Answer:

The 1,200-km-long Philippine fault zone (PFZ) is a major tectonic feature that transects the whole Philippine archipelago from northwestern Luzon to southeastern Mindanao. This arc-parallel, left-lateral strike slip fault is divided into several segments and has been the source of large-magnitude earthquakes in recent years, such as the 1973 Ragay Gulf earthquake (M 7.0), 1990 Luzon earthquake (Mw 7.7) (Figure 1), and 2003 Masbate earthquake (Ms 6.2). The high seismic risk posed by this fault zone requires a large-scale active faults map, a fundamental data set for seismic hazard mitigation.