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1.
Besides generating seismic waves, which eventually dissipate, an earthquake also generates a static displacement field everywhere within the Earth. This global displacement field rearranges the Earth’s mass thereby causing the Earth’s rotation and gravitational field to change. The size of this change depends upon the magnitude, focal mechanism, and location of the earthquake. The Sumatran earthquake of December 26, 2004 is the largest earthquake to have occurred since the 1960 Chilean earthquake. Using a spherical, layered Earth model, the coseismic effect of the Sumatran earthquake upon the Earth’s length-of-day, polar motion, and low-degree harmonic coefficients of the gravitational field are computed. Using a model of the earthquake source that is composed of five subevents having a total moment-magnitude M
w
of 9.3, it is found that this earthquake should have caused the length-of-day to decrease by 6.8 microseconds, the position of the Earth’s generalized figure axis to shift 2.32 milliarcseconds towards 127° E longitude, the Earth’s oblateness J
2 to decrease by 2.37 × 10−11 and the Earth’s pear-shapedness J
3 to decrease by 0.63 × 10−11. The predicted change in the length-of-day, position of the generalized figure axis, and J
3 are probably not detectable by current measurement systems. But the predicted change in oblateness is perhaps detectable if other effects, such as those of the atmosphere, oceans, and continental water storage, can be adequately removed from the observations. 相似文献
2.
A. D. Kostyuk N. A. Sycheva S. L. Yunga L. M. Bogomolov Y. Yagi 《Izvestiya Physics of the Solid Earth》2010,46(3):230-243
For evaluating the deformations of the Earth’s crust in the Northern Tien Shan, we calculated the mode and intensity of the
seismotectonic deformations (STD) for this region. The input for these calculations were the catalog data on the focal mechanisms
of earthquakes, obtained by wave inversion of the signals recorded at the Kyrgyz seismic network (KNET) for the period 1994–2006.
In the construction of STD maps, a modern approach to the classification of seismotectonic deformations was applied. This
approach distinguishes eleven typical patterns of deformation. The areal distributions of the Lode-Nadai coefficient, as well
as of the vertical component and the aspect angle of the deformed state were obtained. At the same time, based on the GPS
measurements in the Northern Tien Shan during 1994–2006, the rates of dilatation and shear deformation of the Earth’s crust
were estimated. A comparison between the directions of strain axes derived from the GPS data and from the earthquake focal
data is carried out. 相似文献
3.
E. E. Khachiyan 《Journal of Volcanology and Seismology》2011,5(4):286-297
This paper describes a technique for determining the potential energy of deformed material around a future earthquake rupture,
with this energy being stored during the precursory period. The basic parameters are the following: rupture length on the
Earth’s surface after the earthquake has occurred L, rupture depth h, and the relative block movement along the rupture strike line [`(u)]\bar u. We compared the results for 44 large earthquakes with those derived by determining seismic wave energy from earthquake magnitude. 相似文献
4.
Mohammad Ashtari Jafari 《Journal of Geodynamics》2010,49(1):14-18
The analysis of seismic activity variations with space and time is a complex problem. Several statistical methods have been adopted to study these variations. One of the tasks that has attracted the attention of the seismological and statistical community is to explain seismicity patterns by statistical models and apply the results for earthquake prediction. Here the probability distribution of recurrence times as described by Exponential, Gamma, Lognormal, Pareto, Rayleigh and Weibull probability distributions and the idea of conditional probability has been applied to predict the next great (Ms ≥ 6.0 and Ms ≥ 6.5) earthquake around Tehran (r ≤ 200 km). Conditional probability specifies the likelihood that a given earthquake will happen within a specified time. This likelihood is based on the information about past earthquake occurrences in the given region and the basic assumption that future seismic activity will follow the pattern of past activity. The rapid growth of Tehran to approximately 12 million inhabitants has resulted in a much more rapid increase in its vulnerability to natural disasters, especially earthquakes. Several earthquakes affected this region in the past, mostly on the Mosha, Taleqan, Eyvankey and Garmsar faults. The estimated recurrence times for Exponential, Gamma, Lognormal, Pareto, Rayleigh and Weibull distributions has been computed to be 66.64, 14.79, 26.88, 2.37, 67.58 and 80.47, respectively. Accordingly, one may expect that a large damaging earthquake may occur around Tehran approximately every 10 years. 相似文献
5.
