p and s waves in the crust of central and western tien shan in order to better understand the attenuation characteristics in the crust of the central and western tien shan orogenic belt we investigate both qp and qs values by applying the extended coda normalization method we estimate the frequency dependent attenuation of both p and s waves in the frequency band of 1 0 20 0 hz using data from local networks the average frequency relations of qp and qs have been derived as qp 61 9 f 1 21 0 08 and qs 77 6 f 1 11 0 04 by fitting a power law frequency dependence model for the study region the low q0 and high values indicate that the central and western tien shan is a tectonically and seismically active region we also find lateral variations of both qp s and qs qp values reflecting complex tectonic structures in the study area in general the relatively high attenuation areas corresponding to tectonically active regions are found beneath mountainous ranges in the central tien shan whereas the relatively low attenuation areas are associated with stable regions such as fergana basin and issyk kul lake besides regions in the central tien shan with qs qp 1 are likely partially saturated with fluids or rich in scattering heterogeneities whereas regions in the western tien shan display qs qp 1 possibly suggesting almost complete fluid saturation

s wave attenuation in the marmara region northwestern turkey the frequency dependent attenuation of shear waves in the crust is estimated by using two different methods based on the rate of time decay of coda wave amplitude qc 1 and the rate of decay of the s wave to coda wave amplitude ratio with distance qs 1 the epicentral distances of selected earthquakes range between 20 and 110 km and magnitudes are around 3 the quality factors qc are calculated at frequencies of 1 5 3 6 12 and 24 hz and lapse times of 40 50 60 and 70 s estimated qc values show a dependence on frequency and lapse time we observed the similarity in the frequency dependency of qc 41 1 07 f1 08 0 03 and qs 50 1 7 f1 09 0 05 for a lapse time of 50 s indicating that the attenuation mechanism for coda waves is similar to that of the direct s waves

evaluating the relevance of moho reflections in accelerometric data application to an inland japanese earthquake the relevance of sms seismic phase or multiple reflected sms on the ground motion away from the earthquake source has been discussed in many studies during the past 30 years the sms and multiples are normally recognized by analyzing travel time arrivals on the basis of a priori well known crustal models moho reflections in borehole and surface accelerometric data of the kik net network for an inland japanese earthquake are investigated when reflected phases are transmitted efficiently both amplitude and frequency content can be retrieved by using a simple time frequency analysis of accelerometric records for the 15 april 2007 m 5 4 kinki crustal earthquake moho reflections are found at epicentral distances from 70 to 180 km borehole data show that sms and multiples can be easily found in the frequency range from 0 25 to 2 s and in the group velocity window from 2 8 to 3 5 km s the coupling of borehole and surface stations of kik net data allows for the separate evaluation of the propagation effect along the source receiver path and of the transfer function due to soft soils for these specific phases an amplitude period scaling relationship is found between the national earthquake hazards reduction program site classification and the observed transfer function for sms phase and multiples online material figures showing the effect of the source time function duration on the multiple filter technique mft diagrams an mft analysis of surface and borehole accelerograms period distance domain spectral amplitudes and the average period velocity transfer function for different nehrp soil classes

lateral variations of high frequency seismic wave propagation at regional distances across the turkish and iranian plateaus in this study we investigate crustal and uppermost mantle physical properties that characterize some of the continental plateaus of the middle east this is done as part of a larger effort to map and compare high frequency wave propagation at regional distances across the earth s continental plateaus thousands of short period wwssn seismograms recorded at stations located in the middle east and produced by earthquakes with epicentral distances less than about 20 were examined visually in an effort to study lateral variations of high frequency 0 5 2 hz seismic wave propagation across this area particularly to the north of the zone of continental collision between the africa arabian and eurasian plates variations of frequencies and amplitudes of sn and lg relative to p are examined and mapped throughout the region and this work is supplemented by a study of velocities of pn sn and lg sn amplitude variations are very striking in this area an important observation of this study is that sn propagates efficiently beneath a major part of the turkish and iranian plateaus sn is strongly attenuated however in the northernmost portion of the plateaus south of the black and caspian seas and in an area between the two seas these regions are characterized in general by active tectonism including volcanism faulting and folding however this active tectonism is not restricted to the areas of high sn attenuation but appears to extend beneath other parts of the iranian and turkish plateaus patterns of lateral variations in the propagation of lg are not as consistent as those for sn lg propagates efficiently across turkey iran and adjacent regions but the lg waves that cross the turkish and iranian plateaus are weak and have relatively long predominant periods of about 2 5 s the lg phase is not observed when the path of propagation crosses the southern caspian and the black seas consistent with the evidence of oceanic type crustal structure beneath these seas lg is also not observed from subcrustal events located in the hindu kush region the velocity of pn beneath most of the plateau areas and particularly in the regions of sn attenuation ranges between 8 0 and 8 2 km s velocities for sn and lg throughout the middle east are about 4 5 and 3 4 km s respectively it is possible to interpret the efficient sn propagation and the relatively normal uppermost mantle p and s velocities beneath a major part of the turkish iranian plateau as indicating a partial underthrusting of the arabian continental plate beneath the iranian and turkish continental blocks alternatively the mapped regions of efficient sn propagation and high sn attenuation may result from a differential cooling of a past thermal anomaly in this case the isostatic compensation of the plateaus could be due to an anomalously hot uppermost mantle that developed behind the mid to upper tertiary subduction zone s in this region and to a subsequent crustal shortening after the collision of the arabian and eurasian plates our results cannot uniquely confirm the validity of the above proposed models

an inversion of lg wave attenuation and site response from seismic spectral ratios in the eastern china region abstract both lg wave attenuation and site responses are determined in the eastern china region the region ranges from 26 n to 33 n and 117 e to 124 e we analyze over 1360 three component seismograms from 92 local and regional earthquakes the seismograms are recorded in the distance range of 100 600 km the earthquakes occurred between 2002 and 2012 in the region and varied in magnitude between 2 0 and 4 7 m l a combined inversion method which can simultaneously estimate attenuation and site response from seismic spectral ratios is implemented in the study modeling errors are determined using a delete j jackknife resampling technique fourier spectral amplitudes are measured from lg phases windowed between the group velocity limits 2 6 and 3 6 km s the inversion are performed in a frequency range of 1 6 hz with an interval of 0 2 hz the frequency dependent quality factor is modeled in the form of q q 0 f the eastern china region displays high q 0 and a weaker frequency dependence characterized by the functions q 335 16 f 0 45 0 02 q 411 21 f 0 26 0 01 and q 432 26 f 0 24 0 01 for vertical north south and east west components respectively the values are similar to the average for other stable regions of the globe site responses from 32 stations are estimated in the region most stations do not show obvious amplification the site responses are mainly smooth flat and less than 5 in the frequency range of 1 6 hz

advancement in source estimation techniques using broadband regional seismograms one important constraint on source retrieval from regional seismograms comes from the amplitude difference between various phases such as pnl surface wave sv sh because the misfit errors used in some waveform inversions are normalized by the data and synthetics the amplitude information in the data has not been fully utilized in this article we modify the cut and paste source estimation technique zhao and helmberger 1994 by removing this type of normalization it is shown that the modified method increases the stability and resolution of inversion when multiple stations at different distance ranges are used a distance scaling factor is introduced to compensate for the amplitude decay with distance by applying the technique to the terrascope data we have determined source mechanisms and depths of 335 southern californian events with m l 3 5 the amplitude decays with distance are r 1 13 for pnl r 0 55 for love waves and r 0 74 for rayleigh waves in contrast to generally shallow source depths reported by the southern california short period network the depth distribution from waveform inversion shows a strong peak around 12 km with few earthquakes occurring above 5 km and below 20 km

