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1.
Introduction Finite element method has a wide application in analyzing the crust tectonic stress field and tectonic deformation field. WANG, et al (1980), for example, reversed the crust stress field and forecast future seismic risky area using finite element way. WANG and CHEN (1980) made the numerical simulation on modern tectonic stress field for China and its adjacent area using finite element and obtained the whole picture of tectonic stress filed in China. Except analyzing the tect… 相似文献
2.
3.
IntroductionFocal depths of shallow strong intraplate earthquakes are mostly distributed in the highstrength range of lithosphere controlled by the rheology property of granite and diorite (Brace,Kohlstedt, 1980; Sibson, 1982; Meissner, Strehlau, 1982; CHEN, Molnap 1983). This is obviouslyrelated to the change of rock deformation characteriStics at different crust depths. So, for earthquake stUdy, both of the rock failure types (fractUre or rock flow) and its mechanical instabilityforms (… 相似文献
4.
Yu Huai-zhong Yin Xiang-chu Xia Meng-fen Xu Zhao-yong Li Min Liang Nai-gang Peng Ke-yin Victor Kukshenko Wu Zhi-shen Li Qi Surguei Elizarov 《地震学报(英文版)》2004,17(1):129-137
According to the critical point hypothesis (CPH), energy release would accelerate in power law before occurrence of large
earthquakes or failure of brittle materials. In the paper, CPH was studied by acoustic emission experiments of large-scale
rock samples. Three kinds of rock samples were used in the experiments. The tri-axial loading condition was applied under
different loading histories. The released elastic energy (Acoustic emission) was recorded with acoustic emission technique
as microcracks emerged and developed inside the rock samples. The experimental results gave a further verification on the
CPH. The elastic energy release of rock samples would accelerate before the failure even under different experimental conditions.
Primary studies were also made on medium-term earthquake prediction by using accelerating energy release (AER) in the paper.
Foundation item: Project of Natural Sciences Foundation of China (10232050), Project of State Key Basic Research (2002CB412706) and Project
of Computer Network Information Center, Chinese Academy of Sciences (2002CB412706). 相似文献
5.
H. Spetzler 《Pure and Applied Geophysics》1978,116(4-5):732-742
Fracture and frictional sliding are considered as phenomena involving brittle failure. Brittle failure is preceded by the formation of small (subcritical) cracks. In non-water-saturated rock, the distribution, shape and size of these suberitical cracks determine the change in the physical properties prior to failure. A model is proposed which suggests that the spatial and temporal distribution, shape and size of subcritical cracks within a stressed rock depend upon the rate of deformation and the volatile content.As a rock is stressed beyond about 50 percent of its ultimate failure stress, dilatancy is initiated. With increasing stress a broad zone of cracks develops within the dilatant region. The seismic velocities through this zone decrease markedly and the cracks grow more numerous., changing in size and shape. Before brittle failure of the rock occurs, the subcritical cracks interact, leading to a concentration of the zone. During the stage when the zone narrows, the seismic velocities in crease in the surrounding volume due to local rotation of stresses and consequent closure of some cracks. In most laboratory experiments the stage during which the velocity increases and the now intense deformation zone becomes narrow is very short and difficult to observe experimentally. At very low strain rates and with volatiles present, the crack growth and subsequent interaction lead to the narrowing of the intense deformation zone and therefore to an observable increase in velocity.The above is based upon an interpretation of a number of experiments. Using optical holography we have observed the development and subsequent intensification of a deformation zone. Ultrasonic velocity measurements showed a distinct anomaly (decrease followed by an increase) before failure. The anomaly was only detectable at our lowest experimental strain rates (3×10–8/sec). 相似文献
6.
