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Location:
81 km SSE of Shimoda, Japan
Period:
30 Jul 2000 00:18:00 - 30 Jul 2000 13:16:08 (12 hours 58 minutes)
Volcanoes in 100km radius:
Miyakejima(21km), Kozushima(22km), Mikurajima(34km), Niijima(38km), Toshima(51km), Izu-Oshima(74km), Kurose Hole(80km), Izu-Tobu(95km)
Earthquakes:
5
12 swarms found nearby.
2000
PS20000629.1(48.6km)
28 Jun
1 day 0 hours
10 earthquakes
PS20000703.1(10.4km)
2 Jul
7 hours
5 earthquakes
S20000706.1(11.3km)
5 Jul
1 day 6 hours
27 earthquakes
11 Jul
2 days 5 hours
10 earthquakes
PS20000720.1(13.3km)
19 Jul
16 hours
6 earthquakes
PS20000723.1(10.4km)
23 Jul
1 day 5 hours
6 earthquakes
PS20000803.1(19.1km)
2 Aug
21 hours
7 earthquakes
3 Aug
1 day 20 hours
45 earthquakes
PS20000815.1(12.1km)
15 Aug
10 hours
7 earthquakes
2001
PS20010704.1(189.5km)
4 Jul
20 hours
12 earthquakes
2005
PS20050119.1(197.1km)
19 Jan
10 hours
6 earthquakes
2023
PS20230514.1(73.1km)
14 May
8 hours
8 earthquakes
AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm PS20000730.1: Analysis of July 2000 Events Near Shimoda, Japan

Seismic swarm PS20000730.1 occurred on 30 July 2000, approximately 81 km south-southeast of Shimoda on Japan’s Izu Peninsula. The sequence began at 00:18 UTC and concluded at 13:16 UTC, encompassing five earthquakes within a 12-hour, 58-minute window. All events originated at a focal depth of 10 km, consistent with shallow crustal seismicity in this tectonically active region.

The recorded events, listed chronologically, include:

  • 00:18:00 UTC, magnitude 5.7
  • 12:25:45 UTC, magnitude 6.5
  • 12:48:55 UTC, magnitude 5.5
  • 13:14:00 UTC, magnitude 4.7
  • 13:16:08 UTC, magnitude 5.0

The peak magnitude of 6.5 represents the most significant shock within the swarm. Such clustered activity is characteristic of the Izu Peninsula, where the Philippine Sea Plate subducts beneath the Eurasian Plate along the Nankai Trough. This convergence drives frequent seismic and volcanic episodes, with the peninsula itself formed by Quaternary volcanism and faulting associated with the Izu-Bonin arc.

Geological records indicate that the broader region has experienced recurrent earthquake swarms linked to fluid migration and stress transfer along active faults. Since 1 January 2000, six swarms have been documented in the area, with PS20000730.1 marking the first recorded instance. These episodes typically feature shallow depths and moderate magnitudes, reflecting the brittle behavior of the upper crust under regional compression.

The Izu Peninsula lies within Japan’s high-seismicity zone on the Pacific Ring of Fire. Ongoing plate motion continues to generate strain accumulation, periodically released through swarms or larger mainshock-aftershock sequences. Monitoring by national seismic networks provides critical data for understanding these patterns and assessing potential hazards to nearby coastal communities.

References

  • Japan Meteorological Agency seismic catalog
  • United States Geological Survey earthquake database
  • SeismoSight internal swarm classification records