Unlike the devastating Boxing Day earthquake and tsunami, which
appeared out of the blue, the latest Indonesian earthquake was loosely
predicted by scientists.

Just over a week after John McCloskey of the University of Ulster published his findings in the scientific journal Nature,
he hypothesised that “the stresses in the earth’s crust which have
resulted from the Sumatra-Andaman earthquake have significantly
increased the risk of another large earthquake in the
already-devastated Indonesian island of Sumatra” and that that quake
could generate another tsunami (see more from the University of Ulster here).

New Scientistsays
according to seismologists the reason no tsunami occurred is probably
because the size of the tremor – magnitude 8.7 – was several times
smaller than the Boxing Day quake which rated 9.0 on the logarithmic
Richter scale. The March quake was “also unlikely to have caused a
significant rupture to the sea floor,” another requirement for a major
tsunami.

Indeed the Pacific Tsunami Warning Center
says it is “the process of sea level returning to equilibrium through a
series of oscillations” after a disturbance or displacement which
produces the characteristic tsunami waves. But the PTWC also notes that
“not all major coastal or near-coastal earthquakes produce tsunamis”.

Nature.com
also says that although the earthquake released just “a quarter of the
energy of its predecessor,” it is still one of the eight most powerful
earthquakes measured since 1900. What’s more perplexing is that lesser
earthquakes in the same region (1861 and 1833) did trigger tsunamis.
Geophysicist Rob McCaffrey, who studies seismic activity at Rensselaer
Polytechnic Institute in Troy, New York, told Nature.com: “It’s very puzzling. It’s probably one of the biggest earthquakes in history.”

One possible explanation for the absence of a tsunami could be the depth at which the latest tremor occurred says Nature. This might have avoided shifts in the seabed that can displace water and prompt a tsunami.

McCaffrey, who was studying the region when the quake occurred, told New Scientist, “I wouldn’t be surprised if these earthquakes keep moving down towards the south east.”

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