simulations of ground motion in the los angeles basin based upon the spectral element method we use the spectral element method to simulate ground motion generated by two recent and well recorded small earthquakes in the los angeles basin simulations are performed using a new sedimentary basin model that is constrained by hundreds of petroleum industry well logs and more than 20 000 km of seismic reflection profiles the numerical simulations account for 3d variations of seismic wave speeds and density topography and bathymetry and attenuation simulations for the 9 september 2001 m w 4 2 hollywood earthquake and the 3 september 2002 m w 4 2 yorba linda earthquake demonstrate that the combination of a detailed sedimentary basin model and an accurate numerical technique facilitates the simulation of ground motion at periods of 2 sec and longer inside the basin model and 6 sec and longer in the regional model peak ground displacement velocity and acceleration maps illustrate that significant amplification occurs in the basin

separation of intrinsic and scattering seismic wave attenuation in northeast india summary we have analysed the local earthquakes 2 0 ml 5 5 occurred in northeast ne india recorded by a temporary seismic network of 10 stations operated by national geophysical research institute ngri hyderabad to evaluate the relative contributions of scattering loss q 1 and intrinsic absorption q 1 to total attenuation q 1 using the multiple lapse time window analysis assuming multiple isotropic scattering in a medium of uniformly distributed scatterers the results show that q 1 is greater than q 1 at high frequencies f 3hz while the opposite is observed at low frequencies f 3hz the observed frequency dependence of q 1 corresponds to the scale length of lithospheric heterogeneity beneath ne india at least comparable with the wavelength for the lowest frequencies analysed of about 1km the observed q 1 for the study region obtained with single scattering theory is close to q 1 at high frequencies in agreement with theoretical prediction for an idealized case of uniform distribution of scatterers however a discrepancy exists between the two at low frequencies which can be explained by a depth dependent velocity and attenuation structure high value of q 1 is correlated with the geology and tectonic settings of the region characterized by himalayan and burman collision zones with a strong lateral heterogeneity the q 1 estimates obtained in this study can be used to infer the average temperature of the lower crust with an upper limit estimate of 800 c assuming a lower crustal gabbroic lithology

the erzincan turkey earthquake ms 6 8 of march 13 1992 and its aftershock sequence the erzincan strike slip earthquake of march 13 1992 ruptured a section of the north anatolian fault naf at the northern margin of the erzincan basin the focal depth of about 10 km was less than given by isc and neic erzincan and the surrounding villages were considerably damaged in the erzincan basin and in the neighbouring mountains a seismic network of ten stations was installed it was operating continuously from march 21 through june 16 1992 more than 3 000 aftershocks were recorded of which 505 could be located the spectral parameters of 394 and the fault plane solutions of 53 aftershocks were determined for the given region the frequency dependent coda q was derived as qc 122 f 0 68 the aftershock area increased with time reflecting the process of stress redistribution some events clustered in the immediate vicinity of the town of erzincan close to the epicentre of the main event and seem to trace the naf their source mechanism is similar to that of the main event strike slip about 150 aftershocks clustered in the southeastern part of the erzincan basin where a concentration of the events in a small volume of 5 5 3 km3 was observed the majority of fault plane solutions available for these aftershocks showed a normal faulting mechanism with an east west directed extension most of the aftershocks southeast of the basin clustered between two lineaments that were mapped by satellite images the p wave velocity below the erzincan basin derived from travel time residual analysis is lower compared to areas ne and sw of the basin three dimen sional stress modelling of the erzincan region qualitatively explains the occurrence of the aftershocks southeast of the basin the calculated displacement distribution which exhibits the north westward motion of the basin and tension at its southeastern margin caused by the erzincan earthquake is in agreement with derived fault plane solutions

the effect of crustal structure on strong ground motion attenuation relations in eastern north america strong ground motion attenuation relations are usually described by smoothly decreasing functions of distance however consideration of wave propagation in the crust suggests that attenuation relations should be more complex such complexity may be present in strong ground motion data for eastern north american earthquakes which show amplitudes in the distance range of 60 to 150 km that lie above the trends at smaller and greater distances using a wavenumber integration method to compute green s functions and close in recordings of several earthquakes as empirical source functions we have generated synthetic seismograms that are in good agreement with regional and strong motion recordings of eastern north american earthquakes from these synthetic seismograms we have shown that the observed interval of relatively high amplitudes may be attributable to postcritically reflected s waves from the moho the presence and location of the interval of relatively high amplitudes is highly dependent on the crustal velocity structure and may therefore be expected to show regional variation however for any realistic structure model there will be a transition in the attenuation relation from an interval at shorter distances less than about 100 km that is dominated by direct waves to an interval at greater distances that is dominated by postcritically reflected waves the synthetic seismograms have response spectral velocities that match those of the recorded data and their m blg values are in good agreement with observed values

qp qs relations in the sedimentary basin of the upper mississippi embayment using converted phases abstract three component digital seismograms recorded by the 40 panda portable array for numerical data acquisition stations in the new madrid seismic zone were analyzed to study seismic wave attenuation in the sedimentary basin using the spectral ratio method a prominent s to p s p converted phase was generated at the boundary between the uppermost sedimentary basin and the underlying paleozoic rocks the direct s wave on the horizontal component is characterized by a lower frequency content than that of the converted s p wave on the vertical component the differences in frequency content between the direct s and the s p converted waves can be attributed to the different attenuation effects between p and s waves in the unconsolidated sediments the spectral ratio between the low frequency s wave and the high frequency converted s p wave from the bottom of the sediments can be used to yield a relationship between q p and q s in the sediments results from panda stations with well constrained spectral ratios in the frequency range from 2 to 25 hz give the q p value ranging from 25 to 60 and q s from 25 to 30 for the sedimentary basin in the upper mississippi embayment

full 3 d tomography for crustal structure in southern california based on the scattering integral and the adjoint wavefield methods we have successfully applied full 3 d tomography f3dt based on a combination of the scattering integral method si f3dt and the adjoint wavefield method aw f3dt to iteratively improve a 3 d starting model the southern california earthquake center scec community velocity model version 4 0 cvm s4 in f3dt the sensitivity frechet kernels are computed using numerical solutions of the 3 d elastodynamic equation and the nonlinearity of the structural inversion problem is accounted for through an iterative tomographic navigation process more than half a million misfit measurements made on about 38 000 earthquake seismograms and 12 000 ambient noise correlagrams have been assimilated into our inversion after 26 f3dt iterations synthetic seismograms computed using our latest model cvm s4 26 show substantially better fit to observed seismograms at frequencies below 0 2 hz than those computed using our 3 d starting model cvm s4 and the other scec cvm cvm h11 9 which was improved through 16 iterations of aw f3dt cvm s4 26 has revealed strong crustal heterogeneities throughout southern california some of which are completely missing in cvm s4 and cvm h11 9 but exist in models obtained from previous crustal scale 2 d active source refraction tomography models at shallow depths our model shows strong correlation with sedimentary basins and reveals velocity contrasts across major mapped strike slip and dip slip faults at middle to lower crustal depths structural features in our model may provide new insights into regional tectonics when combined with physics based seismic hazard analysis tools we expect our model to provide more accurate estimates of seismic hazards in southern california

