Table of Content

04 December 2007, Volume 29 Issue 4

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Research paper

ACTIVE FAULT MOVEMENT AND RECENT TECTONIC STRESS FIELD IN YANHUAI BASIN

XIE Fu-Ren, ZHANG Gong-Yan, CUI Xiao-Feng, JING Zhen-Jie, LI Rui-Sha

2007, 29(4):  693-705.  DOI: CNKI:SUN:DZDZ.0.2007-04-000

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Yanhuai Basin contains Yanfan Basin and Huaizhuo Basin,which are connected one another.According to field seismo-geological investigation and fault slip observation,the active faults in northeast direction in Yanfan Basin are mainly dextral strike-slip,with some cases of normal fault.But in Huaizhuo Basin,the situation is opposite,the active faults in northeast direction are mainly normal faults,with some cases of strike slip.However,in the whole Yanhuai Basin,the active faults in northwest direction are mo

CROSS-FAULT DEFORMATION OBSERVATION AND CRUSTAL STRESS FIELD IN CAPITAL CIRCLE REGION

ZHANG Gong-Yan, XIE Fu-Ren, JIAO Jing, LI Rui-Sha

2007, 29(4):  706-715.  DOI: CNKI:SUN:DZDZ.0.2007-04-001

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Based on the deformation observation data of 11 cross-fault survey points in the capital circle region and taking the two walls of fault as indeformable rigid block,we analyze the quantitative relation between the relative sliding of fault plane and relative displacement of the sites on the two walls on the ground surface,and then taking the Tangshan earthquake and its aftershocks as time-bound,we divide the fault slip complexor into two time-intervals,fit the regional stress state of the two different time

Brief Report

STUDY OF MODERN FAULT ACTIVITIES IN BEIJING AREA USING BOREHOLE STRAIN OBSERVATIONS

QIU Ze-Hua, TANG Lei, HAN Bao-Xiang, YI Zhi-Gang, JIAO Jing, ZHANG Chao-Fan

2007, 29(4):  716-728.  DOI: CNKI:SUN:DZDZ.0.2007-04-002

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One of the principal goals of studying active faults is to understand the possibility of earthquakes.Contemporary faults activities are most important from this point of view.When a fault slips,the surrounding strain field changes.The linear elastic dislocation theory provides a powerful tool to solve problems associated with strain field changes due to fault slip.In some widely acknowledged studies in fields such as interpreting InSAR pattern of seismic fault slip and analyzing stress transfer or stress t

SEQUENCE STRATIGRAPHY STUDY OF LATE QUATERNARY ACTIVITIES OF NANKOU-SUNHE FAULT IN ITS NORTHERN SEGMENT,BEIJING

ZHANG Shi-min, WANG Dan-dan, LIU Xu-dong, REN Jun-jie, LUO Ming-hui, ZHANG Guo-hong, ZHAO Guo-cun, WANG Rui, ZHANG Ying-li

2007, 29(4):  729-743. 

