Earthquake Probability of the “Seismic Gap” on the Longmenshan Fault

Using the layered viscoelastic medium model, this paper calculated the coulomb stress loading effect on the Lushan epicenter generated by the Wenchuan earthquake. Then combined with the rate-state friction law proposed by Dieterich J. (1994), we obtain the probability of an M_W ≥ 6.0 earthquake occurring in the vicinity of Lushan. The results show that the probability of M_W ≥ 6.0 earthquake of the Lushan region in 2013 is up to 18%, indicating that the stress disturbance caused by the Wenchuan earthquake accelerated the Lushan earthquake. This paper also calculates the coulomb stress accumulation on the "seismic gap" generated by the two earthquakes of Wenchuan and Lushan, and combined with the background seismicity, gives the M_W>6.0 earthquake probability of the "seismic gap". Although there may be a certain error in the results because of the Dayi earthquake, selection of the medium model parameters and background seismicity, the seismic probability of the "seismic gap" is increasing. Thus, we think destructive earthquakes are still likely to occur in the "seismic gap".     

The Volutionary Characteristics of Seismic Activity in the SichuanYunnan Region,China

Based on the earthquake activity characteristics of the diamond block in the Sichuan-Yunnan region and by using the method of the meso-scope damage dynamics and damage evolution,we studied the damage evolution process for moderately strong earthquakes along two seismicbelts.The original combination patterns of all the units which illuminate the changes from stable state to destroyed state are given.All these patterns can direct the earthquake prediction practice in this region     

Characteristics of aerosol optical depth and Ångström parameters over Mohal in the Kullu Valley of Northwest Himalayan Region,India

The measurements using a ground based multi wavelength radiometer (MWR) at Mohal (31°54′N, 77°07′E, 1154 m AMSL) in the Kullu valley of Northwestern Himalayan region show that the spectral aerosol optical depth (AOD) and turbidity coefficient, β, are high in summer, moderate in monsoon season, low in winter and lowest in autumn, while wavelength exponent, α, has an opposite trend. Average annual value of AOD at 500 nm is 0.24±0.01, 0.43±0.02, and 0.28±0.02; that of β is 0.14±0.01, 0.22±0.02, and 0.17±0.03; and that of α is 1.06±0.09, 1.16±0.10, and 0.86±0.13, respectively, for clear, hazy and partially clear sky days. The considerably greater value of β on hazy days indicates more coarse particles in mountain haze. The fractional asymmetry factor (AF) is more negative in summer and autumn months. The AOD and β have significantly positive correlation with temperature and wind speed, suggesting high AODs and turbidity on hot and windy days.     

Variation of Seismic Frequency in the Yunnan Region After the Indonesia Earthquake With Ms8.7

The seismic frequency increased significantly in the Yunnan region after the Indonesia earthquake with M_S8.7 on December 26, 2004. This was estimated by analyzing the seismic frequency ratio between the influenced and normal times, the spatial distribution characteristics of the increased seismic frequency, the temporal-spatial distribution and types of seismic swarms. Seismic frequency increased at 71.3% of the statistical sites in the Yunnan area. The maximal increase ratio is 18.2.     

Exploration and Study on Deep Crust Structural Characteristics in the Jiashi-Artux Seismic Region

The data from two deep seismic sounding profiles was processed and studied comprehensively. The results show that crnst-mantle structures in the investigated region obviously display layered characteristics and velocity structures and tectonic features have larger distinction in different geological structure blocks. The boundary interface C between the upper and lower crust and Moho fluctuate greatly. The shallowest depths of C (30.0km) and Moho (45.5km) under Jiashi deepen sharply from Jiashi to the western Kunlun mountain areas, where the depths of C and Moho are 44.0km and 70.0km, respectively. The higher velocity structures in the Tarim massif determine its relatively “stable“ characteristics in crust tectonics. The phenomenon in the Jiashi region, where the distribution of earthquake foci mostly range from 20kin to 40kin in depth, may infer that the local uplift of C and Moho interface, anomalonsly lower velocity bodies and deep large faults control earthquake occurrence and seismogenic processes in the Jiashi strong earthquake swarm.     

Characteristics of Recent Horizontal Crustal Movement and Tectonic Deformation in the Northwest China Region

INTRODUCTIONThe vector diagramof the crustal horizontal movement of the north margin of Qinghai-Xizang(Tibet) block obtained from GPS measurements of 2001 ~2003 shows that the western part of theregion presents a southwestward movement oppositetothetrend beforethe Nov.14 ,2001 west KunlunMountains PassMS8 .1 earthquake ,which mayreflectthe post-earthquake relaxationand adjustment ofthe region (Zhang Xi ,2004) .It was the variation of regional dynamics that led to instability of thepo…     

Recent Crustal Stress Field and Dislocation Along Seismic Faults in the East China Region