april september mean maximum temperature inferred from hailar pine pinus sylvestris var mongolica tree rings in the hulunbuir region inner mongolia back to 1868 ad two robust tree ring width chronologies were developed for the hulunbuir region inner mongolia northeast china both chronologies were significantly correlated with each other and were arithmetically averaged to build a regional chronology nbstd nbstd showed significant and negative correlations with the growing season maximum temperature from april to september based on this relationship the mean maximum temperature of april to september was reconstructed for the period from 1868 to 2008 the percentage of variance in the data explained by the reconstruction was 40 3 during the calibration period of 1953 2008 five severe warm events of two years or more were found in 1905 1909 1996 1997 2000 2001 2003 2005 and 2007 2008 five cold events occurred during the periods 1880 1881 1897 1900 1948 1949 1955 1960 and 1962 1964 on a decadal scale several warm intervals above the 1868 2008 mean were 1904 1913 1920 1933 1968 1975 and 1990 2003 cold intervals below the mean were 1893 1901 1950 1963 and 1976 1989 warmer events and intervals corresponded to dry periods colder events and intervals coincided with wet or moist conditions in and near the study region spatial correlation patterns revealed that our reconstruction represents a regional temperature and drought signal for the central and eastern mongolian plateau comparison with other tree ring based temperature reconstructions from surrounding areas provides a high degree of confidence in our reconstruction power spectrum and wavelet analyses suggest that the reconstructed mean maximum temperature variation may be related to large scale atmospheric oceanic variability such as the pacific decadal oscillation pdo el nino southern oscillation enso and sunspot activity c 2011 elsevier b v all rights reserved less

estimates of attenuation structure in the cinarcik basin of the marmara sea northwest turkey abstract the attenuation structure 1 q in the sediments of the cinarcik basin of the marmara sea was estimated from the raw shot data of a multi channel seismic reflection experiment using a wavelet modeling technique the estimated attenuation called the effective q is the sum of the inelastic absorption and the apparent attenuation the estimated effective q values along the north south trending seismic profiles are interpreted together with their time migrated seismic sections there are several local minima in the boundary separating the low

attenuation of high frequency seismic waves in northeast india summary we studied attenuation of s and coda waves their frequency and lapse time dependencies in northeast india in the frequency range of 1 24 hz we adopted theories of both single and multiple scattering to bandpass filtered seismograms to fit coda envelopes to estimate q for coda waves qc and q for s waves qs at five central frequencies of 1 5 3 6 12 and 24 hz the selected data set consists of 182 seismograms recorded at ten seismic stations within epicentral distance of 22 300 km in the local magnitude range of 2 5 5 2 we found that with the increase in lapse time window from 40 to 60 s q0 qc at 1 hz increases from 213 to 278 while the frequency dependent coefficient n decreases from 0 89 to 0 79 both qc and qs increase with frequency the average value of qs obtained by using coda normalization method for ne india has the power law form of 96 8 21 5 f 1 03 0 04 in 1 24 hz we adopted energy flux model efm and diffusion model for the multiple scattered wave energy in three dimensions the results show that the contribution of multiple scattering dominates for longer lapse time close to or larger than mean free time of about 60 s the estimates of qc are overestimated at longer lapse time by neglecting the effects of multiple scattering some discrepancies have been observed between the theoretical predictions and the observations the difference could be due to the approximation of the uniform medium especially at large hypocentral distances increase in qc with lapse time can be explained as the result of the depth dependent attenuation properties and multiple scattering effect

the shape of ground motion attenuation curves in southeastern canada the shape of the attenuation curve of the fourier spectrum of acceleration is established for southeastern canada from empirical data the dataset is comprised of 1200 digital vertical component seismograms from 100 earthquakes recorded on 30 stations of the eastern canada telemetered network the distance range of the observations is 10 to 1700 km focal depths are from 5 to 30 km results indicate that the attenuation curve has three distinct sections at distances less than 70 km corresponding to attenuation of the direct wave amplitudes decay slightly more rapidly than 1 r r 1 1 between 70 and 130 km where the direct wave is joined by sms spectral amplitudes are approximately constant beyond 130 km corresponding to the lg phase amplitudes decay at a rate that is consistent with r 0 5 and q 670 f 0 33 the findings support the hypothesis of burger et al 1987 that postcritical reflections from the moho discontinuity play an important role in determining the shape of the attenuation curve however the influence of sms is subtle allowing the shape to be approximated by simple functional forms for example the commonly assumed bilinear form r 1 r 0 5 with frequency dependent q fits well if the transition from direct wave to lg spreading is placed at approximately 60 km a linear form r 1 over all distances with constant q 2000 also provides a satisfactory fit overall we find little evidence for the dependence of attenuation on focal depth or tectonic province

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

s wave attenuation characteristics beneath the vrancea region in romania new insights from the inversion of ground motion spectra the s wave attenuation characteristics beneath the vrancea region in romania are analyzed from the spectra frequency range 0 5 20 hz of more than 850 recordings at 43 accelerometric stations of 55 intermediate depth earthquakes m 4 0 7 1 that occurred in the vrancea seismogenic zone the method commonly chosen for this type of investigation in the case of crustal earthquakes is the generalized inversion technique git e g andrews 1986 castro et al 1990 yet the vrancea dataset is entirely different from common crustal datasets because of the strong clustering of the hypocenters within a very small focal volume there are only few crossing ray paths from sources to receivers as a consequence inhomogeneities in the attenuation properties are not averaged out which leads to unphysical results if the standard git approach is adopted the problem is discussed qualitatively by performing tests with synthetic data and solved quantitatively by adapting the git technique in view of these peculiarities with the optimally adapted inversion scheme it is possible to unravel differences in the attenuation characteristics between two or more sets of stations the results show that the attenuation of seismic waves is roughly comparable in the low frequency range 4 5 hz but stronger by up to an order of magnitude at higher frequencies within the carpathian mountain arc as compared with the foreland area modeling this strongly frequency dependent lateral variation of seismic attenuation by a significantly lower q beneath vrancea 1 provides a very good fit of observed strong motion characteristics 2 sheds new light on the distribution of intensities of the previous strong earthquakes 3 will have strong implications for future hazard assessment and 4 is fully compatible with structural models from deep seismic sounding tomography and teleseismic attenuation