Two branches of Tangjiagou rock avalanche were triggered by Lushan earthquake in Sichuan Province, China on April 20th, 2013. The rock avalanche has transported about 1 500 000 m3 of sandstone from the source area. Based on discrete element modeling, this study simulates the deformation, failure and movement process of the rock avalanche. Under seismic loading, the mechanism and process of deformation, failure, and runout of the two branches are similar. In detail, the stress concentration occur firstly on the top of the mountain ridge, and accordingly, the tensile deformation appears. With the increase of seismic loading, the strain concentration zone extends in the forward and backward directions along the slipping surface, forming a locking segment. As a result, the slipping surface penetrates and the slide mass begin to slide down with high speed. Finally, the avalanche accumulates in the downstream and forms a small barrier lake. Modeling shows that a number of rocks on the surface exhibit patterns of horizontal throwing and vertical jumping under strong ground shaking. We suggest that the movement of the rock avalanche is a complicated process with multiple stages, including formation of the two branches, high-speed sliding, transformation into debris flows, further movement and collision, accumulation, and the final steady state. Topographic amplification effects are also revealed based on acceleration and velocity of special monitoring points. The horizontal and vertical runout distances of the surface materials are much greater than those of the internal materials. Besides, the sliding duration is also longer than that of the internal rock mass. 相似文献
7.
Geometric form of Haiyuan fault zone in the crustal interior and dynamics implications 总被引：1，自引：0，他引：1
The deep seismic reflection data on profile HY2 are reprocessed by the method of simultaneous inversion of velocity distribution
and interface position. By the travel-time inversion with the data of the diving wave Pg and fault plane reflection wave,
we determine the geometric form and velocity of Haiyuan fault zone interior and surrounding rock down to 10 km depth. The
measured data show that the amplitudes have strong attenuation in the range of stake number 37–39 km, suggesting the fault
zone has considerable width in the crustal interior. The results of this paper indicate that to the north of the fault zone
the crystalline basement interface upheaves gradually from southwest to northeast and becomes shallow gradually towards northeast,
and that to the south of the fault zone, within the basin between Xihua and Nanhua mountains, the folded basement becomes
shallow gradually towards southwest. The obliquity of the fault zone is about 70° above the 3 km depth, about 60° in the range
of the 3–10 km depths. From the results of this paper and other various citations, we believe that Haiyuan fault zone is in
steep state from the Earth’s surface to the depth of 10 km.
Foundation item: Joint Seismological Science Foundation of China (201001) and State Key Basic Research Development and Programming Project
(95-13-02-02).
Contribution No. RCEG200308, Exploration Geophysical Center, China Earthquake Administration. 相似文献
8.
According to the fact that the Xinfengjiang reservoir earthquakes are caused mainly by water seepage, this paper using the
data ofM
s⩾2. 0 earthquakes, studies the hydraulic diffusivity of the mainshock zone by the expansion of the distribution area of epicenters.
It is indicated thatin-situ hydraulic diffusivity during the preshock activity of the Xinfengjiang reservoir region was about 6. 2 m2/s. However, after the main shock, thein-situ hydraulic diffusivity in the main shock region increased by fifty percent, that is to say, to 9. 7 m2/s. During the long period after main shock occurrence thein-situ hydraulic diffusivity was affected by significant anisotropy of the medium and fluctuation of water level. No regularity
can be found. In addition, we compare the diffusivity found by experiment with rock samples collected with thein-situ hydraulic diffusivity estimated. It is shown that the diffusivity of rock samples with fractures is about the same as the
diffusivity estimatedin-situ. However, the diffusivity of whole rock samples is 3 orders of magnitudes smaller than that estimatedin-situ. Finally, we discuss the limits on the method by the expansion of distribution area of epicenters in the study of reservoir
induced seismicity.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 364–371, 1991.
This subject is sponsored by the Chinese Joint Seismological Science Foundation. 相似文献
9.
Two rock samples with different structures and materials were deformed under a biaxial loading system, and multipoint strain
measurements were performed for each sample. The distribution of strain anomalies during the deformation and the instability
process were analyzed by using C
v value put forward by WANG Xiao-qing and CHEN Xue-zhong, et al, a parameter to describe the heterogeneous distribution of earthquake precursors, so as to examine the method of C
v value and to explore its physical meaning experimentally. The result shows that the change of C
v value is correlated to the change of deformation characteristics and is an effective parameter to describe the heterogeneity
of precursor distribution. C
v value increases firstly and then decreases before the instability, and the instability occurs when C
v value decreases to the level before increasing. This indicates that C
v value may be a useful parameter for earthquake prediction.
