As an important indicator parameter of fluid identification,fluid factor has always been a concern for scholars.However,when predicting Russell fluid factor or effective pore-fluid bulk modulus,it is necessary to intr...As an important indicator parameter of fluid identification,fluid factor has always been a concern for scholars.However,when predicting Russell fluid factor or effective pore-fluid bulk modulus,it is necessary to introduce a new rock skeleton parameter which is the dry-rock VP/VS ratio squared(DVRS).In the process of fluid factor calculation or inversion,the existing methods take this parameter as a static constant,which has been estimated in advance,and then apply it to the fluid factor calculation and inversion.The fluid identification analysis based on a portion of the Marmousi 2 model and numerical forward modeling test show that,taking the DVRS as a static constant will limit the identification ability of fluid factor and reduce the inversion accuracy.To solve the above problems,we proposed a new method to regard the DVRS as a dynamic variable varying with depth and lithology for the first time,then apply it to fluid factor calculation and inversion.Firstly,the exact Zoeppritz equations are rewritten into a new form containing the fluid factor and DVRS of upper and lower layers.Next,the new equations are applied to the four parameters simultaneous inversion based on the generalized nonlinear inversion(GNI)method.The testing results on a portion of the Marmousi 2 model and field data show that dynamic DVRS can significantly improve the fluid factor identification ability,effectively suppress illusion.Both synthetic and filed data tests also demonstrate that the GNI method based on Bayesian deterministic inversion(BDI)theory can successfully solve the above four parameter simultaneous inversion problem,and taking the dynamic DVRS as a target inversion parameter can effectively improve the inversion accuracy of fluid factor.All these results completely verified the feasibility and effectiveness of the proposed method.展开更多
Sikkim Himalaya hosts critical water resources such as glacial,rain,and snow-fed springs and lakes.Climate change is adversely affecting these resources in various ways,and elevation-dependent warming is prominent amo...Sikkim Himalaya hosts critical water resources such as glacial,rain,and snow-fed springs and lakes.Climate change is adversely affecting these resources in various ways,and elevation-dependent warming is prominent among them.This study is a discussion of the elevation-dependent warming(EDW),snowfall shift,and precipitation variability over Sikkim Himalaya using a high-resolution ERA5-land dataset.Furthermore,the findings show that the Sikkim Himalaya region is experiencing a warming trend from south to north.The majority of the Sikkim Himalayan region shows a declining trend in snowfall.A positive advancement in snowfall trend(at a rate of 1 mm per decade)has been noticed above 4500 meters.The S/P ratio indicates a shift in snowfall patterns,moving from lower elevations to much higher regions.This suggests that snowfall has also transitioned from Lachung and Lachen(3600 m)to higher elevated areas.Moreover,the seasonal shifting of snowfall in the recent decade is seen from January-March(JFM)to February-April(FMA).Subsequently,the preceding 21 years are being marked by a significant spatiotemporal change in temperature,precipitation,and snowfall.The potent negative correlation coefficient between temperature and snowfall(–0.9),temperature and S/P ratio(–0.5)suggested the changing nature of snowfall from solid to liquid,which further resulted in increased lower elevation precipitation.The entire Sikkim region is transitioning from a cold-dry to a warm-wet weather pattern.In the climate change scenario,a drop in the S/P ratio with altitude will continue to explain the rise in temperature over mountainous regions.展开更多
Correction maps of P/S amplitude ratios for seismic events distributed in Xinjiang, China and its adjacent areas were established using a Bayesian Kriging method for the two seismic stations WMQ and MAK. The relations...Correction maps of P/S amplitude ratios for seismic events distributed in Xinjiang, China and its adjacent areas were established using a Bayesian Kriging method for the two seismic stations WMQ and MAK. The relationship between correction maps and variations of along-path features was analyzed and the validity of applying the correction maps to improve performances of P/S discriminants for seismic discrimination was investigated. Results show that obtained correction maps can generally reflect event-station path effects upon corresponding P/S discriminants; and the correction of these effects could further reduce scatters of distance-corrected P/S measurements within earthquake and explosion populations as well as improve their discriminating performances if path effects are a significant factor of such scatters. For example, as corresponding Kriging correction map was applied, the misidentification rate of earthquakes by Pn（2-4 Hz）/Lg（2-4 Hz） at MAK was reduced from 16.3% to 5.2%.展开更多
