2010年4月14日玉树7.1级地震前异常特征及强震动力学关系探讨

The authors studied the seismic activity, precursory anomalies and abnormal animal behavior before the April 14, 2010 MS7.1 Yushu earthquake. Analysis showed that anomalies were not rich before the MS7.1 Yushu earthquake, but prominent anomalies were observed, such as the long and mid-term trend anomaly characterized by the seismic quiescence of MS6.0, MS5.0 and MS4.0 earthquakes, and the anomalies in precursor observation of surface water temperature in Yushu and Delingha and electromagnetic measurement in Pingan. There were a large number of animal behavior anomalies appearing one week before the earthquake. An M4.7 earthquake occurred 130 minutes before the main shock. In this paper, we studied the dynamic process of the Yushu earthquake preparation using the earthquake focal mechanism solutions on the Bayan Har block boundary since 1996. The results show that the Kalakunlun M7.1 earthquake in 1996, the Mani M7.5 earthquake and the Yushu MS7.1 earthquake have the same dynamic process. Long and mid-term trend anomalies may be related to the dynamics of evolution of different earthquakes. This paper also discusses the recurrence interval of strong earthquakes, foreshock identification and precursor observation of the Yushu MS7.1 earthquake.     

Analyzing the Relation Between Earthquakes and Active Faults Based on the Parameter Optimization Model

The gestation and occurrence of strong earthquakes are closely related to fault activity, which is not only revealed by abundant experimentation and seismism but also proved by modern seismology. On the Chinese mainland, the relation between earthquake activity and active faults is one of the bases for partitioning potential seismic sources, analyzing the seismotectonics and estimating location of strong earthquakes.Due to the nonuniformity of earth media, instability of observation systems and disturbance of the environment, etc, the variety of observational data is complicated, that is, there is no absolutely "normal" or "abnormal", and seismic anomalies can be divided into many mutually exclusive "abnormal states". In different conditions of combined time-space-strength, determining seismic anomalies by different monomial forecast methods and its efficiency could be different due to the uncertainty of a precursor itself or complexity of the relationship between a precursor and earthquake gestation. It is very difficult to discover and dispose of this difference in actual application in a "two-state" model. But in a "multi-state" model, the difference can be easily reflected and the optimal combination of forecasting parameters for a forecast method can also be determined easily.Based on the "multi-state" precursory model and the optimization method for parameters of earthquake forecast model under the condition of optimal forecast efficiency, the relationship of the spatial location of earthquake with M≥6.0 and active faults in three seismic belts are analyzed. The results demonstrate that in the Hetao Seismic Belt, seismicity is mostly concentrated in the range of 20 km along the fault, the optimization model can forecast the location of potential earthquakes of M≥6.0 near the faults with a relatively high accuracy and the reliability is 0.5; while in the Qilian Mt. Seismic Belt, the reliability only reaches 0.14 when we use the model to estimate earthquakes within 30 km range along the faults. The "multi-state" precursory model, the efficiency-evaluating model and the parameter selection of individual earthquake forecast model based on optimal efficiency are of certain revelatory and practicable meanings for developing knowledge about precursors, investigating the laws of earthquake preparation and searching for optimal forecasting methods.     

Anomalies in Water Level Records in Yunnan Caused by the Great Indonesian Earthquakes and Their Significance

Two great earthquakes occurred in the sea northwest of Sumatra, Indonesia, on December 26, 2004 and March 29,2005. The observation of water levels in Yunnan yielded abundant information about the two earthquakes. This paper presents the water level response to the two earthquakes in Yunnan and makes a preliminary analysis. It is observed that the large earthquake- induced abnormal water level change could be better recorded by analog recording than by digital recording. The large earthquake-caused water level rise or decline may be attributed to the effect of seismic waves that change the stress in tectonic units, and is correlated with the geological structure where the well is located. The water level response mode in a well is totally the same for earthquakes occurring on the same fault and with the same fracture mode. The only difference is that the response amplitude increases with the growth of the earthquake magnitude.     

