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1.
3-D rheological structure is mainly the spatial distribution of lithospheric strength or viscos-ity, its strength and viscosity are indispensable parameters in quantitative study of the lithosphere deformation. Plate tectonics theory initially divided the… 相似文献
2.
Based on fracture mechanics, large amount of practically observed data is analyzed in this paper, and it is disclosed that
seismically-anomalous earthquake resistivity sudden change sequence can be observed at the earth resistivity stations around
the epicenter of a strong event. The maximum sudden change in the sequence tends to shift backward with the increase of epicentral
distance, while it shifts forward with the increase of the magnitude of the earthquake. The maximum sudden change also expands
from the epicenter to the peripheral areas. Therefore, the authors propose that it might be possible to predict the 3 key
elements of a forthcoming earthquake by using the sudden change sequence, the frequency of the sudden change, the expansion
velocity of the maximum sudden change and the time-distance product.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 176–185, 1993. 相似文献
3.
Coseismic water level oscillation and correlated deep water temperature changes have been observed in a water well at Tangshan City by high sensitivity measurement. Amount of water temperature changes depend on ampli-tude of water level oscillation. Coseismic water temperatures always decrease as water level oscillates, drop of temperature ranges from 0.001 °C to 0.01 °C corresponding to amplitude of water level oscillation from several centimeters to about one meter. Temperatures usually recover one to several hours after the oscillation. We suggest that the temperature drop is produced by dispersive transfer of heat as the water oscillates, and follow-up thermal conduction makes temperature recovery. Our finite element calculations support quantitatively the idea. High ac-curacy measurements of water temperature at different depths in the future may test our interpretation. 相似文献
4.
Xinling Qin L. B. Pedersen Yulin Zhao Ping Zhang Fuye Qian Wei Qian Zhengnan Li Jingxian Du 《地震学报(英文版)》1992,5(2):355-365
It is shown by the result of digital magnetotelluric soundings in the Tangshan seismic area and its surrounding regions that
the crust under the surface conductive sediments is divided into two layers,i. e., the resistive upper crust and the conductive
lower crust. The upper crust wherein the Tangshan main shock and most of the aftershocks occurred is a convex lens-like body
which is cut by faults at the east, south and west sides. The focus of the mainshock was located at the position of maximum
thickness of the resistive upper crust while the spatial variation of Curie point isothermal surface and the deepest limit
of the depths of aftershocks coincide with the downward depression of the bottom of the resistive upper crust. Thus, the Tangshan
main shock and most of its aftershocks were related closely to the resistive upper crust from the view points of either vertical
layering or lateral variations. And there were only a very few aftershocks in the conductive lower crust. The mechanical property
of the rocks transforms from being brittle in the upper crust into ductile in the lower crust mainly due to the combination
of different factors, e.g., increase of confining pressure, change in minerals, rise in temperature as well as stabilization
of slips by high pore—pressure. A small amount of water and a rise in temperature may lead to a decrease of the electric resistivity
within the rock while a change in the static pressure and mineral content within the rock causes very little change in the
electric resistivity. Thus it is deduced that a resistive upper crust and a more conductive lower crust from the view points
of either vertical or lateral variations are related to the brittle and ductile properties respectively. Hence it is possible
that there is a relationship between the electric structure of the crust and zones of potential seismic hazard.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 354–363, 1991.
The project is supported by the Chinese Joint Seismological Science Foundation, and the Swedish International Development
Authority. 相似文献
5.
In this paper, the three-dimensional thermal structure and the two-dimensional thermal stress caused by the horizontal inhomogeneity
of the thermal structure in the crust of the Bohai Sea and its surroundings were analyzed using the geothermal and the crust
structural data by means of the finite element method. As resulted, the horizontal distribution of the temperature in the
upper crust is obviously different from that in the lower crust in most part of the region. But the horizontal distribution
of the heat flow is constant in the crust. There is a belt where the thermal structure of the crust is intensely changed around
Tangshan. There are some different characteristics of the thermal stress of the crust around Tangshan, in the North-China
plain, in the Bohai Sea gulf, and in the middle part of the Bohai Sea. Utilizing those results, the distribution features
of the seismic activity in the region were explained in this paper.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 29–35, 1992.
