华北地区6.0级以上地震前非均匀度CV值异常变化特征

通过对非均匀度 CV值等时间、等地震个数时间扫描和空间的扫描 ,对 1970年以来华北地区8次 6 .0级以上地震前 CV值的异常变化进行了研究 ,认为在发震区域内强震前 CV值与地震有较好的对应关系 ,出现较为明显的上升过程后 ,在回落或回落过程中发震 ,表明地震活动的丛集性是强震发生的重要异常特征     

利用震兆曲线非线性特征估计川滇区域地震危险性时间

对川滇及邻区特定构造区域地震活动的时间、强度和空间分布进行了分析,结合研究区1988年以来的8次地震发生前ML≥3.0级地震活动指标缺震(L值)、频度(N值)、活动度(S值)和危险度(D值)的曲线非线性特征进行了分析,给出了下一次地震危险性时间的估计方法。川滇及相邻地区的地震模型ML≥3.0级群体地震活动的震兆曲线,能够很好地描述川滇区域地震活动强、弱变化的异常信息,临震信号是地震失稳的标志,有震异常和临震前的短临异常反映出的时间变化非线性曲线特征能够有效地给出地震发生的时间判断。     

地震形势的模糊综合评判

由中国大陆板块内部地震活动与其周缘地震活动的相关性,可以确定我国大陆未来地震活动的主体和地震活动高潮时间.在此基础上,本文进一步探讨用长时间、大面积的地震活动信息,对重点监测区未来地震作出时、空、强综合评判.全文分为三部分: 1.地震强度的预报.对于确定的能有效地估计未来地震强度的5项地震活动性指标,选择加权平均型的模糊综合评判方法,对监测区未来地震的震级给出明确的结果. 2.发震地点预报.对于扫描单元定义了反映b值时空变化的二项指标:b值异常次数A_y;和b值异常均值b_(yi).通过对二项指标空间分布的综合分析,可以估计未来地震发生的地点. 3.发震时间预报.把缺震时间T_l与b值回升时间T_(bu)作为描述大震前平静过程的二项定量指标.在对未来地震强度作出模糊综合评判后,可用T_l,T_(bu)二项指标综合推断监测区未来地震发生的时间. 总结的九个震例结果表明,该方法可使地震预报定量化、实用化,可以用于地震形势的预测和中、短期地震预报.     

地震活动显著增强指标算法研究

根据华北地区1970年以来地震目录和历史地震文献资料，对地震活动显著增强异常指标进行归纳、总结和实验，对照《中国震例（1966-2012）》中中国东部地区发生的1975年2月4日辽宁海城7.4级、1976年7月28日河北唐山7.8级等典型地震进行震例回溯检验，明确该项指标的计算规则，设计计算机自动化程序，在短时间内对指定区域进行地震活动显著增强异常指标的扫描计算，为开展测震学异常判定及预测指标提取等工作提供参考依据。     

天山地区中强地震预报判据及方案

对新疆6级地震成组活动与7级地震的相关性进行了总结。结合天山地区不同构造环境,开展中强地震孕育阶段不同区域地震活动图像演化和强震短期前兆异常综合特征研究,在总结天山地区中短期异常特征及预报判据基础上,提出中短期阶段预报方案。预报方案：①时间预测。南天山在地震平静背景下,局部地区出现较明显的地震增强现象;北天山3～4级地震出现增强-平静-显著地震过程;大范围前兆观测出现同步异常变化等。②地点预测。地震活动增强区、空区周围、条带端部或空段、显著事件周围,定点前兆短期异常相对集中区域等,可做为地震发生的预测地点。③强度预测。预测区周围历史地震强度、新疆5级地震平静持续时间、震前地震活动强度等可做为强度预测的参考。     

地震大形势预测方法的预测效能与应用研究

采用地震非均匀度(GL值)预测方法, 在震例回朔性检验研究、 室内岩石破裂实验及GPS观测结果等三种途径对该方法预测效能进行评价研究的基础上, 开展对中国大陆未来1～3年强地震活动主体地区和危险性预测工作。 效能评价结果表明, 地震非均匀度(GL值)可以较好地刻画岩石失稳前因破裂成核导致的声发射活动在时间分布上的状态变化, 这种状态变化可能与强地震孕育进入末期、 强地震即将发生有关。 地震非均匀度时空扫描结果表明, 未来1～3年中国大陆强地震活动主体地区将集中在青藏块体中北部及新疆南天山地区, 上述区域在未来一个时期发生多次6.5级乃至7级以上地震的可能性较大。     