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In water area,shallow groundwater area and plains with thick Quaternary sediments,drilling is necessary for active fault survey.Due to complex facies change of Quaternary terrestrial formation,there is no mature scheme for the key problems such as borehole arrangement,decision and correlation of isochron surfaces and deciphering of episodic activity of fault.A test of drillhole exploration was implemented across the northern segment of Nankou-Sunhe Fault buried under Beijing plain.Based on the data of shallow seismic investigation,we drilled a row of boreholes.A combined borehole section was built by sequence stratigraphy,lithology and facies analysis,magnetic susceptibility and absolute chronology,which can define the location,geometry and accumulated displacements in several time spans.The result shows that the fault has an episodic movement since 60ka BP.The active stages of the fault are 60ka to 47ka BP,36ka to 28ka BP,and 16ka to present,respectively.Other intervals are relatively stable.The average vertical slip rate is 0.35mm/a from 60 ka to 37ka BP,0mm/a from 37ka to 32ka BP,0.78mm/a from 32ka to 12ka BP,and 0.35mm/a since 12ka BP.Stratigraphic cyclicity is the main issue of sequence stratigraphy.The cyclicity is of multilevel character.Controlled by climate fluctuations,tectonic movements and matter source factors,each sequence has a specialty itself as effective index to the correlation of borehole strata.Correlation of borehole strata from big to small sequence in turn can effectively reduce the blindness and the uncertainty.Hiatus of sediment strata of low base level such as low-water-level system territory and transgression territory on uplifted side indicates existence of fault scarp and active stage of fault slip.Along with the rise and later fall of base level,together with the attenuation of fault activity,high-water-level system territory and regression system territory may deposit on the uplifted side.Contrarily,homo sequence on both sides indicates weak activity of fault.Magnetic susceptibility reflects well the size difference of terrestrial formation and its vertical fluctuation corresponds well with sequence cyclicity.United application of sequence stratigraphy,lithology and facies analysis,magnetic susceptibility and age dating can achieve high-precision correlation of strata across boreholes.Since the late Quaternary shows distinct climate fluctuation of millenary scale,the substitute index of climate has a potential in high-precision correlation of strata.The borehole correlation of thick stratigraphic succession with a distance of 20～40m is easy in alluvial plains away from the affected zone of fault action.Whereas within rupture zone of fault,the correlation of strata thinner than 1m with a distance no more than 5m is usually difficult if there are no evident horizon markers,although such correlation is necessary for deciphering single surface rupture event.Some fault-scarp-derived colluvial wedges with a width less than the distance of neighbour holes may be missed.Therefore once the fault zone is limited within a bound less than 20m,hole distance less than 2～3m is necessary for probing single event.For the limit of borehole distance and the precision of stratigraphic subdivision,the correlation of borehole strata by sequence stratigraphy cannot reach sub-meter precision,and therefore can only decipher active and quiet stages of fault,but not single surface rupture event.An active stage may include several single surface rupture events.

STUDY ON HOLOCENE PALEOEARTHQUAKE IN XIZHANG TRENCH ON THE JIAOCHENG FAULT ZONE,SHANXI PROVINCE

XIE Xin-sheng, ZHAO Jin-quan, JIANG Wa-li, AN Wei-ping, LI Zi-hong, ZHANG Da-wei, CHENG Xin-yuan, GAO Shu-yi, WANG Chun-he, SUN Chang-bin, YAN Cheng-guo

2007, 29(4):  744-755. 

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Xizhang trench is located at 10 kilometers northwest of the Taiyuan City,Shanxi Province,and it was excavated at the front of a NNW-trending scarp of 4.6m height on the northern segment of the Jiaocheng Fault zone.The dimensions of the trench are 108m in length,8m in width,and 10m in depth.There are 18 strata revealed in the trench.The upper stratum is sandy loam;the upper stratum of the downthrown block of the fault is gravel,the lower stratum is interbed of brown loam and sandy loam.The strata on the upthrown block of the fault are sandy loam containing gravel.The trench shows 3 fault planes,and the upper fault point on the fault plane is 1.5m deep from the ground surface,the newest dislocated stratum is(3.74±0.06)ka BP.The trench reveals a lot of deformation traces,such as fault plane,dislocated strata,colluvial wedge and the dipping of formation.The relation between the strata and the faults in the trench shows that 3 paleoearthquake events have occurred at the Jiaocheng Fault zone since Early Holocene,they are about(3.74±0.06)～(3.06±0.26)ka BP,(8.35±0.09)～(3.74±0.06)ka BP,and(10.66±0.85)～(8.35±0.09)ka BP,respectively.The average interval of the events is2.6～3.6ka.The minimum coseismic vertical displacements of the 3 events are 3.0m,2.5m,and 3.2m,respectively.The significance of Xizhang trench is that the Jiaocheng Fault used to be active thousands years ago,though there wasn't M≥7 earthquake recorded in historical words.The evidence of newest activities of the Jiaocheng Fault zone during Holocene is important for earthquake safety assessment of Taiyuan City in the future.

STUDY OF LATE QUATERNARY SLIP RATE IN THE MID-SEGMENT OF THE TONGDIAN-WEISHAN FAULT

REN Jun-jie, ZHANG Shi-min, HOU Zhi-hua, LIU Xu-dong

2007, 29(4):  756-764. 

