Satellite detection of earthquake thermal infrared precursors in Iran

Stress accumulated in rocks in tectonically active areas may manifest itself as electromagnetic radiation emission and temperature variation through a process of energy transformation. Land surface temperature (LST) changes before an impending earthquake can be detected with thermal infrared (TIR) sensors such as NOAA-AVHRR, Terra/Aqua-MODIS, etc. TIR anomalies produced by 10 recent earthquakes in Iran during the period of Jun 2002–Jun 2006 in the tectonically active belt have been studied using pre- and post-earthquake NOAA-AVHRR datasets. Data analysis revealed a transient TIR rise in LST ranging 2–13°C in and around epicentral areas. The thermal anomalies started developing about 1–10 days prior to the main event depending upon the magnitude and focal depth, and disappeared after the main shock. In the case of moderate earthquakes (<6 magnitude) a dual thermal peak instead of the single rise has been observed. This may lead us to understand that perhaps pre-event sporadic release of energy from stressed rocks leads to a reduction in magnitude of the main shock. This TIR temperature increment prior to an impending earthquake can be attributed to degassing from rocks under stress or to p-hole activation in the stressed rock volume and their further recombination at the rock–air interface. A precise correlation of LST maps of Bam and Zarand with InSAR-generated deformation maps also provides evidence that the thermal anomaly is a ground-related phenomenon, not an atmospheric one.     

吉林地区地电阻率震兆异常对比分析

对采用形态法、归一化变化速率法和各向异性度法提取到的吉林省内深源地震以及浅源地震前的地电阻率异常变化进行对比分析,结果表明:(1)震前地电阻率出现1~2年尺度中期异常,甚至短期异常,异常以负异常为主;(2)震前地电阻率原始月均值异常变化幅度1%,表明数字地电仪捕捉电信号灵敏度的提高,更与台址构造密不可分;(3)震前地电阻率出现异常变化,震后恢复到正常变化形态,反映出震前震中区地下应力的变化,震后区域构造应力场重新调整并逐渐恢复的过程。     

1668年郯城8 1/2 级地震构造应力场分析

1668年郯城8 1/2 级地震,发震断层南起郯城窑上北到莒县土岭,全长为130 km,由5条北北东走向的活断层段组成。郯城地震断层南段沿沂沭断裂带内的F₂断裂分布,倾向南东东,倾角为30°～60°。北段紧邻F₁断裂分布,倾向不稳定,倾角较陡(多为70°以上)。南段表现为右行逆冲或逆右行的运动性质,北段则以右行走滑为主。郯城地震断层南、北两段均发育断层泥带、断层角砾带和碎裂带,南段总宽度为几米到十几米,北段总宽度为几十米到近百米,局部发育多条断层泥带。郯城地震断层的排列方式及其几何学特征表明:为老断层复活,而非新生断层。通过断层擦痕的反演同震应力场显示:北段为北东东-南西西向挤压应力场,南段为北东-南西向的挤压应力场,该地震是发生在区域性挤压应力场状态下。这种应力场空间变化可能是地震断层几何学空间变化导致的。其同震应力场与该地区现代区域应力场是一致的,这说明郯城地震并未造成震后应力场调整或震后应力场调整时间较短,未影响到现今应力场。     

Geostatistical method to delineate anomalies of multi-scale spatial variation in hydrogeological changes due to the ChiChi earthquake in the ChouShui River alluvial fan in Taiwan

This study uses Ordinary Kriging (OK), Sequential Gaussian Simulation (SGS) and Simulated Annealing Simulation (SAS) to relocate the completely heterotopic dataset from the locations of the Standardized Satellite Oriented Control Point System (SSOCPS) stations to the Groundwater Monitoring Networks (GMNS) stations and factorial kriging to analyze and map relationships among seven variables, including the hydraulic conductivities of three aquifers, the vertical displacements of the ground and groundwater level changes in the wells of three aquifers, and also to delineate the anomalies of multi-scale spatial variation of hydrogeological properties associated with the ChiChi earthquake, measuring 7.3 on the Richter scale, in the ChouShui River alluvial fan in Taiwan. In this study, the anomalies of spatial variation of hydrogeological properties associated with the earthquake are illustrated at micro, local and regional scales of 9, 12 and 36 km, respectively. In the study area, regionalization components associated with variation at local and regional scales are obtained and mapped by factorial kriging. Factorial Kriging Analysis (FKA) also demonstrated that the main effects of the ChiChi earthquake on the spatial variations of groundwater hydrological changes include porous media compression at micro scale, hydrogeological heterogeneousness of the sediments within the aquifer at local scale and the cyclic loading of deviatoric stress at regional scale. Finally, maps of spatial variations of regional components fully depicted all of the anomalies of spatial variation of hydrogeological changes due to the ChiChi earthquake and can be used to identify, confirm and monitor the hydrogeological properties in this study area.     

