Table of Content

03 March 2007, Volume 29 Issue 1

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Brief Report

THE MIGRATION CHARACTERISTICS OF STRONG EARTHQUAKES ON THE NORTH-SOUTH SEISMIC BELT AND ITS RELATION WITH THE SOUTH ASIA SEISMIC BELT

WANG Yi-Peng, MA Jin, LI Chuan-You

2007, 29(1):  1-14. 

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Migration of strong earthquakes(M≥7) along the North-South Seismic Belt since 1500 AD shows three patterns: roughly similar time and distance interval migration from N to S, multi-pattern migration from S to N and clusters of strong earthquakes occurring in some periods within the whole seismic belt. Based on analysis of strong earthquakes in the past hundred years, the activity of the North-South Seismic Belt is related to the strong earthquake activity of the South Asia Seismic Belt elongating from Burma to Sumatra, Indonesia. Strong earthquakes along the former belt often occur several months or years after the quakes on the later belt. The above-mentioned migration characteristic of strong earthquakes is likely caused by the northward collision and subduction of the India Plate as well as coaction between the Qinghai-Tibet Plateau and the stable and hard Ordos and Alashan Massif at the northeastern margin of the Plateau. The South-to-North migration of strong earthquakes with different time intervals and different migrating rates may directly reflect the uneven, irregular pushing of the northeastern corner of the India plate, and the gradually northward transmitting and expanding of the related stress as it accumulates and strengthens. While the North-to-South migration of strong earthquakes with long time intervals and uniform rate may relate to the movement of the further deeper materials, or to the interaction between the strongly-deformed Qinghai-Tibet Plateau and the northern hard massif. Perhaps it results from the successive, north-to-south, lateral-slipping and rotational-twisting movement of the strip massifs constituting the Qinghai-Tibet Plateau. As for the phenomenon that strong earthquake clusters occur constantly in a certain time on the North-South Seismic Belt, it may imply that the deformation induced by India Plate indenting strongly into Eurasia continent on the eastern margin of the Qinghai-Tibet Plateau has been strengthened. And the clustering of strong earthquakes on North-South Seismic Belt and South Asia Seismic Belt also confirms that the northern collision zone and the eastern subduction zone of India Plate, as a whole, have impact on the activity of the earthquakes on the Chinese North-South Seismic Belt and Burma, Andaman till Sumatra.

A PRELIMINARY STUDY ON THE CHANGES OF THE REGIONAL SCALE MACROSCOPIC VULNERABILITY TO EARTHQUAKE DISASTERS OF BEIJING,TIANJIN AND TANGSHAN AREA——SPATIAL CHANGES

SU Gui-wu, ZHU Lin, MA Zong-jin, WU Qiong

2007, 29(1):  15-33. 

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Based on exploring and clarifying the conceptual implications,analytical hierarchies and the descriptive aspects of Regional Scale Macroscopic Vulnerability to Earthquake Disasters(RSMVED),and taking Beijing,Tianjin and Tangshan area and its relevant situations in 2000 as example,an index system composed of 25 individual indexes for describing and assessing the RSMVED of the studied area has been set up first in this paper.Then,according to this index system and mainly with the help of Principal Component Analysis method,the spatial change characteristics and regularities of RSMVED of the studied area have been generalized preliminarily but quantitatively and comprehensively.The result shows that,in the researched area,there are 6 main vulnerability patterns controlling the spatial change behaviors of its RSMVED,and the regional differences in style,extent and driving force manifested by these patterns are quite different.Further analysis presents that it is the urban spots of each large and middle-sized cities like Beijing,Tianjin,Tangshan,Qinhuangdao and Chengde,etc that are the most vulnerable with their RSMVED level much higher than the average of the whole studied area.The areas whose RSMVED level is apparently lower than the area's average mainly concentrate in the suburb counties of both Beijing and Tianjin municipalities.Except for these urban spots and such suburb counties,the vulnerability status of other parts of the studied area nearly all fluctuates slightly around the area's average vulnerable level by some small amplitude.

