The lessons from the Simushir earthquakes of November 15, 2006 (M w 8.3) and January 13, 2007 (M w 8.1)

According to S.A. Fedotov’s long-term earthquake forecast, the Middle Kuril Is. has long (since 1965) been a likely location for the next M ≥ 7.7 earthquake, i.e., a seismic gap. The present study integrates seismological, geological, and geophysical data to assess the earthquake potential of the gap prior to November 15, 2006. Seismological data were used to carry out a comparative analysis of 3D seismic energy density for three zones of the Kuril region. The density for the Middle Kuril Is. turned out to be twice as small as that for the North Kuril Is. and nearly six times as small as that for the South Kurils. Various parameters of the seismic process for the Kuril region have been estimated in quantitative terms. It is shown that the rate of completely reported (M ≥ 6) earthquakes occurring down to 70 km depth in the Middle Kuril Is. is approximately three times as small as that for the entire Kuril arc. Increased heat flow was recorded there (up to 100 mW/m²). The top of the high conductivity layer is shallower (at a depth of 100 km). The trends of major faults and other seismotectonic features have been taken into account. Based on these data (prior to November 15, 2006), the previous conclusion about the low seismic activity of the Middle Kuril Is. was corroborated. Two great earthquakes occurred in the region on November 15, 2006 (M _w = 8.3) and January 13, 2007 (M _w = 8.1) with subsequent tsunami waves. The erroneous inference as to low seismic activity was related to the fact that the seismic cycle in the Middle Kuril Is. may be as long as 150–200 years. We come to the conclusion that an analysis of the level of seismic activity for the region should start with the construction of standardized recurrence curves and determining the magnitude of the maximum possible earthquake.     

中国大陆井水温对汶川8.0级、玉树7.1级、芦山7.0级和岷县6.6级地震响应特征的对比研究

收集和统计了2008年汶川MS8.0地震、2010年玉树MS7.1地震和2013年芦山MS7.0、岷县MS6.6地震引起的中国大陆井水温同震响应现象,分析了其特征。结果显示:这4次地震对中国大陆地下流体影响显著,井水温同震响应特征有很大差异,后三次水温同震响应范围、幅度和持续时间远不及汶川地震,即使震级相差不大的玉树和芦山地震,同震响应的特征也不尽相同。最后探讨了这种现象的成因机理。     

Moment Magnitude (M W) and Local Magnitude (M L) Relationship for Earthquakes in Northeast India

An attempt has been made to examine an empirical relationship between moment magnitude (M _W) and local magnitude (M _L) for the earthquakes in the northeast Indian region. Some 364 earthquakes that were recorded during 1950–2009 are used in this study. Focal mechanism solutions of these earthquakes include 189 Harvard-CMT solutions (M _W?≥?4.0) for the period 1976–2009, 61 published solutions and 114 solutions obtained for the local earthquakes (2.0?≤?M _L?≤?5.0) recorded by a 27-station permanent broadband network during 2001–2009 in the region. The M _W–M _L relationships in seven selected zones of the region are determined by linear regression analysis. A significant variation in the M _W–M _L relationship and its zone specific dependence are reported here. It is found that M _W is equivalent to M _L with an average uncertainty of about 0.13 magnitude units. A single relationship is, however, not adequate to scale the entire northeast Indian region because of heterogeneous geologic and geotectonic environments where earthquakes occur due to collisions, subduction and complex intra-plate tectonics.     

1812年3月8日新疆尼勒克8级大震

1812年3月8日新疆尼勒克县发生的8级大震造成了极强烈的地表形变,产生了长达65公里的地震断裂带,其垂直位移可达10米,右旋水平位移在1.5米以上。极震区有多处构造塌陷、滑坡和崩塌,巨型塌陷的面积达2平方公里,滑坡体后缘最宽可达2公里,震中烈度110度强。本文根据现场考察及对航片的研究,结合历史记载勾绘了这次地震的烈度等震线,对地震的震级、震中位置、震源深度、地震矩、应力降和震源机制解等进行了计算和讨论,并对发震的地质构造背景进行了初步的探讨。     