Applicability of regional P/S amplitude ratios for the discrimination of low-magnitude seismic events was tested and proved using earthquakes and explosions in Central Asia. Results obtained show that regional P/S amp...Applicability of regional P/S amplitude ratios for the discrimination of low-magnitude seismic events was tested and proved using earthquakes and explosions in Central Asia. Results obtained show that regional P/S amplitude ratios which may discriminate medium or large magnitude events well, are also applicable to low magnitude events Their performances for low magnitude events are almost as good as that for medium or large events. Statistical comparisons based on 25 P/S discriminate from the four seismic stations WMQ, BLK, MUL and MAK showed that the average misclassification rate for low-magnitude seismic events averagely was only 2 percent higher than that for medium and large magnitude seismic events.展开更多
Seven-day-old maize (Zea mays) plants were grown hydroponically for ten days in deprived nutrient solutions against the corresponding control grown under full nutrition;the effects of S-, N- or P-deprivation on lamina...Seven-day-old maize (Zea mays) plants were grown hydroponically for ten days in deprived nutrient solutions against the corresponding control grown under full nutrition;the effects of S-, N- or P-deprivation on laminas’ mean stomatal conductance (gs), transpiration rate (E) and photosynthetic rate (A) were monitored, along with the impact on the laminas’ total dry mass (DM), water amount (W), length and surface area (Sa). Furthermore, a time series analysis of each parameter’s response ratios (Rr), i.e. the treatment’s value divided by the corresponding control’s one, was performed. Under S-deprivation, the Rr of laminas’ mean gs, E, and A presented oscillations within a ±15% fluctuation zone, notably the “control” zone, whilst those of laminas’ total DM, water amount, surface area, and length included oscillation during the first days and deviation later on, presenting deviation during d10. Under the N-deprivation conditions all Rr time courses except the A one, included early deviations from the control zone without recovering. The deviation from the control zone appeared at d4. Under P-deprivation, all Rr time courses represented oscillations within the control zone. P-deprivation’s patterns resembled those of S-deprivation. Compared to the one of the S-deprivation, the P-one’s oscillations took place within a broader zone. Linear relationships among the various Rr patterns were found between gs-E, gs-A, E-A, DM-W and DM-Sa. In conclusion, the impact of P-deprivation appeared in an early stage and included an alleviation action, the one of N-deprivation appeared early with no alleviation action, whilst that of S-deprivation appeared later, being rather weaker when compared to the impact of the P-deprivation’s impact.展开更多
The Hi-CLIMB seismic array is located in the central-western Tibetan Plateau.The H-κ-c method(Li JT et al.,2019)was applied to receiver function data on the HiCLIMB,which corrects the back-azimuthal variations in the...The Hi-CLIMB seismic array is located in the central-western Tibetan Plateau.The H-κ-c method(Li JT et al.,2019)was applied to receiver function data on the HiCLIMB,which corrects the back-azimuthal variations in the arrival times of Ps and crustal multiples caused by crustal anisotropy and dipping interfaces before performing H-κstacking.Compared to the traditional H-κmethod,the H-κstacking results after harmonic corrections showed considerable improvements,including greatly reduced errors,significantly less scattered H(crustal thickness)andκ(crustal v_(P)/v_(S)ratio)values,and clearer patterns of H andκin different Tibetan blocks.This demonstrates that the H-κ-c method works well even for regions with complex crustal structures,such as the Tibetan Plateau,when there are helpful references from nearby stations or other constraints.The variation in crustal thickness agrees with previous studies but tends to be relatively shallower beneath most of the plateau.Two regions with particularly high crustal v_(P)/v_(S)were observed,namely,one in the northern Himalaya block and beneath the YarlungZangbo suture,and the other in the Qiangtang block.Their correlation with mid-crust low S velocities from previous studies suggests the possible presence of fluid or partial melt in the two regions,which may have implications for the crustal flow model.In contrast,the Lhasa block had relatively lower crustal v_(P)/v_(S)and relatively higher crustal S velocity within the plateau,which is interpreted to be mechanically stronger than the Himalaya and Qiangtang blocks,and without mid-crust partial melt.展开更多
