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20 0 0年 5月发起的GEOALGAR项目旨在致力于阿尔加维地区的地球动力学监测和地震区划。本文简单介绍一下该项目的目标和有关 1 999— 2 0 0 0年地震记录分析的初步结果。经过地震记录和速度模型参数的同步反演 ,对两个选定区域的震源位置进行了重新定位。区域 1使用了 2 5个 1 999— 2 0 0 0年间发生的ML≥ 2 0的地震 ,区域 2使用了 1 2 5个。结果表明 ,主要有两个地区的地震较多 :一个是蒙希克地区 (在内陆 ) ,另一个是瓜达尔基维尔浅滩 (范围从 36 4°N ,8°W～ 36 8°N ,7 2°W )。区域 1 ,震源校正的幅度相对较小 ,震源比原先定位的深度稍微深一些 ;而对于区域范围内其他更多的地震 ,震源校正的幅度较大 ,震源的位置变得更浅。对于近期发生的地震也做了断层面解的估计 ,结果表明 ,最优解受到走滑运动的控制 ,这与NW SE至NNW SSE方向的水平挤压控制的应力一致 ,有两个地震例外 ,它们呈现的是逆冲机制 ,最大水平挤压应力方向稍微转向N S。这与其他作者先前研究的结果也是一致的。重新定位后的震中位置在空间分布上显得更加有条理 ,表明它与一些已知的构造特征可能相关。然而 ,断层面解的结果与新构造特征很难相关起来。
The GEOALGAR project, launched in May 20 0, aims to focus on geodynamic monitoring and seismic zoning in the Algarve region. This article gives a brief introduction of the project’s objectives and the preliminary results of the seismogram analysis from 1999 to 2000. After the simultaneous inversion of seismogram and velocity model parameters, the source positions of the two selected regions were relocated. In Region 1, 25 earthquakes with ML ≥ 20 occurred in 1999-2002 were used, and in Region 2, 125 were used. The results show that there are more earthquakes in two major areas: one in the Monchique region (inland) and one in the Guadalquivir Shoal (range 36 ° N, 8 ° W-368 ° N, 7 2 ° W). For Region 1, the magnitude of the source correction is relatively small, with the source slightly deeper than the original one; and for more of the other earthquakes in the region, the magnitude of the source correction is larger and the location of the source becomes shallower. The estimates of fault solutions for the recent earthquakes have also been done and the results show that the optimal solution is controlled by the strike-slip motion consistent with the horizontal crustal stress control from NW SE to NNW SSE with the exception of two earthquakes A thrust mechanism is presented, with the maximum level of compressive stress being slightly shifted to NS. This is consistent with the results of previous studies by other authors. The location of the epicenter after repositioning appears to be more organized in spatial distribution, indicating that it may be related to some of the known tectonic features. However, the results of fault tomography are difficult to correlate with the new tectonic features.