加卸载响应比的时空变化与美国南加州地区地震趋势

由尹祥础提出的加卸载响应比方法已经在中国的许多地区以及美国、日本和澳大利亚的一些地区应用.这一方法在地震中期预测中已经显示出良好的前景.近年开展的岩石力学实验和数值模拟工作验证了加卸载响应比的可靠性.在研究震例时发现,很多大地震前的几个月至几年加卸载响应比出现异常,该方法在中国、美国、日本等地区做出过一些成功的中期预测.     

Stress Reorientation and LURR: Implication for Earthquake Prediction Using LURR

After reviewing the problems associated with the current implementation of the LURR theory, we suggest that taking account of stress field complexity and stress reorientation may resolve these problems. By introducing the concept of Maximum Faulting Orientation (MFO), we propose a new approach for calculating LURR. Results presented for the case of the Northridge earthquake provide encouragement for the stress-reorientation explanation and the new approach.     

Heterogeneous Features of Temporal and Spatial Variation of Earthquake Occurrence in Process of Earthquake Preparation

By applying the GL-value, a parameter describing the heterogeneities in temporal and spatial distribution of moderate and small earthquakes prior to strong earthquakes, the following problems have been studied in the present paper: a systematic investigations have been made on the features of spatial distribution and temporal variation of the high value anomalies ( GL ≥1.0) prior to 28 moderately strong earthquakes with Ms ≥5.0 in the North China region; a systematic study has been made on the reasonability of the lower limit of magnitude, the time window and the space window for calculations at various seismicity levels in this region; the parameters taken in the calculation have been optimized and modified; the anomalous variations of GL-value prior to various moderately strong earthquakes in North China region have been investigated and followed, using the total time-space scanning method. The results of the study have shown that for 82 % of the moderately strong earthquakes in the North China region, obvious anomalous region with high GL-values appears near the future epicenter about 1 ～ 3.5 years before the earthquakes. The earthquakes usually occur in the marginal area of the anomalous zone or near it. Temporal variations of the GL-values in the anomalous zone show that the duration of anomalous ranges between 3 ～ 25 months with a predominant interval of 5 ～ 19 months, into which about 70% the total anomalies fall. The predominant interval of earthquake occurrences is 0 ～ 14 months after ending of the anomaly, into which about 83 % of the total anomalies fall. Based on these results the GL-value method is considered to be a rather effective prediction method for moderately strong earthquakes in the North China region.     

The Spatial Variation of LURR and Seismic Tendency in Western United States

INTRODUCTIONThe Load-Unload Response Ratio(LURR)is a new promising method for medium-termearthquake prediction put forward by Yin,X.C.(Yin,1987;Yin,and Yin,1991;Yin,et al.,1994;2000).In recent years,by this method,a lot of strong earthquakes have been suc…     

The Temporal Variation of LURR in Kanto and Other Regions in Japan and Its Application to Earthquake Prediction

The temporal variation of LURR(y)for Kanto,Wakayama,and Hugo regions in Japan has been calculated and analysed.The LURR(y)values are significantly higher than 1 before the occurrence of all earthquakes with magnitude M≥6.0 in the Kanto region during the last two decades and the Kobe earthquake(1995-01-17).These results suggest that LURR theory is available for Japan.Recently they-value for Wakayama region has been near 1,while the y-value is remarkably larger than 1 for nearly two years for Kanto.According to these results,it is predicted that a strong earthquake with magnitude of about 6.0 could occur in 1 year or a little longer for in Kanto region or its adjacent regions,but there is little possibility for the Wakayama region.     

关东等地区加卸载响应比的时间变化及其预测意义

计算分析了日本关东，和歌山及兵库地区的加卸载响应比（ｙ）的变化，关东地区近年来所有Ｍ≥６的７个地震及１９９５年１月１７日神户地震，在地震前的一段时间里其ｙ值均显著高于１。这说明加卸载响应比方法也适用于日本的地震预测，和歌山地区近年来Ｙ值接近于１，而关东地区的ｙ值则显著高于１已达２年，据此预测，未来１－２年内，关东地区（或其紧邻地区）有发生６级左右地震的可能，而和歌山地区这种可能性则很小。     