Seismic records produced by different seismic sources vary.In this study,we compared the waveform records and time-frequency characteristics of tectonic earthquakes,artificial explosions,and mine collapses in China’s...Seismic records produced by different seismic sources vary.In this study,we compared the waveform records and time-frequency characteristics of tectonic earthquakes,artificial explosions,and mine collapses in China’s Capital Region.The results show that tectonic earthquakes are characterized by stronger S-wave energy than P-wave energy,obvious high-frequency components,and wide frequency bands of P and S waves.Artificial explosions are characterized by greater P-wave amplitude than S-wave amplitude and near-station surface wave development.Mine collapses are characterized by lower overall frequency,more obvious surface waves,and longer duration.We extracted quantitative discriminants based on the analysis of different event records,with 31 feature values in 7 categories(P/S maximum amplitude ratio,high/low frequency energy ratio,P/S spectral ratio,corner frequency,duration,the second-order moment of spectrum,and energy strongest point).A comparison of the ability of these feature values to recognize distinct events showed that the 6-17 Hz P/S spectral ratio was able to completely distinguish artificial explosions from the other two types of events.The S-wave corner frequency performed relatively well in identifying all three types of events,with an accuracy of over 90%.Additionally,a support vector machine was used to comprehensively distinguish multiple features,with an accuracy for all three types of events reaching up to 100%.展开更多
Objective:Relevance of estimation of pleural adenosine deaminase(PADA) and serum adenosine deaminase (SADA) levels in-pleural effusion especially in cases of lymphocytic predominant exudative tubercular effusions. Met...Objective:Relevance of estimation of pleural adenosine deaminase(PADA) and serum adenosine deaminase (SADA) levels in-pleural effusion especially in cases of lymphocytic predominant exudative tubercular effusions. Methods:Fifty patients(33 male and 17 female;age:44.12±11.51 years) with pleural effusions were selected to assay adenosine deaminase(ADA) activity in pleural fluid and serum in adjunct to pleural fluid analysis.Effusions were individually classified as transudates or exudates after careful evaluation of all the biochemical parameters of pleural fluid and serum of patients and on the basis of Lights criteria.Cutoff value for PADA was taken as 60U/L and that for pleural/serum ADA ratio(P/S ADA) was 1.8.Results:Fourty -three patients had exudative effusions among which 38 patients had tuberculous pleural effusions and 5 had nontubercular effusions.7 cases were transudates.Mean PADA levels in tubercular group(78.95±25.32 U/ L) were found to be much higher P=0.0000) than nontubercular(23.00±5.22 U/L) group.SADA levels in tubercular group(31.05±6.42 U/L) were significantly higher(P=0.0000)as compared to nontubercular group(15.58±8.35 U/L).PADA cutoff at 60 U/L yielded sensitivity and.specificity of 81.5%and 100%respectively,whereas P/S ADA ratio at 1.8 gave sensitivity and specificity of 84.2% and 75%respectively. A positive correlation(r=0.507,P= 0.001 1)between PADA and SADA was found in tubercular group but no such correlation(r=0.302,P=0.3407)was observed in nontubercular group.Conclusion: The measurement of ADA in tubercular pleural effusions has not only relevance but also a high diagnostic utility when other clinical and laboratory tests are either negative or confusing.展开更多