We study the changes in the rate of seismotectonic strains in the Earth’s crust in two of the most seismically active Central
Asian areas, the Garm region in Tadjikistan and the Northern Tien Shan, which are excited by high energy pulsed electromagnetic
irradiation. It is shown that in both areas the average rates of strain release increase by a factor of 10–20. The increment
of the seismotectonic strains initiated during the entire period of electromagnetic treatment is 1.3 × 10−6–6.3 × 10−6, which is comparable with the value of crustal strains observed during the preparation of strong earthquakes and amounts
to 3–13% of the ultimate strains for rocks. Such a contribution to the process of quasi-plastic strains of the crust results
in the additional relaxation of elastic stresses by 0.4–1.67 bar, which corresponds to approximately 1–17% of the stress released
in the sources of strong earthquakes. The spatial variations in the changes of the strain rate during electromagnetic treatment
are studied, and their correlation with the level of stresses in the Earth’s crust is revealed. It is shown that the change
in the strain rate during the electromagnetic excitation can be used as the criterion for active monitoring of the stress
state of the medium for the purposes of predicting the location, time, and magnitude of strong earthquakes. 相似文献
6.
Statistical properties of reported earthquake precursors show apparent focal mechanism dependence. Intensity of anomaly is
described by the ‘anomaly ratio’ as defined by the number of stations/items reporting anomalies before the target earthquake
over the number of stations/items in operation around the target earthquake. Variation of the ‘anomaly ratio’ with the magnitude
of the target earthquake was studied for dip-slip earthquakes all over China, strike-slip earthquakes in eastern China, and
strike-slip earthquakes in western China, respectively. It is observed that for strike-slip earthquakes, the ‘anomaly ratio’
increases linearly with the magnitude of the target earthquake, while earthquakes in eastern China and western China have
different slopes. For dip-slip earthquakes, however, the ‘anomaly ratio’ has no statistically significant change with the
magnitude of the target earthquake. Limited data imply that the ‘anomaly ratio’ seems proportional to the apparent stress
of the target earthquake. The result might be heuristic for the analysis of candidate earthquake precursors.
Foundation item: National Natural Science Foundation of China (40274013) and MOST Project (2001BA601B02).
Contribution No.04FE1020, Institute of Geophysics, China Earthquake Administration. 相似文献
7.
V. P. Antonova N. N. Volodichev S. V. Kryukov A. P. Chubenko A. L. Shchepetov 《Geomagnetism and Aeronomy》2009,49(6):761-767
The unit for detecting thermal neutrons, which makes it possible to study variations in cosmic rays of the interplanetary
and geophysical origin, has been created at the high altitude cosmic ray station (3340 m above sea level) near the Earth’s
crust fault. It has been established that variations in thermal neutrons are of the same nature as high-energy variations
registered with a neutron supermonitor in the absence of seismic activity. The flux of thermal neutrons from the Earth’s crust
during seismic activity in December 2006 has been registered for the first time. The flux value is higher than the background
level by 5–6%. The method for detecting the flux of thermal neutrons from the Earth’s crust with the simultaneous registration
of high-energy neutrons has been proposed. 相似文献
8.
In this study near field strong ground motion generation of Mw 6.9 scenario events on Gemlik Bay was presented at broadband
frequency (0.5–10 Hz) ground motion at 9 stations. In the first stage of the study, focal mechanism of a small earthquake,
which was used as the Empirical Green’s Function (EGF) throughout the scenario simulation, was decided by simulating it with
a smaller magnitude event. The best waveform fitting was judged with the smallest misfit value. In the second stage, near
field ground motion simulation of scenario events was performed. Calculations were achieved by considering three different
rupture processes which have the same magnitude but different asperity locations. Fault and asperity parameters for each scenario
were determined from empirical scaling laws. It has been found that the peak ground acceleration and peak ground velocities
reach maximum values of 1,440 cm/s2 and 125 cm/s, respectively for the worst case scenario. Rupture directivity effect is observed with clear peaks at a forward
station. The design spectra for Turkish seismic design code (TSDC 2007) were either nearly or actually exceeded by the scenario earthquakes at periods lower than 0.6 s at all near field stations.
Majority of structures in the area were built to lower design spectra before the 1998 code was implemented. The strength of
many structures would have been insufficient to resist the forces that may be generated by an earthquake that is similar to
Scenario I and Scenario II in this study. 相似文献
9.