This project is supported by the Chinese Joint Seismological Science Foundation. 相似文献
6.
Rheological properties of the crust and upper mantle are essential data that are needed in modelling the mechanical behaviour of the shallow part of the earth. The importance of such data has been seen in discussions about the strength profile of continen… 相似文献
7.
Using the techniques of seismic tomography three-dimensional velocity images at crust and upper mantle in Yunnan province
and its adjacent region have been successfully reconstructed. The results of image are: (1) The image of the velocity in the
upper crust is closely related to the well-known geological structure of the surface, the Kangdian earth axis is a distinct
high velocity area, and a high velocity rock stratum, which appoaching the surface of the earth, has been formed. (2) There
is a low-velocity layer between 26°–31°N and 100°–104°E in deep crust, the depth of Moho discontinuity in Sichuan bass in
is less than 50 km. (3) The results of seismological tomography not only reveal the lateral heterogeneity in the researched
region, but also find approximately the strike of Honghe fault from the image at bottom of crust, and the velocity in both
side of the fault are different obviously. (4) There is a low-velocity column within 25 km to 110 km in Tengchong region,
which may be occured by upward moving of the basalt in the mantle. (5) In studied area, the thickness of the crust in west
part is thicker than in southeast part. (6) From the image at bottom of the crust we can find that earthquakes with magnitude
greater than 5 occurred in big velocity gradient zones, especially in transition zone between high and low velocity. There
are a few earthquake in the low-velocity area. (7) We can see from Figure 6 that there still clearly exists lateral heterogeneity
at 450 depth.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 61–67, 1993. 相似文献
8.
This paper has made a study of the relationship between the phases of seismic activities from 1966 to 1976 in the region of
the North China Block and the temporal and spatial evolution of temperature anomalies from February 1960 to January 1979 of
the greater North China. The main conclusions are: (1) The temperature variation from February 1960 (rise) to January 1977
(drop) and the temperature rises of September 1975 and February 1976 are connected with the beginning and conclusion of phases
of seismic activity. (2) The relation between the time-duration and the extent of temperature anomaly and that between these
two parameters and the energy released by an earthquake have high credibility. (3) If the time period of 16.5 years between
February 1960 and July 28, 1976, the occurrence time of the the great Tangshan earthquake, is divided into 18 time intervals
according to 0.618N, the earthquakes in this phase of seismic activity and temperature rises fall just into the same intervals.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 76–82, 1993. 相似文献
9.
This paper describes synthetically the seismic activity, deep and shallow structures and rock dynamic features in and near
Chaoyang—Yixian region. It is supposed that there is a low velocity layer in middle crust and the three-layered crustal velocities
are all lower than that in both sides of the region. There exists uplifts of upper mantle and asthenosphere-low resistance
layer. It is also studied the composition of matter of three-layered crust, low velocity layer, upper mantle and asthenosphere.
In the end the direct relations between the deep and shallow structure, composition and the seismic activity and new activities
of faults in this region are discussed.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 180–186, 1992. 相似文献
10.
A lot of researches onb value have been made in seismology. Since the 1960’s Mogi, Scholz and others have studied AE of rock specimens in laboratory
and discovered that it is related to natural earthquakes. All former researchers used integral specimens to studyb value in the laboratory. However a major earthquake is usually related to a existing seismic-fault in that area. For this
reason, a series of fracture experiments with rock and glass specimens having pre-existing crack or notch is performed in
order to examine the effect of preexisting crack tob value. The experimental results show that theb value begins to decrease as soon as the initiation of the crack and finally drop to a very low value when the specimen breaks
unstably. Based on these, a brief discussion on the possible mechanism ofb value change for natural earthquakes is given.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,9, 393–400, 1987.
