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1.
K. F. Tiampo J. B. Rundle W. Klein J. S. SÁ Martins 《Pure and Applied Geophysics》2004,161(9-10):1957-1968
— Attempts to understand the physics of earthquakes over the past decade generally have focused on applying methods and theories developed based upon phase transitions, materials science, and percolation theory to a variety of numerical simulations of extended fault networks. This recent work suggests that fault systems can be interpreted as mean-field threshold systems in metastable equilibrium (Rundle et al., 1995; Klein et al., 1997; Ferguson et al., 1999), and that these results strongly support the view that seismic activity is highly correlated across many space and time scales within large volumes of the earth’s crust (Rundle et al., 2000; Tiampo et al., 2002). In these systems, the time averaged elastic energy of the system fluctuates around a constant value for some period of time and is punctuated by major events that reorder the system before it settles into another metastable energy well. One way to measure the stability of such a system is to check a quantity called the Thirumalai-Mountain (TM) energy metric (Thirumalai and Mountain, 1993; Klein et al., 1996). In particular, using this metric, we show that the actual California fault system is ergodic in space and time for the period in question, punctuated by the occurrence of large earthquakes, and that, for individual events in the system, there are correlated regions that are a subset of the larger fault network. 相似文献
2.
Xue-Ze Wen 《地震学报(英文版)》1993,6(4):993-1004
Spatial distribution of sources of strong and large earthquakes on the Xiaojiang fault zone in eastern Yunnan is studied according
to historical earthquake data. 7 segments of relatively independent sources or basic units of rupture along the fault zone
have been identified preliminarily. On every segment, time intervals between main historical earthquakes are generally characterized
by “time-predictable” recurrence behavior with indetermination. A statistic model for the time intervals between earthquakes
of the fault zone has been preliminarily established. And a mathematical method has been introduced into this paper to reckon
average recurrence interval between earthquakes under the condition of having known the size of the last event at a specific
segment. Based on these, ranges of the average recurrence intervals given confidence have been estimated for events of various
sizes on the fault zone. Further, the author puts forward a real-time probabilistic model that is suitable to analyze seismic
potential for individual segments along a fault zone on which earthquake recurrence intervals have been characterized by quasi-time-predictable
behavior, and applies this model to calculate conditional probabilities and probability gains of earthquake recurring on the
individual segments of the Xiaojiang fault zone during the period from 1991 to 2005. As a consequence, it has shown that two
parts of this fault zone, from south of Dongchuan to Songming and from Chengjiang to Huaning, have relatively high likelihoods
for strong or large earthquake recurring in the future.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 322–330, 1993. 相似文献
3.
2022年9月5日四川泸定发生M6.8地震,为研究泸定地震孕震区的应力变化,选取b值、小震调制比和丛集率这3个参数,对泸定地震前的区域地震活动状态进行计算研究。结果显示:泸定及周边区域几次强震发生前,区域地震活动均存在持续时间较长的低b值时段,且在低b值状态下震前短期内出现小震高丛集、高调制比的现象;鲜水河断裂带的地震活动状态分析显示,此次泸定地震前该断裂带存在持续时间近10个月的低b值状态,且短期内出现丛集率升高、调制比高值现象。通过对比分析,认为泸定地震是鲜水河断裂带构造运动的结果。综合分析认为,结合应力场背景和构造条件研究地震活动b值、固体潮调制比和丛集率的时空变化有助于理解大地震的孕育演化过程。 相似文献
4.
5.