青藏块体东北缘跨断层异常场地比指标及其在地震预测中的应用

为了客观反映跨断层形变资料在地震前出现的异常程度, 减弱场地布设不均匀性造成的影响, 本文基于以往典型震例归纳跨断层异常场地比指标并进行了实例检验。 结果表明: ① 震例统计显示, 异常场地比随震中距增加快速降低, 在青藏块体东北缘5.8级及以上中强地震前, 距震中200 km范围异常场地比约为0.5。 ② 异常场地比等值线高值区对地震震中位置有较好的指示意义, 可以作为中强地震预测的一种定量判定依据, 为区域地震危险性的地点判定提供支持。 ③ 多期异常场地比空间分布特征能够较好地刻画跨断层异常随时间的增强、 减弱或迁移特征, 可为地震紧迫性判定提供一定帮助。     

近年来华北南部地区地震活动增强的力学背景分析

依据青藏高原东北缘与秦岭大地构造格局相关联的地质构造背景,青藏高原物质东流和“稳定”块体的阻挡是华北南部地区构造活动的主要动力来源之一的基本认识,分析了青藏高原东北缘4次8级地震前华北南部地区地震活动的基本特征。8级地震震中区附近地震活动异常变化不明显,但华北南部地区地震异常活跃,其异常活跃过程与青藏高原东北缘强震的孕育与发生存在明显的相关性．具有一定的异地震情指示意义。     

云南地区4级地震频度异常特征与强震关系研究

对云南地区18次MS≥6强震事件前中、小地震活动过程进行了分析,发现在这些地震发生前1—3年近场区2°×2°范围内4级地震频度基本上出现了显著增强现象,可以用4级地震年累计频度进行定量描述。通过全时空的扫描,确定年累计频度N≥4为异常阈值,该指标通过了置信度97.5%的R值内符检验。并用调整单元对强震附近4级地震活动增强现象给予了物理解释。     

地震形势的模糊综合评判

由中国大陆板块内部地震活动与其周缘地震活动的相关性,可以确定我国大陆未来地震活动的主体和地震活动高潮时间[1].在此基础上,本文进一步探讨用长时间、大面积的地震活动信息,对重点监测区未来地震作出时、空、强综合评判.全文分为三部分:1.地震强度的预报.对于确定的能有效地估计未来地震强度的5项地震活动性指标,选择加权平均型的模糊综合评判方法,对监测区未来地震的震级给出明确的结果.2.发震地点预报.对于扫描单元定义了反映b值时空变化的二项指标:b值异常次数A_yi;和b值异常均值b_yi.通过对二项指标空间分布的综合分析,可以估计未来地震发生的地点.3.发震时间预报.把缺震时间T_l与b值回升时间T_bu,作为描述大震前平静过程的二项定量指标.在对未来地震强度作出模糊综合评判后,可用T_l,T_bu二项指标综合推断监测区未来地震发生的时间.总结的九个震例结果表明,该方法可使地震预报定量化、实用化,可以用于地震形势的预测和中、短期地震预报.      

Characteristics of seismic activity before the MS8.0 Wenchuan earthquake

The characteristics of spatio-temporal seismicity evolution before the Wenchuan earthquake are studied. The results mainly involve in the trend abnormal features and its relation to the Wenchuan earthquake. The western Chinese mainland and its adjacent area has been in the seismically active period since 2001, while the seismic activity shows the obvious quiescence of M≥?7.0, M≥?6.0 and M?≥5.0 earthquakes in Chinese mainland. A quiescence area with M?≥7.0 has been formed in the middle of the North-South seismic zone since 1988, and the Wenchuan earthquake occurred just within this area. There are a background seismicity gap of M?≥5.0 earthquakes and a seismogenic gap of M_L?≥4.0 earthquakes in the area of Longmenshan fault zone and its vicinity prior to the Wenchuan earthquake. The seismic activity obviously strengthened and a doughnut-shape pattern of M?≥4.6 earthquakes is formed in the middle and southern part of the North-South seismic zone after the 2003 Dayao, Yunnan, earthquake. Sichuan and its vicinity in the middle of the doughnut-shape pattern show abnormal quiescence. At the same time, the seismicity of earthquake swarms is significant and shows heterogeneity in the temporal and spatial process. A swarm gap appears in the M4.6 seismically quiet area, and the Wenchuan earthquake occurred just on the margin of the gap. In addition, in the short term before the Wenchuan earthquake, the quiescence of earthquake with M_L≥?4.0 appears in Qinghai-Tibet block and a seismic belt of M_L?≥3.0 earthquakes, with NW striking and oblique with Longmenshan fault zone, is formed.     

