Table of Content

08 June 1994, Volume 16 Issue 2

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Brief Report

NUMERICAL MODELING OF STRESS GENERATION AND TRANSFER CAUSED BY THE JAPANESE SUBDUCTION ZONE

Gao Xianglin, Luo Huanyan, Kazuro Hirahara

1994, 16(2):  97-108. 

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Three-dimensional finite element modeling has been used to study the Japanese subduction zone.Contribution to the state of stress in the overriding and suboucting plate by plate push．slab pull,locked interplate fault and decoupling interplate earthquakes is analysed,respectively,The modeling results show that the push of the oceanic plate is the primary origin of the compressive stress in the trench-island arc region. Only a small portion of this stress transfers into the overriding plate.Creep of the asthenosphere can promote this stress transmission leading to stress increasing of the island arc region.Slab pull caused by density contrast produces both compressional and extensional stress in a diffuse pattern. The locked interplate fault determines the site of stress accumulation which is responsible for great coupling interplate earthquakes.Thrust faulting caused by an interplate earthquake can have evident influence over the regional stress state only to a small extent around the rupture.

SEISMIC SIMULATION:CORRELATION OF RESISTANCE-HOMOGENEOUS FAULT SEGMENT WITH LARGE EAPTHQUAKES

Hong Hanjing

1994, 16(2):  109-114. 

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Acom puter sim ulation system of earthquakes was established with mass-spring model．After a series of testing with various models,distribution of slip resistance in a fault segment wasfound to play an importent part during the fault slip process.Basd on the concept of 'Resistances-Uniformizing',suggested by Wan Shengzhu from rock experiment,the 'Resistanc-homogeneous fault segment' was recommended to describe the fault segment with homogeneous resistance during fault slip．The most important for a large earthquake is not the magnitude of faultstrengh,but the length of a Resistance-homogeneous segment.

STUDY OF THE ACTIVITY OF NANKOU-SUNHE FAULT

Che Zhaohong

1994, 16(2):  115-120. 

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This paper deals with the activity of Nankou-Sunhe fault and its controling on the regionaltectonic activity based on the geodetic data.We think that Nankou-Sunhe fault is active recently,with a tension and counterclockwise rotation in the west of Dongshanqi．This fault acts as a con-trol on the regional tectonic activity in Capital Circle.The Nankou-sunhe fault is a trunk fault,with its activity strengthened recently.The fault and its relation to the generation of earthquakesmust be paid attention.

SEGMENTATION OF ACTIVE FAULT ALONG THE TANCHENG-LUJIANG FAULT ZONE AND EVALUATION OF STRONG EARTHQUAKE RISK

Li Jialing, Chao Hongtai, Cui Zhaowen, Zhao Qingyu

1994, 16(2):  121-126. 

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Based on systematic geologic mapping,we found that the active fault in the Tancheng-Lujiang fault zone is not continuous and can be divided into three independent rupture segments,which are Anqiu segment,Juxian-Tancheng segment and Xinyi-Sihong segment．The geometrical pattern,displacment amount and strong earthquake recurrence interval on these three seg-ments are obviously different．Each segment responds to the maximum rupture length of a strongearthquake.At the separation of the segments,the faults are arranged in left-stepover,where an 8～10km wide local uplift was formed．The local uplifts serve as the barriers between the segments.By analysing the strong earthquake recurrence intervals and the age of the latest activity ofeach segment,we suggest that the Xinyi-Sihong segment is the most dangerous segment in thefuture,the Anqiu segment is the secondary one and the Juxian-Tancheng segment has little possibility to suffer the strong earthquake.

GLOBAL ORIENTATIONAL MIGRATION OF EARTHQUAKES WITH MAGNITUDE M_s≥7³/4

Ma Zongjin, Li Xianzhi

1994, 16(2):  127-136. 

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Based on the analysis of the orientational migration of 184 earthquakes of M_s≥7³/4 orgreater along 6 seismic zones which are of a global scale,we found the phenomenom of global ori-entational migration of earthquakes。Generally the migrations take place from the western to theeastern,with their velocities ranging from 700km/a to 140km/a.The global orientational migration of major earthquakes can be interpreted by various geedynamic processes such as the P waveshaped oscillation propagation of the movement of the upper mantle material from the western tothe eastern caused by intermittent extensional break along the Alantic ridge.It can also be interpreted by eastward propagation of strain wave caused by the sequent SW-NE compression on theEurasia seismic zone from the Africa,Arabia,and India plates；and the NW and NE orientatedoblique compression of the oceanic plate on the both sides of the Pacific ridge.

RESEARCH ON THE RELATIONSHIP BETWEEN MODERN CRUSTAL MOVEMENT AND SEISMIC ACTIVITY IN THE WEIHE FAULT BASIN BY THE ARCHAEOLOGICAL DATA

Yi Xuefa, Shi Yaqin

1994, 16(2):  137-145. 