Foundation item: Chinese Joint Earthquake Sciences Foundation (9507435). 相似文献
10.
E. O. Holopainen 《Pure and Applied Geophysics》1967,67(1):156-165
Summary The annual mean distribution of the surface stress curl over the Northern Hemisphere has been estimated from the horizontal vorticity advection in the atmosphere by using the upper-wind statistics as published byCrutcher [2]3). The results are used to compute the wind-driven mass transport (Sverdrup transport) in North Atlantic and North Pacific. The calculated intensity of the Gulf Stream is largest at the latitude 35°N, where a mass transport of 45×106 tons sec–1 is obtained; for the maximum intensity of the Kuroshio current a value of 60×106 tons sec–1 is obtained.Research supported in part by the Section of Atmospheric Sciences, National Science Foundation, Grant GP-2561.The research for this study was started by the author at the Department of Meteorology and Oceanography, The University of Michigan, Ann Arbor, Mich. 相似文献
11.
Eruptions of the active Karymsky stratovolcano began about 5300 (6100 14C) b.p. from within a pre-existing caldera which formed 7700 14C b.p. As indicated by 32 14C determinations on buried soils and charcoal, the volcano has gone through two major cycles of activity, separated by a 2300 year period of repose. The first cycle can be divided into two stages (6100–5100 and 4300–2800 b.p.). The earlier stage began with especially intense eruptions of basaltic andesite to dacite. The later stage was characterized by moderate-strength eruptions of andesite. The second cycle, which is characterized by weak to moderate intermittent eruptions of andesite, started 500 b.p. and continues to the present. Eruptive patterns suggest that this cycle may continue for at least another 200 years with an eruptive character similar to that of the recent past. 相似文献
12.
Summary A charged particle moves with velocityv in a constant non-uniform magnetic fieldH, spiralling with Larmor radiusR. IfR is small compared with the scale lengthL of the field, the magnetic moment associated with the Larmor motion of the particle is nearly constant. Consequently , the (pitch) angle betweenv andH, varies as arcsinH
1/2. Hence in such adiabatic motion is approximately the same at points on the path whereH has the same value. But the magnetic moment and the pitch angle may differ materially at two such points, each in the region whereR/L is small, if between them the particle traverses a region whereR/L is not small. This region of non-adiabatic motion scatters the pitch angles.Such scattering is investigated for regions of weak field (R large), with and without the presence of a neutral line along whichH=0. Either type of region, it is found, can scatter the pitch angles. This gives support to the theory proposed byAkasofu andChapman to explain why auroral arcs and bands are very thin.The scattering here examined is of interest also in connection with magnetic mirror devices for nuclear energy transformation. It may also have applications to phenomena of solar and stellar atmospheres. 相似文献
13.
Fracturing and hydrothermal alteration in normal fault zones 总被引：9，自引：0，他引：9
Ronald L. Bruhn William T. Parry William A. Yonkee Troy Thompson 《Pure and Applied Geophysics》1994,142(3-4):609-644
Large normal fault zones are characterized by intense fracturing and hydrothermal alteration. Displacement is localized in a slip zone of cataclasite, breccia and phyllonite surrounding corrugated and striated fault surfaces. Slip zone rock grades into fractured, but less comminuted and hydrothermally altered rock in the transition zone, which in turn grades abruptly into the wall rock. Fracturing and fluid flow is episodic, because permeability generated during earthquakes is destroyed by hydrothermal processes during the time between earthquakes.Fracture networks are described by a fracture fabric tensor (F). The permeability tensor (k) is used to estimate fluid transport properties if the trace of F is sufficiently large. Variations in elastic moduli and seismic velocities between fault zone and wall rock are estimated as a function of fracture density (). Fracturing decreases elastic moduli in the transition zone by 50–100% relative to the country rock, and similar or even greater changes presumably occur in the slip zone.P-andS-wave velocity decrease, andV
p
/V
s
increases in the fault zone relative to the wall rock. Fracture permeability is highly variable, ranging between 10–13 m2 and 10–19 m2 at depths near 10 km. Changes in permeability arise from variations in effective stress and fracture sealing and healing.Hydrothermal alteration of quartzo-feldspathic rock atT>300°C creates mica, chlorite, epidote and alters the quartz content. Alteration changes elastic moduli, but the changes are much less than those caused by fracturing.P-andS-wave velocities also decrease in the hydrothermally altered fault rock relative to the country rock, and there is a slight decrease inV
p
/V
s
, which partially offsets the increase inV
p
/V
s
caused by fracturing.Fracturing and hydrothermal alteration affect fault mechanics. Low modulus rock surrounding fault surfaces increases the probability of exceeding the critical slip distance required for the onset of unstable slip during rupture initiation. Boundaries between low modulus fault rock and higher modulus wall rock also act as rupture guides and enhance rupture acceleration to dynamic velocity. Hydrothermal alteration at temperatures in excess of 300°C weakens the deeper parts of the fault zone by producingphyllitic mineral assemblages. Sealing of fracture in time periods between large earthquakes generates pods of abnormally pressured fluid which may play a fundamental role in the initiation of large earthquakes. 相似文献
14.
