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1.
By using orthogonal regression method, a systematic comparison is made between surface wave magnitudes determined by Institute of Geophysics of China Earthquake Administration （IGCEA） and National Earthquake Information Center of US Geological Survey （USGS/NEIC） on the basis of observation data collected by the two institutions between 1983 and 2004. A formula is obtained which reveals the relationship between surface wave magnitudes determined by China seismograph network and US seismograph network. The result shows that, as different calculation formulae and observational instruments are used, surface wave magnitude determined by IGCEA is generally greater by 0.2 than that determined by NEIC： for M=3.5-4.5 earthquakes, it is greater by 0.3; for M=5.0-6.5 earthquakes, it is greater by 0.2; and for M≥7.0 earthquakes, it is greater by no more than 0.1.  相似文献   

2.
By using orthogonal regression method, a systematic comparison is made between body wave magnitudes determined by Institute of Geophysics of China Earthquake Administration (IGCEA) and National Earthquake Information Center of US Geological Survey (USGS/NEIC) on the basis of observation data from China and US seismograph networks between 1983 and 2004. The result of orthogonal regression shows no systematic error between body wave magnitude mb determined by IGCEA and mb (NEIC). Provided that mb (NEIC) is taken as the benchmark, body wave magnitude determined by IGCEA is greater by 0.2～0.1 than the magnitude determined by NEIC for M=3.5～4.5 earthquakes; for M=5.0～5.5 earthquakes, there is no difference; and for M≥6.0 earthquakes, it is smaller by no more than 0.2. This is consistent with the result of comparison by IDC (International Data Center).  相似文献   

3.
By using orthogonal regression method, a systematic comparison is made between surface wave magnitudes determined by Institute of Geophysics of China Earthquake Administration (IGCEA) and National Earthquake Information Center of US Geological Survey (USGS/NEIC) on the basis of observation data collected by the two institutions between 1983 and 2004. A formula is obtained which reveals the relationship between surface wave magnitudes determined by China seismograph network and US seismograph network. The result shows that, as different calculation formulae and observational instruments are used, surface wave magnitude determined by IGCEA is generally greater by 0.2 than that determined by NEIC: for M=3.5～4.5 earthquakes, it is greater by 0.3;for M=5.0～6.5 earthquakes, it is greater by 0.2;and for M≥7.0 earthquakes, it is greater by no more than 0.1.  相似文献   

4.
Introduction According to the Rapid Earthquake Information Release of CNDSN (Department of Earth- quake Monitoring and Prediction, China Earthquake Administration, 2002), an earthquake with surface wave magnitude MS=8.1 shook west of Kunlun Mountain Pass (KMP) at the juncture of Xinjiang, Qinghai and Xizang on November 14, 2001. This is the largest and the only MS>8.0 earthquake in Chinese mainland over 50 years since the August 15, 1950 MS=8.6 (MW=8.6) Chayuearthquake in Tibeta…  相似文献   

5.
By linear regression and orthogonal regression methods, comparisons are made between different magnitudes (lo-cal magnitude ML, surface wave magnitudes MS and MS7, long-period body wave magnitude mB and short-period body wave magnitude mb) determined by Institute of Geophysics, China Earthquake Administration, on the basis of observation data collected by China Seismograph Network between 1983 and 2004. Empirical relations between different magnitudes have been obtained. The result shows that: 1 As different magnitude scales reflect radiated energy by seismic waves within different periods, earthquake magnitudes can be described more objectively by using different scales for earthquakes of different magnitudes. When the epicentral distance is less than 1 000 km, local magnitude ML can be a preferable scale; In case M<4.5, there is little difference between the magnitude scales; In case 4.5MS, i.e., MS underestimates magnitudes of such events, therefore, mB can be a better choice; In case M>6.0, MS>mB>mb, both mB and mb underestimate the magnitudes, so MS is a preferable scale for deter-mining magnitudes of such events (6.08.5, a saturation phenomenon appears in MS, which cannot give an accurate reflection of the magnitudes of such large events; 2 In China, when the epicentral distance is less than 1 000 km, there is almost no difference between ML and MS, and thus there is no need to convert be-tween the two magnitudes in practice; 3 Although MS and MS7 are both surface wave magnitudes, MS is in general greater than MS7 by 0.2~0.3 magnitude, because different instruments and calculation formulae are used; 4 mB is almost equal to mb for earthquakes around mB4.0, but mB is larger than mb for those of mB≥4.5, because the periods of seismic waves used for measuring mB and mb are different though the calculation formulae are the same.  相似文献   

6.
Empirical Global Relations Converting M S and m b to Moment Magnitude   总被引：1，自引：0，他引：1  
The existence of several magnitude scales used by seismological centers all over the world and the compilation of earthquake catalogs by many authors have rendered globally valid relations connecting magnitude scales a necessity. This would allow the creation of a homogeneous global earthquake catalog, a useful tool for earthquake research. Of special interest is the definition of global relations converting different magnitude scales to the most reliable and useful scale of magnitude, the moment magnitude, M W. In order to accomplish this, a very large sample of data from international seismological sources (ISC, NEIC, HRVD, etc.) has been collected and processed. The magnitude scales tested against M W are the surface wave magnitude, M S, the body wave magnitude, m b, and the local magnitude, M L. The moment magnitudes adopted have been taken from the CMT solutions of HRVD and USGS. The data set used in this study contains 20,407 earthquakes, which occurred all over the world during the time period 1.1.1976–31.5.2003, for which moment magnitudes are available. It is shown that well-defined relations hold between M W and m b and M S and that these relations can be reliably used for compiling homogeneous, with respect to magnitude, earthquake catalogs.  相似文献   