Ram Bichar Singh Yadav Jayant Nath Tripathi Bal Krishna Rastogi Mridul Chandra Das Sumer Chopra 《Pure and Applied Geophysics》2010,167(11):1331-1342
Northeast India and adjoining regions (20°–32° N and 87°–100° E) are highly vulnerable to earthquake hazard in the Indian
sub-continent, which fall under seismic zones V, IV and III in the seismic zoning map of India with magnitudes M exceeding 8, 7 and 6, respectively. It has experienced two devastating earthquakes, namely, the Shillong Plateau earthquake
of June 12, 1897 (M
w
8.1) and the Assam earthquake of August 15, 1950 (M
w
8.5) that caused huge loss of lives and property in the Indian sub-continent. In the present study, the probabilities of
the occurrences of earthquakes with magnitude M ≥ 7.0 during a specified interval of time has been estimated on the basis of three probabilistic models, namely, Weibull,
Gamma and Lognormal, with the help of the earthquake catalogue spanning the period 1846 to 1995. The method of maximum likelihood
has been used to estimate the earthquake hazard parameters. The logarithmic probability of likelihood function (ln L) is estimated
and used to compare the suitability of models and it was found that the Gamma model fits best with the actual data. The sample
mean interval of occurrence of such earthquakes is estimated as 7.82 years in the northeast India region and the expected
mean values for Weibull, Gamma and Lognormal distributions are estimated as 7.837, 7.820 and 8.269 years, respectively. The
estimated cumulative probability for an earthquake M ≥ 7.0 reaches 0.8 after about 15–16 (2010–2011) years and 0.9 after about 18–20 (2013–2015) years from the occurrence of
the last earthquake (1995) in the region. The estimated conditional probability also reaches 0.8 to 0.9 after about 13–17
(2008–2012) years in the considered region for an earthquake M ≥ 7.0 when the elapsed time is zero years. However, the conditional probability reaches 0.8 to 0.9 after about 9–13 (2018–2022)
years for earthquake M ≥ 7.0 when the elapsed time is 14 years (i.e. 2009). 相似文献
10.
G. C. Yetirmishli S. E. Kazimova I. E. Kazimov 《Izvestiya Physics of the Solid Earth》2011,47(9):847-856
We present the method for determining the velocity model of the Earth’s crust and the parameters of earthquakes in the Middle
Kura Depression from the data of network telemetry in Azerbaijan. Application of this method allowed us to recalculate the
main parameters of the hypocenters of the earthquake, to compute the corrections to the arrival times of P and S waves at the observation station, and to significantly improve the accuracy in determining the coordinates of the earthquakes.
The model was constructed using the VELEST program, which calculates one-dimensional minimal velocity models from the travel
times of seismic waves. 相似文献
11.
Wu Fu-chun Song Li-sheng Zhu Xing-guo Wang Feng Jing Bei-ke Dong Xing-hong Fang Wei Zuo Yong-qing 《地震学报(英文版)》2001,14(4):434-439
Based on the analysis of the induced earthquakes in China and abroad, we get some ideas about earthquakes induced by pumping
water out of a well or injecting water into a well. The induced earthquakes usually occur near the well, and they are generally
small earthquakes. The earthquake sources are shallow, and they belong to the main shock-after shock type of earthquake or
the swarm-type of earthquake. The magnitude and the quantity of the induced earthquakes obviously depend on the pressure and
the quantity of water pumped or injected. These earthquakes happen as soon as pumping or injecting occurrence, or after ten
or twenty days, they may occur at the time of injecting mud or injecting high pressure water when a well is being drilled,
or at the time when the ground water is being normally exploited. A large quantity of hot water has been exploited since 1990
in Xi’an, and the quantity of water exploited has been increasing year by year, as a result the groundwater level has been
dropping with the water pumped out and the water level is high in summer and low in winter. The earthquakes in Xi’an region
belong to the solitary-type and they spread outside Xi’an city where the wells are concentrated but no earthquake happens.
The seismic frequency and the energy released have no relation with the quantity of water exploitation or the water level
in the well. It is considered that geothermal exploitation does not induce earthquakes in and around Xi’an because of its
specially geological condition.
Foundation item: Project sponsored by the Landslide Office of Shaanxi Province and Society of Disaster Reduction of Shaanxi Province. 相似文献
12.
