塔里木盆地红外增温现象与地震关系的初步探讨

利用NOAA卫星热红外遥感图像对新疆塔里木盆地进行研究,对比分析发生在塔里木盆地周边的2次中强地震,结果发现在震前1个月内均有不同程度的红外增温现象。这两次增温现象的分布范围、异常持续时间和地震三要素的关系不明确。2003年2月在巴楚县东部上空出现的增温现象,形态呈放射状,地点相对固定,在时间上具有连续性,分析认为该现象可能和伽师-巴楚MS6.8地震有关。而1999年1月托克逊MS5.6地震前出现的增温现象主要表现为边界清晰、色调均匀的高温雾状物,其分布地点与未来震中位置无关,却始终沿塔里木盆地边缘分布,认为很可能是与地震无关的大气逆温现象。以上震例说明塔里木盆地出现的红外辐射增温现象,并不完全与孕震机制有关。如何对震前红外辐射异常与大气自然现象进行有效甄别,还需要根据增温出现的季节、地形地貌环境,以及增温区演化特征来判断。     

姚安6.5级地震前的热红外增温特征分析

利用NOAA／AVHRR资料，通过遥感图象处理、地表温度反演、空间统计分析等技术方法。分析姚安6．5级地震震前的热红外温度变化。对计算结果的单点采样比较和面域剖面分析表明，2000年1月15日姚安6．5级地震前，震区出现了明显的热红外持续增温；震前两天热红外温度与地震平静时段的同期同区域温度相比出现了大面积的3℃0℃的正值区域；与同期温度背景场相比，在断裂附近震区增温仍较明显。研究还表明，将卫星热红外辐射技术用于实际地震预报还需要解决两个重要问题：一是资料的时间连续性问题；二是热红外异常与地震的孕育、发生的定量关系问题。     

深圳市断裂构造的活动性及其对地质环境的影响

从地质、地貌、地球化学、地壳形变、地震活动等多学科研究分析深圳市断裂第四纪以来的活动，指出晚更新世以前北东向与北西向两组断裂有多期活动，并以后者切截，错移前者为特征。但晚更新世以来至今活动已明显减弱，现今活动微弱。断裂活动对该地区地壳稳定性及其他地质地貌环境没有构成较严重的自然灾害隐患。     

汶川地震区青川县乔庄镇地震断裂问题

汶川特大地震导致了青川县乔庄镇(主城区)遭遇了较为惨重的特大灾难.县城的恢复重建工作受到地震断裂、山体变形、强烈的余震活动等严重制约.尤其是地震断裂问题,更是对能否原址重建起决定性作用.在参考以往研究成果的基础上,结合实地调查,对该镇的地震断裂问题进行了评估,确定了青川-平武断裂(龙门山后山断裂主断裂之一)分三条分支断裂(北支断裂、中间断裂、南支断裂)穿过乔庄镇主城区的大致方位和走势,并且现场发现该三条分支断裂均发生了不同程度的地震破裂(如地表破裂,山体震裂等),已逐渐发展成为中强震的孕震构造.     

扬子准地台西北边缘地区地壳稳定性问题

5·12汶川8级大地震影响到整个四川盆地西部地区,该区是扬子准地台与青藏高原造山带的结合部位--台槽交接区,特殊的地震地质构造及其活动性,加上人类活动的影响,使得那里的地壳变得非常脆弱.扬子准地台从早期到晚期的发展过程中活动性比较大,基底硬化程度较低,有显著而广泛的褶皱和断裂运动.在此着重探讨四川盆地以西即从东面的龙泉山开始经成都平原至龙门山地区地壳稳定性问题.     

2008年3月21日于田7．4级地震的构造背景

2008年3月21日在新疆和田地区于田与策勒县交界处发生7.4级地震.地震发生在塔里木盆地的南边,靠近西昆仑山区边缘的阿尔金地震带.阿尔金断裂带西南端是有三个分支、向西撒开的构造,北面一支分布在硝尔库勒盆地,中间一支就分布在阿什库勒盆地,是这次地震主要的发震断裂构造;南面一支一直延伸到郭扎错盆地,限制了余震的分布范围.地震破裂是以拉张为主兼有走滑运动的倾滑破裂,是阿尔金深断裂左旋扭错的结果,和震源机制解的结果相一致.阿尔金断裂的强烈地震活动,往往伴随有青藏高原周边主要断裂带的大震活动.这次7.4级地震之后的一个多月就发生了四川汶川8级地震,在青藏高原及其边缘和新疆塔里木盆地的西部及帕米尔高原周缘地区是否会引起地震活动的进一步加强,也值得引起注意.     

