1998 Ryukyu Islands earthquake

1998 Ryukyu Islands earthquake

Date	May 4, 1998 (May 3 in UTC)
Magnitude	7.5 Mw
Depth	33.0 km
Epicenter	22°18′N 125°18′E / 22.3°N 125.3°ECoordinates: 22°18′N 125°18′E / 22.3°N 125.3°E
Tsunami	up to 4 cm

The 1998 Ryukyu Islands earthquake (石垣島南方沖地震 Ishigakijima nanpō-oki jishin) occurred on May 4, 1998 at 08:30 local time (UTC+9) (on May 3 at 23:30 UTC) in the Philippine Sea region with M_w 7.5 (USGS) and M7.7 (JMA). The epicenter was 260 km (162 mi) from Ishigaki Island, Japan, 400 km (249 mi) from Basco, Philippines, and 425 km (264 mi) from Hualian, Taiwan. A small local tsunami of 4 cm (2 in) was observed on Miyako. The earthquake was felt in the Ryukyu Islands and in parts of eastern Taiwan. The highest intensity was shindo 3 recorded on Yonaguni, Ishigaki, and Miyako.^[1] In 1999, the former Japan Marine Science and Technology Center (海洋科学技術センター) (Japan Agency for Marine-Earth Science and Technology (JAMSTEC) (海洋研究開発機構) after 2004) conducted an investigation in the region of the source of this earthquake.^[2]

The source of this earthquake was a sinistral (left-lateral) strike-slip fault. It was an intra-plate earthquake inside the Philippine Sea Plate.^[2][3] Such large intra-plate earthquakes inside the Philippine Sea Plate are not very common in this region. This earthquake was the strongest intra-plate earthquake inside the Philippine Sea Plate in the Ryukyu Islands region in 100 years as it occurred.^[4]

References

1. "USGS Earthquake Hazards Program: Earthquake Report: Southeast of Taiwan". Neic.usgs.gov. Retrieved 2010-07-09.
2. "SH-002.PDF" (PDF). Retrieved 2010-07-09.
3. Earthquake Prediction Information Division and Okinawa District Observatory. "The M7.6 Earthquake on May 4, 1998 and M6.3 Earthquake on November 20, 1998 in the South off Ishigakijima Island" (PDF) (in Japanese). Japan Meteorological Agency. Retrieved 2010-07-09.
4. "南西諸島のプレート配置図と地震活動". Seis.sci.u-ryukyu.ac.jp. Retrieved 2010-07-09.