Projects sponsored by the Chinese Joint Seismological Science Foundation. 相似文献
11.
In this paper, structure models of the crust and upper mantle beneath each station have been obtained by way of fitting synthetic
seismograms with P waveforms of deep focus teleseismic records from the 11 stations in the Northeastern Region of China. We
have studied the structure in the region based on those models. Our results show that the medium of the crust and upper mantle
is a layered structure with alternate high and low velocity layers within about 100 km under the region. The crustal thickness
is about 31.8–35.8 km.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 471–479, 1991.
This work is one part of the project funded by the State Seismological Bureau of China. 相似文献
12.
In this paper, the two metnods, rectangular spectrum (RS) and maximum entropy power spectrum (MES), have been used in calculating
the geomagnetic structures of the crust in Haicheng and its adjacent areas and carrying out the geomagnetic stratification
of the crust. The result of the research indicates that the crust can be devided into such three layers as nonmagnetic layer,
magnetic layer and regressive magnetic layer from the top to the bottom. It is also found the distribution of the geomagnetic
bottom interface (Curie surface) is consistent with the lower interface of the upper crust and the top interface of the middle
crust of the velocity structure of the crust. It is very interesting that the Haicheng earthquake of Feb. 4, 1975,M 7.3 occurred at the depth gradient belt of the Curie isotherm surface. So, to research on the geomagnetic layers and the
distribution characteristics of the Curie isotherm surface is meaningful in judging potential seismic foci.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 448–454, 1993.
The data of velocity and electricity materials used in this paper are as reference from the related materials of the maps
and directions etc. of Donggou-Haicheng-Dong Ujimqin Qi Geoscience Transect by Prof. Zao-Xun LU, Huai-Kuan XIA and others. 相似文献
13.
Min-Zheng Zhang 《地震学报(英文版)》1993,6(3):761-768
This paper summarizes the origin and idea of the control of civil engineering structures and reviews the state-of-the art
of recent advances in structural control both theoretically and technologically. The prospects for structural control and
key research objects to remain to be solved are put forward at last.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 375–380, 1993. 相似文献
14.
《地震学报(英文版)》1993,6(3):619-629
In the present study the long period surface wave records of 238 wave-paths from 79 earthquakes within China and its adjacent
regions received by 30 seismic network stations are measured by using the improved match-filtering frequency-time analysis
technique and the grid dispersion inversion method to obtain the rayleigh pure-path dispersion values for 147 slant grids
of 4° × 4° in this area, then a three-dimensional shear wave velocity model of the crust and upper mantle beneath south China
area to a depth of 170 km is inversed.
It is found that there are obvious differences among the main structural units, and there are also certain differences among
the subordinate elements even in the individual unit. The crustal thickness of this area is ranging from 30 to 43 km, and
is getting thicker gradually from the east to the west. The average shear velocity of crust is ranging form 3.48 to 3.68 km/s
with the lowest in the northeast part and highest in the west part. No obvious crustal low velocity layer of large scale is
detected. There exist upper mantle low velocity zones in the most of south China area with the starting depth ranging from
75 to 106 km. The lowest shear velocity within the low velocity zones is about 4.28–4.38 km/s. Despite of the existing of
upper mantle low velocity zones beneath the most of south China area, the interfaces between the important layers are quite
clear, the variation of the bedding surfaces is very gentle, and the lateral changes measured in a larger scale of the underground
structure are rather small. It may indicate that the crustal and upper mantle structure of the main part of south China area
belongs to the relatively stable structure of the continental blocks except for the fringe areas such as the fold-faulted
region in the west part and the fault system along the southeastern coast which may belong to the tectonically active area.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 159–167, 1993.
This subject is supported by the National Science Foundation of China. 相似文献
15.