浅析构造地震根本力来源——以汶川地震为例

目前发生次数最多对人类生活影响最大的地震绝大部分为构造地震,传统上认为构造地震与板块运动有关,是由活动断裂活动产生,构造地震能量主要来源于断层两侧岩体因地壳变形而产生并储集的弹性应变能。笔者认为真正驱使构造地震活动的力不是由活动断裂运动产生,根本来源于使活动断裂运动的能量,该能量可能来自地幔热柱的超临界流体,活动断裂运动只是行为现象,不是本质原因。     

1980~2013年新疆高空大气温度变化特征

基于1980~2013年新疆地区8个探空站逐日观测资料,利用Mann-Kendall非参数检验法,分析新疆30多年来高空大气温度时间序列的变化趋势、突变时间及二者的显著性,探讨其与地面温度变化关系。结果表明：近30多年来,新疆对流层上层至平流层中下层表现为降温趋势,对流层中下层呈升温趋势,对流层上层和平流层中下层降温幅度大于对流层中下层的增温幅度;新疆高空温度的变化存在明显的季节差异;新疆高空各层温度在20世纪90年代初发生显著性突变,晚于北半球地面温度突变年份,早于相对应的地面温度突变时间;新疆对流层中下层温度在不同时段和不同季节与地面温度的变化不同,1980~2013年二者均呈显著的增温趋势,而1998~2013年二者的变暖趋势均减缓,甚至还表现为微弱的下降趋势。     

汶川地震触发的绵远河流域崩塌滑坡的特征

利用地震后ALOS影像自动提取了汶川地震重灾区绵远河流域内的崩塌滑坡,结合野外调查共确定地震触发崩塌滑坡1 073处,面积48.5 km2.其中分布最广、数量最多的是浅层崩滑体;同时由于地震力作用强烈,触发了许多深层、高速、远程滑坡,并形成了大量的滑坡堰塞湖.汶川地震诱发的第二大滑坡文家沟滑坡就位于流域内,该滑坡是本次地震中滑动距离最远的滑坡.地震导致大量的碎屑物质堆积在沟道内或悬挂在斜坡上,为泥石流的发生提供了有利条件.基于GIS的统计分析表明,地震滑坡的空间分布主要受发震断层的控制,流域内的崩塌滑坡受到了映秀-北川断裂和江油-都江堰断裂的双重影响,主要分布于两断裂上盘的一定范围内;地层岩性影响着地震滑坡的类型,岩浆岩、白云岩等硬岩主要发育浅层崩滑体,而上硬下软的地层多发生大型滑坡;大部分崩塌滑坡都发生在海拔1 000～2 000 m的高程内;坡度是崩塌滑坡发生的主要控制因素之一,大部分崩塌滑坡发生在25°～55°的范围内;坡向对滑坡的分布也有一定的影响,背靠震源(发震断层)方向的斜坡比面向震源(发震断层)方向更容易发生滑坡.     

汶川地震旅游资源开发研究

"5·12"大地震使地处中国四川省西北部的小城汶川为世人所熟知,大地震给灾区带来巨大灾难的同时,也产生了大量地震旅游资源.汶川地震旅游资源的数量和种类都很丰富,具有极高的旅游开发价值.结合汶川地区的实际情况,对汶川地震旅游资源的开发有如下构想,主要包括两种开发模式:主体式开发、组合式开发,以及具体的开发设想:震迹和震记资源开发、地震主题公园建设等.开发过程中要注意与周边原有旅游资源有机整合和有针对性的宣传促销等.     

The influence of earthquakes on the Chandler wobble during 1977–1983

Summary. A direct calculation is made of the effect on the Chandler wobble of 1287 earthquakes that occurred during 1977–1983. The hypocentral parameters (location and origin time) and the moment tensor representation of the best point source for each earthquake as determined by the 'centroidmoment tensor' technique were used to calculate the change in the Chandler wobble's excitation function by assuming this change is due solely to the static deformation field generated by that earthquake. The resulting theoretical earthquake excitation function is compared with the 'observed' excitation function that is obtained by deconvolving a Chandler wobble time series derived from LAGEOS polar motion data. Since only 7 years of data are available for analysis it is not possible to resolve the Chandler band and determine whether or not the theoretical earthquake excitation function derived here is coherent and in phase with the 'observed' excitation function in that band. However, since the power spectrum of the earthquake excitation function is about 56 dB less than that of the 'observed' excitation function at frequencies near the Chandler frequency, it is concluded that earthquakes, via their static deformation field, have had a negligible influence on the Chandler wobble during 1977–1983. However, fault creep or any type of aseismic slip that occurs on a time-scale much less than the period of the Chandler wobble could have an important (and still unmodelled) effect on the Chandler wobble.     

