震源深度与矩心深度的分布特征及其与震源机制类型之间的关系

在哈佛全球CMT目录中，震源深度与矩心深度的分布呈现出明显的规律性。从统计上说，浅源地震的震源深度大于矩心深度，而中深源地震不具有这样的特征。将地震按照震源机制进行分类之后发现，上述特征主要属于逆冲型地震和正断层型地震的贡献，而走滑型地震没有这样的特征，这一分布规律或可作为地震的“化学力学”模型的一个间接的支持。     

Erroneous interpretation of historical documents related to the epicenter of the 1927 Jericho earthquake in the Holy Land

The 1927 earthquake was the strongestseismic event (M = 6.2) of the 20th centuryin the Holy Land and the first significantone in the region to be recorded worldwideby seismometers. By quoting theseismological station in Ksara, the ISSlocated the epicenter 40 km north of theDead Sea. This location, which wassupported by secondary and tertiarymacroseismic `evidence' and became one ofthe most accepted `facts', was neverquestioned nor reevaluated.We show how an initial mistaken earthquakelocation, supported by questionableevidence, struck roots and eventually becamean accepted fact. This typical `chain oferrors' may serve as a warning regardingtreatment of historical macroseismicsources, as well as historical microseismicdocuments. The conclusions drawn from thisstudy, while focusing on historicaldocumentation, fit well the new epicenterof the 1927 earthquake, recalculated in ourformer study.     

华北中强地震前Morishita播散指数空间演化特征及其应用

研究了华北中强地震前3年Morishita播散指数的空间演化，发现Iδ异常几乎都是首先在远离震中的地方出现，并逐步向未来震中集中，这种规律可为地震的地点预报提供重要信息。     

On the role of subducting oceanic plateaus in the development of shallow flat subduction

Oceanic plateaus, aseismic ridges or seamount chains all have a thickened crust and their subduction has been proposed as a possible mechanism to explain the occurrence of flat subduction and related absence of arc magmatism below Peru, Central Chile and at the Nankai Trough (Japan). Their extra compositional buoyancy could prohibit the slab from sinking into the mantle. With a numerical thermochemical convection model, we simulated the subduction of an oceanic lithosphere that contains an oceanic crustal plateau of 18-km thickness. With a systematic variation, we examined the required physical parameters to obtain shallow flat subduction. Metastability of the basaltic crust in the eclogite stability field is of crucial importance for the slab to remain buoyant throughout the subduction process. In a 44-Ma-old subducting plate, basalt must be able to survive a temperature of 600–700 °C to keep the plate buoyant sufficiently long to cause a flat-slab segment. We found that the maximum yield stress in the slab must be limited to about 600 MPa to allow for the necessary bending to the horizontal. Young slabs show flat subduction for larger parameter ranges than old slabs, since they are less gravitationally unstable and show less resistance against bending. Hydrous weakening of the mantle wedge area and lowermost continent are required to allow for the necessary deformation of a change in subduction style from steep to flat. The maximum flat slab extent is about 300 km, which is sufficient to explain the observed shallow flat subduction near the Nankai Trough (Japan). However, additional mechanisms, such as active overthrusting by an overriding continental plate, need to be invoked to explain the flat-slab segments up to 500 km long below Peru and Central Chile.     

Seismic moment tensor for intermediate depth earthquakes at regional distances in Southern Spain

A method has been developed to obtain the seismic moment tensor components by linear inversion of P waves recorded at regional distance for intermediate depth earthquakes. The seismic moment tensor is separated into double couple (DC) and compensated linear vector dipole (CLVD) parts. The method has been applied to four earthquakes (64<h<95 km) which occurred in the Malaga region (southern Spain). Solutions for the 1987 event show a percentage of CLVD of 20% with a short source time function and DC part corresponding to vertical motion. For the 1989, 1990 and 1992 earthquakes, percentages of CLVD between 0% and 6% have been found. Comparison with the results obtained in a previous study [Buforn et al., J. Seismol. 1 (1997) 113] by modelling of P waves using a DC model, shows that the use of a more general representation of the source (seismic moment tensor) gives a fit of data for the 1987 event.     

贵州西部多流域水库区地壳三维速度结构

使用基于机器学习构建的贵州西部多流域水库区地震目录和震相报告,采用波速比一致性约束的双差层析成像方法联合反演得到了该地区的地震位置和三维v_p、v_s、v_p/v_s结构。结果显示,研究区内的地壳速度结构具有明显的不均匀性,不同大地构造变形分区展现出不同的速度结构特征。在10km以上深度,横穿黔西中部NW向的威宁构造变形区显示出显著的低速异常条带,揭示了威宁—水城深大断裂带的影响深度和范围。受库区岩性和流体渗透的影响,0km深度的速度结构显示普遍的低波速和高波速比特征,包括夹岩、平寨、光照和马马崖水库区域。重定位后,地震的空间分布勾勒出大量隐伏断层的几何展布特征,结合三维速度结构,推测该区域的地震活动与水库周围的断层活化有关。