Ahulu Sylvanus T, Danuor Sylvester Kojo, Asiedu Daniel K
Geophysics Division, Ghana Geological Survey, Accra, Ghana.
2Department of Physics, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.
J Seismol. 2018;22(3):539-557. doi: 10.1007/s10950-017-9721-x. Epub 2017 Dec 15.
This paper presents a seismic hazard map for the southern part of Ghana prepared using the probabilistic approach, and seismic hazard assessment results for six cities. The seismic hazard map was prepared for 10% probability of exceedance for peak ground acceleration in 50 years. The input parameters used for the computations of hazard were obtained using data from a catalogue that was compiled and homogenised to moment magnitude (Mw). The catalogue covered a period of over a century (1615-2009). The hazard assessment is based on the Poisson model for earthquake occurrence, and hence, dependent events were identified and removed from the catalogue. The following attenuation relations were adopted and used in this study-Allen (for south and eastern Australia), Silva et al. (for Central and eastern North America), Campbell and Bozorgnia (for worldwide active-shallow-crust regions) and Chiou and Youngs (for worldwide active-shallow-crust regions). Logic-tree formalism was used to account for possible uncertainties associated with the attenuation relationships. OpenQuake software package was used for the hazard calculation. The highest level of seismic hazard is found in the Accra and Tema seismic zones, with estimated peak ground acceleration close to 0.2 g. The level of the seismic hazard in the southern part of Ghana diminishes with distance away from the Accra/Tema region to a value of 0.05 g at a distance of about 140 km.
本文展示了采用概率方法编制的加纳南部地震危险性地图以及六个城市的地震危险性评估结果。该地震危险性地图是针对50年内峰值地面加速度超越概率为10%编制的。用于危险性计算的输入参数是利用一个目录中的数据获得的，该目录已汇编并统一为矩震级（Mw）。该目录涵盖了一个多世纪（1615 - 2009年）的时间段。危险性评估基于地震发生的泊松模型，因此，识别出相关事件并从目录中剔除。本研究采用并使用了以下衰减关系——艾伦（适用于澳大利亚南部和东部）、席尔瓦等人（适用于北美中部和东部）、坎贝尔和博尔佐尼亚（适用于全球活动浅地壳区域）以及邱和扬斯（适用于全球活动浅地壳区域）。采用逻辑树形式来考虑与衰减关系相关的可能不确定性。使用OpenQuake软件包进行危险性计算。在阿克拉和特马地震带发现了最高水平的地震危险性，估计峰值地面加速度接近0.2g。加纳南部的地震危险性水平随着远离阿克拉/特马地区而降低，在距离约140公里处降至0.05g。