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The Tongdian-Weishan Fault is a branch of the Honghe Fault zone,which is the boundary between the Yangtze block and the Indo-China block.Due to the limited field conditions,the study of late Quaternary Fault activity on the mid-segment of this fault is lacking and presently the time of its newest faulting and the Quaternary slip rate are not clear.Our field investigations along the fault between the areas of Yangbi county and Xierhe river,by quantitative geomorphologic deformation measurement and dating of young terrace deposits,indicate that the mid-segment of the Tongdian-Weishan Fault is a Holocene dextral strike-slip fault with the component of normal slip and its newest faulting occurred at 2.2ka BP.The terrace T₂,incised during mid-late period of late Pleistocene epoch,was offset by the mid-segment of the Tongdian-Weishan Fault and its right-lateral and vertical displacements are 45m and 6m,respectively.The late-Holocene terrace T1 and the alluvial fan were also displaced with the right-lateral and vertical displacement of 12m and 2m,respectively.The strike-slip rate of the mid-segment of the Tongdian-Weishan Fault is 1.25mm/a since mid-late period of late Pleistocene epoch.The vertical rate becomes obviously stronger from 0.17mm/a of 36～2.2ka BP to 0.91mm/a of 2.2ka BP to the present and this tendency is coherent to the character of vertical movement of Northwest Yunnan during the Holocene epoch.The strike-slip rate of the Tongdian-Weishan Fault is only a quarter of the rate of the Zhongdian Fault and Honghe Fault.It may indicate that the pull-apart basins between the Zhongdian Fault zone and Honghe Fault zone,east of the Tongdian-Weishan Fault,absorbed most of the deformation on the southwestern boundary of Sichuan-Yunnan rhombus block,and the Tongdian-Weishan Fault and its pull-apart basins are tributary to this deformation process.This study on the mid-segment of the Tongdian-Weishan Fault will be beneficial not only to provide the elementary data for seismic hazard assessment of this fault,but also to understand the spatial characteristics of distribution of tectonic deformation on the southwestern boundary of Sichuan-Yunnan rhombus block.

ACTIVE FAULT SEGMENTATION AND THE IDENTIFICATION OF POTENTIAL SEISMIC ZONES ALONG THE DAQINGSHAN PIEDMONT FAULT

HE Zhong-tai, MA Bao-qi, LU Hai-feng

2007, 29(4):  765-775. 

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Identification of potential seismic zone follows the earthquake structure analogy and seismic activity repetition principles at present.Active fault segmentation is an important aspect and should be considered when identifying potential seismic zones.There are three different segmentation plans along Daqingshan piedmont fault,Inner Mongolia.This article compares and analyses the segmentations and then gets a new potential seismic zone identification plan along Daqingshan piedmont fault.Identification of potential seismic zone includes the range subdivision and the estimation on the maximum earthquake magnitude of potential seismic zones.This article sub-divides the ranges of potential seismic zones according to active fault segmentation plan along the Daqinshan piedmont fault proposed by Ran Yong-kang.Ordos Massif is surrounded by depression zones which have similar earthquake structures and historical earthquake records with magnitude over 8 expect the Hu-Bao depression zone.So,this paper compares Daqingshan piedmont fault with other depression zones around Ordos Massif,especially the Huashan piedmont fault,and gets the conclusion of the maximum earthquake magnitude of Daqingshan potential seismic zones.

PROBABILITY MODEL FOR STRONG EARTHQUAKE RECURRENCE OF ACTIVE FAULTS IN URUMQI

ZHANG Yong-qing, XIE Fu-ren, WANG Feng

2007, 29(4):  776-786. 

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Based on the result of quantitative research on active faults,analysis of regional seismicity,and especially the detailed investigation and systematic summary on paleoearthquake in Urumqi region,the recurrence mode and probability models of Xishan Faults that reflect the seismic,geological and kinemics characteristics are established.The strong earthquake recurrence mode considers the Poisson mode and quasi-period mode and reflects the randomicity and determination with chanciness of seismicity on the fault.The probability model involves two levels of content:analyzing the paleoearthquake data and historical strong earthquake catalog on or near the faults to obtain the mean recurrence interval of surface-rupturing earthquakes(M_S≥6.7),and analyzing the modern instrumental earthquake catalog(1970～present,and the size of these earthquakes is in the range of 2.0～5.0) of potential seismic source zone where the active faults locate.The calculation of seismic hazard probability of active faults utilizes the expert-opinion method to assign different weights to the models such as Poisson model and BPT model,and then incorporate the weighted probability result to construct combined model,which is the core of the method.This data-processing method has two advantages:taking complexity of strong earthquake recurrence mode into consideration and reducing the possibility of overestimating the seismic hazard of active faults.The result shows that the recurrence probability of surface rupturing earthquakes is 4.0% in the coming 100 years,and 3.6% in the coming 50 years.This result is consistent with that of the method based on stress environment analysis.The maximum magnitude of Xishan Faults(belt)is M_S 7.5 estimated from paleoearthquake,dimension and dip-slip rate of fault,which is consistent with the upper limit magnitude of potential seismic source zone where the faults locate.This study integrates the newest research results on regional seismology and geology,better describes the complexity of seismic process along fault to a certain extent,and assesses comprehensively seismic hazards of active faults in Urumqi.This multidisciplinary method can be applied to the region like Urumqi where complete seismogeological data are unavailable.

