Seismic Activity and Tectonic Setting of the Ternate Region, Indonesia

The Ternate region in North Maluku, Indonesia, lies within one of the most seismically active zones on Earth. On 15 November 2014 at 02:31 UTC, a magnitude 7.1 earthquake struck 155 km northwest of Ternate at a depth of 45 km. This intermediate-depth event exemplifies the persistent tectonic stresses that shape the Molucca Sea area.

Tectonic forces in the region arise from complex interactions among the Philippine Sea Plate, the Sunda Plate, and smaller microplates. The Molucca Sea Collision Zone produces frequent moderate-to-large earthquakes through subduction and plate convergence. Depths around 45 km typically correspond to events occurring within the downgoing slab, where brittle failure generates significant ground shaking felt across the Maluku Islands.

Instrumental records document several strong earthquakes near Ternate since 2000. A magnitude 7.4 event occurred on 1 April 2026, 127 km west-northwest of Ternate. Earlier, a magnitude 7.1 earthquake struck 141 km northwest on 14 November 2019. The 15 November 2014 event is followed in the sequence by a magnitude 7.5 earthquake on 21 January 2007, located 126 km west-northwest, and a magnitude 7.1 event on 24 February 2001, 137 km west-northwest. These events cluster within roughly 100 km of one another, highlighting a persistently active seismic corridor.

Historical patterns show that the Ternate area experiences recurrent large earthquakes due to ongoing plate convergence rates exceeding 5 cm per year. Intermediate-depth seismicity often produces felt intensities across Halmahera and surrounding islands, though tsunami risk remains lower than for shallow thrust events. Regional geology features volcanic arcs, including the active Gamalama volcano on Ternate Island itself, formed by the same subduction processes driving the earthquakes.

Continued seismic monitoring by regional networks provides essential data for understanding stress accumulation along these plate boundaries. The sequence of magnitude 7+ events underscores the need for resilient infrastructure in North Maluku given the area's long-term seismic hazard.

References

USGS Earthquake Catalog (events 2001–2026)
Global CMT Catalog
Indonesian Agency for Meteorology, Climatology and Geophysics (BMKG) regional reports