Out Of The Abyss

The recent surge in earthquakes and the explanation for the formation of the world's largest exposed fault have provided momentum to seismological research. SHREESHAN VENKATESH looks at the latest findings.

- Shreeshan Venkatesh

THE LAST two months of 2016 proved to be a busy period for seismologists. In November, scientists found out that the abyss under the Pacific Ocean between Indonesia and Papua New Guinea was left behind by a massive earthquake during the last Ice Age and is actually the world’s largest exposed fault. The Banda Detachment Fault is seven kilometres deep, 450 km long and if the bare ocean floor were seen from above, the fault would cover an area of 60,000 sq km. Scientists say that sometime between 10,000 to 30,000 years ago, as the Australian and Pacific tectonic plates grinded against each other, a piece of continental crust the size of Belgium was ripped apart, leaving a huge tear or fault in the surface.

We have known of the existence of the Banda abyss for many years now. But it was not until late last year that scientists were finally able to conclude what formed the Banda abyss, indicating how little we know of the ground beneath our feet.

Since mid-October, a surge in seismic activity, with around 15 temblors measuring more than 6.5 on the Richter scale, has also aroused interest. At least 400 earthquakes of magnitude 5 and above were recorded in December alone, marking an increase of three and a half times the monthly average (see ‘In continuous motion’, p42). The bulk of all quakes occurred along the plate boundaries, especially along the Pacific Ring of Fire. While the surge is within the normal range, it provides seismologists with more seismic observations to chew over and confirms that the Earth’s crust is active and moving.

“There are many things about the inner workings of the Earth and earthquakes themselves that we do not yet understand,” says Vineet Gahalaut, director of the National Centre for Seismology (see ‘A promising start’, p44). It is still an actively developing field with several unknown variables under research.