Preliminary investigation of some large landslides triggered by the 2008 Wenchuan earthquake, Sichuan Province, China

The M _s 8.0 Wenchuan earthquake or “Great Sichuan Earthquake” occurred at 14:28 p.m. local time on 12 May 2008 in Sichuan Province, China. Damage by earthquake-induced landslides was an important part of the total earthquake damage. This report presents preliminary observations on the Hongyan Resort slide located southwest of the main epicenter, shallow mountain surface failures in Xuankou village of Yingxiu Town, the Jiufengchun slide near Longmenshan Town, the Hongsong Hydro-power Station slide near Hongbai Town, the Xiaojiaqiao slide in Chaping Town, two landslides in Beichuan County-town which destroyed a large part of the town, and the Donghekou and Shibangou slides in Qingchuan County which formed the second biggest landslide lake formed in this earthquake. The influences of seismic, topographic, geologic, and hydro-geologic conditions are discussed.     

东秦岭216.8Ma前一个7级隐爆大地震的震源遗迹

依据野外地质勘查、工程揭露、地球物理探测等事实和地球化学测量资料,发现位于华北板块南缘东秦岭216.8Ma前一个古地震的震源遗迹。结合隐爆角砾岩体、系列隐爆角砾岩、岩石地球化学、同位素示踪、同位素测年、稀土元素、包裹体、岩石微观破碎等特征分析表明,该震源遗迹是在印支晚期杨子板块与华北板块碰撞对接的造山阶段,上地幔或下地壳形成的源于变质火山岩深熔的I型造山带花岗岩浆,在结晶分异过程中产生大量气液流体并沿断裂通道上升,进入硅化封闭的局部断裂空间后形成岩浆分异气液流体压力,当积聚的巨大压力超过所处深度的静岩压力与聚压空间围岩的破裂强度极限后,在地壳深部产生强烈隐爆所形成。根据上覆地层厚度、可参照的深成侵入岩体相对高度对比和主震遗迹的尺度等分析,隐爆深度位于当时地表的10km以下,隐爆主震的面波震级MS＞7.0。该震源遗迹的发现,可初步确认岩浆气液隐爆成因地震存在,并有助于克服一些地震成因研究中的震源不可视与不可入性难题,为地震成因乃至地震预测探索提供一些可直接观测研究的震源实体。 该遗迹不是一般的地震遗迹,而是一个“震源”实体遗迹——震源遗迹,而且是一个具有震源深度、发生年代、地震强度等地震要素完整且一致的可见震源遗迹。     

冲积平原区重金属元素异常解析中的矿物学方法

冲积平原区生态地球化学调查方法技术研究中矿物鉴定和化学分析结果对比研究表明，土壤中化学元素的含量及其分布特征主要取决于土壤对成壤母质中各种矿物成分的继承，元素的区域地球化学背景差异和在不同深度的含量变化均可通过矿物和矿物组合特征较为直接地示踪显现，土壤中矿物组成对其化学元素含量的影响是直接的、决定性的。因此，利用土壤的矿物组成确定其常量和微量元素的初始值具有重要意义。据此可进一步解析土壤中元素地球化学异常成因，判别土壤的元素地球化学异常类型。     

利用重磁资料对贵州西部玄武岩出露区火山口的初步圈定

根据火山口及岩浆喷溢后可能在重力和航磁上引起的重力异常和航磁异常的特性，该文利用重磁资料对该区火山口进行了初步圈定。为该区的地质、矿产研究及成矿预测提供一点深部信息。     

A seismic landslide susceptibility rating of geologic units based on analysis of characteristics of landslides triggered by the 17 January, 1994 Northridge, California earthquake

