Location:

Period:

29 Jul 2005 06:01:53 - 30 Jul 2005 04:56:51 (22 hours 54 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

8 swarms found nearby.

2005

PS20050328.2(57.3km)

28 Mar

1 day 2 hours

28 earthquakes

PS20050328.1(51.6km)

28 Mar

3 days 8 hours

24 earthquakes

PS20050329.1(79.0km)

28 Mar

12 hours

5 earthquakes

S20050329.1(39.6km)

28 Mar

3 days 4 hours

56 earthquakes

PS20050406.1(143.9km)

5 Apr

16 hours

5 earthquakes

PS20050407.1(13.1km)

7 Apr

1 day 3 hours

7 earthquakes

PS20050411.1(162.5km)

11 Apr

3 hours

5 earthquakes

2010

PS20100407.1(164.8km)

6 Apr

6 hours

5 earthquakes

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Seismic Swarm PS20050730.1: Analysis of Activity off Singkil, Indonesia

A seismic swarm designated PS20050730.1 was recorded 160 km SSW of Singkil, Indonesia, beginning at 06:01 on 29 July 2005 and concluding at 04:56 on 30 July 2005. The sequence lasted 22 hours and 54 minutes and included five earthquakes. This event represents the earliest swarm documented in the regional catalog since 2000. The individual events unfolded as follows. The initial shock on 29 July 2005 at 06:01:53 registered magnitude 5.0 at a depth of 2 km. On 30 July, a magnitude 5.3 event occurred at 00:36:29 at 25 km depth, followed two minutes later by a magnitude 5.0 shock at 33 km depth. A second magnitude 5.0 earthquake struck at the same instant at 30 km depth. The final event, magnitude 4.1, occurred at 04:56:51 at 30 km depth. Since 1 January 2000, seven swarms have been identified in the area, with this July 2005 sequence being the first. Such swarms consist of multiple events clustered in time and space without a single dominant mainshock, a pattern often linked to fluid migration or stress adjustments along fault interfaces. The swarm location lies within the Sunda subduction zone, where the Indo-Australian plate converges with the Eurasian plate at rates of approximately 5–6 cm per year. This tectonic setting produces frequent shallow to intermediate-depth seismicity and has generated several great earthquakes in the historic record, including the 2004 Sumatra-Andaman event whose rupture zone extended into nearby waters. Depths recorded during the swarm (mostly 25–33 km) align with the expected range for intraslab or interface activity above the subducting slab. Ongoing monitoring in this region supports improved understanding of precursory patterns that may precede larger events. Continued cataloging of swarm activity contributes to refined seismic hazard assessments for coastal Sumatra and the adjacent Indian Ocean basin. References
SeismoSight internal swarm classification records.
USGS Earthquake Hazards Program summaries of Sumatran tectonics.
Global CMT catalog for regional event parameters.