In the paper, for the application of stochastic simulation of ground motion, we put forward a method to determine “the combined
effect of amplification and attenuation” (combined effect for short) of soft rock site by using digital seismic data of moderate
and small earthquakes. Our approach aims at solving the problem of the combined effect of soft rock site, which is difficult
to determine in most regions of China because fewer measures were done for S-wave velocity structure. The combined effect
of soft rock site can be determined by using the approach recommended by us. An example is given to discuss the practical
application of the method.
Foundation item: The Special Funds for Major State Basic Research Project under Grant No.2002CB412706 and National Natural Science Foundation
of China (50468003).
Contribution No.04FE1021, Institute of Geophysics, China Earthquake Administration. 相似文献
15.
Feng Chen Da-Yuan Chen Qi-Ping Cao Shu-Jun Yu Dong-Jun Xu Cong-Xin Chen Yu-Liang Yu Jian-Hao Sheng 《地震学报(英文版)》1993,6(3):721-729
In the strip limestone mine in Guiding county, Guizhou Province the shear and frictionin situ tests of rock body were made for the three typical inclined weak bands C
3
1
/C
3
1
, C
3
1
/C
2
2
and C
2
2
/C
2
1
. The tests were made according to the second scheme of cuneate sample of the standards on rock mechanics test of Water Conservancy
and Electricity Ministry. The changes of the resistivity in the weak band and the acoustic speed across the weak band were
measured in the same time. The apparent resistivity data, obtained for 8 samples on 27 measure lines in 38 cycle tests, show
that the apparent resistivity changes have rather obvious characters as follows: 1. At shear and friction stage, the change
of the apparent resistivity accelerates after the yield point, and reaches the maximum of change rate and change amplitude
near fracture point (except the lines with resistivity invariant); 2. On the same sample, the resistivity changes are different
on the various lines and related to the location settled the lines, there are some “sensitive” location; 3. At the stage of
preloading normal stress before shearing, the resistivity decreases on most lines, but on a few lines the resistivity does
not changes; 4. After unloading shear stress, the resistivity could not recover completely and the hysteresis of resistiviity
takes place on a few lines.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 217–223, 1993.
Support for this research was received from Guiding strip limestone mine, Guizhou Organic Chemistry Factory.
This research is supported by the Chinese Joint Seismological Science Foundation. 相似文献
16.
By the experiment, it is confirmed that water-marble rock system shows obviously chemical anomalous behaviors: the relevant
minerals which formed marble rock are resolved fast, water becomes alkaline, meanwhile H2 emission appears under action of ultrasound; based on rock identification by microscope and chemical analysis of water and
rock, the mechanism of above chemical reaction is analyzed and discussed.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15 498–507, 1993.
This study was supported by the Chinese Joint Seismological Science Foundation. 相似文献
17.
