原位地应力测量与实时监测在地震预报研究中的作用和意义

当2013年4月20日四川芦山Ms 7.0级大地震发生时,中国科学家已不再像2008年汶川Ms 8.0大地震发生时那样茫然和不知所措。其根本原因在于,2008年汶川大地震发生后,龙门山地区开展了大量的科学研究工作,已超前初步认知龙门山断裂带西南端具有潜在地震危险性,特别是原位地应力测量和实时监测已发现绝对地应力大小高值异常和相对地应力大小临震异常变化。论文简要介绍了地震预报国际主流观点与认识,梳理了地应力在地震预报研究中的作用和认识,探讨了2004 Parkfield earthquake钻孔应变监测结果给予的启示,详细介绍了原位地应力测量与实时监测在地震预报研究中应用的实践与探索。实践证明:地震预报是值得探索和研究的,原位地应力测量与实时监测是地震预报的有效方法之一。      

Short-term earthquake prediction by reverse analysis of lithosphere dynamics

Short-term earthquake prediction, months in advance, is an elusive goal of earth sciences, of great importance for fundamental science and for disaster preparedness. Here, we describe a methodology for short-term prediction named RTP (Reverse Tracing of Precursors). Using this methodology the San Simeon earthquake in Central California (magnitude 6.5, Dec. 22, 2003) and the Tokachi-Oki earthquake in Northern Japan (magnitude 8.1, Sept. 25, 2003) were predicted 6 and 7 months in advance, respectively. The physical basis of RTP can be summed up as follows: An earthquake is generated by two interacting processes in a fault network: an accumulation of energy that the earthquake will release and a rise of instability triggering this release. Energy is carried by the stress field, instability is carried by the difference between the stress and strength fields. Both processes can be detected and characterized by “premonitory” patterns of seismicity or other relevant fields. Here, we consider an ensemble of premonitory seismicity patterns. RTP methodology is able to reconstruct these patterns by tracing their sequence backwards in time. The principles of RTP are not specific to earthquakes and may be applicable to critical transitions in a wide class of hierarchical non-linear systems.     

大地震临震预测的研究进展

短临地震预报尤其是临震预报 ,是当今国内外公认的世界性科学难点。文章综述了中国科学家从多学科交叉和内外因耦合的科学途径 ,已在大地震临震信号方面获得了次声波异常、地应力突跳、虎皮鹦鹉跳跃异常、地电和地磁异常、卫星红外异常、重力高频脉冲等临震预测的手段。笔者通过典型分析和普查对比各种地球物理因子和各种天文因子可能影响的整体研究 ,找到了大地震临震的主要触发因子———以月亮为主的非经典引潮力共振的异常叠加。在此基础上 ,采取内外因耦合的途径和方法 ,在 6a多来联合进行的临震预测内部试验表明 ,地震三要素均基本正确的成功率已达40 %。最后 ,还对临震预报问题提出了一些看法。     

芦山地震：一个成功的中期预测案例

2013年4月20日MS 7.0级芦山地震是2008年汶川地震以后龙门山断裂带的又一个灾难性的地质事件。文中回顾了对芦山地震的成功中期预测并给出了预测的依据。2012年11月25日上午,中国地球物理学会天灾预测专业委员会讨论中国西南地区中期地震预测问题。专业委员会主任耿庆国回顾了2012年4月作出的中期预测,认为2012年5月至2013年5月期间,在我国西南地区可能存在MS 7~8级地震。参加会议的委员们同意这一时间预测和震级预测,但是在震中位置预测方面存在不同意见。文章第一作者在会上作了一个报告,并展示了确切的震中预测位置图,即位于四川省雅安与康定连线的中间位置。这一预测的依据主要有两个方面：一方面,雅安西侧与汶川两地,具有两个特征相同的独立的卫星重力局部高异常;二是汶川(5·12)大震只是释放了龙门山断裂带北东段的能量和应力,这导致能量和应力在龙门山断裂带南西段,特别是南西端与重力异常突变叠加区(即中上地壳密度突变区)的加速积累和集中。芦山地震震中位于雅安芦山,与预测震中位置仅相差80 km,发震时间在2013年5月前。芦山地震中期预测的成功给予我们很多启示。作为一种地质过程,地震应该有其自身的规律可循;成功的地震预测需要多方面观测信息的综合分析,正是基于此,目前迫切需要国家的或者国际的具有综合分析经验的专家组和有效的前兆信息平台;卫星重力异常数据的处理和更新将有助于缩小强震预测的包围圈。     