Preliminary study of crust-upper mantle structure of the Tibetan Plateau by using broadband teleseismic body waveforms 总被引：2，自引：0，他引：2
Lu-Pei Zhu Rong-Sheng Zeng Francis T. Wu Thomas J. Owens George E. Randall 《地震学报(英文版)》1993,6(2):305-316
As part of a joint Sino-U.S. research project to study the deep structure of the Tibetan Plateau, 11 broadband digital seismic
recorders were deployed on the Plateau for one year of passive seismic recording. In this report we use teleseimic P waveforms
to study the seismic velocity structure of crust and upper mantle under three stations by receiver function inversion. The
receiver function is obtained by first rotating two horizontal components of seismic records into radial and tangential components
and then deconvolving the vertical component from them. The receiver function depends only on the structure near the station
because the source and path effects have been removed by the deconvolution. To suppress noise, receiver functions calculated
from events clustered in a small range of back-azimuths and epicentral distances are stacked. Using a matrix formalism describing
the propagation of elastic waves in laterally homogeneous stratified medium, a synthetic receiver function and differential
receiver functions for the parameters in each layer can be calculated to establish a linearized inversion for one-dimensional
velocity structure.
Preliminary results of three stations, Wen-quan, Golmud and Xigatze (Coded as WNDO, TUNL and XIGA), located in central, northern
and southern Plateau are given in this paper. The receiver functions of all three stations show clear P-S converted phases.
The time delays of these converted phases relative to direct P arrivals are: WNDO 7.9s (for NE direction) and 8.3s (for SE
direction), TUNL 8.2s, XIGA 9.0s. Such long time delays indicate the great thickness of crust under the Plateau. The differences
between receiver function of these three station shows the tectonic difference between southern and north-central Plateau.
The waveforms of the receiver functions for WNDO and TUNL are very simple, while the receiver function of XIGA has an additional
midcrustal converted phase. The S wave velocity structures at these three stations are estimated from inversions of the receiver
function. The crustal shear wave velocities at WNDO and TUNL are vertically homogeneous, with value between 3.5–3.6 km/s down
to Moho. This value in the lower crust is lower than the normal value for the lower crust of continents, which is consistent
with the observed strong Sn attenuation in this region. The velocity structure at XIGA shows a velocity discontinuity at depth
of 20 km and high velocity value of 4.0 km/s in the midcrust between 20–30 km depth. Similar results are obtained from a DSS
profile in southern Tibet. The velocity under XIGA decreases below a depth of 30 km, reaching the lowest value of 3.2 km/s
between 50–55 km. depth. This may imply that the Indian crust underthrusts the low part of Tibetan crust in the southern Plateau,
forming a “double crust”. The crustal thickness at each of these sites is: WNDO, 68 km; TUNL, 70 km; XI-GA, 80 km.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, Supp., 581–592, 1992. 相似文献
16.
In this paper we discuss two types of crust models with abnormal density, velocity of wave and certain geometrical structures.
The far-field synthetic seismograms of P and SH wave are calculated by the far-field vertical displacement formulas of P and
SH waves with the double couple point source and the formulas of reflection coefficient, radiation pattern and travelling
time difference derived from the models suggested in the paper. It is shown by the results that the effect of special crust
structures near focus on the far-field seismograms can be ignored if the densities and wave velocity of the special structure
are less than average those of the crust (model I). However the effect should be noticed if the densities and wave velosities
of the structure are large than average those of the crust (modelI). The effect of the special crust structure on the far-field seismograms has not been studied further before. Seismic records
of the Haicheng earthquake and the crust structure in Haicheng region are studied by the calculation method in the paper.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 1993. 相似文献
17.
