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Stiff Sediments Made 2004 Sumatra Earthquake Deadliest in History

By Guest PostJune 24, 2011Environmentaccretionary prism, aftershocks, coast of sumatra, column of seawater, deadliest tsunami in recorded history, density zone, earthquake, ganges, geologic fault, geological formation, geoscientists, indian ocean, indo australian plate, indonesia, marginal plateaus, nicobar fan, seabed topography, seafloor, sean gulick, sediments, seismic instruments, sound waves, subduction zone, subsurface structures, sumatra, sunda plate, sunda trench, the agency for the assessment and application of technology, the indonesia institute for sciences, the university of southampton, the university of texas at austin, tsunami waves, undersea earthquake, united kingdom

AUSTIN, Texas — An international team of geoscientists has discovered an unusual geological formation that helps explain how an undersea earthquake off the coast of Sumatra in December 2004 spawned the deadliest tsunami in recorded history.

Instead of the usual weak, loose sediments typically found above the type of geologic fault that caused the earthquake, the team found a thick plateau of hard, compacted sediments. Once the fault snapped, the rupture was able to spread from tens of kilometers below the seafloor to just a few kilometers below the seafloor, much farther than weak sediments would have permitted. The extra distance allowed it to move a larger column of seawater above it, unleashing much larger tsunami waves. (more…)

Mysteries of Unpredictable Tsunami Waves

One of the most terrible consequences of offshore quakes is giant tsunami waves, sweeping everything on their way. Until now, scientists cannot answer a simple question: why in some cases they happen, and in others they do not? If it was established, then a tragedy like the one that has recently occurred in Indonesia could have been avoided.

An earthquake measuring 7.5 points, which occurred late on Monday, October 25 in Indonesia, caused a tsunami, which affected Mentawai islands in the western part of the country. Interestingly, the epicenter of the aftershocks of this earthquake was located 78 km west of the South Island Pagai of the Mentawai archipelago, at a depth of 20 km below the bottom of the Pacific Ocean. Apparently, this is why the first few minutes after the earthquake the Indonesian government reported the tsunami threat, but later canceled the alert. (more…)

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Stiff Sediments Made 2004 Sumatra Earthquake Deadliest in History

Mysteries of Unpredictable Tsunami Waves