3D VISUALIZING OF ACTIVE FAULT SURVEYING DATA

ZHAO Shu-xian, LIU Yu-juan

2007, 29(4):  787-795. 

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In the surveying of earthquake active fault,many methods in geology,geophysics,geochemistry,geodetic survey,and remote sensing,have been widely used,resulting in various formats of surveying data and interpretation data.In this paper,we use ESRI ArcGIS 3D Analyst as interactive 3D graphics environment and present a solution for visualizing,interactive perspective viewing,and analyzing of all active fault surveying data and explanation data.

INTERPRETATION OF MULTI-SOURCE RS IMAGES OF ACTIVE FAULT IN THE NORTH OF HAINAN ISLAND

JIANG Wen-liang, ZHANG Jing-fa, GONG Li-xia

2007, 29(4):  796-804. 

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The occurrence of earthquake is related to active structure,so the active structure is key to seismogeological study.For the broad field of vision of RS technology,it can play an important role in macro-active structure study.Furthermore,the ability of multi-temporal,multi-spectral,high-resolution,dynamic monitoring and so on also makes RS a very important tool for geological application.The studies of active fault using RS image were based on optical image before,therefore the study depends considerably on the fieldwork because of the limited information available from image.In the paper,we combine optical image with SAR image and implement image fusion,as a result,we can obtain more information and interpret more features of active fault.The paper puts emphasis on the study of distribution of active fault in Hainan Island utilizing satellite image.First,MSS,TM and SAR images are selected as the basis datum;preprocessing and image enhancements are manipulated for data fusion to highlight more features of geological body and extract more texture,tonal and other structure features to improve the efficiency of RS image greatly.Then the expression of geological physiognomy is analyzed,the symbol for interpretation is established,and each geological body on image is analyzed.At last,the geologic and geomorphic feature of the study area is analyzed generally,and detailed description of development of active fault in the northern area of Hainan Island is presented.After image processing and interpretation,we can conclude that there are mainly three groups of active faults striking EW,NW and NE,respectively in Qiongbei area.The EW-and NW-trending faults have great effect on the geologic and geomorphic development of the region.The image feature of active fault is clear,the phenomena of crustal movement such as linear distributed lake,volcano crater and flexed coastline,exist on the earth surface or near surface.The three groups of faults intersect with each other and have different movement intensities,which make the crust of the study area bitty and the physiognomic feature various.The movement of EW-and NW-trending faults is strong in this area.Along the NW-trending faults between Wangwu-Wenjiao and Puqian-Qinglan faults,the crustal deformation is intense in the Neoid period.Analysis indicates that the EW-and NW-trending active faults are highly active since the Quaternary,which affect significantly the stability of crust of the northern Hainan Island.

STUDIES ON IN-SITU STRESS MEASUREMENT NEAR FAULT IN URUMQI CITY

LI Hong, XIE Fu-ren, LIU Feng-qiu, DONG Jian-ye, SUN Qi-wei

2007, 29(4):  805-812. 

