Location:

Period:

2 Apr 2026 20:40:37 - 5 Apr 2026 05:10:41 (2 days 8 hours 30 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

M 7.0+:

M 7.1; 137 km WNW of Ternate, Indonesia; (24 Feb 2001) (12km from the swarm center)

15 swarms found nearby.

2001

PS20010225.1(21.2km)

24 Feb

16 hours

5 earthquakes

PS20010226.1(32.3km)

26 Feb

12 hours

5 earthquakes

PS20010827.1(33.6km)

26 Aug

1 day 19 hours

9 earthquakes

2007

PS20070121.1(19.4km)

21 Jan

3 days 13 hours

42 earthquakes

PS20070127.1(24.1km)

26 Jan

1 day 17 hours

7 earthquakes

2014

PS20141115.1(73.2km)

15 Nov

8 hours

8 earthquakes

PS20141126.1(75.0km)

25 Nov

1 day 0 hours

8 earthquakes

PS20141221.1(104.7km)

21 Dec

2 hours

5 earthquakes

2019

PS20190708.1(66.2km)

8 Jul

21 hours

5 earthquakes

PS20191114.1(44.2km)

14 Nov

1 day 7 hours

29 earthquakes

2026

PS20260402.1(3.6km)

1 Apr

2 days 2 hours

23 earthquakes

S20260402.4(14.8km)

1 Apr

11 days 20 hours

228 earthquakes

S20260402.3(26.8km)

2 Apr

5 days 1 hours

114 earthquakes

S20260402.2(23.8km)

2 Apr

5 days 5 hours

150 earthquakes

S20260404.1(10.6km)

3 Apr

1 day 10 hours

43 earthquakes

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Seismic Activity in the Molucca Sea: Insights from Swarm S20260403.1

The Molucca Sea, situated between the islands of Sulawesi and Halmahera in eastern Indonesia, forms part of the tectonically complex Molucca Sea Collision Zone. This region experiences intense seismic activity due to the ongoing collision between the Halmahera and Sangihe volcanic arcs, involving interactions among the Philippine Sea Plate, Australian Plate, and Sunda Plate. Subduction processes, arc-arc collision, and associated thrust faulting generate frequent earthquakes, with hypocenters typically ranging from shallow crustal depths to intermediate levels around 70 km.

Swarm S20260403.1 began at 20:40 on 2 April 2026 and concluded at 05:10 on 5 April 2026, spanning 56 hours and 30 minutes. During this period, 57 earthquakes were recorded in the Molucca Sea. Magnitudes ranged from 2.5 to 4.9, with the largest event (M4.9) occurring at a depth of 35 km on 3 April 2026 at 09:24. Other notable events included an M4.8 at 19 km depth later that day and several M4.0 events clustered between 3 and 10 km depth. Depths varied widely, from as shallow as 3 km to 69 km, indicating activity across multiple fault segments within the collision zone.

The swarm exhibited a typical pattern of clustered, moderate-magnitude events without a single dominant mainshock, consistent with fluid migration or stress redistribution in the highly fractured crust of the Molucca Sea. Event frequency peaked between 3 and 4 April 2026, with diminishing activity toward the swarm's end.

Historically, the Molucca Sea has hosted 14 documented swarms since 1 January 2000. These occurred in 2001 (3 swarms), 2007 (2), 2014 (3), 2019 (2), and 2026 (4). A significant nearby event was the M7.1 earthquake on 24 February 2001, located 137 km west-northwest of Ternate, Indonesia, and approximately 12 km from the center of swarm S20260403.1. This event underscores the region's capacity for strong shaking, driven by its position within the Pacific Ring of Fire.

Such swarms provide valuable data for understanding stress accumulation in the Molucca Sea Collision Zone. Continued monitoring supports improved hazard assessment for nearby populations in North Maluku province.

References

USGS Earthquake Catalog (historical events and regional tectonics)
Global CMT Catalog (plate boundary details)
SeismoSight internal swarm classification S20260403.1