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Strong M5.6 earthquake registered 44 km NNE of Tokyo, Japan

strong-m5-6-earthquake-registered-44-km-nne-of-tokyo-japan

A strong earthquake registered as M5.6 on the Richter scale shook eastern Japan on September 16 at 03:28 UTC (12:28 local time). JMA reported depth of 50 km. USGS reports the same magnitude and depth of 53.9 km (33.5 miles).

Widespread minor damage has been reported.

According to USGS, epicenter was located 2 km (1 mile) WNW of Iwai, 7 km (4 miles) ESE of Sakai, 10 km (6 miles) SW of Ishige and 44 km (27 miles) NNE of Tokyo, Japan

There are 40 464 548 people living within 100 km radius.

A landslide has been reported from Tochigi Prefecture with 1 car buried (without anyone in there). This was reported from Maebashi City and expected given the heavy rain Japan has experienced over the past week (250 houses have been flooded and around 900 000 people affected). 

At least 3 people were injured (2 in Ota, 1 in Kiryu City). (ER)

Japan Atomic Power Co and Tokyo Electric Power Co (Tepco) (9501.T) reported no irregularities at their three nuclear plants in eastern Japan.

Overall, the population in this region resides in structures that are resistant to earthquake shaking, though some vulnerable structures exist.

Recent earthquakes in this area have caused secondary hazards such as landslides and fires that might have contributed to losses.

Population exposure

Population per ˜1 sq. km. from LandScan

Selected cities exposed

from GeoNames Database of Cities with 1,000 or more residents.

MMI City Population
V Satte 55k
V Shiraoka 51k
V Sugito 50k
IV Kasukabe 207k
IV Ishige 25k
IV Toride 81k
IV Saitama 1,193k
IV Tokyo 8,337k
IV Chiba-shi 920k
IV Yokohama-shi 3,574k
III Shizuoka-shi 702k

(k = x1,000)

Seismotectonics of Japan and Vicinity

Japan and the surrounding islands straddle four major tectonic plates: Pacific plate; North America plate; Eurasia plate; and Philippine Sea plate. The Pacific plate is subducted into the mantle, beneath Hokkaido and northern Honshu, along the eastern margin of the Okhotsk microplate, a proposed subdivision of the North America plate. Farther south, the Pacific plate is subducted beneath volcanic islands along the eastern margin of the Philippine Sea plate. This 2,200 km-long zone of subduction of the Pacific plate is responsible for the creation of the deep offshore Ogasawara and Japan trenches as well as parallel chains of islands and volcanoes, typical of Circumpacific island arcs. Similarly, the Philippine Sea plate is itself subducting under the Eurasia plate along a zone, extending from Taiwan to southern Honshu that comprises the Ryukyu Islands and the Nansei-Shoto trench.

Subduction zones at the Japanese island arcs are geologically complex and produce numerous earthquakes from multiple sources. Deformation of the overriding plates generates shallow crustal earthquakes, whereas slip at the interface of the plates generates interplate earthquakes that extend from near the base of the trench to depths of 40 to 60 km. At greater depths, Japanese arc earthquakes occur within the subducting Pacific and Philippine Sea plates and can reach depths of nearly 700 km. Since 1900, three great earthquakes occurred off Japan and three north of Hokkaido. They are the M8.4 1933 Sanriku-oki earthquake, the M8.3 2003 Tokachi-oki earthquake, the M9.0 2011 Tohoku earthquake, the M8.4 1958 Etorofu earthquake, the M8.5 1963 Kuril earthquake, and the M8.3 1994 Shikotan earthquake. (USGS) More information on regional seismicity and tectonic

Featured image credit: USGS

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