One of the most significant effects of the 17 January, 1994 Northridge, California earthquake (M=6.7) was the triggering of thousands of landslides over a broad area. Some of these landslides damaged and destroyed homes and other structures, blocked roads, disrupted pipelines, and caused other serious damage. Analysis of the distribution and characteristics of these landslides is important in understanding what areas may be susceptible to landsliding in future earthquakes. We analyzed the frequency, distribution, and geometries of triggered landslides in the Santa Susana 7.5′ quadrangle, an area of intense seismic landslide activity near the earthquake epicenter. Landslides occurred primarily in young (Late Miocene through Pleistocene) uncemented or very weakly cemented sediment that has been repeatedly folded, faulted, and uplifted in the past 1.5 million years. The most common types of landslide triggered by the earthquake were highly disrupted, shallow falls and slides of rock and debris. Far less numerous were deeper, more coherent slumps and block slides, primarily occurring in more cohesive or competent materials. The landslides in the Santa Susana quadrangle were divided into two samples: single landslides (1502) and landslide complexes (60), which involved multiple coalescing failures of surficial material. We described landslide morphologies by computing simple morphometric parameters (area, length, width, aspect ratio, slope angle). To quantify and rank the relative susceptibility of each geologic unit to seismic landsliding, we calculated two indices: (1) the susceptibility index, which is the ratio (given as a percentage) of the area covered by landslide sources within a geologic unit to the total outcrop area of that unit; and (2) the frequency index [given in landslides per square kilometer (ls/km²)], which is the total number of landslides within each geologic unit divided by the outcrop area of that unit. Susceptibility categories include very high (>2.5% landslide area or >30 ls/km²), high (1.0–2.5% landslide area or 10–30 ls/km²), moderate (0.5–1.0% landslide area or 3–10 ls/km²), and low (<0.5% landslide area and <3 ls/km²).     

汶川地震触发平溪村滑坡特征及成因分析

平溪村滑坡是汶川地震触发的高速岩质滑坡,面积为3.7×104m2,体积约65×104m3。滑坡距离映秀—北川发震断裂带中的石坎断层不足500m,在强大地震力作用下,滑坡滑动面陡峭、粗糙,与重力作用下呈圆弧、平滑的滑面迥异。地震触发的滑坡可分为三个阶段:①震动拉裂阶段;②摩擦阻力降低、"锁固段"剪断阶段;③滑体溃滑,高速流动堆积阶段。然后结合结构面的力学分析,通过数值模拟对地震作用下的应力变化和震裂机制进行了初步分析。     

2005年3月6日台湾宜兰海域6.1级地震速报总结及地震特征分析

对2005年3月6日台湾宜兰海域6.1级有感地震的速报情况进行总结,并对其地震特征进行了初步分析。     

On the Bayesian analysis of the earthquake hazard in the North-East Indian peninsula

The Bayesian extreme-value distribution of earthquake occurrences has been used to estimate the seismic hazard in 12 seismogenic zones of the North-East Indian peninsula. The Bayesian approach has been used very efficiently to combine the prior information on seismicity obtained from geological data with historical observations in many seismogenic zones of the world. The basic parameters to obtain the prior estimate of seismicity are the seismic moment, slip rate, earthquake recurrence rate and magnitude. These estimates are then updated in terms of Bayes’ theorem and historical evaluations of seismicity associated with each zone. From the Bayesian analysis of extreme earthquake occurrences for North-East Indian peninsula, it is found that for T = 5 years, the probability of occurrences of magnitude (M _w = 5.0–5.5) is greater than 0.9 for all zones. For M _w = 6.0, four zones namely Z1 (Central Himalayas), Z5 (Indo-Burma border), Z7 (Burmese arc) and Z8 (Burma region) exhibit high probabilities. Lower probability is shown by some zones namely␣Z4, Z12, and rest of the zones Z2, Z3, Z6, Z9, Z10 and Z11 show moderate probabilities.     