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Through statistic analysis of a lot of archaeological data,the differential subsidence rate areasin the Weihe fault basin have been divided based on the average buried rates of the top surface ofcautural layers. Furthermore,the relationship between the rate of modern crustal vertical differential movement(3000 to 5000 B.P)and seismic activity has been studied quantitatively by theburied depth,thickness and distance form the present surface of the cultural layers. Finally,anestimation of seismic risk for coming tens of years for the Weihe fault basin has been done. It issuggested that there exists a possibility of earthquake with magnitude of 5 occurring in the coming 20 to 30 years in this region only.

LATE QUATERNARY DISPLACEMENT AND SLIP RATE OF ZEMUHE FAULT IN SICHUAN, CHINA

Ren Jinwei

1994, 16(2):  146-146. 

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TECTONIC EARTHQUAKE BELTS IN THE BORDERING LAND OF NINGXIA NEI MONGOL AND SEISMICITICS

Meng Guangkui, Dong Weiguo

1994, 16(2):  147-154. 

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Based on the distribution of active falt and recent earthquake centre,the bordering land ofNingxia and Nei Mongol can be divided into 8 tectonic earthquake belts,and the characteristicsof the earthquake energy which has be released since 1970 as well as of the temperal-spatial distrbution is studied for 8 tectonic earthquake belts.The energy release indicates that the borderingland of Ningxia and Nei Mongol will be in an active peridof earthquake within several years.Authors have forecasted the causative sites for potential mederate－strong earthquake occurring inthis region in view of the earthquake prediction.

THE RESEARCH OF THE PALEOSEISMIC TRACES ON THE SOUTHERN SEGMENT OF THE ERTAI ACTIVE FAUIT AND THE CRACK EXTENDING SOUTH

Xiang Zhiyong, Bai Meixiang

1994, 16(2):  155-159. 

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There are abundant paleoseismic traces along thesouthern segment of the Ertai active fault ,which may be representative of two or three events occurring in the Holocene time that causedsome large-scale surface cracks. The traces can be found more in the north and less in the south,and older in the north,and younger in the south,which is in agreement with the characteristicsof the Ertai faults,suggesting a regular southward propogation of the fault.

THE ACTIVE FAULT IN SHANGHAI OVERBURDEN AREA

Oin Dazheng

1994, 16(2):  160-166. 

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The paper contains two parts：(1)In the research of the Quarternary active fault in theoverburden area in Shanghai,the author discussed and combined the research methed of geophysical(electromagnetic frequency sounding and shallow seismic exploration)and geochemical(fission track and Rn,Hg,As,Sb,Bi,B)approaches because of the thick overlying strata(maximun thickness 480m,average thickness 240m)and has gained satisfactory results.Themethed is valid for researching Quarternary active fault in the study area.(2)The existence ofthe Quarternary active fault in Shanghai overburden area is confirmed for the first time. Thetime these faults underwent the activity is Early Pleistocene.The basic characteristics and the activity of the Quarternary active faults has been discussed as well.

STUDY OF FAULT GOUGE DATING USING TL TECHNIQUE

Ji Fengju, Ma Shengli

1994, 16(2):  167-175. 

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The key to the question about fault gouge dating by TL technique is whether the temperature and pressure effect caused by faulting can lead the origional TL to“zoro”for some minerals.For this purpose,we have made the simulated experiments under different temperature,pressureand strain rate which can lead TL intensity of quartz in fault zone to decrease.The results showthat the frictional heating by dislocation of fault walls during faulting is a main factor leading thequartz TL to decrease on the fault plane and that increment of temperature is closely related withthe value of shear stress,gouge thickness and displacements,and it is confirmed by the measurements of fault gouge on the plane.According to above reseach,the time of activity has been dated along F₇ fault at Xiaowan,Yunnan province.

PRELIMINARY STUDY OF THE TRENCHES AT THE GERAKAROU STTE IN NORTHEAST THESSALONIKI, GREECE

Cheng Shaoping, Fang Zhongjing, S B Pavlides, A A Chatzipetros

1994, 16(2):  176-178. 

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STUDY OF THE INDEX OF ANOMALOUS WATER LEVELS IN THE TAYAN WELL, BEIJING WITH RESPECT TO THE SHORT-TERM PREDICTION OF EARTHQUAKES

Zheng Dawei, Tian Zhujun, Zhu Qingzhong

1994, 16(2):  179-187. 

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A series of processing of the data obtained from the hourly-measured water levels as well asthe data of the atmosphere-pressure and the earth tide was made. The triangular-pressure fittingwas used to rule out the effect of the annual perieds.Following taking both the factors of the atmosphere-pressure related water levels and the remaining errors of the mean square errors of thewater level rasiduals as an index for the short-term prediction of earthquakes, it has been improved to refine the precursory anomalies of the water level．The concept of“entrophy”has beenadopted to make a relativety objective evaluation of these parameters under question.The effective precusory anomalies may be up to 0．65 and 0. 59,suggesting it is better representative of theprecusory infomation of earthquakes.

THE PRELIMINARY RESULT OF THE MAGNETOTELLURIC METHOD TO THE PREDICTION OF THE SHORT-TERM EARTHQUAKE

Shi Shulin

1994, 16(2):  188-191. 

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