Seismic Activity Near Ternate, Indonesia: Tectonic Context and Recent Events

Ternate lies in North Maluku province, Indonesia, within the tectonically complex Molucca Sea region. This area forms part of the Pacific Ring of Fire, where multiple plates converge. The Molucca Sea Collision Zone involves the Philippine Sea Plate, Sunda Plate, and smaller fragments such as the Halmahera and Sangihe arcs. Oblique subduction and arc-arc collision produce frequent large earthquakes at shallow to intermediate depths. The regional geology features active thrust faults and strike-slip systems accommodating rapid plate convergence rates exceeding 10 cm per year. Historical records document repeated M7+ events, consistent with the ongoing deformation along the western and northwestern margins of Halmahera. A magnitude 7.5 earthquake struck 126 km WNW of Ternate on 21 January 2007 at 11:27 local time, at a depth of 22 km. Since 2000, five additional strong earthquakes of M7.1 or greater have occurred within 155 km of Ternate:

• M7.4 on 1 April 2026, 127 km WNW of Ternate
• M7.1 on 14 November 2019, 141 km NW of Ternate
• M7.1 on 15 November 2014, 155 km NW of Ternate
• M7.1 on 24 February 2001, 137 km WNW of Ternate These events cluster along the same corridor, highlighting persistent seismic hazard from the local subduction interface and associated crustal faults. Ground shaking from such earthquakes can affect nearby islands, including volcanic centers such as Gamalama. Depths typically range from 20–40 km, producing both felt intensities and potential tsunami risk in coastal zones. Monitoring by regional networks continues to track aftershock sequences and background seismicity.

References

USGS Earthquake Catalog Global CMT Catalog Indonesian Meteorological, Climatological, and Geophysical Agency (BMKG) reports