In 2004 a Magnitude 9.1 interplate subduction earthquake triggered a tsunami that killed over 230,000 people. Yet a nearby magnitude 8.7 intraplate earthquake in 2012, caused little damage and generated minimal ocean waves. Although the earthquakes appeared similar in magnitude and were close in proximity, they were caused by different tectonic processes related to the greater Indo Australian plate.
Data released in the Sept 2012 Nature journal yielded new information about the 2012 Sumatra earthquake. Surprising elements of this earthquake include, that it was both the largest intra-plate earthquake and the largest strike-slip earthquake ever recorded, plus the 10th largest earthquake of any kind ever recorded. Not to mention the most complex.
This animation describes the different tectonic settings of the two plates, and how the Indo-Australian plate seems destined to become two distinct tectonic plates: the Indian and the Australian plates.
CLOSED CAPTIONING: A .srt file is included with the downloiad. Use appropriate media player to utilize captioning.
Yue, Lay, Koper Nature article:
Animation by Jenda Johnson, Earth Sciences Animated
Oblique view of a highly generalized animation of a subduction zone where an oceanic plate is subducting beneath a continental plate. (See sketch below for parts.) This scenario can happen repeatedly on a 100-500 year cycle. The process which produces a mega-thrust earthquake would generate a tsunami, not depicted here.
Subduction-zone megathrust earthquakes, the most powerful earthquakes in the world, can produce tsunamis through a variety of structures that are missed by simple models including: fault boundary rupture, deformation of overlying plate, splay faults and landslides. From a hazards viewpoint, it is critical to remember that tsunamis are multiple waves that often arrive on shore for many hours after the initial wave.
Causes and casualties of the 14 most-significant earthquakes of that decade. This Flash rollover reveals facts about each of the earthquakes.