Study of directivity effect on electromagnetic emissions in the HF band as earthquake precursors: Preliminary results on field observations

This work focuses on the use of electromagnetic emissions (EM) in the HF band as a warning event for earthquakes. EM at HF components 41 MHz and 46 MHz were monitored and recorded from eight field stations in Greece and correlated with seismological events. Directivity effect raised since EM emissions at specific station locations were correlated to earthquake events from prescribed regions. EM recordings during 1999 were used and by visual inspection were associated to most of the earthquake events greater than 5R. Using these observations a novel algorithm based on the ratio of short term to long term signal average, together with a prediction rules set derived from 1999's EM emissions study were developed to combine results from several field stations. Performance of the system was promising, but was dependent on the geographic area of interest. Overall performance for earthquakes events of magnitude greater than 5.7 R was 75% of seismic events were correctly predicted by EM activity, while 25% were not predicted.     

Increasing critical sensitivity of the Load/Unload Response Ratio before large earthquakes with identified stress accumulation pattern

The Load/Unload Response Ratio (LURR) method is proposed for short-to-intermediate-term earthquake prediction [Yin, X.C., Chen, X.Z., Song, Z.P., Yin, C., 1995. A New Approach to Earthquake Prediction — The Load/Unload Response Ratio (LURR) Theory, Pure Appl. Geophys., 145, 701–715]. This method is based on measuring the ratio between Benioff strains released during the time periods of loading and unloading, corresponding to the Coulomb Failure Stress change induced by Earth tides on optimally oriented faults. According to the method, the LURR time series usually climb to an anomalously high peak prior to occurrence of a large earthquake. Previous studies have indicated that the size of critical seismogenic region selected for LURR measurements has great influence on the evaluation of LURR. In this study, we replace the circular region usually adopted in LURR practice with an area within which the tectonic stress change would mostly affect the Coulomb stress on a potential seismogenic fault of a future event. The Coulomb stress change before a hypothetical earthquake is calculated based on a simple back-slip dislocation model of the event. This new algorithm, by combining the LURR method with our choice of identified area with increased Coulomb stress, is devised to improve the sensitivity of LURR to measure criticality of stress accumulation before a large earthquake. Retrospective tests of this algorithm on four large earthquakes occurred in California over the last two decades show remarkable enhancement of the LURR precursory anomalies. For some strong events of lesser magnitudes occurred in the same neighborhoods and during the same time periods, significant anomalies are found if circular areas are used, and are not found if increased Coulomb stress areas are used for LURR data selection. The unique feature of this algorithm may provide stronger constraints on forecasts of the size and location of future large events.     

中国大陆科学钻探主孔流体地球化学异常与远强震的关系

2001年11月14日发生的昆仑山口西Ms8．1级地震和2004年12月26日发生的印度尼西亚苏门答腊Ms8．7级地震前后,中国大陆科学钻探（CCSD）主孔流体组成出现明显的异常。两次远强震前后的流体异常幅度很大,并具有相似的演化趋势。异常始于震前2—7天,He、N2／O2、He／Ar、N2／Ar为负异常,Ar／O2为正异常。远强震前后流体异常特征与CCSD附近小震前后流体异常特征具有明显的区别,表明昆仑山口西Ms8．1级地震前后和苏门答腊Ms8．7级地震前后的CCSD主孔流体异常可能与两次远强震相关。认为CCSD主孔中的He、N2、Ar是记录远强震的敏感载体,可能记录了震前长周期波传播至CCSD主孔时激发的流体变化,反映了震源区的应力变化,也可能反映了区域构造活动乃至地球深部构造活动产生的场兆、源兆信息。     

Statistical analysis of an earthquake-induced landslide distribution — the 1989 Loma Prieta, California event

The 1989 Loma Prieta, California earthquake (moment magnitude, M=6.9) generated landslides throughout an area of about 15,000 km² in central California. Most of these landslides occurred in an area of about 2000 km² in the mountainous terrain around the epicenter, where they were mapped during field investigations immediately following the earthquake. The distribution of these landslides is investigated statistically, using regression and one-way analysis of variance (ANOVA) techniques to determine how the occurrence of landslides correlates with distance from the earthquake source, slope steepness, and rock type. The landslide concentration (defined as the number of landslide sources per unit area) has a strong inverse correlation with distance from the earthquake source and a strong positive correlation with slope steepness. The landslide concentration differs substantially among the various geologic units in the area. The differences correlate to some degree with differences in lithology and degree of induration, but this correlation is less clear, suggesting a more complex relationship between landslide occurrence and rock properties.     