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In-situ stress measurement was carried out near the eastern segment of Wanyaogou Fault,western segment of Yamalike Fault,and middle-eastern segment of Xishan Fault in the urban area of Urumqi.The characteristics of tectonic stress magnitude,direction and distribution were obtained.The borehole HFZK3 is located on the south side of the eastern segment of Wanyaogou Fault,the depth is 62.13m;The borehole HFZK5 is located on the south side of the western segment of Yamalike Fault,and the depth is 30m;The boreholes HFZK9 and HFZK12 are located on the middle and eastern segment of Xishan Fault,and the depth are 34m and 54.5m,separately.According to stress measurement data,the direction of maximum horizontal principal stress is NE-NEE,different with the direction of regional tectonic stress of SN-NNE.This indicates that,effected by fault activity,the stress state near fault is obvious different with the regional tectonic stress field.The activity of fault zone is discussed using stress measurement data.The horizontal stress increases with depth,and its relation with vertical stress is σ_H>σ_h>σ_v.Such stress state is propitious to reverse faulting.The result is consistent with geological study.According to Coulomb friction criteria and taking m=0.6～1.0,the stress state near fault reaches or exceeds the critical value of generating frictional sliding along reverse fault,indicating that the current tectonic activity is reverse faulting.

GRAIN SIZE CHARACTERISTICS OF NORMAL FAULT COLLUVIAL WEDGES AND THEIR ENVIRONMENTAL IMPLICATION

LIU Xu-dong, ZHANG Shi-min

2007, 29(4):  813-825. 

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On the basis of granulometric analysis of samples from colluvial wedge sediments caused by normal fault,the sedimentary environment is discussed.The total of 21 grain samples come from two sections distributed along the northern Xizhoushan Fault.Of the colluvial wedge sediments deposited at the foot of fault scarp,50～70 percents are gravel particles and they are widely distributed.Frequency curves are multi-ridge-shaped.Granular parameters are also calculated,which show a heterogenetic accumulation of colluvial wedge sediments with the main component of gravel particles.Comparison of granulometric analysis of the colluvial wedge samples with that on its upper side suggests that their granulometric quality is closely inter-related.

NEWLY FOUND SURFACE RUPTURE REMAINS OF LARGE HISTORICAL EARTHQUAKES ON AND NEAR THE TRANSITION SEGMENT OF THE ANNINGHE AND ZEMUHE FAULT ZONES,WESTERN SICHUAN,CHINA

WEN Xue-ze, MA Sheng-li, LEI Xing-lin, NISHIZAWA(KUWAHARA) Yasuto, KIGUCHI Tsutomu, CHEN Qu

2007, 29(4):  826-833. 

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This paper briefly reports our newly findings on remains of earthquake surface ruptures along and near the transition segment(between Lizhou and Xichang)of the Anninghe and Zemuhe Fault zones in western Sichuan and analyzes their relations to historically documented large earthquakes.During geological surveys in recent years we find unknown-aged surface ruptures at three sites on and near the transition segment of the Anninghe and Zemuhe Fault zones.Through analyzing both characters of the surface ruptures and their locations in heavily damaged areas of relevant historical earthquakes in the studied region,we distinguish that ruptures at two of the three sites,north of Yangfushan and west of Dapingzi,should be remains of the surface rupture zone of the large 1536 earthquake.The findings of the remains at these two sites suggest not only that the southern portion of the 1536 rupture zone was yielded along the transition segment of the Anninghe and Zemuhe Fault zones,but also that the southernmost end of the 1536 rupture zone would have arrived at or been very close to Xichang.While,ruptures at and near the other site,east of Lijinbao,north of and not far from Xichang,should be remnants of the surface rupture zone of another historical large earthquake occurring in 1850.These remnants further prove that the most northwestern end of the 1850 rupture zone would have arrived somewhere at least several kilometers north of Xichang.It thus can be inferred from the evidence given in this paper that the major fault at and near Xichang was once ruptured by both the 1536 and 1850 earthquakes.Such an inference is compatible with the described phenomena in literal historical records that very heavy destruction and disaster happened in the city of Xichang during both the 1536 and 1850 earthquakes.

PATTERN AND COMBINATION FEATURES OF THE SURFACE RUPTURES OF THE 1125 A.D.LANZHOU M 7 EARTHQUAKE

SONG Fang-min, YUAN Dao-yang, CHEN Gui-hua, GE Wei-peng, CHENG Jian-wu, SU He-jun, LU Bin, HE Wen-gui

2007, 29(4):  834-844. 