Yusuf Bayrak Serkan Öztürk Hakan Çınar G. Ch. Koravos T. M. Tsapanos 《Pure and Applied Geophysics》2008,165(7):1367-1390
Complete data set of earthquakes in Turkey and the adjacent areas has been used in order to compute the ω values in 24 seismic
regions of Turkey. The parameter is obtained through Gumbel’s third asymptotic distribution of extreme values and is well
known as upper bound magnitude. This is an interpretation that no earthquake magnitude greater than ω can occur in a region. The results also estimate the
most probable magnitude for a time period of 100 years. The estimates of ω exceed the value of 7.00 in 20 of the 24 seismic
regions. An effort is also made to find a relation between the magnitude and the length of a fault in the complicated tectonics
of Turkey and the surrounding area. Earthquake hazard revealed as tables and maps are also considered for Turkey and the surrounding
area. 相似文献
13.
1833年云南省昆明市嵩明杨林地区发生了1次强烈地震,震级被定为8级,这也是迄今为止云南省震级最大的地震。本文选取该地震震中一带为研究区（24.7°～25.5°N,102.3°～103.3°E）,采用网格点密集值计算方法对研究区1966年以来仪器记录的地震进行了计算。根据地震密集等值线图确定研究区有2个地震密集区。通过不同的时窗分析了密集区内地震活动的时间分布特征。利用地震密集时空分布特征与历史强震间的关系,给出了1833年嵩明8级地震震中位置校正的建议。此外,还通过地震密集时空动态变化分析发现,21世纪以来研究区地震密集由NE逐渐向SW方向发展。该现象可能在一定程度上反映出区域应力的变化特征。 相似文献
14.
V. V. Ruzhich 《Izvestiya Physics of the Solid Earth》2009,45(11):987-995
The paper presents the results of long-term geological-geophysical studies of the author, which have a direct relationship
to the structure and development of the sources of the strong earthquakes that occurred on the territory of Mongolia and the
Baikal rift zone. They left imprints in the form of seismic dislocations in the near-surface layers or in the form of thermally
treated rocks (pseudo-tachylites), considered as evidence of the manifestation of seismogenic motions in the segments of seismoactive
faults at depths of 10–20 km. It was revealed that in the regions of the manifestation of denudation shear on the Earth’s
surface with a length of many kilometers it is possible to identify the deep fragments of faults, in which previously the
signs of rapid seismogenic motions along the faults had been manifested. Such deep fragments are revealed from the presence
of friction planes, covered by the finest glass films, which arose under the strong frictional heating of rocks before the
stage of melting. In this way, the possibility of studying such sections of zones of seismo-generating faults is validated,
considering them as deep fragments of earthquake sources, which occurred many million years ago.
New information on the instrumental measurements of the velocity of motions in the seismoactive faults is also discussed in
the work. The ideas on the mechanisms of generating seismic vibrations in the fault zones are presented. The conclusion that
the lower segments of faults in the source regions of earthquakes are capable of penetrating rapidly at depths of 25–40 km,
where the viscoplastic deformations of rocks predominate, causing their nonlinear behavior, is substantiated. On the development
of the new models of earthquake sources, more adequate to geological conditions, it is expedient to consider the ideas presented
in the paper 相似文献
15.
Benedikt Halldorsson Ragnar Sigbjornsson Johannes Schweitzer 《Journal of Seismology》2009,13(1):173-178
A small-aperture, strong-motion array, the ICEARRAY, has been deployed in South Iceland, a region with a history of destructive
earthquakes, some exceeding magnitude 7. The array’s purpose is: (1) monitoring future significant events in the region, (2)
quantifying spatial variability of strong-motion over short distances and (3) shedding light on earthquake source processes.
The number of array stations and their arrangement were based on an optimisation of the shape of the corresponding array transfer
function (ATF). The optimal ICEARRAY configuration comprises 14 stations, has an aperture of ~1.9 km and a minimum interelement
distance of ~50 m and possesses a near-azimuthally independent ATF with a sharp main lobe, negligible sidelobes and a wavenumber
range of 1.5–24 rad/km. Accordingly, the ICEARRAY has the intended capabilities of capturing seismic waves in the frequency
range of 1–20 Hz, which is of main interest to earthquake engineering and engineering seismology applications. 相似文献
16.
ZHANG Heng＇s Seismometer and Longxi earthquake in AD 134 总被引：1，自引：0，他引：1
17.