Numerical simulation of dynamic mechanisms of the 2008 Wenchuan Ms8.0 earthquake: implications for earthquake prediction

The sudden and unexpected Wenchuan earthquake (Ms = 8.0) occurred on the Longmen Shan Fault, causing a large number of casualties and huge property loss. Almost no definite precursors were reported prior to this event by Chinese scientists, who made a first successful prediction of the 1975 Haicheng earthquake (M = 7.3) in China. Does the unsuccessful prediction of the Wenchuan earthquake mean earthquake prediction is inherently impossible? In order to answer this question, the paper simulated inter- and co-seismic deformation, and recurrence of strong earthquakes associated with the Longmen Shan listric thrust fault by means of viscoelastic finite element method. The modeling results show that the computed interseismic strain accumulation in the lower crust beneath the Eastern Tibet is much faster than that in the other regions. In particular, the elastic strain energy density rate accumulates very rapid in and around the Longmen Shan fault in the depth above ~25 km that may explain why the great Wenchuan earthquake occurs in the region of such a slow surface deformation rate. The modeled coseismic displacements around the fault are consistent with surface rupture, aftershock distribution, and GPS measurement. Also, the model displays the slip history on the Longmen Shan fault, implying that the average earthquake recurrence interval on the Longmen Shan fault is very long, 3,300 years, which is in good agreement with the observed by paleoseismological investigations and estimates by other methods. Moreover, the model results indicate that the future earthquake could be evaluated based on numerical computation, rather than on precursors or on statistics. Numerical earthquake prediction (NEP) seems to be a promising avenue to a successful prediction, which will play an important part in natural hazard mitigation. NEP is difficult but possible, which needs well supporting.     

Progress in the Application of Ground Gravity Observation Data in Earthquake Prediction

The mechanism of earthquake inoculation and the process of earthquake occurrence are very complicated. Additionally, earthquakes do not happen very often, and we lack enough cognition to the earth’s interior structure, activity regularity and other key elements. As a result, research progress about the theory of earthquake precursors has been greatly restricted. Ground gravity observation has become one of the main ways to study earthquake precursor information in many countries and regions. This paper briefly summarized the surface gravity observation technology and observation network in China: the surface gravity measurement instrument developed from Huygens physical pendulum in seventeenth Century to today’s high-precision absolute gravimeter, and its accuracy reached to ±1×10^-8 m/s². China has successively established the National Gravity Network, Digital Earthquake Observation Network of China,the Crustal Movement Observation Network of China Ⅰ and the Crustal Movement Observation Network of China, to provide a public platform for monitoring non tidal gravity change, seismic gravity and tectonic movement. The use of specific examples illustrated the role of gravity observation data in earthquake prediction. The gravity observation data of ground gravity can be used to capture the information of gravity change in the process of strong earthquake inoculation, and to provide an important basis for the long-term prediction of strong earthquakes. The temporal and spatial variation characteristics of the regional gravity field and its relation to strong earthquakes were analyzed: Before the earthquake whose magnitude is higher than M_S 5, generally there will be a large amplitude and range of gravity anomaly zones. Strong earthquakes occur mainly in areas where the gravity field changes violently. The dynamic change images of gravity field can clearly reflect the precursory information of large earthquakes during the inoculation and occurrence. Finally, the existing problems of surface gravity technology in earthquake precursor observation were put forward and the use of gravity measurement data in earthquake prediction research was prospected.     