resolution of non double couple components in the seismic moment tensor using regional networks ii application to aftershocks of the 1999 mw 7 4 izmit earthquake summary we study potential non double couple non dc components in aftershocks of the 1999 izmit earthquake the izmit earthquake ruptured a 140 km long segment of the north anatolian fault zone in northwestern turkey and was followed by the mw 7 1 d uzce earthquake that extended the rupture further to the east focal mechanisms of izmit aftershocks clearly indicate a segmentation of the rupture into several segments one of which is the akyazi plain a pull apart structure where significant non dc components might be observed the analysedearthquakecataloguecontainswaveformsofmorethan4000accuratelylocatedevents observedat35three componentshort periodseismicstations toensurehigh qualitydatawith good focal coverage we apply strict quality criteria to the aftershock catalogue reducing the number of events to only 33 aftershocks for which stable moment tensors were calculated using p and s wave amplitudes the moment tensors of the 33 analysed aftershocks display significant differences in the percentage of the non dc components for the three distinct fault segments the izmit sapanca karadere d uzce and the akyazi segments events located in the izmit sapanca and karadere d uzce segments exhibit only small percentages of the non dc components and if existent they are mainly positive this correlates well with the predominant strike slip stress regime along these segment and also with the main shock rupture being rightlateral strike slip in contrary we found a substantial percentage of non dc components for events below the akyazi plain where the sapanca fault splits into the mudurnu and karadere faults there the observed non dc components are entirely positive indicating a tensional regime and ranging from 20 to 48 percent clearly exceeding the defined error bounds found in a synthetic study this observation is in accordance with the post seismic setting following the izmit main shock that left a remarkable slip deficit of 3 5 m below the akyazi bend

attenuative dispersion of p waves and crustal q in turkey and germany we have measured group delays of the spectral components of high frequency p waves along two portions of the north anatolian fault zone nafz in turkey and in a region of southern germany assuming that the observed dispersion is associated with attenuation in the crust and that it can be described by a continuous relaxation model we obtained q and the high frequency relaxation times for those waves for each of the three regions individual p wave q values exhibit large scatter but mean values in the nafz increase from about 25 to 60 over the distance range 5 90 km mean q values are somewhat higher in the eastern portion of the nafz than in the western portion for measurements made at distances between 10 and 30 km p wave q values in germany range between about 50 and 300 over the hypocentral distance range 20 130 km in that region we separated the effects of q for basement rock 2 10 km depth from that of the overlying sediment 0 2 km depth using a least squares method q varies between 100 and 500 in the upper 8 10 km of basement with mean values for most of the distance range being about 250 q in the overlying sediments ranges between 6 and 10 because of large scatter in the q determinations we investigated possible effects that variations of the source time function of the earthquakes and truncation of the waveform may have on q determinations all of our studies indicate that measurement errors are relatively large and suggest that useful application of the method requires many observations and that the method will be most useful in regions where the number of oscillations following the initial p pulse is minimized even though there is large scatter in our q determinations the mean values that we obtained in turkey are consistent with those found in earlier studies our conclusions that q is significantly higher in the basement rock of germany than in the basement rock of turkey and that q is lower in western turkey than in eastern turkey are also consistent with results of q studies using lg coda

tree ring based summer temperature regime reconstruction in xiaoxing anling mountains northeastern china since 1772 ce abstract long term paleoclimatic variability based on high resolution proxy records such as tree ring data are scarce for the xiaoxing anling mountains of china we developed a new tree ring width chronology from korean pine pinus koraiensis spanning the period 1667 2015 climate growth correlation analysis revealed that early growing season temperature was the main climatic factor controlling tree ring growth june mean temperatures from 1772 to 2015 were reconstructed using the standard chronology these results provide the first dendroclimatological reconstruction based on growing season temperature in the xiaoxing anling mountains reconstruction results explained 39 3 of climatic variance over the calibration period 1959 2015 and they indicated that the central xiaoxing anling mountains have experienced six major warm periods five major cold periods and several cold years that coincided with a sequence of major tropical volcanic eruptions temperature reconstructions have successfully captured the most recent climatic warming events and are consistent with other reconstructions from nearby regions on decadal timescales spatial climate correlation analyses with a gridded temperature dataset revealed that our temperature reconstructions contain strong regional temperature signals for the eastern eurasian continent power spectrum revealed the existence of significant frequency cycles of variability at 2 0 2 3 2 5 2 7 2 9 3 0 3 4 4 5 5 6 7 2 7 5 8 0 8 2 8 9 9 9 10 5 11 5 and 70 5 years which may be linked to large scale atmospheric oceanic variability such as the el nino southern oscillation solar activity and the pacific decadal oscillation this reconstruction improves our understanding of long term temperature variation for the xiaoxing anling mountains of china but it can also be used to predict tree growth dynamics within the study area

attenuation of body waves in the central new madrid seismic zone abstract data from the portable array for numerical data acquisition panda deployment in the central part of the new madrid seismic zone have been used to study the attenuation of body waves the spectral decay technique is used to analyze acceleration amplitude spectra of both p and s waves in a frequency range of 5 to 25 hz in order to obtain the high frequency attenuation parameter a multiple weighted least squares method is applied to obtain the site attenuation factor 0 at each station and to get d dr which were interpreted in terms of a two layer q structure consisting of a sedimentary layer overlying the upper crust the 0 values for s waves are stable and show a positive correlation with sediment thickness the 0 values for p waves in the sediments show significant scatter which may be due to greater sensitivity of p wave attenuation to water content of the soils than that of s waves which gave more stable 0 values consistency checks on the assumptions made in obtaining the p and s values are made by studying the source spectrum of several events and the differential sp s from the spectral ratio of the converted sp to s phases the three sets of values are found to be internally consistent but our results are limited to deep sediment sites since the complete vertical distribution of q with sediment depth is not known

separation of source propagation and site effects from s waves of local earthquakes in bursa region northwestern turkey we have used micro earthquake recordings m 1 8 4 1 of local events in the distance range of 5 60 km in order to quantify the attenuation and site effects in the vicinity of the bursa city marmara region turkey the data set consists of 120 three component recorded accelograms from 69 earthquakes recorded at six stations each station is deployed on different geologic units such as massive limestone slope deposit and quaternary young sediments in the framework of the marmara poly project in this study a nonparametric inversion method was applied to acceleration records from the bursa region to estimate source site and path effects using a two step inversion at the first step we determined attenuation functions by analyzing the distance dependence of the spectral amplitudes and retrieved values of q s f 46 59f 0 67 at the second step the corrected s waves spectral records for the attenuation function including the geometrical spreading effect were inverted to separate source and site response for 21 different frequencies selected between 0 5 and 25 hz the near surface attenuation value was also estimated by using the model proposed by anderson and hough 1984 at each site we observed that 0 is smaller for stations located on rock site igd r sigd 0 0 004 compared to the one that is located on neogene sediment cukurca sckr 0 0 018 site amplifications from inversion showed that the station located within the bursa basin cukurca sckr is the most important site with about 4 0 amplification value at 1 8 hz demirtas sdem amplifies the spectral amplitudes about 3 0 times at 2 0 hz shmk about 3 5 times between 2 5 and 3 5 hz and shmt nearly reaching 3 5 times between 1 5 and 4 0 hz however stations located on the uludag mountain massif skay and sigd which correspond to a deep limestone geological unit have the smallest amplification that values between 0 6 and 1 4

