Bansal Brijesh K, Singh S K, Suresh G, Mittal H
National Centre for Seismology, Ministry of Earth Sciences, New Delhi, India.
Indian Institute of Technology Delhi, New Delhi, India.
Nat Hazards (Dordr). 2022;111(2):1885-1905. doi: 10.1007/s11069-021-05121-w. Epub 2021 Nov 30.
We study source parameters of 10 local earthquakes (2.7 ≤ ≤ 4.5) that have occurred in the National Capital Region (NCR) since 2001 and the ground motions produced by these events. Moment rate spectra of the earthquakes retrieved from the recordings at hard sites after applying corrections for geometrical spreading (1/, ≤ 100 km), anelastic attenuation ( = 253 ) and cutoff frequency ( = 35 Hz) are reasonably well fit by the Brune -source model with stress drop ranging between 0.9 and 13 MPa. Neglecting the outlier low-stress drop value, the average stress drop is 6 MPa. We apply a modified standard spectral ratio technique to estimate site effect at 38 soft sites in the NCR as well as the geometrical mean site effect with respect to a reference hard site. Application of the stochastic method, with source characterized by the Brune - model with stress drop of 6 MPa and the mean site effect for soft sites, yields peak horizontal ground acceleration and velocity curves that are in good agreement with the observed values. These results provide the parameters needed for the application of the stochastic method to predict ground motions at hard and soft sites in the NCR during postulated ≤ 5.5 earthquakes.
我们研究了自2001年以来在国家首都地区（NCR）发生的10次局部地震（2.7≤震级≤4.5）的震源参数以及这些地震产生的地面运动。在对几何扩散（1/r，r≤100 km）、非弹性衰减（Q = 253）和截止频率（fc = 35 Hz）进行校正后，从硬场地记录中获取的地震矩速率谱能较好地用布伦点源模型拟合，应力降范围在0.9至13兆帕之间。忽略异常低应力降值后，平均应力降为6兆帕。我们应用一种改进的标准谱比技术来估计NCR地区38个软场地的场地效应以及相对于参考硬场地的几何平均场地效应。采用以应力降为6兆帕的布伦点源模型表征震源并结合软场地平均场地效应的随机方法，得到的水平地面峰值加速度和速度曲线与观测值吻合良好。这些结果为在假定震级≤5.5的地震期间应用随机方法预测NCR地区硬场地和软场地的地面运动提供了所需参数。
