Jakarta, Scientists are getting closer to
understanding the tsunami that struck Palu in Indonesia in September.
Damaging waves rushed ashore after a Magnitude 7.8 quake, but
researchers said at the time that they were surprised by their size.
Now, a survey in the bay in front of the Sulawesi city shows
significant subsidence of the seabed. This likely contributed to the
abrupt displacement of water that then crashed on to land.
More than 2,000 people lost their lives in the disaster.
Preliminary results of various investigations are being reported here at
the Fall Meeting of the American Geophysical Union – the largest
annual gathering of Earth and space scientists.
The quake occurred on what is called a strike-slip fault, where the
ground on one side of a rupture moves horizontally past the ground on
the other side. It is not a configuration normally associated with very
Nevertheless, this is what happened in the early evening of 28
September, around prayer time. Two main surges of water were
observed, the second being the biggest and pushing up to 400m
Udrekh al-Hanif from the Indonesian Agency for Assessment and
Application of Technology (BPPT) in Jakarta, told the meeting that the
generation source of the tsunami had to be very close to the city
because of the short interval between the onset of the quake and the
arrival of the high water – less than three minutes.
He and colleagues have sought answers in a depth
(bathymetric) map of the long, narrow inlet that leads to Palu at its
head. The team is still working through the results, but the data
indicates the seafloor in much of the bay dropped down in the quake.
This, combined with a sharp movement of the crust northwards, could
certainly have produced a tsunami. When we overlap the bathymetric
data from before and after, we can see that almost all of the area of the
seafloor inside the bay subsides,” the Indonesian scientist said, the
BBC news reported.
Source: Oman News Agency