On intermediate-term prediction of strong earthquakes in the Himalayan arc region using pattern recognition algorithm M8

Seismicity of the Himalayan arc lying within the limits shown in figure 1 and covering the period 1964 to 1987 was scanned using M8 algorithm with a view to identifying the times of increased probabilities (TIPs) of the occurrence of earthquakes of magnitude greater than or equal to 7·0, during the period 1970 to 1987. In this period, TIPs occupy 18% of the space time considered. One of these precedes the only earthquake in this magnitude range which occurred during the period. Two numerical parameters used in the algorithm, namely the magnitude thresholds, had to be altered for the present study owing to incomplete data. Further monitoring of TIPs is however warranted, both for testing the predictive capability of this algorithm in the Himalayan region and for creating a base for the search of short-term precursors.     

浅谈地震灾害预报

本文阐述了地震预报与地震灾害预报的相互区别及其相互联系 ,并分析通过自然科学研究与社会科学研究两种途径进行地震灾害预报 ,以达到防震减灾的目的。建议 :加强地震预报与地震灾害预报的管理 ,地震灾害预报只能在具备一定条件的地区进行 ,而不应全面铺开。     

Seismo-induced effects in the near-earth space: Combined ground and space investigations as a contribution to earthquake prediction

The paper aims at giving a few methodological suggestions in deterministic earthquake prediction studies based on combined ground-based and space observations of earthquake precursors. Up to now what is lacking is the demonstration of a causal relationship with explained physical processes and looking for a correlation between data gathered simultaneously and continuously by space observations and ground-based measurements. Coordinated space and ground-based observations imply available test sites on the Earth surface to correlate ground data, collected by appropriate networks of instruments, with space ones detected on board of LEO satellites. At this purpose a new result reported in the paper is an original and specific space mission project (ESPERIA) and two instruments of its payload. The ESPERIA space project has been performed for the Italian Space Agency and three ESPERIA instruments (ARINA and LAZIO particle detectors, and EGLE search-coil magnetometer) have been built and tested in space. The EGLE experiment started last April 15, 2005 on board the ISS, within the ENEIDE mission. The launch of ARINA occurred on June 15, 2006, on board the RESURS DK-1 Russian LEO satellite. As an introduction and justification to these experiments the paper clarifies some basic concepts and critical methodological aspects concerning deterministic and statistic approaches and their use in earthquake prediction. We also take the liberty of giving the scientific community a few critical hints based on our personal experience in the field and propose a joint study devoted to earthquake prediction and warning.     

关于滑坡预报问题

边坡观测点位移-时间曲线出现变陡段作为滑坡预报的判据是不充分的。还有一些判据也是不充分的。本文对这些观点从经验和理论上作了阐述。     

Increased correlation range of seismicity before large events manifested by earthquake chains

“Earthquake chains” are clusters of moderate-size earthquakes which extend over large distances and are formed by statistically rare pairs of events that are close in space and time (“neighbors”). Earthquake chains are supposed to be precursors of large earthquakes with lead times of a few months. Here we substantiate this hypothesis by mass testing it using a random earthquake catalog. Also, we study stability under variation of parameters and some properties of the chains. We found two invariant parameters: they characterize the spatial and energy scales of earthquake correlation. Both parameters of the chains show good correlation with the magnitudes of the earthquakes they precede. Earthquake chains are known as the first stage of the earthquake prediction algorithm reverse tracing of precursors (RTP) now tested in forward prediction. A discussion of the complete RTP algorithm is outside the scope of this paper, but the results presented here are important to substantiate the RTP approach.     

