Bolivia

Bolivia has a seismic profile dominated by intermediate-to-deep earthquakes generated within the subducting Nazca Plate rather than by shallow crustal faulting or direct [[subduction-zone]] interface events. The country has no Pacific coastline and sits inland from the main Peru-Chile Trench, where the Nazca Plate is already at substantial depth beneath the South American continent. The subducting slab reaches depths of 100 to 600 kilometres beneath Bolivia, generating earthquakes within the cold, brittle slab material as it is stressed by gravitational sinking, dehydration reactions, and phase transitions. These deep intraslab earthquakes can be very large — Bolivia hosted the second largest deep-focus earthquake ever recorded — and while their depth means surface shaking is distributed across large areas rather than concentrated locally, they can still cause significant damage. Onshore crustal seismicity is generated by thrust faults in the Subandean Zone (the fold-and-thrust belt on the eastern flank of the Andes) and by extensional faults on the Altiplano plateau. The Altiplano, at an average elevation of 3,800 metres, is the world's highest plateau outside Tibet and is structurally bounded by active fault systems that generate moderate earthquakes periodically. The city of La Paz, built in a canyon below the Altiplano rim, has complex urban seismic exposure from both regional deep events and local Altiplano faults.

The most remarkable seismic event in Bolivia's history — and in global deep-earthquake records — was the 9 June 1994 Bolivia deep-focus earthquake (magnitude 8.2 at a depth of 647 kilometres), the largest deep-focus earthquake ever recorded and one of the few to exceed magnitude 8 at such extreme depths. The earthquake was felt across all of South America and was even felt in Canada, becoming one of the most widely felt earthquakes in recorded history due to the efficiency with which [[seismic-wave]]s from deep events travel through the rigid mantle and are transmitted globally. Despite its enormous energy release, the earthquake caused only minimal damage at the surface because the 647-kilometre depth meant enormous attenuation of ground motion. The city of Sucre and mining communities in Potosí have experienced moderate damage from shallower Subandean thrust events. The 1998 Aiquile earthquake (magnitude 6.6) killed 105 people and caused widespread damage in rural communities of Cochabamba department built primarily of unreinforced adobe. Regional events from the Arica region of the Andes occasionally cause felt shaking in western Bolivia.

Bolivia's tectonic position places it at the transition between the outer (shallow) and inner (deep) Andean seismogenic zone. The Subandean fold-and-thrust belt represents the eastern front of the Andean orogen, where thick sequences of Paleozoic and Mesozoic sedimentary rocks have been detached from the basement and pushed eastward over the South American craton in a series of thrust sheets. This ongoing shortening generates the shallow crustal seismicity of eastern Bolivia and represents the same deformation front that continues northward into Peru and southward into Argentina. The Altiplano is internally drained and structurally complex, with ancient lake sediments and volcanic deposits creating locally amplifying conditions for [[seismic-wave]]s. The deep [[subduction-zone]] seismicity within the Nazca slab is the product of metastable olivine and serpentinite transformation reactions at depth, creating stress concentrations within the slab that occasionally release in great intraslab ruptures. Bolivia's FUNVISIS and regional network partnerships provide basic seismological monitoring, though coverage in remote Altiplano and Subandean areas remains sparse.