Characteristics of Strain Release before Large Earthquakes of M≥7. 0 in the Chinese Mainland

The enumerating algorithm has been introduced into the fitting procedure of the ASR model. Based on the detailed study of 21 large earthquakes with M≥6. 8 in the Chinese Mainland,the statistical features of seismic strain release before large earthquakes have been summarized. In the mass,the strain release models can be divided into five types. The first is the DA model,in which the strain release accelerates in broader areas and decelerates in small areas around the epicenter. Approximately 38% of earthquake samples are of this type. The second is the AD model,in which the strain release decelerates in broader areas and accelerates in smaller areas around the epicenter with an occupying ratioof approximately 19%. The third is ASR,in which only accelerating strain release can be observed. Cases of this model amount to about 14%. The fourth is DSR,in which only decelerating strain release can be checked,amounting to about 24%. There is only one earthquake sample of the fifth type (LSR),which shows a linear strain release. There is a 3～6 years difference in the duration of pre-shock sequences between the accelerating and decelerating models. This means that seismic quiescence against a background of increased seismicity of small earthquakes before large earthquakes are a typical feature in general. For the DA model,the average size of critical regions for steady accelerating and decelerating strain release is about 260km to 400km and 100km to 200km,respectively,3 to 5 times and 1 to 2 times the rupture size of an earthquake of magnitude 7. 0. The AD model is the opposite of the DA model. The model parameter,m value,has good stability. The ratio of ASR is about the same for accelerating seismic strain release phenomena,no matter what the strain release models are,or how large the strain release quantity is. With regard to decelerating seismic strain release phenomena, the DA model has the most distinctive decelerating strain release characteristic and is the typical feature of seismic strain release,i. e. "decelerating in-accelerating out seismic strain model".     

A New Study Item of Earthquake Precursors: The Escaping Gas Rn in Groundwater

In this paper,the authors discussed the high sensibility of gas Rn to the deformation of rock in the crust by contrasting observation of Rn gas with dissolved Rn in groundwater and by studying the precursors of earthquakes of Rn gas and dissolved Rn.The change of earth tide of rock in the crust can be observed with the methods of gas Rn in groundwater.Before the 1989 Datong-Yanggao earthquake,the changes of gas Rn indicated that the gas Rn can reveal the slight related changes of stress of rock in the crust in a magnified way.So the research of the gas Rn in groundwater,as a new observation item of earthquake precursors in groundwater,has broad prospects.     

Characteristics of Geoelectric and Geomagnetic Data before Strong Earthquakes in the North China Region

The earth resistivity and geomagnetic observation data of the Z component from many stations in near-epicentral areas of strong earthquakes are combined and calculated by using a spatial linearity method and a new characteristic value, the spatial linearity a, describing the precursory field in near-epicentral area of strong earthquake, is obtained. The analysis and calculation results of geoelectric and geomagnetic observation data prior to 8 earthquakes with M≥5.5 occurring in the North China region show that a value near the epicentral area tendsto decrease significantly half a year before strong earthquakes.     

汶川8．0级地震前兆异常对比研究

The contrast research results show that the number of items and stations with imminent, short and medium term precursor anomalies for the Wenchuan M_S 8. 0 earthquake is less than that of the Menglian earthquake. The number of anomalies and stations associated with the Wenchuan earthquake increased in the early stage of the short-term range,as opposed to the later period for the Menglian and Lijiang earthquakes. Most of the medium term anomalies occurred two to three years before the Wenchuan earthquake,when the number of anomaly stations and items was eleven,and a great change appeared in the observation values in about half of the stations ( items ) . However,for the Menglian earthquake,medium term anomalies happened one to two years before the earthquake, the number of abnormal stations and items reached 20,and a sharp change appeared in the observation values six months to one year before the earthquake in about 30 percent of the stations or items. In the epicenter and the nearby area,the macroscopic abnormalities started 3 years before the Wenchuan earthquake and lasted intermittently until 1 month before the earthquake. Within 2 percent of the total area of the province,the macroscopic abnormalities accounted for 30 to 50 percent of the total number of anomalies of the Province. For the Xingtai,Tangshan,Haicheng,Songpan earthquakes,the macroscopic anomalies started two to three months before,or on the very day of the earthquakes. The common feature of the precursors between the Wenchuan and other strong earthquakes is the appearance of tremendous changes in a certain number of observation values of anomalies in the mid and short terms before all these earthquakes.     

Mining seismicity, gas outburst and the significance of their relationship in the study of physics of earthquake source

This paper presents an overview of mining seismicity, gas outburst and their origin. The internal relation of mining seismicity and gas outburst in the dynamic process is studied on the basis of the fact that these disasters sometimes occur simultaneously. The examples show a close relationship between mining seismicity and gas outburst in high gassy coal mines. It is proposed that strong mine shocks plus the response of low value and delay time are early warning signals. The mechanism of the relationship between mining seismicity and gas outburst is analyzed by using the location of mining shocks, focus mechanism, cause of mining shocks and conditions of gas outburst. The trigger action of gas fluid on mining shocks, especially the effect of the anomalous property of supercritical fluid on the preparation and occurrence of mining shocks is discussed. According to the similarity between min-ing-induced earthquakes and tectonic earthquakes in terms of mechanism, the significance of the above results in the study of physics of earthquake source is also discussed.     