7.
Introduction The characteristics of generalized foreshock and direct foreshock and their identification,as well as their application to medium and short-term prediction of strong earthquake is a major study objective in seismometry both in China and abroad.China has made many short-term and imminent earthquake predictions.Among the ones with clear hazard-mitigating effect and social manifestation,direct foreshock has made an obvious contribution,for example,the MS=7.2Menglian earthquake occu…  相似文献   

8.
WANG  Jian 《地震学报(英文版)》2004,17(4):381-388
In this paper, we calculated the seismic pattern of instrumental recorded small and moderate earthquakes near the epicenter of the 1303 Hongtong M=8 earthquake, Shanxi Province. According to the spatial distribution of small and moderate earthquakes, 6 seismic dense zones are delineated. Temporal distribution of ML≥2 earthquakes since 1970 in each seismic dense zone has been analyzed. Based on temporal distribution characteristics and historical earthquake activity, three types of seismicities are proposed. The relationship between seismic types and crustal medium is analyzed. The mechanism of three types is discussed. Finity of strong earthquake recurrence is proposed. Seismic hazard in mid-long term and diversity of earthquake disaster in Shanxi seismic belt are discussed.  相似文献   

9.
使用中国地震台网全面完成数字化之后的观测资料（2008 2012年）,对中国地震台网和美国地震台网测定的体波震级从震级大小、震中距、震源深度和震中方位进行对比分析.由对比结果可知：中国和美国地震台网测定的mb之间无系统化差异,但中国地震台网测定的mB与美国地震台网测定的mb存在一定系统偏差（mB平均偏大0.22）;震源深度对震级偏差有一定影响,具体表现为浅源地震偏差大于中深源地震;震中距及四象限分布对偏差基本没有影响.  相似文献   

10.
Data from 753 earthquakes are used to determine a relationship between surface-wave magnitude (M s) and bodywave magnitude (m b), and from 541 earthquakes to determine a relationship between surface-wave magnitude (M s) and local magnitude (M L) for China and vicinity: M s=0.9883 m b-0.0420, M s=0.9919 M L-0.1773. The relationship of M s versus m b is obtained for 292 events occurred in the Chinese mainland in the time period from 1964 to 1996, 291 events occurred in Taiwan in the time period from 1964 to 1995 and 170 events occurred in the surrounding area. Standard deviation of the fitting is 0.445. Relationship of M s versus M L is obtained for 36 events occurred in the Chinese mainland, 293 events occurred in Taiwan, China and 212 events occurred in the surrounding area. The total amount is 541 events. Standard deviation of the fitting is 0.4673. The uncertainties of the converted M s in different magnitude intervals can be estimated using complementary cumulative distribution function (CCDF). In the relationship of M s versus m b, taking ±0.25 as a range of uncertainties, in magnitude interval m b 4.0–4.9, the probabilities for the converted M s taken value less than (M s-0.25) and more than (M s+0.25) are 17% and 27% respectively. Similarly, we have probabilities for m b 5.0–5.9 are 34% and 20% and that for m b 6.0–6.9 are 11% and 47%. In the relationship of M s versus M L, if the range of uncertainties is still taken as ±0.25, the corresponding probabilities for magnitude interval M L 4.0–4.9 are 22% and 38%, for M L 5.0–5.9 are 20% and 15% and for magnitude interval M L 6.0–6.9, are 15% and 29%, respectively. The relationships developed in this paper can be used for the conversion of one magnitude scale into another magnitude scales conveniently. The estimation of uncertainties described in this paper is more accurate and more objective than the usual estimation expressed by deviation. The estimations described in this paper indicate various dispersions in different magnitude intervals of original data. The estimations of uncertainties described by probabilities can be well connected with the total estimations of uncertainties in seismic hazard assessment.  相似文献   

11.
依据《地震震级的规定（GB 17740—2017）》,分析了2009—2017年新疆地震台网所记录的新疆及邻区476次中深源地震事件,测定了13601个mb（短周期体波震级）和12035个mB（BB）（宽频带体波震级）的数据样本,回归分析mb和mB（BB）得到回归方程及量规函数,结果显示mb和mB（BB）相关系数为0.966,表明两者显著相关。因此,建议对于中强型中深源地震可以直接从原始速度型宽频带数字地震记录上测定长周期体波震级mB（BB）,提高地震速报测定的速度和精度。通过震级偏差统计和台站场地响应计算,分析新疆地震台网中的XKR、HTA、ATS和KSZ等地震台站震级偏差较大的原因为砂岩、灰岩、砂土层等类型的台基放大了场地响应,说明台基类型对体波震级偏差的影响较大。与NEIC测定的体波震级对比时,发现新疆地震台网测定体波震级平均偏大0.42级,且偏差随着震源深度的增加有增大的趋势。  相似文献   

