'Fault-finding' coral reefs can predict site of future earthquakes

Washington: In the wake of Japan disaster, the urgent question is
where the next big earthquake will hit.

Geologist Prof. Zvi Ben-Avraham and his doctoral student Gal Hartman
of Tel Aviv University have discovered that 'fault-finding' coral
reefs could be a reliable indicator to predict the site of future
earthquakes.

They are examining coral reefs and submarine canyons to detect
earthquake fault zones.

Ben-Avraham and his team are developing a new method to determine what
areas in a fault zone region are most at risk.

Using a marine vessel, they are surveying a unique geological
phenomenon of the Red Sea, near the coastal cities of Eilat and Aqaba
— but their research could be applied anywhere, including Japan and
the west coast of the U.S.

The research details a 'mass wasting' of large detached blocks and
collapsed walls of submarine canyons along the gulf region of the Red
Sea. They believe the geological changes were triggered by earthquake
activity.

"Studying fossil coral reefs and how they''ve split apart over time,
we''ve developed a new way to survey active faults offshore by looking
at the movement of sediment and fossil structures across them," said
Hartman.

"What we can''t say is exactly when the next major earthquake will
hit. But we can tell city engineers where the most likely epicenter
will be," he added.

While geologists have been tracking underwater faults for decades, the
new research uniquely tracks lateral movements across a fault line (a
'transform fault') and how they impact the sediment around them.

This is a significant predictive tool for studying the San Andreas
Fault in California as well, said Hartman.

The researchers analysed the structure of the seabed and discovered
active submarine canyons, mass wasting, landslides, and sediment
slumps related to tectonic processes and earthquake activity.

"There are several indicators of seismic activity. The most
significant is the location of the fault. Looking at and beneath the
seafloor, we saw that the faults deform the upper sediments. The
faults of the Red Sea are active. We managed to find some other faults
too and now know just how many active faults are in the region. This
should help make authorities aware of where the next big earthquake
will strike," said Hartman.

What made their study particularly unique is that they used the offset
along linear structures, of fossil coral fringing reefs to measure
what they call 'lateral slip across active faults'.

The study is recently published in the journal Geo-Marine Letters.