QUANTITATIVE STUDY ON THE LARGE SCALE DEXTRAL STRIKE-SLIP OFFSET IN THE SOUTHERN SEGMENT OF THE RED RIVER FAULT SINCE MIOCENE

XIANG Hong-fa, GUO Shun-min, ZHANG Wan-xia, HAN Zhu-jun, ZHANG Bing-liang, WAN Jing-lin, DONG Xing-quan, CHEN Li-chun

2007, 29(1):  34-50. 

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The Zhonggu Fault,located in the Yuanjiang-Yuanyang basin and active strike-slip fault since Neogene,is part of the southern segment of the Red River Fault.Its neotectonic movement resulted in the separation of the Red River basin(a Miocene basin)into two sub-basins and a dextral slip extending to the Guotoushan-Damanmi region.The concomitant mountain frontal fault,which was the dominant fault in Oligocene,is of normal faulting.Its activity resulted in the accumulation of red continental clastic sediments in the eastern and northeastern Yuanyang.The mountain frontal normal fault extended to the northwest of Honghe County and formed the deposition of conglomerate in early Miocene.Along the Zhonggu Fault,which offset Miocene sediments with high angles,the geological features,including the compressive fold with axis trending NE,the compressional deformation landforms,the distribution the Miocene to Quaternary sediments migrating from SE to NW successively and their delayed distribution at the northeastern wall of the Zhonggu Fault,all suggest that the southern segment of the Red River fault has been expanding from SE to NW and there has been the dextral strike-slip faulting since Miocene.The geological evidences,such as thick lower-mid Miocene conglomerate deposited in mountain front,the shear deformation involved in Zhonggu Fault which was more intense in Miocene than that in Pliocene,the shear zone of Zhonggu Fault mainly located in lower-mid Miocene sediments,indicate the large scale dextral slip occurring at mid Miocene,and its fission track age is 13.7Ma.The magnitude of dextral offset on the south segment of Red River Fault since Miocene was calculated by multiple means,e.g.the horizontal dimensions of the offset of Miocene sediment,the length of foreland basin and deformation width relating to the Zhonggu Fault slip,and the relationship between the offset and width of fault,with the result ranging from 62～69km(the mean is 65km).The data also suggest that dextral slip of the Red River fault experienced the process of transition(N₁),initial dextral slip(N₁²),large scale dextral slip(N₁³—N₂¹),and dextral slip propagation(N₂²—Q_p¹)phases.The related activity of the Red River fault altered between shear slip and extensional slip.

TEXTUAL RESEARCH ON THE TIANSHUI M 7 EARTHQUAKE IN 734 AD AND ANALYSIS OF ITS CAUSATIVE STRUCTURE

LEI Zhong-sheng, YUAN Dao-yang, GE Wei-peng, HE Wen-gui, LIU Xing-wang

2007, 29(1):  51-62. 

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Tianshui area locates at the northeastern margin of Qinghai-Tibetan plateau and the middle segment of the north margin of western Qinling tectonic zone.In history,several strong destructive earthquakes happened in the area.Because of the very long history and that the historical records are not quite clear,it is very difficult to study them in nowadays,and most of them became historical knotty problems.The Tianshui earthquake in 734 AD is one of the large earthquakes.On March 23,734 AD,a large earthquake happened in Qinzhou of Tang Dynasty,now the vicinity of Tianshui City,causing serious seismic disasters as "the earth ruptured and closed again,nearly all the houses damaged,about 4000 people dead,hills changed into valleys,and towns covered by landslip,and so on".According to the detail textual research of the historical earthquake records,the meizoseismal area of the 734 AD Tianshui earthquake is in the Qinzhou and Maiji area,now,the Qincheng,Beidao and Maijishan area of Tianshui City.The epicenter intensity is about Ⅹ,the magnitude is about M 7 1/2.The direction of long axis of isoseismal line is NW,consistent with the strike of the eastern segment of Wushan-Gangu Fault of the northern margin of western Qinling active fault zone.The meizoseismal area is just in the step-over zone between the left-lateral strike-slip faults,i.e.the Tianshui-Baoji Fault and the Gangu-Wushan Fault,an area prone to strong earthquake.Comprehensive analysis indicates that the causative structure of the 734 M 7 1/2 Tianshui earthquake is the east segment of the Gangu-Wushan Fault of the northern margin of western Qinling active fault zone.