The earthquakes of Calabria are among the strongest in the whole Mediterranean, and they all occurred between the disruptive sequences of 1638 and 1908 (6.7 ≤ M ≤ 7.2). Recent paleoseismological studies show that the return time of these events on their causative fault are larger than 1 ky, thus making ancient earthquakes not recognizable through ‘conventional’ historical research. On the other hand, in those areas characterized by highly erodible deposits, the identification and paleoseismic trenching of active seismogenetic faults has remained a challenge. In order to overcome these issues, we took an archaeoseismological approach for casting light on earthquake occurrence in one of these regions, i.e., the SE area of central Ionian Calabria (Marchesato region). The extensive traces of simultaneous and abrupt collapses in the Roman settlement of Capo Colonna (in the area of the sixth and fifth b.c. sanctuary of Hera Lacinia, near the town of Crotone) are evidence of a disruptive earthquake, which occurred possibly in the third century a.d. To the same event we ascribe the definitive collapse of the Hera Lacinia temple. Considering the seismotectonic framework of the region, this event could be tentatively associated with the active fault system which cuts from NW to SE the whole Sila massif and its Ionian slope, and which should be responsible for all the others known M > 6 earthquakes in the area. 相似文献
18.
Cities’ ability reducing earthquake disasters is a complex system involving numerous factors, moreover the research on evaluating
cities’ ability reducing earthquake disasters relates to multi-subject, such as earthquake science, social science, economical
science and so on. In this paper, firstly, the conception of cities’ ability reducing earthquake disasters is presented, and
the ability could be evaluated with three basic elements — the possible seismic casualty and economic loss during the future
earthquakes that are likely to occur in the city and its surroundings and time required for recovery after earthquake; based
upon these three basic elements, a framework, which consists of six main components, for evaluating city’s ability reducing
earthquake disasters is proposed; then the statistical relations between the index system and the ratio of seismic casualty,
the ratio of economic loss and recovery time are gained utilizing the cities’ prediction results of earthquake disasters which
were made during the ninth five-year plan; at last, the method defining the comprehensive index of cities’ ability reducing
earthquake disasters is presented. Thus the relatively comprehensive theory frame is set up. The frame can evaluate cities’
ability reducing earthquake disasters absolutely and quantitatively and consequently instruct the decision-making on reducing
cities’ earthquake disasters loss.
Foundation item: State Important Research Project of China (95130603). 相似文献
19.
The relation between the local mean lunar time τ of earthquake occurrence and their fault trends is studied in this paper.
The local mean lunar times τ of 53 earthquakes in 24 groups are calculated. Because the tidal generation force arisen by the
moon is a cyclic function of about 12 hours 25 minutes in the main, the two tidal generation forces anywhere in the earth
arising by the moon are equal in general when the moon lies to the two sites of 180° interval of local mean lunar time. Based
on this phenomenon the values Δτ of τ1–τ2 or τ1–τ2 ± 180° of two earthquakes occurring repetitiously in the same place are also calculated. The calculated results show that
if the fault trends of the two earthquakes in the same place is near, the Δτ is usually smaller and if the fault trends of
the two ones is not near, the Δτ is usually larger and the distribution of the local mean lunar time τ of earthquakes in different
places is dispersive even if fault trends of these earthquakes are near, and the τ does not concentrate on the lower and upper
transit of the moon. The above phenomena clear up that the triggering earthquake of earth solid tide arisen by the moon is
relative with the fault trends of earthquakes and we ought to think over the difference of environmental conditions of earthquake
preparation of each seismogenic zone and can not make statistics to earthquakes in different places when we study the relation
between the solid earth tide arisen by the moon and earthquakes. 相似文献
20.
I. S. Vladimirova G. M. Steblov D. I. Frolov 《Izvestiya Physics of the Solid Earth》2011,47(11):1020-1025
Continuous measurements at the Kuril GPS network since 2006 have revealed anomalous coseismic and postseismic displacements
of the Earth’s crust, which accompanied the great 2006–2007 earthquake doublet in the central Kuriles and were observed during
2.5 years after the events. Prior to the earthquakes, all observation sites of the Kuril network were moving towards the continent
due to the subduction deformation of the continental margin. After the events, the direction of displacement had changed to
the opposite direction at the stations located on the Matua, Ketoy, and Kharimkotan Islands, which were the nearest to the
seismic events, and experienced a significant turn on the Urup Island nearby. Modeling of postseismic viscoelastic relaxation
of strains in the asthenosphere suggested an acceptable explanation for the long-term anomalous offsets revealed. By solving
the corresponding inverse problems, we estimated the viscosity of the upper mantle and constrained the slip distribution of
the 2006 Simushir earthquake. 相似文献