The characteristics of spatio-temporal seismicity evolution before the Wenchuan earthquake are studied. The results mainly involve in the trend abnormal features and its relation to the Wenchuan earthquake. The western Chinese mainland and its adjacent area has been in the seismically active period since 2001, while the seismic activity shows the obvious quiescence of M≥?7.0, M≥?6.0 and M?≥5.0 earthquakes in Chinese mainland. A quiescence area with M?≥7.0 has been formed in the middle of the North-South seismic zone since 1988, and the Wenchuan earthquake occurred just within this area. There are a background seismicity gap of M?≥5.0 earthquakes and a seismogenic gap of ML?≥4.0 earthquakes in the area of Longmenshan fault zone and its vicinity prior to the Wenchuan earthquake. The seismic activity obviously strengthened and a doughnut-shape pattern of M?≥4.6 earthquakes is formed in the middle and southern part of the North-South seismic zone after the 2003 Dayao, Yunnan, earthquake. Sichuan and its vicinity in the middle of the doughnut-shape pattern show abnormal quiescence. At the same time, the seismicity of earthquake swarms is significant and shows heterogeneity in the temporal and spatial process. A swarm gap appears in the M4.6 seismically quiet area, and the Wenchuan earthquake occurred just on the margin of the gap. In addition, in the short term before the Wenchuan earthquake, the quiescence of earthquake with ML≥?4.0 appears in Qinghai-Tibet block and a seismic belt of ML?≥3.0 earthquakes, with NW striking and oblique with Longmenshan fault zone, is formed. 相似文献
6.
Numerous cases of precursory seismic quiescence have been reported in recent years. Some investigators have interpreted these observations as evidence that seismic quiescence is a somewhat reliable precursor to moderate or large earthquakes. However, because failures of the pattern to predict earthquakes may not, in general, be reported, and because numerous earthquakes are not preceded by quiescence, the validity and reliability of the quiescence precursor have not been established.We have analyzed the seismicity rate prior to, and in the source region of, 37 shallow earthquakes (M 5.3–7.0) in central California and Japan for patterns of rate fluctuation, especially precursory quiescence. Nonuniformity in rate for these pre-mainshock sequences is relatively high, and numerous intervals with significant (p<0.10) extrema in rate are observed in some of the sequences. In other sequences, however, the rate remains within normal limits up to the time of the mainshock. Overall, in terms of an observational basis for intermediate-term earthquake prediction, no evidence is found in the cases studied for a systematic, widespread or reliable pattern of quiescence prior to the mainshocks.In earthquake sequences comprising full seismic cycles for 5 sets of (M 3.7–5.1) repeat earthquakes on the San Andreas fault near Bear Valley, California, the seismicity rates are found to be uniform. A composite of the estimated rate fluctuations for the sequences, normalized to the length of the seismic cycle, reveals a weak pattern of a low rate in the first third of the cycle, and a high rate in the last few months. While these observations are qualitative, they may represent weak expressions of physical processes occurring in the source region over the seismic cycle.Re-examination of seismicity rate fluctuations in volumes along the creeping section of the San Andreas fault specified by Wyss and Burford (1985) qualitatively confirms the existence of low-rate intervals in volumes 361, 386, 382, 372 and 401. However, only the quiescence in volume 386 is found by the present study to be statistically significant. 相似文献
7.
Mircea Radulian Cezar-Ioan Trifu Florin Octavian Cârbunar 《Pure and Applied Geophysics》1991,136(4):499-514
A numerical algorithm is proposed for the simulation of the earthquake process during a seismic cycle. The algorithm is based on a heterogeneous discrete model of the fault plane and assumes there are two kinds of seismicity: background crack-like earthquakes and asperity-like events. An active zone of the fault contains an asperity distribution with a characteristic elementary area. The background seismicity randomly develops shear stress-free surfaces which tend to surround the asperities as in a 2D percolation process. The model parameters are taken from observations on the Vrancea (Romania) intermediate depth seismic region. The results emphasize the significant role of the geometry in the mechanism of the seismic failure. The algorithm predicts the nonlinear behavior in the frequency-magnitude distribution, the decrease of theb-slope associated with the asperity-like events, the magnitude range of major earthquakes, and their recurrence times. 相似文献
8.
