The 2002 Manokwari Earthquake and Regional Tectonics

On 10 October 2002 at 10:50 local time, a magnitude 7.6 earthquake struck 102 km south-southeast of Manokwari, Indonesia, at a shallow depth of 10 km. The event occurred within the tectonically complex Bird’s Head Peninsula of West Papua, a region shaped by ongoing convergence between the Australian and Pacific plates.

Manokwari lies near the western terminus of the Sorong Fault system, a major left-lateral strike-slip structure that accommodates oblique convergence. The fault zone forms part of the broader Australia–Philippine Sea plate boundary, where multiple microplates and subsidiary faults create a diffuse deformation zone. Shallow crustal earthquakes are common because slip is concentrated along these near-surface structures rather than at greater depths.

Geological mapping and GPS measurements show that the Sorong Fault has accommodated several centimeters of annual displacement over recent decades. The 2002 rupture is interpreted as reactivation along a segment of this fault or an associated splay, consistent with the observed focal mechanism of left-lateral strike-slip motion. The shallow focal depth increased the potential for strong ground shaking in nearby coastal communities, although damage reports remained limited owing to sparse population density at the time.

Seismic records indicate that the Bird’s Head Peninsula has experienced recurrent moderate-to-large events throughout the instrumental era. Historical accounts from the early twentieth century document damaging shocks in 1914 and 1935, both attributed to the same fault system. Paleoseismic studies along the Sorong Fault reveal evidence of prehistoric surface-rupturing earthquakes, underscoring a long-term recurrence pattern on the order of centuries.

Since 2002, continued monitoring by regional and global networks has refined understanding of strain partitioning across the peninsula. Updated plate-motion models confirm that convergence rates remain high, maintaining elevated seismic hazard. No subsequent event of comparable magnitude has occurred in the immediate vicinity, yet smaller aftershocks and background seismicity continue to delineate active fault strands.

The 2002 Manokwari earthquake therefore serves as a reminder of the persistent tectonic forces operating at this plate-boundary junction. Improved seismic instrumentation and fault-mapping efforts since the event support ongoing hazard assessment for communities along the northern coast of the Bird’s Head Peninsula.

References

• USGS Earthquake Catalog, event ID usp0000b9n
• Global Centroid Moment Tensor Project
• Tectonic map compilations, Geological Survey of Indonesia