Investigating the Influential Factors of Ground Motions from Central Himalayan Seismicity

Abstract

Earthquakes (abbreviated as EQ in the paper) are catastrophic events resulting from the rupture of faults deep below the ground surface. Past earthquakes in the Himalayan region caused severe damage to various sites in terms of high ground acceleration, leading to subsidence and liquefaction. Due to a prolonged locking period despite continuous subduction of the Indian plate under the Eurasian plate, scientists dread future earthquakes in the Central Himalayas that would gravely affect Eastern India. Researchers communicated about repeated liquefaction events at Madhubani, a city in Bihar state of Eastern India, due to earthquakes in the Central Himalayas. This paper takes into account specific parameters like the moment magnitude (M_W) of the earthquake, focal depth (D), stress drop (∆σ), hypocentral distance (R) to Madhubani, and the average fault slip (d) at the source. These factors serve as input variables towards determining the individual and collective variance due to a seismic event triggered in the Himalayas. Computation of parametric influence from such a cluster of parameters tends to be a tedious and complex process. Hence, the current study employs Principal Component Analysis (PCA) to reduce the dimensionality of the data and estimate the contributions of various influencing factors to induce a peak acceleration value at Madhubani. The principal components obtained from the analysis enable understanding the extent of contribution by various input features on the dataset. Reducing the redundancy in the acquired dataset helped propose a relationship between stress drop (∆σ) and average fault slip (d). The developed relationship turns out to precisely accommodate stress drops for earthquakes with magnitudes 2-7.2 .