THE INTENSITY AND EPICENTER OF THE 2004 M_S 5.6 DUNG CO EARTHQUAKE AND THE RELATION WITH ACTIVE FAULTING IN CENTRAL TIBET

WU Zhong-hai, WU Zhen-han, HU Dao-gong, PENG Hua, YE Pei-sheng

2007, 29(1):  63-76. 

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The M_S 5.6 earthquake occurred in Amdo county of central Tibet on March 7,2004.The epicenter is 31.68°N,91.31°E and 31.64°N,91.24°E from CENC(China Earthquake Netwosks Center)and NEIC(National Earthquake Information Center of America)respectively(Fig.1).It is the maximum magnitude earthquake near Golmud-Lhasa railway after the 2001 M_S 8.1 Kunlun earthquake.Based on field intensity susveying,the iso-seismal contours map of the earthquake was drawn.The map shows that iso-seismal lines for the earthquake are NNE-trending and the area of the same intensity is larger to north and west than to south and east(Fig.2).Its maximum intensity is Ⅶ and lies between Gongbatang and Jianong at the east of Dung Co Lake(Photo 1,2),so this earthquake is called the 2004 M_S 5.6 Dung Co earthquake.The intensity survey results suggest that the macroscopic epicenter is 31.70°N,91.26°E,which approximately coincides with the epicenter located based on instrument monitoring.The distribution of intensity indicates the earthquake probably results from faulting of NNE-trending fault zone along the eastern margin of the Dung Co basin.The results of active faults survey confirm that the fault zone controlling the earthquake is a main boundary normal fault zone of the Dung Co basin and called the eastern boundary fault zone of the NNE-trending Dung Co basin,which is a half graben about 10～15km wide and 40km long,connecting with the NNE-trending Peng Co basin to the south and adjacent to the NE-trending Tsona-Amdo graben to the north.The boundary fault zone of Dung Co graben is NNE-trending,about 40km long and composed of three minor normal faults,all dipping to west and forming a right-stepped en echelon array indicating the left lateral strike-slip component of the fault zone(Fig.3).Surface observation along the faults shows that the fault underwent prominent normal faulting during late Quaternary.The severe faulting is expressed by the prominent northwest facing triangular facets along mountain front and multiple generations of fault scarps in late Quaternary sediments(Photo 5～7).The results of in-suit measurement with level instrument and tape show that there are three sets of fluvial terrace surfaces and a piedmont slope that were vertically offset by 1～1.2m(terrace 0～1 and 0～2),2～3m(terrace 1)and 13～19m(or piedmont slope)along the northern segment of the fault zone,respectively;and there are three sets of fluvial terrace surfaces which were vertically offset by 0.5～0.7m(terrace 1),2～3m(terrace 2)and 12～15m(terrace 3)along the central segment of the fault zone,respectively.The offset of terraces all took place during late Pleistocene and Holocene,implying that the normal faulting has continued and the average rate of vertical displacement is estimated as 0.2±0.1mm/a and about 0.06mm/a on the northern and central segment respectively since late Pleistocene based on the relationship between the terraces evolution and climate change during late Quaternary and comparing the distributions of similar terraces in the adjacent areas of Dung Co.Along the northern segment of fault zone,a ～6km long surface rupture,which offset the terrace 0～1 and terrace 0～2 of late Holocene,was discovered,indicating the latest paleo-earthquake event since late Holocene.The vertical displacement is 1.0～1.2m across the surface rupture,which represents the minimum offset during the last paleo-earthquake event on the northern segment(Photo 6).In space,the central segment of the eastern margin fault zone of Dung Co graben coincides with the maximum intensity area of the 2004 M_S 5.6 Dung Co earthquake.It indicates that the earthquake results from the normal faulting along the central section of the fault zone.The results of field survey are in agreement with the fault plane solution from CENC,but are inconsistent with the focal mechanism solution from HRV.It suggests the results from CENC are reasonable for explaining the 2004 M_S 5.6 Dung Co earthquake.Studies on regional tectonics and distribution features of earthquake suggest that the NNE-trending Peng Co basin,Dung Co graben,and Amdo-Tsona basin make up apparently of a regular left-lateral en echelon distributed rift system trending N35°～45°E from south to north,about 120 long(Fig.1).This rift zone constitutes a NNE-trending seismic zone called Dung Co-Amdo earthquake zone.The magnitude of late Quaternary faulting varies remarkably along different segments of Dung Co-Amdo seismic zone.Based on field survey,the vertical slip rates on the northern segment of Dung Co fault zone and the western segment of northern boundary fault zone of Amdo-Tsona graben are much faster than that of the central-southern segment of Dung Co fault and eastern segment of Amdo-Tsona northern boundary fault,and there are records about paleo-earthquakes of late Holocene along the two fault segments,but recent earthquakes(M_S≥3)since 1971 are almost distributed around the central-southern segment of Dung Co basin and eastern segment of Amdo-Tsona graben.The prominent differences indicate that the southern segment of Dung Co fault zone and the eastern segment of northern boundary fault zone of Amdo-Tsona graben are the sites where future earthquake will possibly occur because the strain accumulating time is longer at these areas.

