Investigating the Crustal Structure near the Mahakandarawa seismic station in Sri Lanka through the Receiver Function Method

Abstract

Sri Lanka has a very ancient geological history that begins in the Precambrian, when it formed part of the Gondwana supercontinent. It was connected to India, Madagascar, Antarctica, and Africa, sharing the same crustal evolution. When Gondwana began to break apart around 180 million years ago, Sri Lanka drifted with the Indian plate to reach its present position in the Indian Ocean. The present work analyzes the subsurface structure beneath the Mahakandarawa (MALK) broadband seismic station using teleseismic P-wave conversions. A combination of converted wave analysis and H-κ stacking was applied to determine both Moho depth and the velocity ratio of compressional to shear waves. The approach indicates a crustal thickness of nearly 37.8 km with a velocity ratio of 1.73, giving a Poisson’s ratio close to 0.25. Such values are typical of silica-rich, felsic material rather than mafic compositions. When compared with previous studies from neighboring Gondwanan fragments such as southern India and Madagascar, which report Moho depths of ~36–39 km and similar felsic crustal compositions, the results from MALK show strong consistency. This agreement reinforces Sri Lanka’s geological affinity with East Gondwana and provides new regional constraints on its tectonic evolution, particularly regarding the preservation of ancient felsic crust across separated continental blocks.
Keywords: Teleseismic Receiver Function, Gondwana, Sri Lanka, Crustal Structure, H-κ stacking