Scientists at the Annual Fall Meeting of American Geophysical Union stated that preliminary investigations of September’s devastating tsunami at Palu in Indonesia that happened within minutes of an earthquake was due to earth movement as a result of strike-slip fault in the region. Scientist Udrekh Al Hanif from Jakarta’s Indonesian Agency for Assessment and Application of Technology (BPPT) told the audience that the speed with which sea water rose and rushed nearly 400 meters inland made them realized that its source could be very close to the city as it arose within three minutes of 7.8 magnitude earthquake which killed more than 2000 people.
Detailed survey of the region showed that underwater sea floor around of Sulawesi city’s bay which was devastated by the tsunami had sunk low due to rupture in the earth’s crust which moved horizontally. Mr. Hanif’s team of researchers searched for answers in the depth map of narrow land inlet that leads to Palu and noticed that drop of seafloor combined with sudden and sharp movement of earth’s crust towards the north produced the tsunami in which waves of sea water rose several meters high and crashed unto the city. By collating the bathymetric data before and after the tsunami they found that the seafloor region inside the bay had subsided and has moved northwards.
This data helped them realized that the earthquake was combined effect of both vertical and horizontal displacement of earth’s surface which caused the displacement of water. They are still trying to gauge if there were more than one underwater landslide in the region as there is evidence of several underwater land movements. Geologists are also studying an upward thrust of seabed some distance away from Palu where the fault has split into diverging tracks as movement along two tracks compressed the crust between them. According to Finn Lovholt from Norwegian Geotechnical Institute the tectonic movements show that this unusual event can happen again.