Summary

Historical Seismicity

Impacts

Tsunami Model

Actual Observation

Aftershocks

PHIVOLCS Response

References

 

Summary of the event:
Ma. Leonila P. Bautista and et al.

The earthquake occurred on March 6, 2002 at 05:15 am (local time).  Its epicenter as located by PHIVOLCS is at 6.1 N; 124.0 E; 81 km or about 81 km SW of Isulan, Sultan Kudarat.  PHIVOLCS computed its depth of focus at 15 km.  Its surface magnitude was computed by the Pacific Tsunami Warning Center as 6.8 while its moment magnitude (Mw) and body wave magnitude (mB) were computed by the the U.S. Geological Survey (USGS) as 7.2 and 6.3, respectively.  Based on the earthquake location and mechanism solutions, its source is attributed by PHIVOLCS to subduction along the Cotabato Trench. 


Fig 1. Shows the PHIVOLCS earthquake bulletin for this event.

As of March 9, 2002, the Office of Civil Defense (OCD) records show that 8 people had died and 41 were injured due to the earthquake.  It affected 7,684 families in the provinces of Sultan Kudarat, Sarangani, North Cotabato and South Cotabato including four cities and 17 municipalities (OCD Memorandum dated March 9, 2002).  The quake damaged 4 road networks, 7 bridges, 36 school buildings, 29 business establishments, 1 megadike, 2 health centers and 17 public buildings.  Damage amounted to 4.175 million pesos or about 80,000 US dollars.

The focal mechanism as determined by Harvard University (Figure 2a) is underthrusting along a NW-trending plane with minor strike-slip component.  The strike conforms to the established trend of the trench.  The USGS's solution for the event (Figure 2b) shows an almost similar mechanism with a slightly larger strike-slip component than the solution of Harvard University.


Fig 2a. Focal Mechanism of the earthquake as determined by Harvard University


Fig 2b. Focal Mechanism of the earthquake as determined by USGS.

 


PHIVOLCS, 2002
Seismological Observation and Earthquake Prediction Division