Simulating a seismic series using geostatistical and stochastic methods: application to the seismic series in the Alborán Sea (1997 June 24–?)

Seismic series can be taken as examples of correlated unstationary sets of time-stochastic sequences. We investigate the possibility of estimating what is most probable to occur subsequently, if we know the events that have occurred up to a given moment.
The stochastic methods can be used with data of the seismic series, irrespective of their genesis and origin. Using three stochastic methods, namely (1) simulating the likelihood of occurrence by conditional geostatistical simulation; (2) developing a stochastic analysis of the energy release by means of energy packages; and (3) calculating the occurrence time of the most probable next earthquake, we were able to simulate the occurrence of earthquakes that took place during the Alborán Sea seismic series (1997–1998).
We conclude that it is possible to set limits on the time of occurrence and energy release, understood as the magnitude of the most probable earthquake, during the development of a seismic sequence and prior to the actual occurrence of the earthquake.     

The MARNET radiolinked seismometer network spanning the Marmara Sea and the seismicity of Western Turkey

Summary. The MARNET telemetered seismic network spanning the Marmara Sea supplements the ISK network of conventional seismic stations and increases the resolution for monitoring the seismicity in Western Turkey. Seismicity maps for the period 1976 to 1981 display pronounced swarm-type activity where small earthquakes cluster in the same locality. Three types of seismic activity can be identified and related to present-day tectonic deformation: normal earthquake episodes associated with the main line of the North Anatolian Fault; continuous swarm activity, but with marked fluctuations and bursts of activity in the tensional regime south of a line from Izmir to Adapazari; and continuous activity with only minor fluctuations within the Marmara region as it is sheared by the westward movement of the main Anatolian plate.     

Estimating Stable Measured Values and Detecting Anomalies in Groundwater Geochemistry Time Series Data Across the Athabasca Oil Sands Area,Canada

Regional groundwater monitoring in the Athabasca region of Alberta, Canada, provides information on groundwater quality and geochemical changes over time, including data useful for evaluating potential impacts of industrial activity such as oil sands mining and in situ operations. Data collected from over 5000 wells from the 1950s to 2014, including 161 wells from government’s monitoring network, were used to develop and apply bootstrap techniques for the detection of changes in groundwater geochemistry over time and at specific points in time. Increasing temporal anomalies were identified in Cl, TDS, B, and naphthenic acids in the McMurray formation across 2003 and 2008, while decreasing anomalies were found for SO₄. Temporal variance for 15 indicators was quantified for a smooth bootstrap approach to arrive at stable values representative of the most recent samples taken from wells in the study area. Stable values revealed sampling bias in the Devonian, Grand Rapids, Empress, Channel Beverly, and Muriel Lake formations suggesting expansion of sampling may be necessary. Although temporal anomalies were found in the McMurray formation, sampling bias was not identified. The entropy and relative magnitude of time series were evaluated to identify candidate wells for continued observations, which consist of wells with low measurements and low entropy that are near active industry lease boundaries. Temporal anomalies, stable values, and entropy were combined into type-well information to provide plots for visual inspection and interpretation. Stable values are useful for regional mapping, for detecting future changes and trends, and for identifying areas of interest warranting further investigation.

     

The Turkish Dilatancy Project (TDP3): multidisciplinary studies of a potential earthquake source region

Summary. The section of the North Anatolian Fault lying near the city of Izmit, at the east of the Marmara Sea, has been identified as a seismic gap and the possible site of a future major earthquake. Previously published studies of records from an earthquake swarm within the gap (TDP1 and TDP2) provided the first evidence that shear-wave splitting occurs in earthquake source regions, a conclusion since verified by many studies at other locations. A third field study (TDP3) was mounted in the Izmit region during the summer of 1984. Observations were made over an eight-month period and included geomagnetic and geoelectric measurements in addition to a series of observations utilising dense arrays of three-component seismometers. Earthquake activity in the principal study area was monitored over a period of eight months. Records showed features similar to those observed in the earlier studies. In particular: (1) almost all shear waves emerging within the shear-wave window displayed shear-wave splitting; and (2) the polarizations of the first arriving (faster) split shear-waves showed sub-parallel alignments, characteristic of propagation through a distribution of parallel vertical cracks striking perpendicular to the minimum compressional stress.
These and other observations support the conclusion of earlier studies – that the upper crust is pervaded by distributions of micro-cracks aligned by stress, known as extensive-dilatancy anisotropy. A search for time dependence in shear-wave phenomena has revealed temporal variations in the delays between the split shear-waves throughout the course of the TDP3 study, but as yet this has not been correlated with specific earthquake activity.     