We estimated crustal v p/ v s ratio of Tibetan Plateau by combined inversion of Love and Rayleigh wave dispersion data. It is developed by us that the joint inversion methods using both Love and Rayleigh wave dispersi...We estimated crustal v p/ v s ratio of Tibetan Plateau by combined inversion of Love and Rayleigh wave dispersion data. It is developed by us that the joint inversion methods using both Love and Rayleigh wave dispersion data. Thickness and S\|wave velocity of each sub layer are taken from Love wave dispersion data, then P\|wave velocity structure was deduced using Rayleigh wave dispersion data. Densities of sub layers were estimated by the empirical relationships between seismic velocity and rock density. Having S\| and P\|wave velocities, v p/ v s ratio is calculated for each sub layer. Six sub layers in crust of Tibetan Plateau has been identified, which are 0～8km, 8～30km, 30～40km, 40～62km, 62～68km and 68～75km respectively. The S\|wave velocity structure of the Plateau is 3 13, 3 32, 3 15, 3 92, 3 45 and 3 87 km/s for each sub layer; and P\|wave velocities are 6 00, 6 10, 5 72, 6 35, 6 78 and 6 64km/s respectively v p/ v s ratios in sub layers are 1 92, 1 84, 1 82, 1 62, 1 96 and 1 72; and corresponding Poisson ratios are 0 31, 0 29, 0 28, 0 19, 0 32 and 0 24. Our result on Poisson ratios of Tibetan crust was supported by seismic waveform modelling by Rodgers and Schwartz (1998).展开更多
In order to understand the site soil response of the Xiangtang borehole seismic array under real strong ground motion, reveal the site response, verify the technique of borehole exploration, and improve the precision ...In order to understand the site soil response of the Xiangtang borehole seismic array under real strong ground motion, reveal the site response, verify the technique of borehole exploration, and improve the precision of in-situ test and laboratory test, this paper presents a new approach, which is composed of two methods. One is the layered site seismic response method, whose layer transform matrix is always real. The other is a global-local optimization technique, which uses genetic algorithm （GA）-simplex method. An inversion of multi-component waveforms of P, SV and SH wave is carried out simultaneously. By inverting the records of three moderate and small earthquakes obtained from the Xiangtang borehole array （2^#） site, the soil dynamic characteristic parameters, including P velocity, damping ratio and frequency-dependent coefficient b, which has not been given in previous literatures, are calculated. The results show that the soil S wave velocity of the Xiangtang 2^# borehole is generally greater than that obtained from the 1994 in-situ test, and is close to the velocity of the 3^# borehole, which is more than 200 m away from the 2^# borehole. Meanwhile, perceptible soil nonlinear behavior under peak ground motion of about 60×10^-2 m/s^2 is detected by the inversion analysis. The presented method can be used for studying the soil response of other borehole array sites.展开更多
基金the National Natural Science Foundation of China(41904116,41874156,42074167 and 42204135)the Natural Science Foundation of Hunan Province(2020JJ5168)the China Postdoctoral Science Foundation(2021M703629)for their funding of this research.
文摘As an important indicator parameter of fluid identification,fluid factor has always been a concern for scholars.However,when predicting Russell fluid factor or effective pore-fluid bulk modulus,it is necessary to introduce a new rock skeleton parameter which is the dry-rock VP/VS ratio squared(DVRS).In the process of fluid factor calculation or inversion,the existing methods take this parameter as a static constant,which has been estimated in advance,and then apply it to the fluid factor calculation and inversion.The fluid identification analysis based on a portion of the Marmousi 2 model and numerical forward modeling test show that,taking the DVRS as a static constant will limit the identification ability of fluid factor and reduce the inversion accuracy.To solve the above problems,we proposed a new method to regard the DVRS as a dynamic variable varying with depth and lithology for the first time,then apply it to fluid factor calculation and inversion.Firstly,the exact Zoeppritz equations are rewritten into a new form containing the fluid factor and DVRS of upper and lower layers.Next,the new equations are applied to the four parameters simultaneous inversion based on the generalized nonlinear inversion(GNI)method.The testing results on a portion of the Marmousi 2 model and field data show that dynamic DVRS can significantly improve the fluid factor identification ability,effectively suppress illusion.Both synthetic and filed data tests also demonstrate that the GNI method based on Bayesian deterministic inversion(BDI)theory can successfully solve the above four parameter simultaneous inversion problem,and taking the dynamic DVRS as a target inversion parameter can effectively improve the inversion accuracy of fluid factor.All these results completely verified the feasibility and effectiveness of the proposed method.