scattering and anelastic attenuation of seismic energy in the vicinity of north anatolian fault zone eastern turkey abstract erzincan basin eastern turkey is seismically very active pull apart basin and developed in between the eastern segments of the north anatolian fault zone a study of the regional and site attenuation of seismic waves of earthquakes in this area will contribute in predicting earthquake generated ground motion and becomes vital in making decisions for earthquake regulations and building codes especially for the cities on the north anatolian fault zone in this paper anelastic and scattering attenuation in erzincan region is investigated by using of multiple lapse time window mltw method based on the hypothesis of multiple isotropic scattering with uniform distribution of scatters it is found that the scattering and intrinsic q 1 are almost equal for 3 hz and lower frequencies and intrinsic attenuation is dominant over scattering attenuation for 6 hz and higher frequencies model fitting was quite good for almost all frequencies at long distances more scattered data and observed poor model fitting at low frequencies 1 5 hz and short distances 5 15 km may indicate the complexities in the shallower part of crust in erzincan the seismic albedo is 0 52 for 1 5 hz and 0 32 for 12 hz l e 1 value increases slightly with frequency as 0 058 for 1 5 hz and 0 032 for 12 hz the coda q c 1 determined from the decay rate of coda waves is similar to q s 1 for 1 5 and 3 hz and it is close to q t 1 for frequencies higher than 3 hz we found that the scattering attenuation is strongly frequency dependent decreasing proportional to f 1 48 whereas intrinsic q i 1 is considerably less frequency dependent f 1 1 a decrease of q s 1 faster than f 1 0 with increasing frequency implies that the medium may be characterized by a gaussian rather than exponential auto correlation function

spectral analysis of k net and kik net data in japan part ii on attenuation characteristics source spectra and site response of borehole and surface stations abstract in this study we apply a nonparametric spectral inversion scheme to a data set of accelerograms recorded by the k net and kik net networks in japan in order to derive attenuation characteristics source spectra and site response for this purpose we use a total of more than 67 000 s wave records from 2178 earthquakes m jma 2 7 8 obtained at 1555 stations at the earth s surface and more than 29 000 records from 1826 events recorded at 637 borehole stations at depths of 100 to 3000 m attenuation characteristics are investigated in five separate regions showing that crustal q depicts lower values in central compared to southern japan and a significant frequency dependence is observed in every region the source spectra follow the 2 model with higher stress drops for subcrustal earthquakes as compared with crustal ones while strong amplification effects dominate the site contributions for the surface sensors those for the borehole sensors are characterized by smaller variability nevertheless consistent with observations from deconvolution of borehole surface recording pairs downgoing wave effects are visible in the site contributions for many borehole stations finally the site amplification functions obtained at the surface are compared with surface to borehole s b and horizontal to vertical h v spectral ratios showing that the s b ratios generally provide better estimates of the horizontal amplification than the h v ratios due to amplification of the vertical component of ground motion

seismic attenuation effects of pore fluids and frictional sliding seismic wave attenuation in rocks was studied experimentally with particular attention focused on frictional sliding and fluid flow mechanisms sandstone bars were resonated at frequencies from 500 to 9000 hz and the effects of confining pressure pore pressure degree of saturation strain amplitude and frequency were studied observed changes in attenuation and velocity with strain amplitude are interpreted as evidence for frictional sliding at grain contacts since this amplitude dependence disappears at strains and confining pressures typical of seismic wave propagation in the earth we infer that frictional sliding is not a significant source of seismic attenuation in situ partial water saturation significantly increases the attenuation of both compressional p and shear s waves relative to that in dry rock resulting in greater p wave than s wave attenuation complete saturation maximizes s wave attenuation but causes a reduction in p wave attenuation these effects can be interpreted in term

oxygen 18 16 variability in greenland snow and ice with 10 3 to 105 year time resolution the 3 km long greenland ice sheet project 2 gisp2 ice core presents a 100 000 year detailed oxygen isotope profile covering almost a full glacial interglacial cycle measuranents of isotopic fluctuations in snow frost and atmospheric water vapor samples collected during summer field seasons up to 20 0 are compatible with the large and abrupt 80 160 changes observed in accumulated tim snow pit 15 80 profiles from the gisp2 summit area however show rapid smoothing of the 180 160 signal near the surface beyond about 2 m depth the smoothedi5180 signal is fairly well preserved and can be interpreted in terms of average local weather conditions and climate the longer climate fluctuations also have regional and often global significance in the older part of the record corresponding to marine isotope stages mis 5a to 5d the effect of orbital climate forcing via the 19 and 23 kyr precession cycles and the 41 kyr obliquity cycle is obvious from the end ofmis 5a at about 75 000 years b p till the end of the glacial at the younger dryas preboreal transition at 11 650 years b p the o180 160 record shows frequent rapid switches between intermediate interstadial and low stadial values fourier spectra of the oscillations that are superimposed on the orbitally induced changes contain a strong periodicity at 1 5 kyr a broad peak at 4 0 kyr and additional shorter periods detailed comparison of the gisp2 180 160 record with the vostok antarctica 15d record pacific ocean foraminiferal 180 160 grande pile france tree pollen and insolation indicates that a counterpart to many of the rapid 180 160 fluctuations of gisp2 can be found in the other records and that the gisp2 isotopic changes clearly are the local expression of climate changes of worldwide extent correlation of events on the independent gisp2 and specmap time scales for the interval 10 000 50 000 years b p shows excellent chronometric agreement except possibly for the event labeled 3 1 the glacial to interglacial transition evidently started simultaneously in the arctic and the antarctic but its development and its expression in greenland isotopes was later suppressed by the influence of meltwater especially from the barents sea ice sheet on deep water formation and ocean circulation meltwaters from different ice sheets bordering the north atlantic also influenced ocean circulation during the bolling allerod interstadial complex and the younger dryas and led to a distinct development of european climate and greenland 180 160 values the holocene interval with long term stable mean isotopic values contains several fluauations with periods from years to millennia dominant is a 6 3 year oscillation with amplitude up to 3 to 4 0 periodicities of 11 and 210 years also found in the solar modulated records of the cosmogenic isotopes 1obe and 14c suggest solar processes as the cause of these cycles depression of180 160 values cooling by volcanic eruptions is observed in stacked gisp215 80 records but the effect is small and not likely to trigger major climate changes

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

site response attenuation and source spectra of s waves along the guerrero mexico subduction zone acceleration spectra from nine earthquakes and up to 11 stations per earthquake are inverted to find the source spectra the site response and the quality factor q of s waves this method is applied to moderate earthquakes 4 0 0 8 hz does not follow a simple linear relation as observed in previous studies of attenuation in other regions when the source spectra are interpreted in terms of brune s model the stress drops obtained are less than 20 bars for the four larger events analyzed the site functions obtained indicate that although all the stations used are on rock the effect of the near surface geology caused important amplifications at some stations

reconstructed may july mean maximum temperature since 1745ad based on tree ring width of pinus tabulaeformis in qianshan mountain china abstract a tree ring width chronology of pinus tabulaeformis was developed from the qianshan mountain liaoning province northeastern china based on the correlation between the ring width and instrumental data a transfer function was designed and the may july mean maximum temperature mmt from 1745 to 2012 was reconstructed the reconstruction explains 42 7 of the instrumental variance during the calibration period 41 7 after adjusting for the loss of the degrees of freedom the reconstructed mmt is similar to several observed mmt series and the temperature index in north central china which indicated that the decrease in summer temperatures in the 20th century was a large scale phenomenon the reconstruction also showed that high mmt values corresponded to historical drought events in liaoning in addition a spatial correlation analyses revealed that the mmt reconstruction is regionally representative significant 128 2 64 1 18 6 3 46 3 19 2 43 2 15 and 2 10 year cycles were detected in the reconstructed mmt series from qianshan mountain