THE RESEARCH ON REGIONAL CHARACTERISTICS OF TECTONIC STRESS FIELD IN JIASHI,XINJIANG AND ITS SURROUNDING AREAS

GAO Guo-ying, WANG Hai-tao, NIE Xiao-hong, LONG Hai-ying

2007, 29(1):  77-87. 

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Jiashi and its surrounding areas are composed of many structural zones.Using the focal mechanism solutions of 59 mid-strong earthquakes in Jiashi and its surrounding areas,and combining with the calculation result of system cluster and stress field inversion,we analyzed the evolvement characteristics of the stress field for the different times and the different regions.The result shows as follows:The earthquakes in Jiashi are mainly of strike-slip.However,those of Kalpin block are mainly of reverse events,showing an obvious thrusting.The regional characteristics are different from other areas.The direction of the regional principal stress field is near NS.However,under the different tectonic background,the directions of stress fields are different.The direction of the principal compression stress is near NS in Kashi-Wuqia area.But before and after the 3 earthquakes with M 7,the dynamic evolution from NW to NS and then to NE with time process was observed.Kalpin block has been dominated by the consistent stress field of the NW direction for a long time.However,the direction of the stress field of Jiashi region is NE.From 1996,the direction of the regional stress field has changed obviously.The direction of the P axis was deflected towards NE,and the elevation angle increased.The result shows clearly the regional characteristic and variation of distribution pattern of stress field in different tectonic environments.

PREDICTION OF SAND BODY WITH THE CORRELATION ANALYSIS OF HIGHER-ORDER CUMULANTS OF SEISMIC DATA

GAO Yun, SONG Wei-qi, LIU Shi-you, YANG Kai

2007, 29(1):  88-94. 

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The relationship of superposed formations in Es4 in the west of Dongying Sag is complex,the physical property varies acutely in both vertical and lateral directions,and the divergence of reflection feature is small,thus posing difficulties in discriminating sand body,especially its borders.In view of the foregoing problem and based on the theories and techniques relating to wavelet multi-scale analysis and higher-order statistics for seismic signals,the paper carries on the transformation of the seismic records using higher-order cumulants first,then the results are decomposed to multi-scales.To insure the reliability of the correlation analysis,proper multiscale seismic envelop results have been incorporated in the correlation analysis.The algorithm has been verified by theoretical modeling and actual data,especially in the aspect of capability of practical problem solving,for example,the originally obscure or weak seismic signals can be distinguished clearly after the processing using this method.As a result,the originally unrecognizable sand body and its borders become explicit.