Comment on ‘Testing earthquake prediction methods: “The West Pacific short-term forecast of earthquakes with magnitude MwHRV ≥ 5.8”’ by V.G. Kossobokov

In his paper Kossobokov investigates the efficiency of our short-term forecast for two western Pacific regions. Although we agree with the basic results of his evaluation that the forecast statistics is much better than a random guess, we have reservations about his definition of earthquake prediction, some of his tests, and his interpretation of the test results. We distinguish between deterministic earthquake predictions and statistical forecasts. We argue that some techniques used by Kossobokov may not be appropriate for testing our forecasts and discuss other testing methods, based on the likelihood function. We demonstrate that Kossobokov's null hypothesis may be biased, and this bias can influence some of his conclusions. We show that contrary to Kossobokov's statement, our algorithm predicts mainshocks when they are preceded by foreshocks.     

地壳放气动态监测与张北—尚义Ms6.2级地震预报

笔者从新的地球观出发,论述地壳放气与地震活动的关系,及其在张北－尚义Ｍｓ６．２级地震中短期,短临预报中应用,认为地震是可以预报的。因此,笔者提出地震预报探索中应加强地壳放气动态监测与研究,特别是加强断层带土壤气ＣＯ２、Ｈ２,Ｈｅ与Ｈｇ动态监测的观点。     

A worldwide test of three long-term premonitory seismicity patterns—a review

Worldwide analysis of the clustering of earthquakes has lead to the hypothesis that the occurrence of abnormally large clusters indicates an increase in probability of a strong earthquake in the next 3–4 years within the same region. Three long-term premonitory seismicity patterns, which correspond to different non-contradictory definitions of abnormally large clusters, were tested retrospectively in 15 regions. The results of the tests suggest that about 80% of the strongest earthquakes can be predicted by monitoring these patterns.Most of results concern pattern B (“burst of aftershocks”) i.e. an earthquake of medium magnitude with an abnormally large number of aftershocks during the first few days. Two other patterns, S and Σ often complement pattern B and can replace it in some regions where the catalogs show very few aftershocks.The practical application of these patterns is strongly limited by the fact that neither the location of the coming earthquake within the region nor its time of occurrence within 3–4 years is indicated. However, these patterns present the possibility of increasing the reliability of medium and short-term precursors; also, they allow activation of some important early preparatory measures.The results impose the following empirical constraint on the theory of the generation of a strong earthquake: it is preceded by abnormal clustering of weaker earthquakes in the space-time-energy domain; corresponding clusters are few but may occur in a wide region around the location of the coming strong earthquake; the distances are of the same order as for the other reported precursors.     

Prediction of strong earthquake within the southwestern shelf of Sakhalin Island and its realization during the August 2, 2007, Nevelsk earthquake

Materials of the long- and short-term predictions of the destructive earthquake with the magnitude M _LH = 6.6 ± 0.6 within the southwestern shelf of Sakhalin Island are described. The long-term prediction was issued in December 2005 and was affirmed by the Russian Council of Experts on Earthquake Forecasting and Seismic Hazard Assessment in August 2006. The August 17(18), 2006, Gornozavodsk earthquake with a magnitude of M _w = 5.6 was the beginning of the realization of this prediction. Six days after its occurrence, the short-term prediction of a much more serious seismic event in the alarm region was prepared. One year later, the prediction of the August 2, 2007, Nevelsk earthquake with a magnitude of M _w = 6.2 (M _LH = 6.2) proved to be correct.     

论地震数值预报——关于我国地震预报研究发展战略的思考

随着中国工业化和社会现代化进程的加快 ,中国城市化进程必将进一步加速。如何减轻地震灾害的问题正变得日益严峻。尽管地震预测是一个举世公认的国际性科学难题 ,但在强化各种减轻地震灾害措施的同时 ,仍须大力推进地震预测研究。为此 ,需要打破长期徘徊在以地震前兆异常监测为基础的经验性预测局面 ,把注意力尽快转向研究以动力学为基础的数值预报。以GPS为代表的空间对地观测技术 ,岩石圈巨型高分辨率宽频带流动地震台阵观测技术以及数值模拟技术已经为地震数值预报研究提供了前所未有的技术基础。以地震数值预报为目标的GPS阵列地壳形变连续观测 ,高分辨率地壳上地幔结构探测 ,地壳动力学 ,地震孕育和破裂过程的理论、模拟试验和实际观测 ,数据同化和计算软件的开发应成为今后研究的重点。现在的问题是 ,需要积极借助数值天气预报的经验 ,强化多学科 ,多部门的组织协调 ,尽早在有条件的地区开展地震动力学数值预报的科学试验。地震数值预报研究必将极大地促进中国地震科学基础研究和地震预报的进一步发展。     