derivation of a reference shear wave velocity model from empirical site amplification abstract the definition of a reference bedrock condition representative of a region of interest is of great significance in seismic hazard assessment it is highly beneficial when ground motion prediction equations are referenced to a specific site condition particularly in the case of site specific seismic hazard analyses when known the effect of any given site with respect to the reference can then be applied to the predicted ground motion however the choice of a reference velocity profile is not straightforward mainly due to the high variability of the velocity structure in the shallower layers a new method to define the regional reference rock profile is proposed the method relates quarter wavelength average velocity at a site to frequency dependent amplification a reference bedrock velocity profile can then be directly defined in relation to expected amplification characteristics over a number of sites we compare 27 quarter wavelength velocity profiles from seismic station locations in switzerland with empirical amplification functions derived from spectral modeling from this comparison a set of frequency dependent calibration relationships is established assuming that the reference profile is defined by a lack of any relative amplification the quarter wavelength velocity profile that corresponds to unitary spectral amplification can be extracted the reference velocity profile can then be obtained through an inversion procedure and defines the reference for the ground motion prediction equation gmpe the proposed reference velocity profile is compared with previous reference velocity profiles a good agreement is found between the different methods additionally an estimation of the transfer function for the swiss reference rock condition is provided this can be used to correct recorded or estimated spectral amplitudes for the local response of the reference site finally it is shown that the coefficients from the aforementioned correlations can be used to estimate a generic amplification function at any site with a known quarter wavelength velocity profile

high frequency attenuation of shear waves in the southeastern alps and northern dinarides summary we investigated the high frequency attenuation of s waves in the southeastern alps and northern external dinarides using waveforms from 331 earthquakes 3 0 mw 6 5 the spectral decay parameter k was computed using 1345 three component high quality records collected by the italian strong motion network ran and by the short period seismometric network of northeastern italy nei in the period 1976 2007 weak motion data from 11 stations of the nei network and strong motion data collected by five accelerometers of the ran were analysed the k parameter was estimated in the 0 250 km distance range in a frequency band extending from the corner frequency of the event up to 25 or 45 hz using the amplitudeaccelerationfourierspectraofs waves theobservedrecord to recordvariabilityof k was modelled by applying a generalized inversion procedure using both parametric and nonparametric approaches our results evidence that k is independent on earthquake size while it shows both site and distance dependence stations of the nei network present the same increase of k with epicentral distance re and show values of the zero distance k parameter k0 s between 0 017 and 0 053 s for the whole region the k increase with distance can be describedthroughalinearmodelwithslopedk dre 1 4 0 1 10 4 skm 1 assumingan average s wave velocity 3 34 km s 1 between 5 and 15 km depth we estimate an average frequency independent quality factor qi 2140 for the corresponding crustal layer the non parametric approach evidences a weak positive concavity of the curve that describes the k increase withre at about 90 km distance this result can be approximated through a piecewise linear function with slopes of 1 0 10 4 and 1 7 10 4 sk m 1 in accordance with a three layers model where moving from the intermediate to the bottom layer both qi and decrease two regional dependences were found data from earthquakes located westward to the nei network evidence weaker attenuation properties probably because of s wave reflections from different parts of the moho discontinuity under the eastern po plain at about 25 30 km depth while earthquakes located eastward in western slovenia where the moho deepens up to 45 50 km evidence a higher attenuation moreover the k estimates obtained with data from earthquakes located in the area of the 1998 mw 5 7 and 2004 mw 5 2 kobarid events are 0 017 s higher than the values predicted for the whole region probably because of the high level of fracturing that characterizes fault zones the comparison between measured and theoretical values of k computed at a few stations with available s wave velocity profiles reveals that the major contribution to the total k0 s is due to the sedimentary column from surface to 800 m depth the hard rock section contribution is limited to 0 005 s in accordance with a maximum contribution of 0 010 s predicted by the non parametric inversion

determination and uncertainty of moment tensors for microearthquakes at okmok volcano alaska summary efforts to determine general moment tensors mts for microearthquakes in volcanic areas are often hampered by small seismic networks which can lead to poorly constrained hypocentres and inadequate modelling of seismic velocity heterogeneity in addition noisy seismic signals can make it difficult to identify phase arrivals correctly for small magnitude events however small volcanic earthquakes can have source mechanisms that deviate from brittle double couple shear failure due to magmatic and or hydrothermal processes thus determining reliable mts in such conditions is a challenging but potentially rewarding pursuit we pursued such a goal at okmok volcano alaska which erupted recently in 1997 and in 2008 the alaska volcano observatory operates a seismic network of 12 stations at okmok and routinely catalogues recorded seismicity using these data we have determined general mts for seven microearthquakes recorded between 2004 and 2007 by inverting peak amplitude measurements of p and s phases we computed green s functions using precisely relocated hypocentres and a 3 d velocity model we thoroughly assessed the quality of the solutions by computing formal uncertainty estimates conducting a variety of synthetic and sensitivity tests and by comparing the mts to solutions obtained using alternative methods the results show that mts are sensitive to station distribution and errors in the data velocity model and hypocentral parameters although each of the seven mts contains a significant non shear component we judge several of the solutions to be unreliable however several reliable mts are obtained for a group of previously identified repeating events and are interpreted as compensated linear vector dipole events

tree ring stable carbon isotope based may july temperature reconstruction over nanwutai china for the past century and its record of 20th century warming growth anomaly of trees in some regions was detected under current episode of rapid warming thisraises a dilemma for temperature reconstructions by using tree ring width which is believed to be themost important proxy on inter annual temperature reconstruction during the past millenniums here weemployed the tree ring d13c to reconstruct temperature variations for exploring their potential oncapturing signals of rapid warming and to test how its difference with the tree ring width basedreconstruction in this study the mean mayejuly temperature tmej was reconstructed over the pastcentury by tree ring d13c of chinese pine trees growing in the nanwutai region the explained varianceof the reconstruction was 43 3 42 1 after adjusting the degrees of freedom compared to a ring widthtemperature reconstruction mayejuly from the same site the tree ring d13c based temperaturereconstruction offered two distinct advantages 1 it captured a wider range of temperature variability i e at least mayejuly even over a longer part of the year januaryeseptember and 2 the reconstructionpreserved more low frequency climate information than that of ring width did the 20th century warming was well represented in the nanwutai tree ring d13c temperature reconstruction which implied that stable carbon isotope of tree rings potentially represents temperaturevariations during historical episodes of rapid warming a spatial correlation analysis showed that ourtemperature reconstruction represented climate variations over the entire loess plateau in north centralchina significant positive correlations p 0 1 were found between the temperature reconstruction andenso as well as ssts in the pacific and indian oceans the reconstruction showed the periodicities of22 78 4 16 3 45e3 97 and 2 04e2 83 year quasi cycles at a 95 confidence level our results suggestedthat temperature variability in the nanwutai region may be linked to pacific and indian ocean sstvariations and solar activity less