STUDY ON MULTI-STATION SEISMIC VELOCITY RATIOS IN SHANDONG AREA

ZHANG Xue-min, ZHANG Tian-zhong, LI Yong-hong, LI Xia, DIAO Gui-ling

2007, 29(1):  95-104. 

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Starting with the method and theory of multistation velocity ratio calculation,we thoroughly analyzed the differences between velocity ratios calculated by different formulae.Through mathematic demonstration,it is thought that the basic theory of two systems of calculation methods is coherent,and the discrepancy of velocity ratios mainly results from the selection of independent variable.In view of the effects of different seismographs with different periods at different stations,t_s-p is selected as independent variable in this paper.Based on the data of P and S wave travel times of local earthquakes recorded at 52 digital and analog stations located in Shandong Province and northern Jiangsu from Jan 2002 to Jul 2005,seismic events recorded at more than 4 stations are collected before calculation.The results show that,the average velocity ratio of whole area is 1.716,which is close to and a little higher than the velocity ratios at other areas in North China.To ensure reflecting the local feature,the studied area is divided into units of 1°×2°,and some far stations relative to epicenters are eliminated.Comparing velocity ratios of different units in the studied area,it is found that the values at 34°～37°,115°～119°are obviously higher than that of other units,which are located nicely at the two sides of Tancheng-Lujiang Fault,and it is supposed to be closely related to underground media properties and deeper focal depth.The main results obtained are as follows:(1)The discrepancy in velocity ratios by two systems of calculation methods is related to the collection of independent variable.In fact,the theory is consistent.So in the future calculation of V_p/V_s,it is reasonable to choose more accurate variation as independent variable;(2)The velocity ratios in Shandong area are a little higher than that in other areas of North China,especially at the middle and southern segments of Tancheng-Lujiang Fault,which should be correlated to the thin deposit layer at surface,distribution of granite and high pressure metamorphic rocks in upper crust at the two sides of the fault,and the averaged crustal effects due to deep focal depths in this area;(3)The residual rms error is closely related with the number of stations.When data is plenteous,we should pick out those seismic events which can not be located accurately and choose those events recorded by much more stations in order to assure the higher precision and credibility of results.

THE RESEARCH ON THE ACQUISITION TECHNOLOGY OF 3-D SEISMIC EXPLORATION IN COAL FIELD IN COMPLICATED MOUNTAINOUS AREA

ZHOU Jun-jie, LI Shi-xiang, JIA Yun-qiao, LIU Hai-xin

2007, 29(1):  105-113. 

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It is difficult to acquire the 3-D seismic exploration data in coal field in the mountainous area due to complex topography and surface geology.The key is to find the appropriate acquisition technology which can be adopted in such areas.This paper mainly analyzes those complicated surface conditions in the course of the 3-D seismic exploration in mountainous Xin'an coal field,where the topography is extremely complicated,the relative height difference is big,the underground water level is fluctuating,and there is big lateral lithologic variation on the surface,and so on.We select the suitable excitation and receiving conditions by matching with the field survey results in the 3-D seismic exploration in coal field in mountains and apply many technical measures,such as the non-linear surveillance systems,to guarantee the quality of the seismic records so as to facilitate the seismic data processing and explanation at the next step.The research findings indicate that the technical methods used in the data gathering of the 3-D seismic exploration are effective,and have yielded good results.These methods are of reference value to the areas with similar surface geological conditions.

THEORY AND METHOD OF INDENTIFYING WELL WATER LEVEL ANOMALIES IN GROUNDWATER OVERDRAFT AREA

ZHANG Su-xin, ZHANG Zi-Guang, REN Xiao-xia, WANG Xiang

2007, 29(1):  114-121. 