对流层大气温度"蝴蝶形"震前异常

利用美国国家和海洋大气管理局(NOAA)的大气温度数据, 分析陆地地震和海洋地震震前震中上空的大气温度变化, 研究其作为地震短临前兆的可能性.地震样本包括2014年2月12日于田M_s7.3地震、2008年5月12日汶川M_s8.0地震、2011年3月11日日本M_s9.0地震、2014年4月1日智利M_s8.1海洋地震、2013年3月27日台湾南投县M_s6.1地震和2014年5月30日云南盈江M_s6.1地震.结果表明: (1)震前, 震中位置300~1 000 hPa大气温度有较为一致的变化趋势; (2)200 hPa与400 hPa处(根据不同地点可选择其他, 诸如350 hPa、300 hPa等高度数据)温度折线图在震前趋近或者相交, 出现类似蝴蝶翅膀的"蝴蝶形"特殊曲线形状; (3)200 hPa与400 hPa温度差等值线图在(震前数月、数周或数天不等)震中附近区域的数值减小, 温度差等值线图的塌陷最低点对应震中位置.以上规律有望应用于地震短临预测的时间与震中的确定.      

Seismicity pattern in north Sumatra-Great Nicobar region: In search of precursor for the 26 December 2004 earthquake

We analyse the seismicity pattern including b-value in the north Sumatra-Great Nicobar region from 1976 to 2004. The analysis suggests that there were a number of significant, intermediate and short-term precursors before the magnitude 7.6 earthquake of 2 November 2002. However, they were not found to be so prominent prior to the magnitude 9.0 earthquake of 26 December 2004 though downward migration of activity and a 50-day short-term quiescence was observed before the event. The various precursors identified include post-seismic and intermediate-term quiescence of 13 and 10 years respectively, between the 1976 (magnitude 6.3) and 2002 earthquakes with two years (1990–1991) of increase in background seismicity; renewed seismicity, downward migration of seismic activity and foreshocks in 2002, just before the mainshock. Spatial variation in b-value with time indicates precursory changes in the form of high b-value zone near the epicenter preceding the mainshocks of 2004 and 2002 and temporal rise in b-value in the epicentral area before the 2002 earthquake.     

Earthquake prediction: Is it a practicable scientific perspective or a challenge to science?

It is shown that the main problem in earthquake prediction consists not in separating a useful signal on an imminent strong earthquake from noise but in determining the character of the signal itself. The signal, due to the fractal and roughly discontinuous nature of the geological medium, is not an isolated precursor anomaly but always presents a host of varied-rank wavelets that are not distinctly recognizable and, in addition, are fluctuating in their amplitudes and duration. Bifurcation and the extreme dependence of the behavior of nonlinear geological system upon initial and continuously variable current conditions explain the inevitable unreliability of predicting the most mature earthquake sources.     

Development of medium-term prediction methods: A case study of the August 14, 2016 Onor (Mw = 5.8) earthquake on Sakhalin

The potential of the load-unload response ratio (LURR) method for medium-term earthquake prediction is studied for Sakhalin Island as an example. An approach to the generation of predicted conditions and assessment of their implementation in real time is considered. The results of a retrospective analysis of other large Sakhalin earthquakes are used for generalization. It is shown that deviations of prediction parameters from specified values are satisfactory for this method. It is recommended that this method be used to compile summaries of medium-term predictions for Sakhalin provided that catalogs are filled as soon as possible.