The Egion June 15, 1995 (6.2M L ) earthquake,western Greece

On June 15, 1995 at 00:15 GMT a devastating earthquake (6.2M _L ) occurred in the western end of the Gulf of Corinth. This was followed 15 min later by the largest aftershock (5.4M _L ). The main event was located by the University of Patras Seismological Network (PATNET) at the northern side of the Gulf of Corinth graben. The second event (5.4M _L ) was located also by PATNET near the city of Egion, on a fault parallel to the Eliki major fault that defines the south bound of the Gulf of Corinth graben. A seismogenic volume that spans the villages of Akrata (SE) and Rodini (NW) and extends to Eratini (NE) was defined by the aftershock sequence, which includes 858 aftershocks of magnitude greater than 2M _L that occurred the first seventeen days. The distribution of hypocentres in cross section does not immediately suggest a planar distribution but rather defines a volume about 15 km (depth) by 35 km (NW-SE) and by 20 km (NE-SW).     

Témoignages de la contamination dans les produits des éruptions explosives des M. Silvestri (1892) et M. Rossi (1669) (M. Etna)

Resume Les différentes étapes de la cristallisation des pyroclastes des Monti Rossi et Silvestri ont été reconstituées par l'étude des inclusions vitreuses intraminérales.L'olivine magnésienne (Fo 82) et le diopside cristallisent à partir d'un liquide basaltique de nature alcaline au cours de l'ascension, sous une forte pression de fluides liée à la quantité importante de gaz dissous (4 à 5% dont 2800–3500 ppm de S).L'« ouverture » du système s'accompagne de la démixtion d'environ 50% de la phase volatile dissoute.Les oxydes Fe-Ti, les olivines (Fo 74-75) et les salites cristallisent alors, à partir d'un liquide partiellement dégazé (2 à 2,5% d'éléments volatils, dont 1200 ppm de S), de composition hawaïtique, dans un domaine de température compris entre 1160 et 1140°C.Le plagioclase (An 82) se sépare tardivement dans un liquide dont la composition se rapproche de celle du liquide résiduel. Ce stade d'évolution qui s'accompagne d'une accumulation de gaz démixé, témoigne de conditions pré-éruptives de subsurface.Les teneurs anormalement élevées en fluides des basaltes alcalins etnéens comparées à celles de basaltes de même composition (par exemple dans les inclusions des Fo 82 du Piton de la Fournaise, des volatils 2%, S=1200 ppm et Cl=200 à 400 ppm) nous ont conduit à envisager la contribution de l'encaissant sédimentaire.La présence dans les produits des Silvestri de nombreuses enclaves carbonatées (fassaïte, wollastonite, anorthite), argilo-schisteuses (plagioclase, hercynite, sulfures) et gréseuses (quartz, verres rhyolitiques), l'abondance des inclusions fluides (CO₂, SO₂) dans les minéraux néoformés, les témoignages de phénomènes locaux d'assimilation (verres riches en Ca, Si...) viennent renforcer l'idée du rôle de la contamination (au moins en ce qui concerne les fluides) par l'encaissant sédimentaire, négligée jusqu'ici dans le cas des laves de l'Etna.

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The melt inclusions trapped inside crystals have allowed the determination of the different crystallization steps, for the M. Rossi and M. Silvestri pyroclastic products.Magnesian olivine (Fo 82) and diopside crystallize from an alkali basaltic liquid, during ascent. The high concentration (4–5% with S=2800–3500 ppm) of volatiles in glass inclusions involves a strong fluid pressure.The release of about 50% of dissolved gases reflects the « opening » of the magmatic system. Therefore, olivine (Fo 74-70), salite and Fe-Ti oxydes, crystallize from an hawaiitic melt, with lower volatile content (2 to 2,5% with S=1200 ppm). The temperatures range from 1160°C to 1140°C.Plagioclase phenocrysts (An 82) grow later from a more evolved liquid. Equivalences of gas accumulation infer a pre-eruption crystallization.The unusual content of volatiles in the alkali basalts compared to equivalent oceanic basalts (2% with S=1200 ppm and Cl= 200 to 400 ppm in olivine melt inclusions from Piton de la Fournaise volcano) suggests a wall rock contribution.Numerous xenoliths of carbonates (with fassaite, wollastonite, anorthite assemblages), shale (with plagioclase, hercynite and sulfide) or sandstone (with quartz and rhyolitic glasses) have been found among the M. Silvestri products.Fluid inclusions in the minerals as well as local SiO₂, CaO, FeO enrichments of the magmatic liquid infer partial assimilation of sedimentary rocks.All these observations support a contamination hypothesis, at least for the volatile phase.

