Seismic Hazard in terms of Peak Ground Acceleration (PGA) for coast of Calicut, State of Kerala (INDIA)

Seismic hazard assessment involves quantitatively estimating ground shaking at site. There are two main approaches for estimating seismic hazard, Deterministic seismic hazard assessment (DSHA) and Probabilistic seismic hazard assessment (PSHA). In the present investigation DSHA is used, it relies on the worst-case scenario earthquake. The state of Kerala (9°N - 13°N and 75°E - 78°E) which lies in the seismic zone III, having a zone factor 0.16, has been considered to estimate seismic hazard in terms of PGA. Based on analyses of seismotectonics of the area, 26 seismogenic sources were identified and used for the PGA estimation. The peak horizontal accelerations (A_h) 0.2344g and peak vertical accelerations (A_v) 0.1395g were computed for the city of Calicut. For other cities, Thiruvananthapuram, Kollam, Palakkad, Kochi, and Thrissur horizontal (A_h) and vertical accelerations (A_v) were also estimated. However, the highest value was found to be at Calicut followed by Palakkad. In case of Palakkad, the values were influenced by cluster of faults located there while, at Calicut was caused by the Fault – 1 (source) which is in the Arabian Sea near the coast of the city. It has been observed that the seismic hazard assessment of Kerala advocate the PGA (A_h) falls in the range of 0.02g to 0.47g and PGA (A_v) varies from 0.01g to 0.33g. These accelerations seem to be more realistic since they are based on consideration of many seismotectonic sources in the region that may rupture causing earthquakes. The ratio of Av/Ah was found to be in the range of 0.70 to 0.38. The prepared contour maps for the region show that larger peak ground accelerations are present in the region where there is a higher density of larger faults and vice versa. The findings highlight the need for further studies and enhanced preparedness measures in Kerala, aiming to mitigate potential seismic risks and ensure the safety of its residents in this seismically active region.