Unlike the devastating Boxing Day earthquake and tsunami, whichrnappeared out of the blue, the latest Indonesian earthquake was looselyrnpredicted by scientists.

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

New Scientistsaysrnaccording to seismologists the reason no tsunami occurred is probablyrnbecause the size of the tremor – magnitude 8.7 – was several timesrnsmaller than the Boxing Day quake which rated 9.0 on the logarithmicrnRichter scale. The March quake was “also unlikely to have caused arnsignificant rupture to the sea floor,” another requirement for a majorrntsunami.

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

Nature.comrnalso says that although the earthquake released just “a quarter of thernenergy of its predecessor,” it is still one of the eight most powerfulrnearthquakes measured since 1900. What’s more perplexing is that lesserrnearthquakes in the same region (1861 and 1833) did trigger tsunamis.rnGeophysicist Rob McCaffrey, who studies seismic activity at RensselaerrnPolytechnic 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.”