MANILA - Metro Manila and other provinces transected by the West Valley Fault should prepare for a powerful quake as the fault is ripe for movement, the head of Philippine Institute of Volcanology and Seismology (Phivolcs) said.

Phivolcs Director Renato Solidum said the last major earthquake generated by the 100-km-long fault--which runs through different cities and towns of Bulacan, Rizal, Metro Manila, Cavite and Laguna--was in 1658 or 357 years ago.

He added, data from paleoseismology or the study of past earthquake events show that the fault moves every 400 to 600 years.

• READ: Will you be affected by the East, West Valley quake fault? See this atlas

"Therefore, the West Valley Fault can move within our generation. But to say exactly when this will move, there is no evidence to use, for us to to say exactly when," he said in an interview with ANC's "Dateline Philippines."

Nevertheless, Solidum urged citizens and government officials to prepare for it, noting that "preparedness cannot be done overnight."

He said, if a magnitude 6.5 to 6.7 earthquake occurs, such as what jolted Surigao del Norte last Friday, the number of casualties in Metro Manila alone could reach 21,000.

"That means that there are some buildings which need to be inspected and evaluated and retrofitted and that is a massive endeavor. If we do not start doing this, we cannot make the number of casualties much less that what can be expected," he said.