large amplitude moho reflections sms from landers aftershocks southern california closely spaced aftershocks of the 28 june 1992 landers earthquake m w 7 3 were used to make event record sections that show the transverse components of s and sms arrivals at a distance of 70 to 170 km for the data recorded toward the north in the mojave desert large sms phases are observed with amplitudes 2 to 5 times greater than the direct s for similar distances to the south the sms arrival is comparable to or smaller than the s comparisons to synthetic seismograms indicate that the large amplitude sms phases are produced by the simple crustal structure of the mojave desert that allows a large moho reflection in contrast the more complex geologic structure to the south partitions the seismic energy into a more complicated set of seismic phases so that the moho reflection is diminished in amplitude the large sms phases observed in the mojave enhance the overall ground motions by a factor of 2 to 3 this suggests that when damaging earthquakes occur in other regions of simple crustal structures moho reflections will produce amplified strong motions at distance ranges around 100 km depending on the local structure

the influence of critical moho reflections on strong ground motions recorded in san francisco and oakland during the 1989 loma prieta earthquake the amplitudes of strong ground motions from the loma prieta earthquake recorded in the san francisco and oakland areas exceeded the levels predicted by standard empirical attenuation relations preliminary analysis of accelerograms having known trigger times strongly suggests that the elevation of ground motion amplitudes in the distance range of approximately 40 to 100 km was due to critical reflections from the base of the crust these reflections which are identified on the basis of their arrival times and phase velocity and by comparison with simulated accelerograms were large and occurred at relatively close range because of the deep focal depth of the earthquake and the strong velocity gradient at the base of the crust these motions were further amplified presumably by impedance contrast effects at soft soil sites in san francisco and oakland the effect of the critical reflections in amplifying peak accelerations of the loma prieta earthquake in the san francisco and oakland regions was as large as the effect of soft soil site conditions focal depth has an important influence on strong motion attenuation at distances beyond about 40 km and empirical attenuation relations derived from shallow crustal earthquakes may underpredict the ground motions of deeper crustal events in this distance range further analyses using an expanded data base that includes recordings of aftershocks are required to rigorously test the proposed explanation of the ground motions recorded in san francisco and oakland and the conclusions drawn from that explanation

source spectra and site response from s waves of intermediate depth vrancea romania earthquakes abstract seismograms from 55 intermediate depth vrancea earthquakes m 4 0 7 1 recorded at 43 stations of an accelerometric network in romania are used to derive source spectra and site amplification functions from s waves in the frequency range 0 5 20 hz with the generalized inversion technique git castro et al 1990 attenuation is taken into account using the nonparametric attenuation functions derived by oth et al 2008 from the same dataset and the attenuation corrected data are then split into source and site contributions the source spectra follow the 2 model brune 1970 1971 with high corner frequencies and a related brune stress drop of the order of 100 mpa the site amplification functions are separately determined for both horizontal and vertical components contrary to widespread expectation the vertical component shows significant amplification effects at high frequencies the h z ratios determined from the git results compare well with h v ratios computed directly from the s wave window of the accelerograms lermo and chavez garcia 1993 the basic assumption for the determination of site effects from h v ratios is that the vertical component is not or only little affected by site effects for vrancea earthquakes this assumption is incorrect consequently site effects should not be estimated from h v ratios the reason for this peculiar fact is the geometry of intermediate depth seismicity that leads to almost vertical ray paths beneath the stations

calibration of an ml scale in northwestern turkey from 1999 izmit aftershocks a local magnitude scale is derived for northwestern turkey using data collected by a temporary network installed by the german task force for earthquakes after the 1999 izmit earthquake m w 7 4 and the permanent sapanca bolu network we computed wood anderson seismograms for over 5353 arrivals at 27 three component stations from 530 earthquakes the hypocentral distances considered range from 5 to 140 km with the best represented range being from 5 to 70 km we inverted the measured amplitudes following both the nonparametric richter s 1958 and parametric bakun and joyner 1984 approaches these methods yield consistent magnitude values and station corrections however the calculated nonparametric distance correction log a implies that ground motion attenuation is higher than what is accounted for by the equation calibrated in central california in the range 5 62 km the best fit is provided by log a log r 17 0 00960 r 17 2 this equation is obtained constraining the geometrical spreading parameter n to 1 the calculated value of k 0 00960 confirms that in this range of distance seismic waves could propagate through a low q volume station corrections which allow for a significant reduction of m l residuals range between 0 5 magnitude units suggesting a strong influence of local site effects on the amplitude of ground motion in accord with the obtained attenuation and station corrections the magnitudes of the considered events range from 0 4 to 4 8

source parameter scaling and radiation efficiency of microearthquakes along the irpinia fault zone in southern apennines italy we analyzed the p and s wave displacement spectra of 717 microearthquakes in the moment range 4 109 2 1014 n m recorded at the dense networks operating in southern apennines italy and deployed along the 1980 ms 6 9 irpinia earthquake fault zone source attenuation and site parameters are estimated by using a parametric modeling approach which is combined with a multistep nonlinear inversion strategy we found that in the analyzed frequency band an attenuation model with constant q has to be preferred to frequency dependent q models consistent estimates of the median p and s quality factors q p 167 90 296 and q s 226 114 417 are obtained from two different techniques and relatively high values of qs qp median value 1 3 0 8 2 1 are found in the same depth range where high vp vs and a peak in seismicity distribution are observed this is the evidence for a highly fractured partially or completely fluid saturated medium embedding the irpinia fault zone down to crustal depths of 15 20 km a nearly constant stress drop 1 4mpa 0 4 5 0 and apparent stress a 0 1mpa 0 03 0 4 scaling of p and s corner frequencies and seismic energies is observed above a seismic moment value of about 1011 n m the measured radiation efficiency is low sw 0 06 0 030 13 e g the radiated energy is only a small fraction of the whole energy spent by friction and fracture development a large positive dynamic overshoot high dynamic shear strength can be the dominant mechanism controlling the microearthquake fractures along the irpinia fault zone

seismic source summary for all u s below surface nuclear explosions a summary of information is presented for all u s nuclear tests detonated below the earth s surface the data include explosion times locations yields and depths of burial as well as geophysical information about working point media and for the underground explosions data about surface collapse subsidence phenomena this summary is intended to furnish available and up to date data useful for studies of seismic and hydroacoustic sources as well as for studies of the seismic and hydroacoustic transmission characteristics of the earth manuscript received 2 july 2001

