Yesterday, following two earthquakes (the second a magnitude 7.5 quake) and a series of aftershocks off the west coast of Sulawesi Island, a tsunami struck Palu, at the end of a long, narrow bay. Both the Island and the adjacent Makasser Strait lie squarely on a southern extension of the Eurasian Plate, which encompasses all of Indonesia.
Destructive tsunami's are generally triggered by Subduction Earthquakes, where one tectonic plate dips beneath another; such a subduction zone stretches along the outer border of Indonesia, where the Australian and Philippine Plates are subducting beneath the Eurasian Plate. Yesterday's series of quakes and aftershocks are thought to have developed along a transverse fault, where two microplates (of the Eurasian Plate) are scraping past one another; such faults do not generally produce vertical lift of the overlying sea, the tectonic process that usually generates tsunamis.
Geologists suspect that some vertical movement of one of the microplates may have occurred and that the topography of the narrow bay likely amplified the wave that was produced. Regardless of the geologic explanation, the tsunami struck Palu and killed at least 384 residents and visitors.
Update: As of 10-3-18, more than 1400 bodies have been recovered and the death toll is expected to rise.
Destructive tsunami's are generally triggered by Subduction Earthquakes, where one tectonic plate dips beneath another; such a subduction zone stretches along the outer border of Indonesia, where the Australian and Philippine Plates are subducting beneath the Eurasian Plate. Yesterday's series of quakes and aftershocks are thought to have developed along a transverse fault, where two microplates (of the Eurasian Plate) are scraping past one another; such faults do not generally produce vertical lift of the overlying sea, the tectonic process that usually generates tsunamis.
Geologists suspect that some vertical movement of one of the microplates may have occurred and that the topography of the narrow bay likely amplified the wave that was produced. Regardless of the geologic explanation, the tsunami struck Palu and killed at least 384 residents and visitors.
Update: As of 10-3-18, more than 1400 bodies have been recovered and the death toll is expected to rise.