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In the many years practice of earthquake analysis and prediction,it has been noticed that the overexploitation of underground water would cause changes in environmental geology,thus having obvious impact on the water level regime.The overexploitation of underground water would lead to continuous drop of groundwater level,change of water quality and dry-up in dynamic water level observation wells.Due to land subsidence,the well pipes would uplift and the observation piping systems would be damaged.These environmental geology problems bring a great deal of difficulties to earthquake anomalies identification from groundwater level.Although a lot of studies have been made on the influence of water pumping on well water level,the results were mainly on the influence of massive water pumping in a short time on the water level of the nearby wells.Since the time of pumping water is short,the hydrogeological environment of aquifer is relatively stable.The characteristic of water level change in groundwater overdraft area is different from the influence of massive short-time water pumping on water level of the nearby wells.Since the water level in the overexploiting area declines year by year,it makes the aquifer dense and consolidated,so consequently,the hydrogeological environment has changed.Basing on the hydrogeological theories and methods,the paper analyzes the relations of hydraulic equilibrium state of water-bearing stratum with the stress-strain condition and the water level regime,then discusses preliminarily the theory and practices of identifying the well water level anomalies in the groundwater overdraft area.The result shows that we can accurately judge the nature of the anomaly according to the diffusion character of water level declining funnel in the well area,the aforementioned theory and method and the multi-years variation pattern obtained from existing data.The results of the research are helpful to the discrimination of influence of the individually centralized water pumping from long-term overexploiting of water on the water level,the correct recognition of water level anomalies in the groundwater overdraft area and the improvement of earthquake prediction level.

CO-SEISMIC WATER LEVEL,TEMPERATURE RESPONSES OF SOME WELLS TO FAR-FIELD STRONG EARTHQUAKES AND THEIR MECHANISMS

CHEN Da-qing, LIU Yao-wei, YANG Xuan-hui, LIU Yong-ming

2007, 29(1):  122-132. 

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The observation of water temperature in deep well has been carried out for more than 20 years in China.However,the study on the mechanism of water temperature co-seismic response is inadequate at present.On December 26,2004,the great earthquake of M_S 8.7 occurred in the northwest offshore of Sumatra,Indonesia.After the shock,most of the observation wells in China recorded the coseismic response of water level and temperature.We studied the co-seismic response characteristics of water level and temperature in 121 wells and found the regular response characteristics.When the water level in a well oscillates,its water temperature will drop at the same time.The process will continue from dozens of minutes to several hours,and the process of the water temperature drop corresponds to the process of the water level oscillation.Once the water level oscillation stops,it restores to the level before the earthquake immediately.But,the water temperature rises at a slow speed and will take several hours to attain its former level.

PRESSURE CALIBRATION FOR THE SOLID MEDIUM VESSEL OF PISTON-CYLINDER APPARATUS UNDER HIGH PRESSURE AND HIGH TEMPERATURE

DANG Jia-xiang, ZHOU Yong-sheng, HE Chang-rong

2007, 29(1):  133-143. 

