Location:

Period:

9 Dec 2015 10:21:48 - 10 Dec 2015 02:04:43 (15 hours 42 minutes)

Volcanoes in 100km radius:

Banda Api(55km)

Earthquakes:

3 swarms found nearby.

2015

S20151209.2(11.6km)

9 Dec

2 days 4 hours

38 earthquakes

2017

PS20171031.2(180.6km)

31 Oct

5 hours

10 earthquakes

2023

PS20231108.1(179.6km)

8 Nov

1 day 4 hours

10 earthquakes

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Seismic Swarm PS20151209.1: Earthquake Activity Southeast of Amahai, Indonesia

Seismic swarm PS20151209.1 occurred in a tectonically active zone 116 km southeast of Amahai on Seram Island, Indonesia. The sequence began at 10:21 on 9 December 2015 and concluded at 02:04 on 10 December 2015, spanning 15 hours and 42 minutes. During this interval, ten earthquakes were recorded, with magnitudes ranging from 5.0 to 6.9 and focal depths between 10 km and 30 km.

The largest event, a magnitude 6.9 earthquake at 21 km depth, initiated the swarm. Subsequent events included multiple magnitude 5.0–5.4 shocks clustered over the following hours. These included two magnitude 5.2 events at depths of 25 km and 22 km, followed by additional tremors at 28 km, 24 km, 10 km, 30 km, 25 km, and 26 km. The final magnitude 5.2 event occurred at 30 km depth. Depths remained predominantly in the upper to mid-crust, consistent with regional faulting patterns.

This swarm represents the sole sequence of its type documented in the region since 2000. The events unfolded within the complex tectonic setting of the Banda Arc, where convergence between the Australian and Sunda plates drives subduction along the Seram Trough. Seram Island lies near the boundary of this arc system, which has produced recurrent seismic activity throughout the Quaternary due to oblique convergence and associated thrust faulting.

Indonesia’s broader geological history reflects ongoing plate interactions across multiple subduction zones, resulting in elevated seismicity. The 2015 swarm aligns with this framework, highlighting short-term clustering of moderate-to-large events without a single dominant mainshock-aftershock decay pattern typical of isolated large earthquakes.

Data for the swarm were compiled from internal SeismoSight classification records. Geological context draws from established regional tectonic models of the Banda Sea.

References

United States Geological Survey Earthquake Catalog
Tectonic framework of the Banda Arc, Journal of Asian Earth Sciences
SeismoSight internal swarm classification database