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According to the results of 1/10,000 stripped geologic mapping of the northwest segment of the Maxianshan north marginal fault and historical accounts of past events,we discuss in this paper the range of the magistoseismic area,seismogenic fault,pattern and combination feature of the surface ruptures of the 1125 A.D.Lanzhou M7 earthquake.The results show that the magistoseismic area of this earthquake is located in Lanzhou City and its southwest,and the epicenter can be located at the Xianshuigou area.The seismogenic fault of this earthquake is the Xianshuigou-Maquangou sub-segment on the northwest segment of the Maxianshan north marginal fault.This earthquake has produced a surface rupture zone of about 7km long and 300～1000m wide,extending along the seismogenic fault.The surface ruptures consist of earthquake fractures,fault scarps,seismic fissures,seismic landslides,and seismic pits.The surface rupture zone can be sub-divided into 2 sub-segments:the Maidiwan-Xianshuigou sub-segment in the southwest and the Damajiatan-Maquangou sub-segment in the northwest.Among them,the Maidiwan-Xianshuigou sub-segment consists of two parallel surface ruptures,while the Damajiatan-Maquangou sub-segment comprises a single surface rupture.Basing on large scale mapping,it is determined that the left-lateral displacement produced by this event is 2.4～2.5m,and the vertical offset is 0.45～0.92m.Regionally,the Maxianshan north marginal fault is located at the junction of the northern margin of the Qinghai-Xizang plateau and the northern segment of the North-south tectonic belt,which have been strongly active since neotectonic period.A rhombic block confined by major faults of different strikes is developed in this region,and we call it the Gansu-Ningxia rhombic block.The 1125 A.D.Lanzhou M7 earthquake just occurred on the western edge of the rhombic block,i.e.the Wuwei-Zhuanlanghe-Maxianshan Fault zone.The strong uplift and northeastward pushing of the active Qinghai-Xizang block may cause the stress relief on the boundary faults of the Gansu-Ningxia rhombic block,and hence the occurrence of several strong earthquakes.

THE NEWLY-GENERATED NE-TRENDING YELLOW RIVER ESTUARY—NORTHWEST MIAO FAULT ZONE IN SOUTHEASTERN BOHAI BASIN

XU Jie, ZHANG Jin, ZHOU Ben-gang, L? Yue-jun, CHEN Guo-guang, JI Feng-ju, GAO Xiang-lin

2007, 29(4):  845-854. 

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Based on structural data of the Minghuazhen Formation(N₁²—N₂)and base of Quaternary system from Research Center of China Offshore Petroleum Company,there are about 600 faults developed in the region from Yellow River Estuary to the Changxing Island.Among them,nearly 500 faults trend NE-NEE,amounting to 83 percent of the whole fault group.The faults are about 5～20km long,and the longest one is 40～50km.Some of this set of faults result from reactivation of NE—NEE trending Tertiary faults,and the rest are the newly-generated.They form a NE-striking fault zone about 50km wide with right-lateral strike slip component.This fault zone is not controlled by Tertiary faults;it is a newly generated fault zone during Neogene.It proves the former speculation of the existence of the newly-formed Yellow River Estuary-Northwest Miao fault zone.

A PRELIMINARY STUDY ON DATONG FAULT BELT

LI Zhi-min, TIAN Qin-jian, YAO Sheng-hai, LI Wen-qiao, GAO Zhan-wu

2007, 29(4):  855-862. 

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Datong Fault belt is a northwest trending fault in the north of Qinghai-Tibet plateau which controls the boundary of Xining Basin and Datong Basin.It consists of the Maziying-Miaogou(F₁)Fault and the Laoye mountain-Nanmenxia Fault(F₂).There is obvious displacement in vertical direction along the fault belt.The field investigation results show that this belt has long-term activity.There are several meters-long crushed zone and veins along the fault side in the basement rock.In the visible profile of fault,the Cambria system thrusts to the red brick Quaternary gravel,and there are several centimeters-thick fault gouges along the fault side.ESR dating of the fault gouge in the fault profile shows an age of(610?61)ka.The covering deluvial loess is not offset,and the OSL result is(14.6?1.5)ka.So it can be concluded that the fault belt was active in middle Pleistocene but not in later Pleistocene according to the age data and geomorphologic feature.Interior stratum of the Datong Basin is mainly featured with fold with the major axis in northwest direction.According to the relation of fault and fold deformation,Datong Fault is a transversal tear,which is due to uneven compression of the folds in different parts and the NNE-oriented regional compressional stress.It is common among the NE-trending faults in northeastern Qinghai-Tibet plateau.These NE-trending faults aren't large,and most are located in the active plate.They are all nearly vertical to the axis of the folds and compressive basins.