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Pressure calibration for solid medium vessel under high pressure and high temperature is an important step before apparatus is employed,because precise pressure calibration directly determines the preciseness of measurement of experimental pressure.Sound and effective methods are premises of pressure calibration.Pressure calibration includes confining pressure calibration and axial load calibration.The best way of axial load calibration is to estimate axial friction by multi-cycle of piston-in and piston-out.There are two key points during the test:(1)ensuring the hit-point of piston and sample:The hit-point is determined by an intersection of two beelines,one is the linear fit to the part of load-displacement curve of piston contacting with soft metal,the other is the linear fit to the part of load-displacement curve of sample's elastic deformation;(2)confirming dynamic friction:The dynamic friction which is dependent with displacement is established by the linear fit to the part of load-displacement curve of piston contacting with soft metal.Then,the final axial calibration includes cutting the load-displacement curve before hit-point,and correcting the load-displacement with dynamic friction.The best method for calibrating confining pressure is mineral phase transition,such as quartz-coesite,albite-jadeite + quartz,fayalite + quartz-ferrosilite and farringtonite-Mg₃(PO₄)₂-Ⅱ,because those phase transitions are more stable and the transition equations are widely used in previous calibrating confining pressure.It is proposed that quartz-coesite and albite-jadeite + quartz be used as pressure standards for the piston-cylinder apparatus in the pressure-temperature range of 2.5～3.2GPa,500～1200℃ and 1.6～3.2GPa,600～1200℃.Tests were performed for calibrating the axial friction using 2GPa confining pressure vessel.The sample is gabbro.Two experiments have been performed:(1)a number of cycle-experiments with different piston-rate under 500MPa and 820℃,1000MPa and 900℃,1000MPa and 25℃;(2)under 500MPa and 1000℃,firstly cycle-experiments were conducted,and then piston rate reduced from 2×10^-4mm/s to 5×10^-5mm/s after rock sample's plastic deformation,and the rate dependence of creep observed.The result of the experiment shows that the factors which affect the dynamic friction are confining pressure,temperature and piston rate.Confining pressure is the main factor,dynamic friction increases with the increase of confining pressure.Temperature and piston rate only influence on intercept.Hence,axial calibration should be conducted under specific experimental condition.Finally,axial calibration of an experimental load-displacement curve was conducted.

APPLICATION OF MOGI MODEL AT CHANGBAISHAN TIANCHI VOLCANO

HU Ya-xuan, WANG Qing-liang, CUI Du-xin, WANG Wen-ping, LI Ke, CHEN Hong-wei

2007, 29(1):  144-151. 

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Classical least-squares methods have been used widely.For Mogi model,the product about the partial derivative matrix A is singular when the changing size is small,so damping least-squares method is chosen.The method is introduced at first in the paper.In order to conquer the limitation to vertical deformation,the inversion formula of Mogi model with vertical and horizontal rates is gotten.Before the inversion is run,the initial data of different parameters are given based on other researches.From the scale relation between rates and R,the different initial R can be obtained.Through comparing the inversion results using those different initial R,the proper initial data assumption is chosen.At last,with proper damping least-squares method,the magma source position and changing size are inversed in Changbaishan-Tianchi volcano using four periods of leveling measurements and GPS data during 2002—2005.Here,the regional rates can show the volcano activity well,so the GPS velocity during different periods is calculated based on mean reference(the velocities related to mean site rates).The source parameters are inversed jointly with vertical and horizontal data.The position near to the source is inversed by earthquake data.Considering other analyses at the same time,the following results are gotten:the magma positions change with time,its volume increment becomes smaller after 2003 and the magma activity becomes weaker.

A REVIEW TO ELECTRICAL CONDUCTIVITY OF MANTLE MINERALS

WANG Duo-jun, MA Jin, YANG Xiao-song, ZHOU Ping

2007, 29(1):  152-160. 

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The knowledge of electrical prosperities of mantle minerals can help us to learn the distribution of the electrical conductivity in the interior of the earth and the polarization mechanism of the earth's material.The experimental results of electrical conductivity of mantle minerals were summarized and analyzed.We reviewed several important influential factors on the electrical conductivity of mantle minerals.The conduction mechanism of dry mantle minerals is different to that of wet mantle minerals.There is a small polaron conduction mechanism for dry mantle minerals,however,the conduction mechanism of wet mantel minerals is attributable to free proton.The results of typical electrical conductivity of mantle minerals were plotted and compared,and several electrical conductivity depth models were also introduced.We concluded that the water should play an important role in the electrical conductivity and the conductivity depth models.At last,we also point out the prospects of research in the future.

FRICTION CONSTITUTIVE PARAMETERS OF MAFIC ROCK AND POSSIBILITY OF EARTHQUAKE NUCLEATION IN THE LOWER CRUST

TAN Wen-bin, HE Chang-rong

2007, 29(1):  161-171. 