A Long-term earthquake forecast for the Kuril-Kamchatka Island arc for the period 2006–2011 and a successful forecast of the MS = 8.2 middle kuril earthquake of November 15, 2006

Results are reported from continuous long-term earthquake prediction work for the Kuril-Kamchatka island arc using the patterns of seismic gaps and the seismic cycle. A five-year forecast (April 2006 to April 2011) for all portions of the Kuril-Kamchatka seismogenic zone is presented. According to this, the most likely locations of future M ≥ 7.7 earthquakes include the Petropavlovsk-Kamchatskii area where the probability of an M ≥ 7.7 earthquake causing ground motions of intensity VII to IX in the town of Petropavlovsk-Kamchatskii is 48% for 2006–2011, and the area of Onekotan I. and the Middle Kuril Islands where the probability of an M ≥ 7.7 earthquake was estimated as 26.7%. The forecast was fulfilled on November 15, 2006, when an M_s= 8.2, M_w = 8.3 earthquake occurred in the Middle Kuril Islands area. An updated long-term forecast is presented for the Kuril-Kamchatka arc for the period from November 2006 to October 2011. These forecasts provide good reasons to enhance seismic safety by strengthening buildings and structures in Kamchatka.     

Source parameters of the Gonghe,Qinghai Province,China,earthquake from inversion of digital broadband waveform data

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Partial breaking of a mature seismic gap: The 1987 earthquakes in New Britain

To better understand the mechanics of subduction and the process of breaking a mature seismic gap, we study seismic activity along the western New Britain subduction segment (147°E–151°E, 4°S–8°S) through earthquakes withm _b 5.0 in the outer-rise, the upper area of subducting slab and at intermediate depths to 250 km, from January 1964 to December 1990. The segment last broke fully in large earthquakes of December, 28, 1945 (M _s =7.9) and May 6, 1947 (M _s =7.7.), and its higher seismic potential has been recognized byMcCann et al., (1979). Recently the segment broke partially in two smaller events of February, 8, 1987 (M _s =7.4) and October 16, 1987 (M _s =7.4), leaving still unbroken areas.We observe from focal mechanisms that the outer-rise along the whole segment was under pronounced compression from the late 60's to at least October 1987 (with exception of the tensional earthquake of December 11, 1985), signifying the mature stage of the earthquake cycle. Simultaneously the slab at intermediate depths below 40 km was under tension before the earthquake of October 16, 1987. That event, with a smooth rupture lasting 32 sec, rupture velocity of 2.0 km/sec, extent of approximately 70 km and moment of 1.2×10²⁷ dyne-cm, did not change significantly the compressive state of stress in the outer-rise of that segment. The earthquake did not fill the gap completely and this segment is still capable of rupturing either in an earthquake which would fill the gap between the 1987 and 1971 events, or in a larger magnitude event (M _s =7.7–7.9), comparable to earthquakes observed in that segment in 1906, 1945 and 1947.     

Seismicity anomalies before the great earth—quake of Ms=8.1 in the Kunlun Pass and its significance to earthquake prediction

A great earthquake of M _S=8.1 took place in the west of Kunlun Pass on November 14, 2001. The epicenter is located at 36.2°N and 90.9°E. The analysis shows that some main precursory seismic patterns appear before the great earthquake, e.g., seismic gap, seismic band, increased activity, seismicity quiet and swarm activity. The evolution of the seismic patterns before the earthquake of M _S=8.1 exhibits a course very similar to that found for earthquake cases with M _S≥7. The difference is that anomalous seismicity before the earthquake of M _S=8.1 involves in the larger area coverage and higher seismic magnitude. This provides an evidence for recognizing precursor and forecasting of very large earthquake. Finally, we review the rough prediction of the great earthquake and discuss some problems related to the prediction of great earthquakes.     