K. F. Tiampo W. Klein H.-C. Li A. Mignan Y. Toya S. Z. L. Kohen-Kadosh J. B. Rundle C.-C. Chen 《Pure and Applied Geophysics》2010,167(6-7):763-782
Recently the equilibrium property of ergodicity was identified in an earthquake fault system (Tiampo et al., Phys. Rev. Lett. 91, 238501, 2003; Phys. Rev. E 75, 066107, 2007). Ergodicity in this context not only requires that the system is stationary for these networks at the applicable spatial and temporal scales, but also implies that they are in a state of metastable equilibrium, one in which the ensemble averages can be substituted for temporal averages when studying their behavior in space and time. In this work we show that this property can be used to identify those regions of parameter space which are stationary when applied to the seismicity of two naturally-occurring earthquake fault networks. We apply this measure to one particular seismicity-based forecasting tool, the Pattern Informatics index (Tiampo et al., Europhys. Lett. 60, 481–487, 2002; Rundle et al., Proc. National Acad. Sci., U.S.A., Suppl. 1, 99, 2463, 2002), in order to test the hypothesis that the identification of ergodic regions can be used to improve and optimize forecasts that rely on historic seismicity catalogs. We also apply the same measure to synthetic catalogs in order to better understand the physical process that affects this accuracy. We show that, in particular, ergodic regions defined by magnitude and time period provide more reliable forecasts of future events in both natural and synthetic catalogs, and that these improvements can be directly related to specific features or properties of the catalogs that impact the behavior of their spatial and temporal statistics. 相似文献
9.
（黄培华）（苏维加）（陈金波）ＳｅｉｓｍｉｃｉｔｙａｎｄｓｔｒｅｓｓｆｉｅｌｄｉｎＯｋｉｎａｗａＴｒｏｕｇｈａｎｄＲｙｕｋｙｕｒｅｇｉｏｎｓ￥Ｐｅｉ－ＨｕａＨＵＡＮＧ；Ｗｅｉ－ｊｉａＳＵａｎｄＪｉｎ－ＢｏＣＨＥＮ（ＤｅｐａｒｔｍｅｎｔｏｆＥａｒｔｈａ... 相似文献
10.
A seismic gap on the Anninghe fault in western Sichuan,China 总被引：10，自引：0，他引：10
Through integrated analyses of time-varying patterns of regional seismicity, occurrence background of strong and large historical earthquakes along active faults, and temporal-spatial distribution of accu- rately relocated hypocenters of modern small earthquakes, this paper analyzes and discusses the im- plication of a 30-year-lasting seismic quiescence in the region along and surrounding the Anninghe and Zemuhe faults in western Sichuan, China. It suggests that the seismic quiescence for ML≥4.0 events has been lasting in the studied region since January, 1977, along with the formation and evaluation of a seismic gap of the second kind, the Anninghe seismic gap. The Anninghe seismic gap has the background of a seismic gap of the first kind along the Anninghe fault, and has resulted from evident fault-locking and strain-accumulating along the fault during the last 30 years. Now, two fault sections either without or with less small earthquakes exist along the Anninghe fault within the An- ninghe seismic gap. They indicate two linked and locked fault-sections, the northern Mianning section and the Mianning-Xichang section with lengths of 65 km and 75 km and elapsed time from the latest large earthquakes of 527 and 471 years, respectively. Along the Anninghe fault, characteristics of both the background of the first kind seismic gap and the seismicity patterns of the second seismic gap, as well as the hypocenter depth distribution of modern small earthquakes are comparable, respectively, to those appearing before the M=8.1 Hoh Xil earthquake of 2001 and to those emerging in the 20 years before the M=7.1 Loma Prieta, California, earthquake of 1989, suggesting that the Anninghe seismic gap is tending to become mature, and hence its mid- to long-term potential of large earthquakes should be noticeable. The probable maximum magnitudes of the potential earthquakes are estimated to be as large as 7.4 for both the two locked sections of the Anninghe fault. 相似文献
11.
Dynamic simulation of interactions between major earthquakes on the Xianshuihe fault zone 总被引：3，自引：0，他引：3
The authors firstly evaluate the strain accumulation rate of the Xianshuihe fault zone based on earth- quake activity. We calculated the stress and seismic moment accumulation rate for each subsection of the Xianshuihe fault zone based on the distribution of geological slip rate and GPS survey results. According to the results, we get the recurrence intervals of characterized earthquakes on each sub- section respectively. A three-dimensional finite element model for western Sichuan is constructed to discuss the earthquakes triggering among major earthquakes (M>6.7) that occurred along the Xianshuihe fault zone since 1893. The calculated Coulomb failure stress changes (ΔCFS) show that 5 of the 6 earthquakes with Ms>6.7 were triggered by positive ΔCFS. The interactions between major earthquakes not only influence recurrence intervals of characterized earthquakes on each subsection, but also change recurrence behavior of major earthquakes along the whole fault zone. 相似文献
12.
