Understanding subduction zone earthquakes: The 2004 Sumatra earthquake

Location map of Sumatra, Indonesia, depicting rupture areas for the AD 2004 as well as 2005 subduction zone earthquakes.



The 26 Dec 2004 Mw 9.2 Indian Ocean earthquake (also known every bit the Sumatra-Andaman or Aceh-Andaman earthquake), which generated massive, destructive tsunamis, peculiarly along the Aceh coast of northern Sumatra, Indonesia, clearly demonstrated the ask for a improve agreement of how oft subduction zone earthquakes as well as tsunamis occur.

Using subsidence stratigraphy, the squad traced the unlike modes of coastal sedimentation over the course of pedagogy of fourth dimension inwards the eastern Indian Ocean where relative sea-level alter evolved from chop-chop ascent to static from 8,000 years agone to the acquaint day.

Kelsey as well as colleagues discovered that 3,800 to 7,500 years ago, spell bounding main degree was gradually rising, in that place were 7 subduction zone earthquakes recorded inwards coastal deposits. This was determined inwards usage past times the fact that each earthquake caused burial of a mangrove soil past times sediment and/or deposition of seismic sea wave sand at the fourth dimension of the earthquake.
The squad likewise discovered that bounding main degree gradually stopped ascent almost 3,800 years ago, which meant that buried soils no longer formed. Thus, detecting subduction zone earthquakes required a unlike approach. They institute a tape of successive earthquakes inwards a sequence of stacked seismic sea wave deposits on the coastal plain. Individual seismic sea wave deposits were 0.2 to 0.5 one thousand thick. Based on this information, Kelsey as well as colleagues determined that inwards the past times 3,800 years in that place were betwixt 4 as well as half dozen tsunamis caused past times Andaman-Aceh-type earthquakes.
The authors conclude that knowing the relative sea-level tape for a coastal share on a subduction zone margin is the initial measuring inwards investigating paleoseismic history. For mid-latitude coasts that edge subduction zones, sequences of buried soils may furnish a long-duration, subsidence stratigraphic paleoseismic tape that spans to the present, merely inwards other settings such every bit the Aceh coastal plain, articulation question approaches, for event targeted foraminiferal analyses as well as palynology, are required to both exploit the changing shape of the relative sea-level crimp as well as characterize coastal development inwards the context of the diminishing importance of accommodation space.
The higher upwards postal service is reprinted from materials provided by Geological Society of AmericaNote: Materials may live on edited for content as well as length.


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