APPLICATION OF THE INSIDE-OUTSIDE TEMPERATURE RELATION ANALYSIS METHOD IN STUDY ON SATELLITE INFRARED ANOMALIES PRIOR TO EARTHQUAKE

CHEN Mei-hua, DENG Zhi-hui, MA Xiao-jing, TAO Jing-ling, WANG Yu

2007, 29(4):  863-872. 

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The Yaoan M_S 6.5 earthquake on Jan.15,2000 and Mani M_S 7.5 earthquake on Nov.8,1997 are taken as cases to study the temporal process of the satellite infrared anomalies on the active faults near the epicenter.The inside-outside temperature relation analysis method(IOTRAM)was used in the middle segment of the Red River Fault.The result shows that the inside temperature is about 0～1.5℃ higher than the outside temperature in the normal periods.But the brightness temperature inside the Red River Fault is 2～3℃ higher than that outside the fault 15 days before the Yaoan M_S 6.5 earthquake on Jan.15,2000.The Mani M_S 7.5 earthquake occurred on Nov.8,1997 in northern Qingzang-Tibetan plateau.Curves of the average brightness temperature in the east section of the Margaichaca fault belt and the difference inside and outside the region of the fault belt in 1996,1997 and 1998 were contrasted.The result shows that temperature difference in Oct.and Nov.in 1997 was2～3℃ higher than that in 1996 and 1998,though the inside temperature in the same term in 1997 was the lowest in the three years because of a heavy snow.It returned to normal after earthquake.IOTRAM was used to study the active faults in Huabei and Chuandian regions where less earthquakes have occurred recently and no infrared anomalies appeared.

ABNORMAL WATER LEVEL RECORDS CAUSED BY INDONESIA LARGE EARTHQUAKES IN YUNNAN AND ITS SIGNIFICANCE

FU Hong, WU Cheng-dong, LIU Qiang, WANG Shi-qin, CHEN Yan

2007, 29(4):  873-882. 

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Two large earthquakes occurred continuously in the sea northwest of Sumatra,Indonesia,on 26 Dec.2004 and 29 Mar.2005.The observation of water level in Yunnan recorded abundant information about the two earthquakes.This paper presents the water level response to the two earthquakes in Yunnan and makes a preliminary analysis.The present digital water level recording may possibly lose some information,so large earthquake caused abnormal change of water level recorded by analog recording is clearer than that by digital recording.The well water level rise or decline caused by the two large earthquakes respectively was centralized in a small tectonic unit divided by large faults in Yunnan,and the change of water level rise or decline is evidently correlated with geological configuration.Water level rise or decline may be correlated with the change of regional stress field,but it wasn't caused by the change in direction of original stress field.The recent tectonic stress field in Yunnan is mainly divided into three areas.The first area is located east of Xiaojiang Fault;the second located in Sichuan-Yunnan Rhomboid Block,west of Xiaojiang Fault,north of Honghe Fault and east of Jinshanjiang fault;and the third located west of Honghe Fault.Water level rise or decline areas caused by Indonesia large earthquakes are not consistent with subareas according to direction of original stress field.The direction of stress field west of Lancangjiang Fault is basically same,but the change of water level caused by Indonesia large earthquake is divided into two sections by Nandinghe Fault,the north rises and the south declines.We think the reason for water level rise or decline is possibly that the seismic wave changes the stress state of the tectonic unit.Abnormal change of water level caused by large earthquake is mainly attributed to well water bearing bed responding to seismic wave.The change is mainly elastic deformation,so the records are mostly water wave-like as seismic wave.Because of difference of hydrogeologic conditions and effect of regional stress field and seismic wave additive stress field,the water bearing bed appeared to be in a stress adjustment stage after earthquake in a block or a fault.So in some wells,changes of water level rise or decline appeared,and the changes are also correlated with geological configuration.The two Indonesia large earthquakes occurred along the Sumatra Fault,its focal mechanism is similar to reverse fault.The shape of recordings of water level response to the two earthquakes in a same well is very similar except amplitude.So we inferred the water level response mode in same well is completely same for earthquake occurring on same fault and its fracture mode is similar,the difference is just that the response amplitude increases with the growth of magnitude.