We investigate spatio-temporal properties of earthquake patterns in the San Jacinto fault zone (SJFZ), California, between Cajon Pass and the Superstition Hill Fault, using a long record of simulated seismicity constrained by available seismological and geological data. The model provides an effective realization of a large segmented strike-slip fault zone in a 3D elastic half-space, with heterogeneous distribution of static friction chosen to represent several clear step-overs at the surface. The simulated synthetic catalog reproduces well the basic statistical features of the instrumental seismicity recorded at the SJFZ area since 1981. The model also produces events larger than those included in the short instrumental record, consistent with paleo-earthquakes documented at sites along the SJFZ for the last 1,400 years. The general agreement between the synthetic and observed data allows us to address with the long-simulated seismicity questions related to large earthquakes and expected seismic hazard. The interaction between m ≥ 7 events on different sections of the SJFZ is found to be close to random. The hazard associated with m ≥ 7 events on the SJFZ increases significantly if the long record of simulated seismicity is taken into account. The model simulations indicate that the recent increased number of observed intermediate SJFZ earthquakes is a robust statistical feature heralding the occurrence of m ≥ 7 earthquakes. The hypocenters of the m ≥ 5 events in the simulation results move progressively towards the hypocenter of the upcoming m ≥ 7 earthquake. 相似文献
13.
Simulation and properties of a non-homogeneous spring-block earthquake model with asperities 总被引：1，自引：0，他引：1
Alejandro Muñoz-Diosdado Adolfo H. Rudolf-Navarro Fernando Angulo-Brown 《Acta Geophysica》2012,60(3):740-757
The spring-block model proposed by Olami, Feder and Christensen (OFC) has several properties that are similar to those observed
in real seismicity. In this paper we propose a modification of the original model in order to take into account that in a
real fault there are several regions with different properties (non-homogeneity). We define regions in the network that is
reminiscent of the real seismic fault, with different sizes and elastic parameter values. We obtain the Gutenberg-Richter
law for the synthetic earthquake distributions of magnitude and the stair-shaped plots for the cumulative seismicity. Again,
as in the OFC-homogeneous case, we obtain the stability for the cumulative seismicity stair-shaped graphs in the long-term
situation; this means that the straight line slopes that are superior bounds of the staircases have a behavior akin to the
homogeneous case. We show that with this non-homogeneous OFC model it is possible to include the asperity concept to describe
high-stress zones in the fault. 相似文献
14.
The numerical block-model of the lithosphere dynamics is used to simulate seismicity in Italy and its surroundings, based
on the available structural and geodynamics information. The purpose of the study is to understand which are the tectonic
processes that control the main features of the observed seismicity and the kinematics of the region. The influence of the
rheology of the fault systems is studied as well. The model we use differs from other modeling approaches in that it simulates
earthquakes and hence it possibly relates to seismicity and geodynamics. The model provides an effective capability to include
the set of documented constraints supplied by widely available earthquake catalogs. This is done by means of the comparison
of the GR relation, of the focal mechanisms and of the space distribution for observed and computed seismicity. The region
is modeled as a system of perfectly rigid blocks, separated by infinitely thin fault planes, in viscoelastic interaction between
themselves and with the underlying medium. The movement of the boundary blocks and of the underlying medium determines the
motion of the blocks. The synthetic seismicity obtained with the defined block-model is similar to the observed one for the
most seismically active areas. A linear frequency-magnitude (FM) relation (Gutenberg-Richter law) is obtained for synthetic
earthquakes; the slope (b-value) of the FM plot appears larger for the synthetic seismicity than for the observed one. Nevertheless, the b-value is essentially larger in northern and central Italy than that in southern Italy, both in the model and in the observations.