文摘Sikkim Himalaya hosts critical water resources such as glacial,rain,and snow-fed springs and lakes.Climate change is adversely affecting these resources in various ways,and elevation-dependent warming is prominent among them.This study is a discussion of the elevation-dependent warming(EDW),snowfall shift,and precipitation variability over Sikkim Himalaya using a high-resolution ERA5-land dataset.Furthermore,the findings show that the Sikkim Himalaya region is experiencing a warming trend from south to north.The majority of the Sikkim Himalayan region shows a declining trend in snowfall.A positive advancement in snowfall trend(at a rate of 1 mm per decade)has been noticed above 4500 meters.The S/P ratio indicates a shift in snowfall patterns,moving from lower elevations to much higher regions.This suggests that snowfall has also transitioned from Lachung and Lachen(3600 m)to higher elevated areas.Moreover,the seasonal shifting of snowfall in the recent decade is seen from January-March(JFM)to February-April(FMA).Subsequently,the preceding 21 years are being marked by a significant spatiotemporal change in temperature,precipitation,and snowfall.The potent negative correlation coefficient between temperature and snowfall(–0.9),temperature and S/P ratio(–0.5)suggested the changing nature of snowfall from solid to liquid,which further resulted in increased lower elevation precipitation.The entire Sikkim region is transitioning from a cold-dry to a warm-wet weather pattern.In the climate change scenario,a drop in the S/P ratio with altitude will continue to explain the rise in temperature over mountainous regions.
基金Foundation of Verification Researches for Army Control Technology (513310101).
文摘Correction maps of P/S amplitude ratios for seismic events distributed in Xinjiang, China and its adjacent areas were established using a Bayesian Kriging method for the two seismic stations WMQ and MAK. The relationship between correction maps and variations of along-path features was analyzed and the validity of applying the correction maps to improve performances of P/S discriminants for seismic discrimination was investigated. Results show that obtained correction maps can generally reflect event-station path effects upon corresponding P/S discriminants; and the correction of these effects could further reduce scatters of distance-corrected P/S measurements within earthquake and explosion populations as well as improve their discriminating performances if path effects are a significant factor of such scatters. For example, as corresponding Kriging correction map was applied, the misidentification rate of earthquakes by Pn（2-4 Hz）/Lg（2-4 Hz） at MAK was reduced from 16.3% to 5.2%.
基金Foundation of Verification Researches for Army Control Technology (513310101).
文摘Applicability of regional P/S amplitude ratios for the discrimination of low-magnitude seismic events was tested and proved using earthquakes and explosions in Central Asia. Results obtained show that regional P/S amplitude ratios which may discriminate medium or large magnitude events well, are also applicable to low magnitude events Their performances for low magnitude events are almost as good as that for medium or large events. Statistical comparisons based on 25 P/S discriminate from the four seismic stations WMQ, BLK, MUL and MAK showed that the average misclassification rate for low-magnitude seismic events averagely was only 2 percent higher than that for medium and large magnitude seismic events.