1738 years of mongolian temperature variability inferred from a tree ring width chronology of siberian pine 1738 years ad 262 1999 of temperature variability are inferred from tree ring widths of siberian pine at solongotyn davaa sol dav a timberline 2420 m site in mongolia this chronology can account for 33 of the temperature variance from 1882 1993 the warmest conditions over the past millennium are during the 20th century the 1999 ring width has the highest index value over the past millennium both warmer and colder intervals are inferred during the medieval warm epoch the most severe cold occurred in the 19th century unusual cold and frost in ad 536 545 coincide with extremes in other proxies and historical accounts confirming a widespread catastrophic event trends resemble those of other eurasian paleoseries and hemispheric scale reconstructions over the past millennium more chronologies such as sol dav are essential to improve coverage in the uncertain earlier centuries of these reconstructions and their estimates of natural variability relative to recent anthropogenic change

site response estimation from earthquake data abstract aftershocks of the 1989 loma prieta california earthquake are used to estimate site response along the san francisco peninsula a total of 215 shear wave records from 24 sources and 21 sites are used in a linear inversion for source and site response spectra the methodology makes no assumptions about the shape of the source spectrum however to obtain a stable unique inverse a q model and geometrical spreading factor are assumed as well as a constraint on site response that sets the site response averaged over two specific stations to 1 0 site responses calculated by this formulation of the problem are compared with other studies in the same region that use different methodologies and or data the shear wave site responses compare favorably with estimates based on an 2 constrained source model comparison with coda amplification factors is not as close but still favorable considering that the coda values were determined for nearby locations with similar geology and not the same sites the degree of agreement between the three methods is encouraging considering the very different assumptions and data used

tree ring precipitation reconstruction in the chifeng weichang region china and east asian summer monsoon variation since a d 1777 1 the total precipitation of previous august to current july was reconstructed on the basis of the pinus tabulaeformis ring widths from three sites in chifeng and weichang regions china for the past 236 years the explained variance of reconstruction is 47 4 the intervals with below average precipitation 1768 2003 comprise 1779 1806 1853 1883 1926 1972 and 1980 1989 the intervals with above average precipitation consist of 1807 1852 1884 1925 1973 1979 and 1990 1999 precipitation in the study area is dependent on the east asian summer monsoon strength the reconstructed series is significantly correlated with the average dryness wetness index series of datong and beijing as well as with previous results from baiyinaobao helan mountains and even the state of mongolia a significant negative correlation r 0 63 p 0 0001 is also found between the reconstruction and our previously reconstructed temperatures of weichang for the period 1884 2002 our result suggests that the variations of the east asian summer monsoon on a decadal scale are coincident with the other regions within the environmentally sensitive zone of northern china as well as mongolia for the past 236 years and our reconstruction is representative of regional climate patterns

cumulative attenuation along source to receiver paths in northwestern turkey the attenuation of shear waves propagating in the crust of northwestern turkey has been investigated in the frequency range 1 10 hz a standard spectral inversion scheme is applied to a data set of 245 aftershocks m l 4 5 of the 1999 izmit earthquake the obtained attenuation with distance curves have been described in terms of the t cumulative attenuation parameter and its dependence on frequency and distance investigated at 1 hz q 1 evaluated by normalizing t to the travel time is generally larger than 0 025 for source to station distances smaller than 40 km indicating the presence of a highly attenuating upper crust in the area over longer distances q 1 decreases suggesting a decrease in the attenuation with depth by contrast the normalized t computed for earthquakes recorded at stations having almost the same distance from the sources do not show a strong dependence on the backazimuth these results suggest that the decrease of q 1 with depth is more significant than its lateral variations regarding its frequency dependence q 1 almost linearly decreases with frequency finally the near surface attenuation parameter k is evaluated at 12 stations and the results discussed in terms of site event and propagation contributions the event contribution is not negligible and shows a significant positive correlation with magnitude the site term is smaller than 0 020 sec for rock or topographic sites while it assumes values of 0 036 sec and 0 042 sec for two stations installed over thick soft sedimentary layers

hydrometeorological reconstructions for northeastern mongolia derived from tree rings 1651 1995 reconstructions of annual prior august current july precipitation and streamflow 345 yr in length 1651 1995 are presented for northeastern mongolia based on tree ring width data these precipitation and streamflow reconstructions account for 54 and 48 of the respective variance in instrumental data over the past 50 years variations in instrumental precipitation and streamflow are within the range of those reconstructed over the length of tree ring records however there appear to be more frequent extended wet periods during the twentieth century multitaper spectral analysis revealed statistically significant peaks at 10 8 and 12 8 yr for the precipitation reconstruction and at 12 8 and 20 3 23 8 yr for the streamflow reconstruction similarly singular spectrum analysis identified spectral modes of variation at 12 and 21 yr for both series these spectra resemble those found for tree ring based precipitation reconstructions in central china as well as the western united states and may reflect solar influences on the climate of mongolia

attenuation of high frequency p and s waves in garhwal himalaya india abstract tectonics of a region plays important role on the attenuation characteristics of the region attenuation characteristics have been estimated to understand the effect of the heterogeneity of the region in a tectonically active garhwal region of himalaya seismic body wave attenuation characteristics in the region is studied using 234 short period seismic observations from local events the p wave attenuation qp 1 and s wave attenuation qs 1 were estimated by applying the state of the art extended coda normalization method for the frequency range from 1 5 to 24 hz estimates of qp 1 and qs 1 decrease from 15 86 0 90 10 3 and 5 35 0 51 10 3 at 1 5 hz to 0 54 0 11 10 3 and 0 34 0 06 10 3 at 24 hz respectively the values of qp 1 and qs 1 show strong frequency dependence and fit the power law relation qp 1 f 27 43 3 15 10 3f 1 16 0 06 and qs 1 f 8 05 0 74 10 3f 0 93 0 05 respectively obtained results are in the range of those reported for qp 1 and qs 1 of the other seismically active regions the ratio of qp 1 qs 1 is larger than unity in the entire analyzed frequency range and may suggest high degree of heterogeneity in the region

precipitation reconstruction from hailar pine pinus sylvestris var mongolica tree rings in the hailar region inner mongolia china back to 1865 ad article precipitation is the major limiting factor for the radial growth of hailar pine pinus sylvestris var mongolica i n the hailar northeast china herein the amount of precipitation from the previous july to current june was chosen for reconstruction from 1865 to 2003 ad this reconstruction accounts for 51 of the variance in the instrumental precipitation data during the 1952 2003 period the reconstruction reveals the precipitation fluctuation history over the last 139 years some severe drought events lasting for more than 3 years are displayed in theseries such as 1905 1909 1926 1929 asevere drought event in central northern china with tremendous losses of human lives and 1968 1970 extreme wet events are 1867 1870 1932 1934 1939 1941 and 1955 1957 on the decadal scale there are two dry periods with precipitation lower than the mean of 1865 2003 1888 1929 and 1963 1975 and two wet intervals more than the mean 1930 1962 and 1976 2003 drought events or dry intervals correspond to weak and wet events to strong east asian summer monsoon easm the reconstructed precipitation can be well compared with the baiyinaobao ortindag sand land in eastern inner mongolia and northeastern mongolia rainfall series derived from tree rings the four curves show similar variation related to weak strong easm a power spectrum analysis shows that there are 7 67 and 7 08 year quasi periodicities which may be associated with enso activity

attenuation of high frequency p and s waves in the crust of the east central iran summary we simultaneously estimated qp 1 and qs 1 by applying the extended coda normalization method at 39 stations of three local networks in the east central iran we measured frequencydependent attenuation of both p and s waves for the frequency range of 1 5 3 0 6 0 12 and 24 hz we have analysed 266 three component seismograms of 53 local earthquakes having focal depths less than 25 km which occurred from 2003 december 28 to 2005 april 11 by fitting power law frequency dependence to the estimated values over the whole stations we obtained qp 1 25 3 10 3 f 0 99 0 04 and qs 1 19 2 10 3 f 1 02 0 06 in the upper crust of the east central iran where f is frequency in hz our results are in the range of those estimated for qp 1 and qs 1 of the other seismically active regions