Cambodia

Cambodia lies on the stable interior of the Indochina Block, a relatively rigid crustal fragment that has been displaced southward from mainland Asia by the extrusion tectonics driven by the India-Asia collision. The Indochina Block is bounded by major fault systems — the Red River Fault to the north and the Mae Klong Fault to the west — but Cambodia's interior is far from these active boundaries. The Mekong River Valley, which bisects the country, follows an ancient structural trough but is not associated with active seismicity. Cambodian seismic hazard is among the lowest in Southeast Asia.

The historical and instrumental seismic record of Cambodia shows only minor events, most of them too small to be felt by the general population. Occasional magnitude 4–5 earthquakes have been recorded in northwestern Cambodia near the Thai border, where more complex fault systems associated with the Three Pagodas Fault Zone approach the country. The Tonle Sap lake basin, Cambodia's great seasonal lake, occupies a tectonic depression but is not underlain by currently active faulting. The 2004 Sumatra-Andaman earthquake (magnitude 9.1) and the resulting [[tsunami]] crossed the Gulf of Thailand and Andaman Sea toward Southeast Asia, but Cambodia's coastal exposure to the Gulf of Thailand provided some protection, and the direct impact was limited.

The deeper tectonic context places Cambodia within the broad accommodation zone where the rigid Sunda Shelf meets the more actively deforming regions of mainland Southeast Asia. GPS measurements show that Cambodia is moving roughly southward with the Sunda Block relative to the Eurasian reference frame, at very low velocities. The country's position well away from any active plate boundary means that the generation of large earthquakes beneath Cambodian territory is unlikely. The primary seismic concern for Cambodia would be [[seismic-wave]]s generated by earthquakes on the Sagaing Fault in Myanmar or the Sumatra Fault, both of which can produce strong ground motion across a wide region, though the attenuation with distance means intensity in Cambodia would be modest.