中强地震前地震波参数异常的研究

本文研究了1988年5月26日库尔勒M_35.5地震和1991年2月25日柯坪M_s6.5地震前后的地震波初动符号、振幅比、尾波持续时间比和尾波衰减系数的变化特征,发现两次地震前上述参数均具有不同程度的异常。地震前(?)波初动一致性越强,持续时间越长,未来地震震级越大;振幅比突跳是即将发生地震的明显信号;首先出现尾波衰减系数异常的台站距未来地震震中较近。根据上述参数的异常特征,成功地预报了1991年6月6日和静M_s5.2地震。     

关于云南丽江7级地震的中短期预报

总结了对 1 996年 2月 3日云南丽江 7级地震的中短期监视及跟踪预报过程 .根据川滇地区地震活动特征和可公度性计算结果 ,在该次地震前对地震大形势进行了预测 .1 995年 1 0月以后 ,滇西北地区出现了大面积、大幅度、多手段的同步异常 ,其中以水氡、水位和CO2 异常为主 ,沿中甸─南涧地震区分布较为集中 .根据上述异常特征及异常分布情况 ,作者在该次地震前 2个月向大理州政府提出了书面预报意见 ,认为 1 996年 2月底以前在中甸─丽江─剑川─华坪一带有可能发生 5～ 6级地震 .     

新疆天山地震带的地震流体地质效应

天山地区的高压自流水、高压油气藏及地热异常区的出露与天山地震带分布的一致性表明,孔隙水压异常高的动力条件可能成为触发浅源地震的重要机制。本文以丰富的震例为依据,认为天山地震带中强地震前地下流体出现两类异常:一类是应力应变能积累阶段的趋势性异常;一类是应力应变能预释放阶段的临震突发性异常。两类异常在形态上和时空分布上有完全不同的特征,它们显示出地震孕育过程中的两个完全不同的物理、化学过程。     

Probabilistic Seismic Hazard Assessment for Iraq Using Complete Earthquake Catalogue Files

Probabilistic seismic hazard analysis (PSHA) has been carried out for Iraq. The earthquake catalogue used in the present study covers an area between latitude 29°–38.5° N and longitude 39°–50° E containing more than a thousand events for the period 1905–2000. The entire Iraq region has been divided into thirteen seismogenic sources based on their seismic characteristics, geological setting and tectonic framework. The completeness of the seismicity catalogue has been checked using the method proposed by Stepp (1972). The analysis of completeness shows that the earthquake catalogue is not complete below M_s=4.8 for all of Iraq and seismic source zones S1, S4, S5, and S8, while it varies for the other seismic zones. A statistical treatment of completeness of the data file was carried out in each of the magnitude classes. The Frequency Magnitude Distributions (FMD) for the study area including all seismic source zones were established and the minimum magnitude of complete reporting (M_c) were then estimated. For the entire Iraq the M_c was estimated to be about M_s=4.0 while S11 shows the lowest M_c to be about M_s=3.5 and the highest M_c of about M_s=4.2 was observed for S4. The earthquake activity parameters (activity rate , b value, maximum regional magnitude m_max) as well as the mean return period (R) with a certain lower magnitude m_min m along with their probability of occurrence have been determined for all thirteen seismic source zones of Iraq. The maximum regional magnitude m_max was estimated as 7.87 ± 0.86 for entire Iraq. The return period for magnitude 6.0 is largest for source zone S3 which is estimated to be 705 years while the smallest value is estimated as 9.9 years for all of Iraq.The large variation of the b parameter and the hazard level from zone to zone reflects crustal heterogeneity and the high seismotectonic complexity. The seismic hazard near the source boundaries is directly and strongly affected by the change in the delineation of these boundaries. The forces, through which the geological structure along the plate boundary in Eastern and Northeastern Iraq are evolved, are still active causing stress-strain accumulation, deformation and in turn producing higher probabilities of earthquake activity. Thus, relatively large destructive earthquakes are expected in this region. The study is intended to serve as a reference for more advanced approaches and to pave the path for the probabilistic assessment of seismic hazard in this region.     

Seismicity anomalies before the great earthquake of <Emphasis Type="Italic">M</Emphasis><Subscript>S</Subscript>=8.1 in the Kunlun Pass and its significance to earthquake prediction

A great earthquake of M _S=8.1 took place in the west of Kunlun Pass on November 14, 2001. The epicenter is located at 36.2°N and 90.9°E. The analysis shows that some main precursory seismic patterns appear before the great earthquake, e.g., seismic gap, seismic band, increased activity, seismicity quiet and swarm activity. The evolution of the seismic patterns before the earthquake of M _S=8.1 exhibits a course very similar to that found for earthquake cases with M _S≥7. The difference is that anomalous seismicity before the earthquake of M _S=8.1 involves in the larger area coverage and higher seismic magnitude. This provides an evidence for recognizing precursor and forecasting of very large earthquake. Finally, we review the rough prediction of the great earthquake and discuss some problems related to the prediction of great earthquakes.