INTRODUCTIONThere exist many methods for studying recent crustal stress field.One of the most commonmethodsis to use focal mechanismsolution data of earthquakes to deduce the recent crustal stressfield.The method is simple and feasible and the data obtained is reliable.Yan Jiaquan,et al.(1979)usedthe method to study the recent tectonic stress field in China and its adjacent areas andgave a rough configuration and regional characteristics of the stress field.Li Qinzu(1980),WeiGuangxing,e…     

How Can One Test the Seismic Gap Hypothesis? The Case of Repeated Ruptures in the Aleutians

—The test that Kagan and Jackson (1991, 1995) applied to the seismic gap hypothesis did not bring us closer to understanding the generation of large earthquakes. On the contrary, it led some to the conclusion that the rebound theory of earthquake generation should be rejected. We disagree with this point of view and argue that a global test of the simplified gap hypothesis cannot be done because it cannot account for differences in the slip history of fault segments and tectonic differences between separate plate boundaries. Kagan and Jackson did show, however, that the original gap hypothesis was oversimplified and should be refined. We propose that consideration of all the facts, including slip history and seismicity patterns in the Andreanof Islands, show that the concept of seismic gaps and the elastic rebound theory are correct for that segment of the plate boundary. The coseismic slip in the M _w 8.7 earthquake that broke this plate boundary segment in 1957 was only 2 m, as published before the repeat earthquake of 1986 (M _w 8), and thus, using a plate convergence rate of 7.3 cm/year, the return time in this cycle was expected to be less than 30 years, unless substantial aseismic creep occurs. This supports the time predictable model of mainshock recurrence. In addition, Kisslinger et al. (1985) and Kisslinger (1986) noticed a seismic quiescence in the subsequent source volume before the 1986 earthquake and attempted to predict it. The specific parameters he estimated were not entirely correct although his interpretation of the observed quiescence as a precursor was. We conclude that the 1986, M _w 8, Andreanof earthquake was not an example that disproves the seismic gap hypothesis. On the contrary, it shows that the hypothesis that plate motions reload plate boundaries after most of the elastic energy is released in great ruptures was correct in this case. This suggests that great earthquakes occur preferably in mature gaps. We believe the testing of the seismic gap hypothesis by algorithm on a global scale is an example that illustrates that overly simplified tests can lead to erroneous conclusions. To make progress in the actual understanding of the physics of the process of great earthquake ruptures, one must consider all the facts known for case histories.     

Study on the Relationship of Seismic Design Ground Motion at Different Fortification Levels in the Xinjiang Region

The seismic risk analysis results of 79 cities in Xinjiang are presented, and the bedrock peak ground accelerations under three seismic levels and their ratios are discussed. Then, the relationship between earthquake environments and the seismic risk analysis results of different exceeding probabilities are researched. The results show that minor and major earthquake motion parameters calculated from moderate earthquakes do not have a consistent probability and the ratio of bedrock peak accelerations under different exceedance probabilities are closely correlated with earthquake environments.     

A Seismic Mishap: the “Ural” Earthquake in 1693

The paper considers the problem of how Russian and European researchers of the 19th century became acquainted with the sources of the information about earthquakes in the Urals. Particular attention is devoted to the earliest known event in 1693. It is shown that this earthquake was mistakenly related to the Urals due to the primary source not being learned; in fact, it was fixed in Transbaikalia. The problem is posed about the need for professional work with historical materials and cataloging the events of the historical past.     

Seismic Hazard Assessment in the Boundary Region of Indo-China:First Phase of Implementation of the Global Seismic Hazard Assessment Program (GSHAP) in Continental Asia

The primary goal of the demonstration project endorsed by the Scientific and Technical Committee for IDNDR in 1992 is to ensure that national agencies are able to assess seismic hazard in a regionally coordinated fashion by using advanced methods.China,as a Regional Center of Central Southern Asia,has contacted with countries of the region to realistically practice seismic hazard assessments of Continental Asia.A test area located in the collision boundary between the Indian and Eurasian plates was chosen to examine the seismic hazard assessment approach in the regional coordinates.The seismotectonics and three versions of seismic sources of the test area are described in this paper and under the Global Seismic Hazard Assessment Program(GSHAP),guidelines an earthquake catalogue of the test area was assembled.Because of the incompleteness of earthquake data in different countries,we adopt different time windows for different magnitude intervals in order to obtain the seismicity parameters of sources.By u     

Corresponding Relation Between the Space-time Evolution of Seismic Apparent Strain and the Region of Strong Earthquakes in Yunnan

On the basis of our predecessors' research,we study the distribution and the space-time evolution characteristics of the seismic apparent strain field in Yunnan since the 1970's using the seismic data of Yunnan and its surrounding areas.The result shows that there is a rather strong corresponding relationship between the anomaly region of seismic apparent strain and strong earthquakes.In the nine earthquakes studied,anomaly areas of seismic apparent strain had appeared before eight earthquakes,including five occurring in the anomaly region and three on the edge.Finally,the investigative result is demonstrated primarily.     