The analysis of the source mechanisms of the synthetic earthquakes shows a good agreement with the observations. In the model
normal faulting is typical for the Apennines, the eastern edge of Sicily and the Calabrian arc, while reverse faulting takes
place at the northwestern boundary of the Adriatic Sea, in the southern Alps and along the eastern edge of the Adria, along
the Dinarides. The model correctly reproduces the extension zone along the Apennines and the contraction zone along the northwestern
boundary of the Adriatic Sea; the counter-clockwise rotation of the Adria is mimed. The resulting movements of the blocks
are in overall agreement with GPS (Global Positioning System) observations. The results of the modeling experiments suggest
that the main features of dynamics and seismicity in the central Mediterranean region cannot be satisfactorily explained as
a consequence of Africa and Eurasia convergence only; the passive subduction in the Calabrian arc and the different rheology
of faults are essential as well. 相似文献
15.
Based on the morphostructural zoning scheme of the Caucasus, the block structure reflecting the real fault geometry and the block formation of the region is constructed. Several dozens of numerical experiments are conducted for simulating the dynamics of the block structure and the arising seismicity. The modeling relies on the following principles. It is assumed that the structure is composed of perfectly rigid blocks separated by infinitely thin fault planes. On the fault planes and on the blocks' bottoms, the blocks viscoelastically interact with each other and with the underlying medium. At each time instant, the translational displacements and rotations of the blocks are calculated from the condition of the quasi-static equilibrium of the entire block structure. The earthquakes occur in accordance with the dry friction model at the time instants when within a certain segment of the fault the stress-to-pressure ratio exceeds the given threshold. The modeling yields the synthetic catalog of the Caucasian earthquakes the spatial distribution of which reflects a set of characteristic features of the real seismicity. The similarity is observed in the magnitude–frequency diagrams of the synthetic and real seismicity. The comparison of the positions of the epicenters of the strong synthetic earthquakes with the results of recognizing the highly seismically active areas in the Caucasus demonstrates the presence of such epicenters in a few highly active areas where, according to the observations, strong earthquakes have not occurred to date. 相似文献
16.
利用2000—2013年四川数字地震台网和水库台网的波形资料以及川西流动台阵的事件波形,通过辨识发生在同一断层位置上的重复地震来定量研究鲜水河断裂带南段的深部变形.针对研究区台站分布稀疏的客观情况,应用了子采样条件下基于S-P相对到时差来约束震源位置一致性的方法,在鲜水河断裂带识别出11组重复地震,并利用连续波形资料进行了重复地震完整性的初步测试,同时运用结合波形互相关资料的双差法来完成研究区背景地震和重复地震位置的精确定位.重新定位后的地震图像展示研究区中上地壳存在明显缺震层,其与壳内的低速低阻层相吻合.利用重复地震的地震矩和重复间隔,估算出鲜水河断裂带南段孕震深部的滑动速率为3.0~10.2mm·a-1,显示研究区不同地震构造区的深部滑动速率存在明显差异. 相似文献
17.
This study is concerned with quantitative estimation of the relationship between earthquakes and tectonic crustal fragmentation
based on a correlation analysis of fault density with seismicity parameters (the number and energy of earthquakes per unit
area) for the Sredne-Yamskoi seismic junction and adjacent area. The highest level of seismic activity and the highest probability
of earthquake occurrence with energy classes K ≥ 12 within areas that have a continental crust with a well-pronounced granite layer occur in those areas with the mean fault
density. Within areas with a thinner granite layer in the crust, the most likely seismic events are K ≥ 12 earthquakes that occur in areas with lower fault density. We estimated the relationship between the degree of crustal
fragmentation and the topography of stratification interfaces in the crust as identified by new interpretative gravimetry.
Zones with the lowest degree of fragmentation tend to be areas where the top of the crystalline basement lies deeper. 相似文献
18.