12.
Using the earthquake sequences data with MS≥6.5 since 1966 in Sichuan-Yunnan region, we research the charac-teristic of the magnitude difference distribution between main shocks and their strong aftershocks; and then study the spatial distribution characteristic of the strong aftershocks away from their main shocks. The result shows that the magnitude difference distribution obeys intercepted exponential distribution, while the spatial distribution of strong aftershocks obeys normal distribution and the dominated distribution area of strong shocks is 10~39 km away from main shock. Finally the probability density function of the magnitude difference distribution and the spatial distribution of strong aftershocks is deduced.  相似文献   

13.
In recent years, some researchers have studied the paleoearthquake along the Haiyuan fault and revealed a lot of paleoearthquake events. All available information allows more reliable analysis of earthquake recurrence interval and earthquake rupture patterns along the Haiyuan fault. Based on this paleoseismological information, the recurrence probability and magnitude distribution for M≥6.7 earthquakes in future 100 years along the Haiyuan fault can be obtained through weighted computation by using Poisson and Brownian passage time models and considering different rupture patterns. The result shows that the recurrence probability of M S≥6.7 earthquakes is about 0.035 in future 100 years along the Haiyuan fault. Foundation item: Joint Seismological Science Foundation of China (103034) and Major Research “Research on Assessment of Seismic Safety” from China Earthquake Administration during the tenth Five-year Plan.  相似文献   

14.
We re-examine the utility of teleseismic seismic complexity discriminants in a multivariate setting using United Kingdom array data. We measure a complexity discriminant taken on array beams by simply taking the logarithm of the ratio of the P-wave coda signal to that of the first arriving direct P wave (βCF). The single station complexity discriminant shows marginal performance with shallow earthquakes having more complex signatures than those from explosions or deep earthquakes. Inclusion of secondary phases in the coda window can also degrade performance. However, performance improves markedly when two-station complexity discriminants are formed showing false alarm rates similar to those observed for network mb − Ms. This suggests that multistation complexity discriminants may ameliorate some of the problems associated with mb – Ms discrimination at lower magnitudes. Additionally, when complexity discriminants are combined with mb – Ms there is a tendency for explosions, shallow earthquakes and deep earthquakes to form three distinct populations. Thus, complexity discriminants may follow a logic that is similar to mb – Ms in terms of the separation of shallow earthquakes from nuclear explosions, although the underlying physics of the two discriminants is significantly different.  相似文献   

15.
IntroductionMany anomalies due to earthquake have been recorded in observation of earth-resistivity for30 years and over, which showed that there objectively existed the anomalies of each-resistivity.The crustal strUcture and medium conditions are quite complex, so the complexity of the temporal,spatial and intensive development of the anomalies is inevitable. Both of time and amplitUde ofanomalies among some stations near an epicenter are different (even among different observational directi…  相似文献   

16.
A method estimating the stress level in the focal region of an earthquake is proposed here. Taking the 2001 M=8.1 Western Kunlun Mountain Pass earthquake as an example, we estimate its stress level in the focal region before and after it by this method. The results show that the stress level in the focal region just prior to the initiation of this event is approximately 6.3–8 MPa, and about 5–6.7 MPa remained in the focal region after its occurrence. The stress in the focal region decreased by roughly twenty percent after this event. Contribution No. 05FE3026, Institute of Geophysics, China Earthquake Administration.  相似文献   

17.
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   

18.
IntroductionEarthquakelocationisoneoftheoldestinverseproblemsinseismology.Preciseearthquakelocationisthebasisoftheseismicresearch.Theprecisionoftheearthquakelocationdependsonmanyfactors,suchasthequalityofthestationnetwork,theprecisionoftheseismicwavearrivaltimemeasured,andtheknowledgeaboutthecrustalvelocitystructureandsoon.AccordingtotheresearchmadebyZhao(1983),thehorizontallocationerroroftheeanhquakelocatedbythetraditionalabsolutemethodinthecentralareaofNorthChinaisabouttZkin,intheedgeregio…  相似文献   

19.
Introduction In seismology, medium isotropy and anisotropy is defined by the direction of seismic wave propagation. If the seismic wave velocity does not vary with the direction, the medium is isotropy, whereas it is anisotropy. Recently, the study of anisotropy in crack medium becomes a focus forseismologists. Crampin (1978) made a deeply research on crustal anisotropy and put forward a theory of extensive dilatancy anisotropy (EDA) that there are a lot of cracks parallel to the hori- zonta…  相似文献   

20.
IntroductionThe development and occurrence of macroseismic activity come from the specific structUreenvironment and stress condition. So the space-time distribUtion of strong quakes appears to bevery inhomogeneous. Earthquakes with Ms27.0 in a seismicity period presented often a speeding-up pattern with time in different seismic provinces. That is, the cumulative frequency of earthquakes with Ms27.0 increase with exponent N(t)=ae', in a seismicity period (ZHANG, FU, 1989).It means that t…  相似文献   

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