Likelihood analysis of earthquake catalogues

We apply several classes of stochastic multidimensional models to statistical analysis of earthquake catalogues using likelihood methods. We investigate the importance of including different earthquake parameters in the model: epicentral coordinates, hypocentral depth, time limits for interearthquake interaction, and especially spatial distribution of earthquakes as well as spatial aftershock patterns. Results of this study combined with other investigations, suggest that most distributions controlling earthquake interaction have a fractal or scale-invariant form. Developed models are used for statistical analysis of several earthquake catalogues to evaluate parameters of earthquake occurrence. These parameters are shown to be similar for shallow earthquakes of different magnitude ranges and seismogenic regions, confirming self-similarity of the earthquake process. Whereas intermediate earthquakes seem to emulate the pattern of shallow earthquake occurrence, albeit at a much smaller aftershock rate, deep earthquakes differ significantly in their properties. Predictability of standard shallow earthquake catalogues has been analysed; we present evidence that for the best available catalogues the predictability is close to 10 bits per earthquake. Several synthetic earthquake catalogues have been created and processed through the likelihood inversion scheme. The results from likelihood analysis of these catalogues confirm our approach.     

Climate anomalies in the southern high latitudes associated with the Subtropical Dipole Mode

Climate anomalies in the southern high latitude associated with the Subtropical Dipole Mode (SDM) are investigated using a 23-year database consisting of SLP (sea level pressure), surface air temperature (SAT) and sea surface temperature (SST). The analysis depicts, for the first time, the spatial variability in the relationship of the above variables with the Subtropical Dipole Mode Index (SDI). It suggests that the SDM signal exists in the southern high latitudes and the correlation fields exhibit a wavenumber-3 pattern around the circumpolar Southern Ocean. Lead-lag correlation analysis used to the SLP, SAT, and SST anomalies with the SDI time series at the positive and negative correlation extremes shows that the southern-high-latitude climate responses to SDM almost instantaneously proposing the connection is by atmospheric and not by oceanic propagation.     

Relation between deformation and seismicity in the active fault zone of Kamchatka, Russia

In the regional geodetic network of the Russian Far East, an active fault zone of the Kamchatka peninsula has been selected in order to study the relation between seismic activity and deformation. This paper provides the first results of a detailed and high-precision 3-km long levelling profile, along which geodetic data have been collected weekly for almost three years. The data processing and analytical methods that were originally used have been elaborated for this particular type of very small local network. In the active fault zone, two distinct ways of releasing accumulated potential energy, i.e. seismicity and 'fault superintensive movements', have been registered. The inverse correlation that is discovered between deformation rate and seismic activity could be useful in earthquake forecasts.     

Observations and origin of Rayleigh-wave amplitude anomalies

This is a report of observations of amplitude anomalies of fundamental-mode Rayleigh waves ( R 1) between periods of 17 and 100  s. The anomalies are with respect to amplitudes predicted by Rayleigh-wave excitation for a reference earth model and catalogued centroid earthquake source parameters, such as are used in large-scale waveform inversions. The observations indicate that the amplitude anomalies are consistent for nearby recordings of the same event, while there is no obvious relation between the observed anomalies and the paths travelled by the waves. This is in contrast to Rayleigh-wave phase anomalies, which are consistent for similar propagation paths, and hence form the input in many inversions for along-path structure. The observations in this paper show that a similar inversion of intermediate-period amplitude anomalies for along- and near-path structure is not warranted without eliminating source effects, since the amplitude anomalies are dominated by scattering off near-source earth structure and by possible uncertainties in the source parameters. Sensitivity kernels that take the coupling between the moment tensor and displacement field into account demonstrate that Rayleigh-wave amplitude sensitivity is largest near the source. This report argues that the interaction between source-radiated Rayleigh waves and near-source earth structure may not be ignored in amplitude inversion procedures.