LURR and the San Simeon M 6.5 Earthquake in 2003 and the Seismic Tendency in CA

The spatial and temporal variation of LURR (Load/Unload Respond Ratio) in California during April 2002 to June 2004 was studied in this paper. The result shows that before the San Simeon earthquake (35.7 N, 121.1 W) on Dec. 22, 2003, Y/Y _c anomalous region occurred successively near the epicenter from April 2002 to June 2002, and the maximum anomaly of Y/Y _c occurred in May, 2002. The published research work pointed out that the Y/Y _c anomaly near the San Simeon earthquake appeared from March, 2002. Compared with the five earthquake cases out of the six with M ≥ 6.5 in California during the period from 1980 to 2001, the maximum Y/Y _c and duration of Y/Y _c anomaly before this earthquake are among the normal ranges, but the time delay from the maximum anomaly time to the occurrence time of this earthquake is the longest one. The result also shows that two areas with Y/Y _c anomalies occurred from Oct. 2002 and Dec. 2002, respectively. According to statistical characteristics of the relationship between Y/Y _c anomalies and the coming earthquakes, the seismic tendency in California was discussed in this paper.     

Fast Computing for LURR of Earthquake Prediction

The LURR theory is a new approach for earthquake prediction, which achieves good results in earthquake prediction within the China mainland and regions in America, Japan and Australia. However, the expansion of the prediction region leads to the refinement of its longitude and latitude, and the increase of the time period. This requires increasingly more computations, and the volume of data reaches the order of GB, which will be very difficult for a single CPU. In this paper, a new method was introduced to solve this problem. Adopting the technology of domain decomposition and parallelizing using MPI, we developed a new parallel tempo-spatial scanning program.     

汶川8.0级地震前四川地区地震视应力时空变化特征

本文根据Brune模式,在近震源条件下,利用中国数字遥测地震台网观测的波形资料,测定了2000年5月至2008年4月四川地区439次ML≥3.0地震的视应力值,给出了2008年5月12日汶川8.0级地震前四川地区视应力空间分布图象,分析了四川地区、龙门山断裂带以及龙门山断裂带上小震频次高值区视应力随时间变化过程。结果表明:①汶川地震前,视应力较高的地震主要集中在四川南部的川、滇交界地区;②2001—2006年,四川地区视应力随时间的变化表现为突升突降型变化形态,且视应力高值点有逐渐增大的现象,从2007年初至2008年初视应力在较低水平呈缓慢下降,临近汶川地震前有小幅升高变化;③龙门山断裂带上视应力在2004年中至2005年初曾出现过较为明显的、短暂的上升—下降变化过程。而Δσapp值的变化则相对复杂,出现过二次上升—下降变化过程;④龙门山断裂带上小震频次高值区视应力在2003—2005年间,曾出现过二次较为明显的上升—下降变化过程,临震前,视应力出现突然上升。而Δσapp值随时间的变化则主要表现为2003—2004年的上升和其后的下降过程。临近地震发生前,Δσapp值也有一定幅度的上升变化。     

Comparison Between LURR and State Vector Analysis Before Strong Earthquakes in Southern California Since 1980

There are seven strong earthquakes with M ≥ 6.5 that occurred in southern California during the period from 1980 to 2005. In this paper, these earthquakes were studied by the LURR (Load/Unload Response Ratio) method and the State Vector method to detect if there are anomalies before them. The results show that LURR anomalies appeared before 6 earthquakes out of 7 and State Vector anomalies appeared before all 7 earthquakes. For the LURR method, the interval between maximum LURR value and the forthcoming earthquake is 1 to 19 months, and the dominant mean interval is about 10.7 months. For the State Vector method, the interval between the maximum modulus of increment State Vector and the forthcoming earthquake is from 3 to 27 months, but the dominant mean interval between the occurrence time of the maximum State Vector anomaly and the forthcoming earthquake is about 4.7 months. The results also show that the minimum valid space window scale for the LURR and the State Vector is a circle with a radius of 100 km and a square of 3°×3°, respectively. These results imply that the State Vector method is more effective for short-term earthquake prediction than the LURR method, however the LURR method is more effective for location prediction than the State Vector method.     