ANALYSIS ON CHARACTERISTICS OF COSEISMIC RESPONSE OF WATER LEVEL RECORDED IN THREE WELLS IN HAINAN AREA TO THE TWO SUMATRA-ANDEMAN STRONG EARTHQUAKES

LI Zhi-xiong, GU Shen-yi, YUAN Xi-wen, LIU Wei. MING Sui-hua, YANG Guang, GUO Nan

2007, 29(4):  883-893. 

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The characteristics of seismic water-level fluctuations of the two Sumatra-Andeman strong earthquakes with magnitude 8.7 and 8.5 on December 26,2004 and March 29,2005 recorded at Jiaji station,Qionghai,Hainan were analyzed,the features of the infreguent "terrace" changes of the well water-level after the two earthquakes also were analyzed,the mechanism of "terrace" of the well water-level changes has been primarily discussed.Then the digital observation information with high sample ratio of the Sumatra-Andeman strong earthquakes with magnitude 8.7 and 8.5 at Nanbin station,Sanya and Tanniu station,Wenchang was analyzed.The results suggest that the dominant period of the seismic wave of well water-level at the two wells was comparatively accordant,the amplitudes of seismic water-level fluctuations of the same earthquake at the two wells were clearly different,the time duration of seismic water-level fluctuations of different earthquakes at the same well was also clearly different.

APPLICATION OF SEISMIC REFLECTION METHOD TO ADVANCED PREDICTION IN TUNNELING

YAN Xiao-bing, ZHOU Yong-sheng, YANG Xiao-song

2007, 29(4):  894-904. 

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Advanced Prediction is one of the most effective methods to assure the safety in tunneling.The histories and case experiences show that the TSP203(Tunnel Seismic Prediction203)combined with other techniques can meet the requirements of advanced prediction in tunneling and the prediction implementation costs.This paper firstly introduces the principle of the TSP203,and then compares the prediction result with the excavated conditions of the Dayaoshan railway tunnel.As an example,we introduce the prediction method,explain how to use TSP203 in complicated geological conditions.and analyze the main reason about predication errors according to several years'operation experiences in site as well as seismic theory.The method of TSP203 is a kind of mature technology,it is suitable for planar faults with large intersection angle to the axis of tunnel,but not fit for small intersection angle.However because the karsts terrain has the character of complexity,changeability and uncertainty,the predicting accuracy is a little lower in this kind of place.In addition,groundwater prediction is a technological problem in construction of tunnel that has not been solved both at home and abroad.TSP prediction accuracy is also related with operator's practice levels.Finally,some suggestions are given about how to improve data acquisition accuracy and reliability of explaining the reflected objects.Some important items in predication using TSP203 are summarized.

THE EXHALATION CHARACTERISTIC OF Rn AND CO₂ AT THE XIDATAN SEGMENT OF EAST KUNLUN ACTIVE FAULT ZONE

LI Chen-xia, XU Xi-wei, F Perrier, P Richon, CHEN Gui-hua, Y Klinger, J-M Nocquet, C Romieu, ZHANG Xiao-qing, CHANG Zhen-guang

2007, 29(4):  905-909. 

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It's the first time to observe the exhalation flux of soil Rn and CO₂ in Xidatan segment of East Kunlun active fault in September,2006 and first-hand data of the Rn and CO₂ in this fault were obtained.A significant Rn flux,reaching up to 433 mBq·m^-2·s^-1 and the concentration of Rn ranging from 505 up to 2380 Bq·m^-3 was observed in the excavated trench with 2～3 meters deep across the fault.On the surface,the Rn flux ranges from 7 to 28.19mBq·m^-2·s^-1,with the mean value of 14.7 mBq·m^-2·s^-1,similar to the world average.The CO₂ flux on the surface with an average value of 18.9g·m^-2·s^-1also remains similar to regular background values.It shows no systematic spatial variation up to a distance of 1.2 km from the fault and no clear change in the trench.But a high CO₂ flux of 421g·m^-2·s^-1 is observed at phyllite outcrops on a hill 3km north of the fault.A large Rn flux,503 mBq·m^-2·s^-1,is observed at the point where the maximal CO₂ flux is observed.These results indicate the advective pore gas transport from the subsurface to the atmosphere in the vicinity of the East Kunlun active fault zone.