Textual research of 1219 A.D. Guyuan earthquake in Ningxia Hui Autonomous Region,China and discussion on its causative structure

On the basis of textual research on the historical earthquake data and the field investigation of 1219 A.D.Guyuan earthquake,we suggest that there is only one strong earthquake occurred in Guyuan area in 1219 A.D.,instead of two or three strong earthquakes.We further suggest that the earthquake parameters recorded in the present earth-quake catalogs are not definite and should be modified.The occurrence time of this earthquake should be about 11 am,August 7,1219 A.D.and the heavily-damaged area of this earthquake,the VIII intensity area,should be lo-cated among the regions of Guyuan,Pingliang and Longde county cities.The epicenter area should be near Gu-yuan city.The magnitude of this earthquake is about 7 and it has intensity about larger than or equal to IX within the epicenter area.The major axis direction of the heavily-damaged area strikes in north-northwest that is ap-proximately consistent with the strike of the Liupan Shan thrust fault zone.The new tectonic activity of the Liupan Shan thrust fault zone resulted in the M7 Guyuan earthquake in 1219 A.D.     

A Preliminary Study on the Phenomenon of Microseismic Fluctuations before Impending Strong Earthquake

Based on repeated comparison studies of broadband digital seismic records before the Wenchuan M_S8. 0,Yushu M_S7. 1 and Qingchuan M_S5. 4 earthquakes,the possible microseismic fluctuations before impending earthquakes were preliminarily identified. In order to verify and test this phenomenon,a real-time tracking technical system was established by using continuous waveform records of more than 200 wide-band digital seismic stations in regional networks such as Gansu,Qinghai,Sichuan,Yunnan and Tibet.Through real-time tracking and dynamic monitoring of 24 earthquakes with M≥5. 0 occurring in the Qinghai-Tibetan block during the period of 2012-2014 and the observations of stations in some non-seismic areas,the reproducibility and objectivity of the impending earthquake phenomenon were verified. The main characteristics of the microseismic fluctuation phenomena immediately preceding the strong earthquakes are as follows:(1)the spectrum range is wider,the dominant frequency is 11-16 Hz,and the spectrum shape is more regular;(2)it appears 6-24 days before the earthquake,averaging about 15 days;(3)it is possible to be recorded by the stations within the epicenter distance of 50 km,and the stations with the epicenter distance of more than 50 km generally cannot record it;(4)this phenomenon is directional,i. e. the direction in which the activity degree,N-value,varies significantly may be related to the location of the seismic source,the seismogenic fault and the distribution of aftershocks of the strong earthquake. The preliminary study shows that the impending-earthquakes microseismic phenomena may be related to the pre-activity,micro-vibration and micro-rupture in the source region in the imminent stage,or the microactivity and micro-rupture associated with the active tectonics.     

北京五里营井流体前兆观测到的两次异常及讨论

分析了延庆五里营井汶川M8.0地震和玉树M7.1地震数字化流体前兆观测资料,对比研究了五里营井流体在2次强震中的响应差异.结果显示,流体异常响应灵敏度与地震震级和观测点震中距有一定关系,地震震级越大,观测点距离震中越近,流体异常响应越灵敏.2次大震前流体前兆都观测到氦气释放活动最先出现异常反应,其释放强度与震级有关,震...     

青海平安电磁波观测资料在中强震前变化特征分析

平安电磁波东西向数据在2008年汶川8.0级地震、2010年玉树7.1级地震前都有明显的高脉冲反应,因此统计了1993年平安电磁波仪器架设以来的观测数据变化与地震的对应情况。根据震级和震中距的约束条件选取了12次6级以上地震,发现其中在8次强震前有明显的异常现象,说明该测项在青藏块体北部地区6级以上地震前有较好的异常显示。     

中国大陆井水温对汶川8.0级、玉树7.1级、芦山7.0级和岷县6.6级地震响应特征的对比研究

收集和统计了2008年汶川MS8.0地震、2010年玉树MS7.1地震和2013年芦山MS7.0、岷县MS6.6地震引起的中国大陆井水温同震响应现象,分析了其特征。结果显示:这4次地震对中国大陆地下流体影响显著,井水温同震响应特征有很大差异,后三次水温同震响应范围、幅度和持续时间远不及汶川地震,即使震级相差不大的玉树和芦山地震,同震响应的特征也不尽相同。最后探讨了这种现象的成因机理。     

地球自转对强震震中附近中小地震的影响

论述2008年5月12日四川汶川Ms8.0地震和2010年4月14日青海玉树Ms7.1地震前震中附近中小地震和地球自转季节性变化的关系,介绍1970年以来中国大陆其他14例M≥7.0地震震例.研究发现,在强震前几年时间内,震中附近地区的中小地震有偏向发生于地球自转速率季节性变化加速或者减速某一阶段的现象.该结果对深入认识地震与地球自转之间的关系具有一定启示意义,对地震预测具有一定指导意义.     