河北及邻区地磁加卸载响应比映震分析

应用地磁加卸载响应比方法,选取河北及邻区2008年1月至2016年10月FHD观测数据,研究地磁响应比异常与该区M 4.0以上地震的对应关系。结果表明：①近9年符合判据标准的地磁加卸载响应比异常有11组33次,其中7组异常有震例对应,在选定的14次震例中9次对应震前异常;②异常面积通常与最大异常强度成正比关系;③前兆异常时间与震级之间一般正相关;④组内各次异常位置多具有连续性和迁移性;⑤震中大部分出现在异常高值区。     

Temporal and Spatial Variation of Focal Dynamic Parameters in Southwest Yunnan before the 2007 Ms6.4 Ning'er Earthquake

本文根据在近震源条件下,利用Brune模式,由昆明数字遥测地震台网观测到的波形资料,测定了2005年1月至2007年5月期间滇西南地区98次ML≥2.5地震的震源动力学参数,分析了在2007年6月3日云南泞洱Ms6.4地震前视应力和拐角频率的时空变化特征.泞洱Ms6.4地震前,较高视应力(2.5×105 Pa以上)主要分布在红河断裂与无量山断裂之间,较低视应力(2.5×105 Pa以下)在空间的分布则显得较为分散、随机.较低的拐角频率(1.5 Hz以下)集中分布在泞洱地震震中东北部的红河断裂与无量山断裂之间,随着频率的增大,分布范围逐渐向西南扩展,直到整个区域,较高的拐角频率(3.5 Hz以上)则集中分布在泞洱地震震中西南部的区域内.从视应力和拐角频率的时间变化曲线看,泞洱Ms6.4地震前滇西南地区视应力表现出了明显的升高变化过程;含ML3.6以上地震的拐角频率随时间的变化呈下降—上升—下降的复杂过程,ML＜3.6地震的拐角频率呈趋势下降过程.     

Occurrence of DDA in DDT-contaminated sediments of the Southern California Bight

DDT, DDE and some additional lipophilic derivatives are recognized contaminants in sediments of Southern California Bight (SCB). Only about 10% of total DDTs discharged into the SCB are accounted for using available monitoring data (sediment, water, and biota). DDA represented up to 0.03% DDTs (DDT/DDE/DDD) in SCB surface sediments (top 2 cm) in amounts up to 76 μg DDA/kg dry weight. Highest DDA levels were found where DDT and DDD levels were maximal at the primary wastewater outfall indicating a natural precursor-product relationship for DDT and DDA. Still culture of SCB sediment revealed limited DDA formation following DDT fortification. DDA residues have also been found in contaminated Long Island, NY sediments provided by USGS. The formation of DDA and its potential release from sediments may be significant in resolution of uncertainties concerning the natural recovery of sediments in DDT-contaminated environments.     

The Spatial and Temporal Variatiion of Modern Tectonic Stress Field in North CHina before and after the 1976 Tangshan Earthquake

By using 126 earthquake focal mechanism solutions (M S≥4.7) during the period of 1963～1998, modern tectonic stress field in North China is inverted by means of the step by step convergence. The inversion results indicate that the tectonic stress field in the research region is clearly variational in space and time: (1) The middling principal stress axis σ 2 is basically vertical. The maximum and minimum principal stress axes σ 1 and σ 2 are nearly horizontal, but the azimuths of σ 1 and σ 3 are inconsistent in different districts and periods. (2) Before the Tangshan earthquake in 1976, the three principal stress axes are uniform. The azimuth of maximum principal stress axis σ 1 is 68° (striking in a NEE-SWW direction). (3) After the Tangshan earthquake, the maximum principal stress axis σ 1 and minimum principal stress axis σ 3 have variations in different districts. In the northern area of North China and on the eastern side of the Tancheng-Lujiang fault zone, the maximum principal stress axis σ 1 is also striking in a NEE-SWW direction. Its azimuth is 68°. It is the same as that before the Tangshan earthquake. In the southern area of North China, the maximum principal stress axis σ 1 is striking in a E-W direction and its azimuth is 87°.     