A model, in which various seismic environmental factors are involved, has been developed in the paper on the bases of relevant
data. The environmental factors include the crust structure, lithological conditions, fault plan attitude, the crust stress
state, pore-fluid pressure and geothermal conditions, etc. The effect of each of the factors on the tectonic movement energy index has been analyzed. The model calculation results
indicate that shear fracture energy of a fault generally increases with depth; it reached a peak value at a certain depth,
then turns gradually attenuated. Of all the factors, the effects of pore-fluid pressure and geothermal conditions on the energy
index are of prominence. High pore-fluid pressure and high temperature circumstance may result in decline of the peak value
of the shear fracture energy curve, making the depths of the peak value and of the bell-waist value deepened. Such effects
restrict strong seismic events, but suitable for micro-seismic activity and/or fault creep. The lower limit of focal depth
under such an environment is relatively deep. Contrarily, low pore-fluid pressure and low geothermal temperature circumstance
result in increase of the peak value of the shear fracture energy curve, and the curve becoming steep. The later circumstance
is favorable to the formation of locked segment where possesses high strength and high-energy accumulation. If these two kind
of segments are arranged interactively along a fault zone, such arrangement would boost the energy transition among the segments,
forming mechanical circumstance of energy highly accumulated in one segment with adjacent segment(s) less-locked. Such contrast
of the strength and energy would provide conditions for strong earthquakes with high stress drop. An analysis of the northwest
segment of the Honghe fault has provided some evidence for the modeling results.
Foundation item: Chinese Joint Seismological Science Foundation (No. 9507424). 相似文献
18.
Moment tensors of eleven major earthquakes in the Tibetan Plateau and its surrounding region from 1966 to 1980 are estimated
by generalized inverse technique. The seismic source time function and focal depth are immediately determined in the inversion.
The results show that moment tensors of some events differ significantly from double couple, the deviation increases with
decreasing plunge angle of null axis. All these events occurred in the upper crust, much shallower than those reported so
far, for example, in NEIS Bulletin. Focal mechanism solution obtained from the moment tensors are consistent with the idea
that the Indian plate collides northwards with the Eurasian plate and that an eastward spreading exists in the crust of the
Tibetan Plateau. The stress drops for earthquakes of intraplate are systematically higher than those of earthquakes in suture
zone. The source process duration becomes longer with seismic moment, but for the same seismic moment, the process duration
for earthquakes in suture zone is about 1.4 times of those for intraplate event, these results suggest that the earthquakes
near suture zone may be of a special characteristics in source process differently from those in intraplate.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 423 – 434, 1992. 相似文献
19.
Wojciech Stopinski 《地震学报(英文版)》1992,5(4):831-840
The paper presents the results of measurements of electric resistivity changes in the sample subject to uniaxial loading in
the automatic press. Four-electrode method was used. All minielectrodes were fixed inside the samples. The zone of future
fracture was determined by a kind of pre-cut. Distribution of minielectrode sets in various parts of the samples ensured the
possibility of monitoring the changes of electric resistivity either in the direct fracture zone, or outside of that zone.
The comparison of the measurement data obtained in the fracture zone and outside of it shows that electric resistivity method
can be used to failure prediction in both zones, although the precursor phenomena are much better visible in the direct fracture
zone. The typical progress of changes obtained in the fracture zone is similar to that observed while investigating the resistivity
changes in mines. Decreased repetition time of measurements improved the quality of results. New precursor phenomena were
found out in the course of electric resistivity changes.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 220–228, 1992. 相似文献
20.
We have made a data collection and analysis system for recording microcracks in rock to study the three dimensional pattern
of fracture and the dynamic properties of rock during pressurization. This system, with 8 channel data detection, records
in real-time, from the initial microcracks to the final vibration waveform excited by the master fracture. The detected data
are recorded digitally at the hard disk of an IBM computer (or 286, 386 personal computer) as well as transmitted to disk.
The sampling rate for each channel is 10 MHz.
Collecting every acoustic emission events in the loaded rock sample with 8 channels by this system, mathematically modelling
the AE event travel time, and taking the coordinates of the AE event hypocenter and the three components of P wave velocity
as unknown parameters, we set up a set of residual equations for joint inversion, so that the three dimensional localization
of AE event hypocenters can be completed under variable velocities, which will lay foundations for the research on rock fracture
clearly.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismological Sinica,13, 489–495, 1991.
The design and development of the system, and the experiments are sponsored by the Chinese Joint Seismological Science Foundation. 相似文献