2010年玉树7.1级地震趋势预测研究回顾

本文整理了自2008年5月12日汶川8.0级地震至2010年4月14日玉树7.1级地震前, 年度地震趋势预测和日常会商中提出的地震活动和前兆异常及其分析意见。 结果表明, 玉树7.1级地震前存在一些较为明确的有关地震活动水平和危险区域判定的预测依据, 但由于玉树地区地震监测能力较弱, 缺乏较为可靠的中短期前兆异常, 因此未将该区划定为年度地震重点危险区, 仅在我国大陆地震形势预测和强震主体活动地区估计上有所涉及。 2010年青藏块体中东部地区强震危险性增强, 但由于玉树地区震前地震活动性异常以平静为主, 地震前兆数量也较少, 因此未能在玉树7.1级地震前形成短临预测意见。     

2008年汶川MS8.0与2010年玉树 MS7.1地震前电磁现象研究

应用全局小波能谱法对2008年四川汶川M_S8.0地震、 2010年青海玉树M_S7.1地震前地电、 地磁场变化情况进行了分析研究. 结果表明: ① 在汶川地震震中周围的台站观测到震前地电、 地磁场全局小波能谱值增大的现象; ② 青藏高原东北缘的代乾等3个地电、 地磁台站在玉树地震前均发生显著的小波能谱增大的现象, 震后恢复; ③ 对于上述两次大震周边地区的不同台站的不同测道, 在震前多次出现谱值时间上同步增大或减少的现象; ④ 距玉树地震震中距离相同的山丹和古丰地电场台站, 北南、 北西测向长极距在地震前后能谱值的变化几乎一致. 基于上述分析, 初步研究认为震源孕育激发的电磁辐射是造成震前电磁异常现象的主要原因.      

玉树7.1级地震前地震拟合优度异常分析

中强地震孕育过程中,震中周边一定区域内的小震活动会因次级破裂的非均匀性,而在各震级档的比例分配失调,会导致采用古登堡公式拟合时的拟合优度下降.利用该规律,对玉树地震前一定区域内的地震,运用地震拟合优度进行计算,结果表明,在玉树地震前一段时间,震中周边一定区域和青海省及邻区地震拟合优度均表现出明显的下降异常.该方法可为地震监测能力较弱地区的中期地震预报提供参考依据,弥补地震前兆台网分布稀疏的不足.     

几次强震及震前震中附近地区中小地震与地球自转的关系

本文分析了1975年海城7.3级、 2008年汶川8.0级和2004年印尼苏门答腊9.0级地震与地球自转的关系, 给出了震前震中附近地区中小地震与地球自转之间较好的相关关系。 结果对深入认识地球自转与地震发生之间的关系具有裨益。     

基于深度学习神经网络方法的中国大陆地震伤亡预测模型

对地震伤亡人口的预测需要同时考虑地震破裂特征本身、灾区人口及其生活环境等特征,其是一个典型的复杂预测系统。本文基于深度学习神经网络方法和1976—2020年间78次地震伤亡事件,构建了中国大陆地震伤亡预测模型,综合使用发震年代、发震时刻、发震季节、Ⅵ度及以上区域受灾面积、Ⅵ度及以上区域受灾人口数、震源深度、极震区烈度和震源机制类型等8个参数,对包括2008年汶川8.0级和2010年玉树7.1级地震在内的9次地震事件进行了预测检验。结果显示,该预测模型能够较好地反映出中小地震的伤亡人口特征,除汶川地震和玉树地震外的7次地震伤亡事件预测值与实际值误差均在一个数量级上,对于2008年汶川8.0级和2010年玉树7.1级地震,预测值明显小于实际伤亡人口;其中玉树地震发震断层位于玉树州府结古镇之下,造成了相对较多的人口伤亡数量;汶川地震的伤亡人口数量不仅由地震直接导致,还包括了地震滑坡等次生灾害引起的伤亡数量。