文摘Seven-day-old maize (Zea mays) plants were grown hydroponically for ten days in deprived nutrient solutions against the corresponding control grown under full nutrition;the effects of S-, N- or P-deprivation on laminas’ mean stomatal conductance (gs), transpiration rate (E) and photosynthetic rate (A) were monitored, along with the impact on the laminas’ total dry mass (DM), water amount (W), length and surface area (Sa). Furthermore, a time series analysis of each parameter’s response ratios (Rr), i.e. the treatment’s value divided by the corresponding control’s one, was performed. Under S-deprivation, the Rr of laminas’ mean gs, E, and A presented oscillations within a ±15% fluctuation zone, notably the “control” zone, whilst those of laminas’ total DM, water amount, surface area, and length included oscillation during the first days and deviation later on, presenting deviation during d10. Under the N-deprivation conditions all Rr time courses except the A one, included early deviations from the control zone without recovering. The deviation from the control zone appeared at d4. Under P-deprivation, all Rr time courses represented oscillations within the control zone. P-deprivation’s patterns resembled those of S-deprivation. Compared to the one of the S-deprivation, the P-one’s oscillations took place within a broader zone. Linear relationships among the various Rr patterns were found between gs-E, gs-A, E-A, DM-W and DM-Sa. In conclusion, the impact of P-deprivation appeared in an early stage and included an alleviation action, the one of N-deprivation appeared early with no alleviation action, whilst that of S-deprivation appeared later, being rather weaker when compared to the impact of the P-deprivation’s impact.
基金the National Natural Science Foundation of China(Nos.U1939204,and 41774056).
文摘The Hi-CLIMB seismic array is located in the central-western Tibetan Plateau.The H-κ-c method(Li JT et al.,2019)was applied to receiver function data on the HiCLIMB,which corrects the back-azimuthal variations in the arrival times of Ps and crustal multiples caused by crustal anisotropy and dipping interfaces before performing H-κstacking.Compared to the traditional H-κmethod,the H-κstacking results after harmonic corrections showed considerable improvements,including greatly reduced errors,significantly less scattered H(crustal thickness)andκ(crustal v_(P)/v_(S)ratio)values,and clearer patterns of H andκin different Tibetan blocks.This demonstrates that the H-κ-c method works well even for regions with complex crustal structures,such as the Tibetan Plateau,when there are helpful references from nearby stations or other constraints.The variation in crustal thickness agrees with previous studies but tends to be relatively shallower beneath most of the plateau.Two regions with particularly high crustal v_(P)/v_(S)were observed,namely,one in the northern Himalaya block and beneath the YarlungZangbo suture,and the other in the Qiangtang block.Their correlation with mid-crust low S velocities from previous studies suggests the possible presence of fluid or partial melt in the two regions,which may have implications for the crustal flow model.In contrast,the Lhasa block had relatively lower crustal v_(P)/v_(S)and relatively higher crustal S velocity within the plateau,which is interpreted to be mechanically stronger than the Himalaya and Qiangtang blocks,and without mid-crust partial melt.
文摘Seismic records produced by different seismic sources vary.In this study,we compared the waveform records and time-frequency characteristics of tectonic earthquakes,artificial explosions,and mine collapses in China’s Capital Region.The results show that tectonic earthquakes are characterized by stronger S-wave energy than P-wave energy,obvious high-frequency components,and wide frequency bands of P and S waves.Artificial explosions are characterized by greater P-wave amplitude than S-wave amplitude and near-station surface wave development.Mine collapses are characterized by lower overall frequency,more obvious surface waves,and longer duration.We extracted quantitative discriminants based on the analysis of different event records,with 31 feature values in 7 categories(P/S maximum amplitude ratio,high/low frequency energy ratio,P/S spectral ratio,corner frequency,duration,the second-order moment of spectrum,and energy strongest point).A comparison of the ability of these feature values to recognize distinct events showed that the 6-17 Hz P/S spectral ratio was able to completely distinguish artificial explosions from the other two types of events.The S-wave corner frequency performed relatively well in identifying all three types of events,with an accuracy of over 90%.Additionally,a support vector machine was used to comprehensively distinguish multiple features,with an accuracy for all three types of events reaching up to 100%.