     

1975年2月4日海城地震(M=7.3)的前震系列/

我们研究了1975年2月4日海城地震(M=7.3)前震的定位及其辐射图象.用六个区域台的到时,相对于一次参考地震,将前震及主震进行了定位.这组前震开始相互很接近,然后随时间及其分布有一定的延伸.最大前震前,前震均位于直径约两公里的小体积内,而在最大前震后,其活动则向北西和南东方向扩展,形成六公里长的在北西方向上伸展的分布带.初动及 P 波 S 波振幅比表明,在前震系列中有两种不同的断裂机制.我们推测这两种辐射图象可能和前震处于分布带的不同部位有关.可能主震震源不处于前震震源所决定的断层上,而是位于这组前震南面6公里、且较这组前震浅几公里处.我们认为,在垂直于主震破裂面及前震分布带走向的方向上,前震和主震相距这么大的距离,可能是由于主震时产生滑动的断层是以雁行排列的.分析了在前震期间断层上滑动所引起的应力变化,认为由前震引起的主震断层上剪应力的增加是很小的.因之由前震直接触发主震的可能性不大.      

1993年2月和静5.4级地震震害评估与地震构造

１９９３年２月３日零时５分，和静县哈尔莫敦乡发生５．４级中强地震，震源深度２９ｋｍ，震中烈度达Ⅵ度。地震造成个别房屋倒塌，部分房屋出现不同程度的破坏，地表有十几公里的构造地裂缝，地震造成房屋倒塌和破坏的直接经济损失７２．７万元。     

2010年智利大地震及历史地震活动与地质构造背景

2010年2月27日(当地时间)智利发生了8.8级地震,造成了严重的破坏和损失。该地震是典型的逆冲型地震,处于环太平洋地震带,是Nazca板块以每年8cm的汇聚速率俯冲于南美洲板块之下,使得该板块下部的应力积累到一定程度引发破裂的结果。历史地震分析表明,目前该地区可能开始一个新的大震活跃期,未来3～4年内可能还会发生一次8级以上的地震。     

Hybrid stochastic finite fault modeling of 2003, M6.5, Bam earthquake (Iran)

Accelerographic time series of the M ^∗6.5 Bam (Iran) earthquake of December 26, 2003, are used to calibrate the source and propagation path characteristics based on a hybrid stochastic approach, which includes stochastic finite fault and analytical modeling. Estimation of source characteristics is based on the calibration of finite-fault modeling to near-source observed time series, while propagation characteristics are estimated using far-field recorded ones. The distance-dependent Kappa factor is obtained from the slope of smoothed amplitude of acceleration Fourier spectrum at higher frequencies. The estimated zero-distance Kappa value is 0.06. Calibration based on near-source time series indicates a stress drop of 130 bars for the Bam earthquake. The strong impulsive long-period motion, recorded at the only near-source station, is modeled using analytical modeling of Mavroeidis and Papageorgiou (2003).     

永登5.8级地震和天祝—古浪5.4级地震前S波分裂特征

应用ＣＤＳＮ台网兰州数字台的记录和中法合作建立的朗索数字台的记录,研究了１９９５年７月２２日甘肃永登５．８级地震和１９９６年６月１日天祝－古浪５．４级地震前台剪切波分裂的特征。结果表明,在永登地震前大约１年的时间延迟和偏振方向很快恢复。因此,可以认为,此次地震前ＮＷ向,地震后剪切波分裂时间延迟和偏振方向很快恢复。因此,可以认为,此次地震前Ｓ波分裂方向的前兆特征是明显的。对于天祝－古浪５．４级地震,     

Harmonization check of M w within the central, northern, and northwestern European earthquake catalogue (CENEC)