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Mechanical behaviors of frictional sliding can be described well by rate-and state-dependent friction laws.This paper reviews factors that control sliding stability of crustal rocks,and summarizes as follows:(1)analysis of small perturbation around steady state sliding(linear analysis)shows that an important condition for self-sustained instability to occur is a negative rate dependence of friction(a-b<0).Under such a condition,earthquake slips can nucleate on active faults.(2)Measurement of water content in crustal rocks implies that both "dry" and "wet" conditions in the lower crust are possible,and previous creep experiments show that deformation mechanisms under dry conditions are notionally brittle fracture and faulting.(3)Attention has been paid to gabbro under high pressure and temperature as a number of strong earthquakes were discovered to have occurred in the lower crust.Experiments on dry gabbro indicate that velocity weakening may be the typical sliding behavior with temperature ranging from 420℃ to 615℃.Synthetically considering the relevant conditions such as "dry" condition that may exist in relatively cool interior of continental lower crust,and mafic rock that is not likely to deform by plastic flow under such conditions,we may extrapolate this result to actual tectonic settings where the environments are more complex.This may explain why earthquakes occur in the lower crust in some areas.

TIME SERIES ANALYSIS ON THE RATIO OF PIXELS WITH ABNORMAL BRIGHTNESS TEMPERATURE INCREASING AND ITS VARIATION BEFORE SOME EARTHQUAKES OF M_S≥5 IN TAIWAN AREA

LIU Fang, XIN Hua, REN Yue-xia, ZHANG Tie-bao, LU Qian

2007, 29(1):  172-179. 

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In the study of application of MODIS satellite remote sensing data to earthquake prediction,the paper put forward for the first time a quantificational method for the ratio of the pixels with abnormal brightness temperature(BT)increasing and a preliminary scheme for cloud removal.The principle is that firstly,the cloudless data observed by the same satellite at the same period of time but in different days(usually 1 to 3 days)are mosaiched to get high cloudless rate data,and then the brightness temperature variation curve and mean variance of each pixel are calculated with the data from the covered area to determine daily whether the brightness temperature data of the day is normal or not at certain pixel by using twice of the mean variance as criterion.The ratio of the pixels with abnormal BT increasing can be calculated by dividing the total number of abnormal pixels with the total pixels of the whole area.Analysis on a series of recent earthquakes in Taiwan area shows that the ratio of pixels with abnormal BT increasing,which normally undulates around zero,had a sudden jump 1 to 20 days before the medium-strong earthquakes.It is expected that a new method for identifying earthquake auspice could be found through special studies in regions with frequent seismic activity by analyzing the change of ratio of the pixels with abnormal BT increasing from MODIS satellite remote sensing infrared information on which the effect of cloud has been removed to a certain extent.

THE METHOD TO EXTRACT URBAN BUILDINGS'HEIGHT AND LOCATION FROM SINGLE HIGH RESOLUTION AERIAL IMAGERY

ZHANG Gui-fang, SHAN Xin-jian, YIN Jing-yuan, MA Zhao-song, ZHAO Jun-juan

2007, 29(1):  180-187. 

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With the fast development of city,to acquire and update urban fundamental data is more and more important.After the high-resolution satellite systems were put into operation,people attach more importance to the real-time,precise and authentic aerial imagery.The high-resolution aerial photographs are applied in more and more fields,and detecting buildings information from these photographs will be the important means of acquiring and updating urban fundamental information.Based on the relationship between the buildings shadow and the buildings real height of aerial imagery,the methods to extract the buildings height from their cast shadow are described in this article and the computer technology of detecting automatically buildings information from aerial imagery is realized.Taking the aerial imagery of Baoshan District of Shanghai as example,the autoptical data was compared with the computational data,and the result shows that the high-resolution imaging has a whopping potential of acquiring urban fundamental data.