九寨沟M_S7.0地震的前兆异常时空演化特征及其分析

以2017年8月8日九寨沟MS7.0地震震中为中心,对震前不同震中距前兆异常的时空演化过程进行分析。研究表明,震中距100km范围内无前兆异常,前兆异常主要分布在震中距100～500km范围内。震前2年新增前兆异常开始逐渐增多;不同震中距范围内的新增异常测项所占比例在震前1.5年左右达到最大,在震前又降低。在震中距300km范围内的异常测项所占比例相对较高。前兆异常时空演化过程存在3个不同的变化阶段,即α阶段(前兆异常的早期阶段,包括α_1和α_2,震前1000天以上)的异常主要分布在震中东北方向和西南方向,异常具有向外扩展的特征;β阶段(前兆异常的中期阶段,震前500～1000天)的异常表现为大范围出现异常;γ阶段(前兆异常的短期阶段,包括γ_1和γ_2,震前500天内)的异常分布在震中的东北方向,表现为远源区的异常向震中收缩过程(γ_1)和近源区的异常向外扩展的过程(γ_2)。通过与其他震例对比分析发现,前兆异常的3个阶段现象可能是大震前的共性特征,大震前前兆异常的显著增加对发震时间的预测具有一定的指示意义。     

A Statistical Investigation of the Earthquake Predictions Using LURR

In terms of the spatial scanning of LURR (Load-Unload Response Ratio), we have been predicting the seismic tendency within the next year for the mainland of China from 1995 to 2003. In order to make the quantitative retrospective assessment of LURR method, we compare the results with Poisson null hypothesis. The results show that the prediction by LURR method is much better than Poisson hypothesis.     

青海玛多MS7.4地震前b值时空变化特征

大量研究表明地震孕育过程中存在相对平静期,该阶段b值会相对下降,b值变化在地震活动性研究中起着十分重要的作用。2021年5月22日青海玛多发生MS7.4地震,为研究地震前b值时空变化特征,本文截取2009年至震前地震目录,将地震目录分为去除余震目录、完整地震目录,对比研究b值变化特征。研究发现,玛多MS7.4地震前1年b值开始低于均值且不断下降,至b值有上升趋势时地震发生,扩大到区域内其它5级以上地震,也符合此规律,地震发生后b值明显上升,短时间内又下降至较低位置,并一直处于较低位置直至下次地震发生;从b值空间扫描结果看,玛多MS7.4地震前,震中位于低b值区域,该位置为b值最低处;通过不同时间段的b值空间扫描结果,可发现玛多MS7.4地震发生前低b值区域向震中不断迁移,表明地震发生前震中附近应力不断集中;b值空间扫描时,完整地震目录掩盖了中强震震中区域低b值特性,去余震地震目录较好的凸显了中强震震中区域低b值特性。     

孕震过程中地震活动时空演化的非均匀特征

运用刻画强震前中,小地震在时空分布上不均匀性的参量ＧＬ值的方法,系统研究了华北地区２８次Ｍｓ≥５．０中强震前ＧＬ≥１．０的高值异常在空间上的分布特征和时间上的变化特征,系统开展了该地区不同地震活动水平的计算震级下限,时间窗,空间窗的合理性研究。对计算中所选取的参数进行优化和修改;采用全时空扫描的方法研究,追踪华北地区历次中强震前ＧＬ值的异常变化。结果表明：华北地区８２％的中强震前约１～３．５年内,在未来震中的附近出现明显的高值异常区,地震多发生在异常区的边缘或附近。ＧＬ值异常区的时间曲线表明,异常持续时间为３～２５个月不等,异常持续时间优势分布为３～１４个月,约占总异常的７８％;异常结束后,地震发生的优势分布为０～１４个月,约占总异常数的８３％,由此认为,ＧＬ值方法可能成为华北地区中强震预测的一个较为有效的方法     

2019年6月17日长宁MS6.0地震前后b值时空变化分析

选取2014年1月至2019年8月宜宾地区(28.0°N~28.5°N, 104.6°E~105.1°E)记录的地震资料, 利用最大似然法估算b值, 得到了宜宾地区b值的时空变化特征。结果显示: ① 2019年长宁M_S6.0地震前5个月, b值出现加速下降变化, 震后快速回升。这一现象很可能反映了地震孕育中的应力积累集中到地震发生后的应力释放过程。② 长宁地震前震中区及附近地区一直存在低b值异常(≤0.85), 震前5个月, 震中附近出现了b值下降, 尤其是长宁地震西偏北方向出现了b值显著下降, 后续珙县发生的3次M_S5地震正位于该异常区及边缘。③ b值空间低值异常可用于判定未来中强地震发生的危险区域, 而b值的下降可用于判定强余震的可能发生地点。④ 分析地震危险性时, 更应关注低b值背景下的b值下降, 即高应力集中区域的地震危险性增强。