Introduction Data mining (SHAO and YU, 2003) is a new kind of technique developed with database and artificial intelligence in recent years, which processes the data in the database to abstract the im- plied and pre-unknown, but potentially useful information and knowledge from large amounts of incomplete, noisy, blurring and stochastic data. For data mining, data purging is an important link beforehand that includes eliminating noise, making up lost domain, and deleting ineffective data, as… 相似文献
18.
Ray equation migration of wide-angle reflections in 2-D medium is one kind of Kirchhoff prestack depth migration method. Based
on ray theory, this method can be used extensively in 2-D inhomogeneous medium, and shows its advantage in wide-angle reflection
study. After calculating ray fields, we can get the wave fields of sources and receivers by interpolation, and the intensity
(or amplitude) A
p
corresponding to the depth point P at travel-time t
P
=t
SP
+t
PR
can be found in seismograms. Ray equation migration is completed by transforming A
P
according to the specific relation, migrating it to the depth point, then calculating the ray fields of lots of sources and
receivers in the same way and finally stacking the outcomes. Numerical calculation has yielded satisfactory results. Data
processing of the Zhuangmu-Yuexi-Huangmei-Zhanggondu profile passing through the Dabie orogenic zone provides a structural
form of M-discontinuity along the profile. The result shows that the high pressure metamorphic rock zone of South Dabie rock
mass is related to the uplifting of M-discontinuity here. "Mountain root" exists under North Dabie rock mass, which conforms
with gravity isostasy theory. The Xiaotian-Mozitan fault is a suture zone as a result of the collision of North China plate
with Yangtze plate, and extends through M-discontinuity. The abyssal fault near Liu’an is the extended eastern section of
the Luonan-Minggang fault, which is also confirmed here.
Contribution No. RCEG 96012, Research Center of Exploration Geophysics, SSB, China.
This project was supported by the National Natural Science Foundation of China and the Chinese Joint Seismological Science
Foundation. 相似文献
19.
2-D crustal Poisson’s ratio from seismic travel time inversion in Changbaishan Tianchi volcanic region 总被引：1，自引：0，他引：1
Based on the inversion method of 2D velocity structure and interface, the crustal velocity structures of P-wave and S-wave
along the profile L
1 are determined simultaneously with deep seismic sounding data in Changbaishan Tianchi volcanic region, and then its Poisson’s
ratio is obtained. Calculated results show that this technique overcomes some defects of traditional forward calculation method,
and it is also very effective to determine Poisson’s ratio distribution of deep seismic sounding profile, especially useful
for study on volcanic magma and crustal fault zone. Study result indicates that there is an abnormally high Poisson’s ratio
body that is about 30 km wide and 12 km high in the low velocity region under Tianchi crater. Its value of Poisson’s ratio
is 8% higher than that of surrounding medium and it should be the magma chamber formed from melted rock with high temperature.
There is a high Poisson’s ratio zone ranging from magma chamber to the top of crust, which may be the uprise passage of hot
substance. The lower part with high Poisson’s ratio, which stretches downward to Moho, is possibly the extrusion way of hot
substance from the uppermost mantle. The conclusions above are consistent with the study results of both tomographic determination
of 3D crustal structure and magnetotelluric survey in this region.
Foundation item: Key Project from China Earthquake Administration and the Project (95-11-02-01) from Ministry of Science and Technology (2001DIA10003).
Contribution No. RCEG200401, Geophysical Exploration Center, China Earthquake Administration. 相似文献
20.
The relationship between temporal-spatial evolution of gravity and earthquake activity during 1992–2001 has been analyzed
systematically by integrally adjusting the gravity observation data of the northeastern edge of Qinghai-Xizang (Qingzang)
block. The result shows that the gravity observation data of the northeastern edge of Qingzang block obtained by using the
uniform starting datum can completely reflect the precursory gravity information appearing during the seismogenic process.
In the genesis stage of an earthquake, regional gravity anomaly appears in a large area, resulting in related local gravity
anomaly. The dynamic image of gravity field can clearly reflect the orderly evolution and earthquake activity.
Foundation item: Key Project of China Earthquake Administration during the tenth Five-year Plan (100501-05-05). 相似文献