—We report the analysis of over 16 years of fault creep and seismicity data from part of the creeping section of the San Andreas fault to examine and assess the temporal association between creep events and subsequent earthquakes. The goal is to make a long-term evaluation of creep events as a potential earthquake precursor. We constructed a catalog of creep events from available digital creepmeter data and compared it to a declustered seismicity catalog for the area between San Juan Bautista and San Benito, California, for 1980 to 1996. For magnitude thresholds of 3.8 and above and time windows of 5 to 10 days, we find relatively high success rates (40% to 55% 'hits') but also very high false alarm rates (generally above 90%). These success rates are statistically significant (0.0007 < P < 0.04). We also tested the actual creep event catalog against two different types of synthetic seismicity catalogs, and found that creep events are followed closely in time by earthquakes from the real catalog far more frequently than the average for the synthetic catalogs, generally by more than two standard deviations. We find no identifiable spatial pattern between the creep events and earthquakes that are hit or missed. We conclude that there is a significant temporal correlation between creep events and subsequent small to moderate earthquakes, however that additional information (such as from other potential precursory phenomena) is required to reduce the false alarm rate to an acceptable level. 相似文献
19.
本文根据历史地震(Ms6.0)的资料,研究了鲜水河断裂带的地震活动性,并利用断层的位错模式进一步研究该断裂带的应力积累和释放过程.结果表明,该断裂带的强震活动大致以道孚为界,形成北西和南东两个活动地段,呈现南北交替活动的特征.地震能量的这种交替释放似具有准周期性质,Ms7.0级地震的平均复发周期为27.6年.给出该断裂带在三个不同时间段(1700-1811,1816-1967,1816-1982)强震断层作用引起的应力释放图象,讨论了前两个时间段地震应力场对其后发生的第一个大地震的重要影响.计算了1893年以来在断裂带南东段(相对闭锁段)的应力积累,示出相应的最大剪应力和流体静应力等值线图.最后,根据应力积累、附加应力变化、地震活动规律和应变释放曲线特征,估计了鲜水河断裂带的地震趋势.认为在本世纪末,在断裂带南东段的(1)康定-磨西段或(2)道孚-乾宁段或(3)乾宁-康定段将可能发生 Ms=7.40.3地震. 相似文献
20.
Noureddine Beghoul Jean-Luc Chatelain Mohamed-Salah Boughacha Hadj Benhallou Rida Dadou Amira Mezioud-Saïch 《Pure and Applied Geophysics》2010,167(3):277-321
Seismic events that occurred during the past half century in the Tellian Atlas, North Africa, are used to establish fundamental seismic empirical relations, tying earthquake magnitude to source parameters (seismic moment, fault plane area, maximal displacement along the fault, and fault plane length). Those empirical relations applied to the overall seismicity from 1716 to present are used to transform the magnitude (or intensity) versus time distribution into (1) cumulative seismic moment versus time, and (2) cumulative displacements versus time. Both of those parameters as well as the computed seismic moment rate, the strain rate along the Tellian Atlas strike, and various other geological observations are consistent with the existence, in the Tellian Atlas, of three distinct active tectonic blocks. These blocks are seismically decoupled from each other, thus allowing consideration of the seismicity as occurring in three different distinct seismotectonic blocks. The cumulative displacement versus time from 1900 to present for each of these tectonic blocks presents a remarkable pattern of recurrence time intervals and precursors associated with major earthquakes. Indeed, most major earthquakes that occurred in these three blocks might have been predicted in time. The Tellian Atlas historical seismicity from the year 881 to the present more substantially confirms these observations, in particular for the western block of the Tellian Atlas. Theoretical determination of recurrence time intervals for the Tellian Atlas large earthquakes using Molnar and Kostrov formalisms is also consistent with these observations. Substantial observations support the fact that the western and central Tellian Atlas are currently at very high seismic risk, in particular the central part. Indeed, most of the accumulated seismic energy in the central Tellian Atlas crust has yet to be released, despite the occurrence of the recent destructive May 2003 Boumerdes earthquake (M w = 6.8). The accumulated seismic energy is equivalent to a magnitude 7.6 earthquake. In situ stress and geodetic measurements, as well as other geophysical field data measurements, are now required to practically check the validity of those observations. 相似文献