Discussion on the Relation Between the Probabilistic Distribution of Magnitude in a Seismic Province and That in an Area with Potential Seismic Source

According to the joint probabilistic distribution model of magnitude and space,the author discusses the relationship between the probabilistic distribution of magnitude in a seismic province and that in an area with potential seismic sources.The results show that if the magnitude probabilistic distribution follows the truncated exponential form in a seismic province,there must be some potential source in which the magnitude probabilistic distribution does not conform to that form.The result is consistent with the concept of "characteristic earthquake" derived from the study of actual records of seismicity and the study of geology.The author suggests that the relationship between the probabilistic distribution of magnitude in a seismic province and that in a seismic potential area must be considered in the study of the analysis of seismicity,seismic zonation and engineering seismology,for the purpose of the evaluation of the probabilistic distribution of magnitude correctly in every area with potential s     

Estimation of Strong Ground Motion from a Great Earthquake Mw 8.5 in Central Seismic Gap Region, Himalaya (India) Using Empirical Green’s Function Technique

In the present study ground motions for a Mw 8.5 scenario earthquake are estimated at 13 sites in Kumaun-Garhwal region using the empirical Green’s function technique. The recordings of 1991 Uttarkashi earthquake of Mw 6.8 at these sites are used as an element earthquake. A heterogeneous source model consisting of two asperities is considered for simulating the ground motions. The entire central seismic gap (CSG) can expect acceleration in excess of 100 cm/s² with NW portion in excess of 400 cm/s² and SE between 100 and 200 cm/s². The central portion can expect peak ground acceleration (PGA) between 200 and 400 cm/s². It has been observed from simulation of strong ground motion that sites located near the rupture initiation point can expect accelerations in excess of 1g. In the present analysis, Bhatwari and Uttarkashi can expect ground accelerations in excess of 1g. The estimates of the PGA are compared with earlier studies in the same region using different methodologies and it was found that the results are comparable. This has put constrains on the expected PGAs in this region. The obtained PGA values can be used in identifying the vulnerable areas in the central Himalaya, thereby facilitating the planning, design and construction of new structures and strengthening of the existing structures in the region.     

Moment tensor inversion of small to moderate earthquakes in the Capital Region in 2004

The moment tensor solutions of 51 small to moderate earthquakes occurred in the Capital Region in the year of 2004 are obtained by inverting the broadband waveform data. Accordingly, other source parameters, such as scalar seismic moments, moment magnitudes, double-couple （DC） components and compensated-linear-vector-dipole （CLVD） components, are determined as well as fault parameters and stress-axis parameters. The inverted results are evaluated by groups of numerical tests.     

Seismic Activity and Structures of the Crust and Upper Mantle in the Areas of Source Zones of the Largest Earthquakes in the Altai–Sayan Region

The results of studies of the shear wave attenuation field in source zones of the 2003 Chuya, 1970 Ureg-Nur, 1991 Busingol, 2011 Sayan, and 2011–2012 Tuva earthquakes are presented. Attenuation fields in these source zones include blocks with a high Q-factor and linear weakened zones. The surface ruptures from the mainshocks of the 2003 Chuya and 2011–2012 Tuva earthquakes are located in the zones of strong attenuation. Epicenters of the mainshocks are located where the maximum contrast in attenuation is observed. In the source zones of large earthquakes in the Altai–Sayan region or near them, the zones similar to so-called seimogenic bodies described in the literature are found. These objects tend to linear zones with high attenuation and are characterized by an increased density of deepened earthquakes and also by deformations of near-vertical elongation. The obtained data suggest that the fluid factor could play certain role in the occurrence of large earthquakes in the Altai–Sayan region.     

Erratum to: Seasonal Variations in the b-Value of the Reservoir-Triggered Seismicity in the Koyna–Warna Region,Western India

Izvestiya, Physics of the Solid Earth - An Erratum to this paper has been published: https://doi.org/10.1134/S1069351322090014     

Seismic sentinel? An analysis of captive giant panda behavior in response to the Lushan earthquake in China

It is widely believed that various animal species can sense and respond to the geophysical stimuli that precede earthquakes, especially electromagnetic fields, although supporting field evidence is mostly anecdotal. Here we report on the reactions of four female giant pandas under observation over the three days prior to the Lushan (30.1°N, 103.0°E) magnitude 7.0 earthquake that occurred in Sichuan province, China, on April 20, 2013. We observed no significant generalized behavioral anomalies indicative of them perceiving an impending earthquake. We also observed no startle behaviors in the 5 s prior to tremors commencing, indicating that these pandas either did not detect or did not respond to precursor P-waves. Our findings suggest that although giant pandas have evolved in, and continue to occupy exclusively, a seismically active range in central China, they do not appear to perceive pre-earthquake geophysical warning signs.