青海玉树Ms7.1级地震同震地表破裂构造

分析了青海玉树Ms7.1级地震中形成的同震地表破裂分布与构造特征。本次地震造成的地表破裂长达46km,地震造成240cm的最大相对水平走滑错动量,最大垂直错动量60cm。地表破裂所经之处可看到原有断层新近活动的明显迹线。依次分析了按空间尺度划分的4个层次破裂的走向变化、同级破裂排列、破裂末端变化等构造特征。Ⅰ级破裂作为本次地震产生的整个破裂带,总体走向119°,由3段自然分开、左阶斜列的Ⅱ级破裂组成。3段Ⅱ级破裂自NW向SE依次为隆宝镇段、结古镇段和禅古寺段,破裂性质总体以左旋走滑为主,各段略有不同。各Ⅱ级破裂带内部,分别由若干Ⅲ级破裂段落组成,总体呈现右阶斜列排列模式。Ⅲ级破裂本身由一系列简单的Ⅳ级破裂雁列或羽列右阶斜列构成。不同层次的地表破裂具有简单剪切构造带的变形特征,共识别出R、R’、Y、T和P五组基本破裂面。其初始破裂面展布特征可以用库伦破裂准则来解释,其中岩土体材料的内摩擦角大致为26~44°。各级破裂端部出现分叉、转向及逐渐消失等变形特征。     

青海玉树Ms7.1级地震同震地表破裂构造

分析了青海玉树Ms7.1级地震中形成的同震地表破裂分布与构造特征。本次地震造成的地表破裂长达46km,地震造成240cm的最大相对水平走滑错动量,最大垂直错动量60cm。地表破裂所经之处可看到原有断层新近活动的明显迹线。依次分析了按空间尺度划分的4个层次破裂的走向变化、同级破裂排列、破裂末端变化等构造特征。Ⅰ级破裂作为本次地震产生的整个破裂带,总体走向119°,由3段自然分开、左阶斜列的Ⅱ级破裂组成。3段Ⅱ级破裂自NW向SE依次为隆宝镇段、结古镇段和禅古寺段,破裂性质总体以左旋走滑为主,各段略有不同。各Ⅱ级破裂带内部,分别由若干Ⅲ级破裂段落组成,总体呈现右阶斜列排列模式。Ⅲ级破裂本身由一系列简单的Ⅳ级破裂雁列或羽列右阶斜列构成。不同层次的地表破裂具有简单剪切构造带的变形特征,共识别出R、R’、Y、T和P五组基本破裂面。其初始破裂面展布特征可以用库伦破裂准则来解释,其中岩土体材料的内摩擦角大致为26～44°。各级破裂端部出现分叉、转向及逐渐消失等变形特征。     

浅析吉林省临江市花山镇北部地热异常成因

通过分析井温曲线类型、断裂构造以及热水化学特征,揭示地热异常具有以对流为主的特点,热水赋存于构造裂隙系统中,地下水补给来源为大气降水。地热异常区是研究、开发地热资源的主要对象。     

2010年新西兰M7.1地震前的长波辐射变化特征

以2001—2011年美国NOAA长波辐射数据为背景数据,利用涡度背景场法研究2010年9月3日新西兰南岛M7.1级地震前后卫星长波辐射数据变化特征。结果表明,地震当月在震中西南侧出现显著的长波辐射异常变化,这种变化在全年各月及2001—2011年11年历年同月变化中都是最为显著的,认为其是本次地震的1次映震表现。用同样方法对区内2001—2011年11年间发生6次7.0级以上地震的长波辐射数据进行分析,结果在3次陆地地震发震前都检测到了长波辐射异常变化,而海域地震前则未发现这种现象。检索前人的相关研究结果,发现仅有2次海域地震(2004年12月26日印度尼西亚苏门答腊西北海域8.7级地震和2010年1月12日海地7.0级地震)前有长波辐射异常变化的报道,而根据全球云量分布资料显示,这2个地震所发生的区域是全球洋面云量分布最少的2个区域,而新西兰地震发生的区域位于全球洋面云量分布最多的区域。因此,认为由于水汽和云层对地表红外辐射的强吸收作用,长波辐射捕捉陆地地震红外辐射异常变化更加灵敏,对陆地地震的映震效能要强于海洋地震。