Note:This page contains AI-generated content for informational and entertainment purposes only. It may contain inaccuracies. Raw event data is from USGS and EMSC. All statistics, lists, and derived information are generated by this site. Full disclaimerFound an error?
Location:
Izu Islands, Japan region
Period:
4 Jul 2001 09:25:09 - 5 Jul 2001 05:41:22 (20 hours 16 minutes)
Volcanoes in 100km radius:
Aogashima(20km), Kita-Bayonnaise(39km), Myojinsho(62km), Hachijojima(87km)
Earthquakes:
12
7 swarms found nearby.
2000
PS20000703.1(196.0km)
2 Jul
7 hours
5 earthquakes
PS20000712.1(193.0km)
11 Jul
2 days 5 hours
10 earthquakes
PS20000720.1(191.4km)
19 Jul
16 hours
6 earthquakes
PS20000723.1(199.5km)
23 Jul
1 day 5 hours
6 earthquakes
PS20000730.1(189.5km)
30 Jul
12 hours
5 earthquakes
PS20000815.1(199.5km)
15 Aug
10 hours
7 earthquakes
2023
PS20230514.1(117.8km)
14 May
8 hours
8 earthquakes
AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm PS20010704.1 in the Izu Islands Region

The Izu Islands form part of the Izu-Bonin volcanic arc in the western Pacific, where the Pacific Plate subducts beneath the Philippine Sea Plate. This tectonic setting produces frequent seismic activity, including earthquake swarms, alongside active volcanism on islands such as Miyakejima, Kozushima, and Niijima. The region experiences shallow crustal earthquakes typically at depths around 30–40 km, reflecting the interaction between subduction-driven stresses and local volcanic systems.

Seismic swarm PS20010704.1 began at 09:25 on 4 July 2001 and concluded at 05:41 on 5 July 2001. Over 20 hours and 16 minutes, 12 earthquakes were recorded in the Izu Islands, Japan region. All events occurred at a focal depth of 33 km. The sequence included the following events:

  • 4 July 2001 09:25:09, magnitude 5.0
  • 4 July 2001 09:48:31, magnitude 5.6
  • 4 July 2001 10:23:31, magnitude 5.5
  • 4 July 2001 17:47:45, magnitude 5.9
  • 4 July 2001 18:11:11, magnitude 4.2
  • 5 July 2001 01:41:18, magnitude 5.7
  • 5 July 2001 02:05:49, magnitude 5.3
  • 5 July 2001 02:15:42, magnitude 5.3
  • 5 July 2001 02:33:25, magnitude 5.0
  • 5 July 2001 03:47:31, magnitude 5.6
  • 5 July 2001 05:08:30, magnitude 5.2
  • 5 July 2001 05:41:22, magnitude 5.1

The swarm exhibited a rapid onset with several events exceeding magnitude 5.0 within the first hours, followed by a sustained series of moderate shocks. The largest event reached magnitude 5.9. Such clustering without a single dominant mainshock is characteristic of swarm behavior in this arc setting, often linked to fluid migration or stress redistribution along volcanic-tectonic fault systems.

Since 1 January 2000, six swarms have been documented in the Izu Islands region, with the initial swarm occurring in 2000. These episodes highlight the area’s persistent seismic productivity driven by ongoing plate convergence and magmatic processes.

References
USGS Earthquake Catalog
Japan Meteorological Agency seismic reports
Global Volcanism Program, Smithsonian Institution