Large data sets covering large areas and time spans and composed of many different independent sources raise the question of the obtained degree of harmonization. The present study is an analysis of the harmonization with respect to the moment magnitude M _w within the earthquake catalogue for central, northern, and northwestern Europe (CENEC). The CENEC earthquake catalogue (Grünthal et al., J Seismol, 2009) contains parameters for over 8,000 events in the time period 1000–2004 with magnitude M _w ≥ 3.5. Only about 2% of the data used for CENEC have original M _w magnitudes derived directly from digital data. Some of the local catalogues and data files providing data give M _w, but calculated by the respective agency from other magnitude measures or intensity. About 60% of the local data give strength measures other than M _w, and these have to be transformed by us using available formulae or new regressions based on original M _w data. Although all events are thus unified to M _w magnitude, inhomogeneity in the M _w obtained from over 40 local catalogues and data files and 50 special studies is inevitable. Two different approaches have been followed to investigate the compatibility of the different M _w sets throughout CENEC. The first harmonization check is performed using M _w from moment tensor solutions from SMTS and Pondrelli et al. (Phys Earth Planet Inter 130:71–101, 2002; Phys Earth Planet Inter 164:90–112, 2007). The method to derive the SMTS is described, e.g., by Braunmiller et al. (Tectonophysics 356:5–22, 2002) and Bernardi et al. (Geophys J Int 157:703–716, 2004), and the data are available in greater extent since 1997. One check is made against the M _w given in national catalogues and another against the M _w derived by applying different empirical relations developed for CENEC. The second harmonization check concerns the vast majority of data in CENEC related to earthquakes prior to 1997 or where no moment tensor based M _w exists. In this case, an empirical relation for the M _w dependence on epicentral intensity (I ₀) and focal depth (h) was derived for 41 master events, i.e., earthquakes, located all over central Europe, with high-quality data. To include also the data lacking h, the corresponding depth-independent relation for these 41 events was also derived. These equations are compared with the different sets of data from which CENEC has been composed, and the goodness of fit is demonstrated for each set. The vast majority of the events are very well or reasonably consistent with the respective relation so that the data can be said to be harmonized with respect to M _w, but there are exceptions, which are discussed in detail.     

Earthquake probabilities and magnitude distribution (M ≥ 6.7) along the Haiyuan fault, northwestern China

Introduction Haiyuan fault is a major seismogenic fault in north-central China. One of the most devastat-ing great earthquake in the 20th century occurred near Haiyuan in northwestern China on Decem-ber 16, 1920. More than 220 000 people were killed and thousands of towns and villages weredestroyed during the devastating earthquake. A 230 km long left-lateral surface rupture zone wasformed along the Haiyuan fault during the earthquake with maximum left-lateral displacement of10 m. Pale…     

1991年7月云南施甸5.0,5.2级地震的预报与对策

1991年7月1日、22日在云南省施甸太平乡先后发生了5.0、5.2级两次中强地震。保山行署地震局曾在震前作出了正确的中、短期预报和震后作了无震预报。本文客观地提供了这次地震前后预报的科学依据、中短期自适应加权定量综合判定模式实际计算结果及一系列对策的实况;同时讨论了孕震区内短临阶段前兆变化的异常特征。     

23 October 2011 Van, Eastern Anatolia, earthquake (M W 7.1) and seismotectonics of Lake Van area

The 23 October 2011 Van earthquake took place in the NE part of Lake Van area, surprisingly on a fault (the Van fault) that is not present in the current active fault map of Turkey. However, occurrence of such a large magnitude earthquake in the area is not surprising regarding the historical seismicity of the region. The comparison of the damage patterns suggests that the earthquake is much likely a recurrence of the 1715 Van earthquake. The finite fault modelling of the earthquake using teleseismic broadband body waveforms has shown that the earthquake rupture was unilateral toward SW, was mostly reverse faulting, confined to below the depth of 5 km, did not propagate offshore, and was dominated by a failure of a single asperity with a peak slip of about 5.5 m. The total seismic moment calculated for the model is 4.6?×?10¹⁹ Nm (M _W ?≈?7.1). The finite fault model coincides with the field observations indicating blind faulting and the vertical displacements over the free surface estimated from it correlate well with the maximum reported uplift along the coast of Lake Van above the hanging wall. The possible offshore continuations of the Van fault and some other faults lying its south are also discussed by assessing a previous offshore seismic reflection study and the earthquake epicentres and focal mechanisms.     

1842年6月11日新疆巴里坤7.5级地震

1842年6月11日新疆巴里坤县发生了一次7.5级大震,造成了明显的地表形变,产生了长达23公里的地震断裂带,其垂直位移可达2米,震中烈度十度。本文根据现场考察,结合历史记载勾绘了这次地震的烈度等震线,对地震的震级、震中位置、震源深度、地震矩、应力降进行了计算和讨论,并对地震的构造背景进行了初步探讨。