文摘Objective:Relevance of estimation of pleural adenosine deaminase(PADA) and serum adenosine deaminase (SADA) levels in-pleural effusion especially in cases of lymphocytic predominant exudative tubercular effusions. Methods:Fifty patients(33 male and 17 female;age:44.12±11.51 years) with pleural effusions were selected to assay adenosine deaminase(ADA) activity in pleural fluid and serum in adjunct to pleural fluid analysis.Effusions were individually classified as transudates or exudates after careful evaluation of all the biochemical parameters of pleural fluid and serum of patients and on the basis of Lights criteria.Cutoff value for PADA was taken as 60U/L and that for pleural/serum ADA ratio(P/S ADA) was 1.8.Results:Fourty -three patients had exudative effusions among which 38 patients had tuberculous pleural effusions and 5 had nontubercular effusions.7 cases were transudates.Mean PADA levels in tubercular group(78.95±25.32 U/ L) were found to be much higher P=0.0000) than nontubercular(23.00±5.22 U/L) group.SADA levels in tubercular group(31.05±6.42 U/L) were significantly higher(P=0.0000)as compared to nontubercular group(15.58±8.35 U/L).PADA cutoff at 60 U/L yielded sensitivity and.specificity of 81.5%and 100%respectively,whereas P/S ADA ratio at 1.8 gave sensitivity and specificity of 84.2% and 75%respectively. A positive correlation(r=0.507,P= 0.001 1)between PADA and SADA was found in tubercular group but no such correlation(r=0.302,P=0.3407)was observed in nontubercular group.Conclusion: The measurement of ADA in tubercular pleural effusions has not only relevance but also a high diagnostic utility when other clinical and laboratory tests are either negative or confusing.
文摘We estimated crustal v p/ v s ratio of Tibetan Plateau by combined inversion of Love and Rayleigh wave dispersion data. It is developed by us that the joint inversion methods using both Love and Rayleigh wave dispersion data. Thickness and S\|wave velocity of each sub layer are taken from Love wave dispersion data, then P\|wave velocity structure was deduced using Rayleigh wave dispersion data. Densities of sub layers were estimated by the empirical relationships between seismic velocity and rock density. Having S\| and P\|wave velocities, v p/ v s ratio is calculated for each sub layer. Six sub layers in crust of Tibetan Plateau has been identified, which are 0～8km, 8～30km, 30～40km, 40～62km, 62～68km and 68～75km respectively. The S\|wave velocity structure of the Plateau is 3 13, 3 32, 3 15, 3 92, 3 45 and 3 87 km/s for each sub layer; and P\|wave velocities are 6 00, 6 10, 5 72, 6 35, 6 78 and 6 64km/s respectively v p/ v s ratios in sub layers are 1 92, 1 84, 1 82, 1 62, 1 96 and 1 72; and corresponding Poisson ratios are 0 31, 0 29, 0 28, 0 19, 0 32 and 0 24. Our result on Poisson ratios of Tibetan crust was supported by seismic waveform modelling by Rodgers and Schwartz (1998).
基金Joint Seismological Science Foundation of China (604036 and 105034)
文摘In order to understand the site soil response of the Xiangtang borehole seismic array under real strong ground motion, reveal the site response, verify the technique of borehole exploration, and improve the precision of in-situ test and laboratory test, this paper presents a new approach, which is composed of two methods. One is the layered site seismic response method, whose layer transform matrix is always real. The other is a global-local optimization technique, which uses genetic algorithm （GA）-simplex method. An inversion of multi-component waveforms of P, SV and SH wave is carried out simultaneously. By inverting the records of three moderate and small earthquakes obtained from the Xiangtang borehole array （2^#） site, the soil dynamic characteristic parameters, including P velocity, damping ratio and frequency-dependent coefficient b, which has not been given in previous literatures, are calculated. The results show that the soil S wave velocity of the Xiangtang 2^# borehole is generally greater than that obtained from the 1994 in-situ test, and is close to the velocity of the 3^# borehole, which is more than 200 m away from the 2^# borehole. Meanwhile, perceptible soil nonlinear behavior under peak ground motion of about 60×10^-2 m/s^2 is detected by the inversion analysis. The presented method can be used for studying the soil response of other borehole array sites.
