Earthquake offshore Honshu

Impact
Country Displaced Injured Dead Damaged Buildings Destroyed Buildings
Japan 39 186 1 4569 67

Source: Earthquake Impact Database

Affected Population
High intensities, limited damage

Many injuries and damaged buildings: Saturday's Mw7.1 earthquake near the east coast of Honshu, Japan was one of the strongest quakes in nothern Honshu since 2011. The earthquake happened near the coast of the prefectures Fukushima and Miyagi in a depth of about 60 kilometers. Focal parameters indicate a rupture within the subduction slab and therefore no direct relation with the megathrust fault. However, despite the depth and the offshore location, the japanese network registered  unusual high intensities across the Tohoku region with largest detections close to Shindo 7, the highest value on the japanese intensity scale. Shindo 6- and 6+ (Modified Mercalli: VIII - IX) affected several prefectures, Shindo 5- (MM V - VI) even most parts of Tokyo area. For most areas in Northern Honshu this quake caused the highest intensities since the Great Tohoku Earthquake 2011 (Mw9.1). 

The depth however prevented any significant tsunami threat. Neither the Japanese Meteorological Agency nor the Pacific Tsunami Warning Center have issued a warning for the coast of Honshu. Minor sea level fluctuations are always possible after quakes of this size but in this case, no hazardous events were expected or observed. 

As of February 14th, 7 UTC, 144 people were reported injured. Most injuries are minor and related to panic-related accidents or falling objects within houses. Besides Fukushima (77 injuries) and Miyagi (52) prefectures, injuries were reported from Tochigi (5), Ibaraki (3), Chiba (2), Saitama (2), Gunma (1), Kanagawa (1) and Yamagata (1). 
Building damage is so far limited to about 30 structures, according to official information. But the evaluation continues and it is expected that the number of damaged buildings will rise. However, no cases of destruction or severe damage were reported yet. Due to the building codes in Japan, most buildings can even withstand the highest intensities. 

Aftershocks are defined as earthquakes that follow on a larger one in the same region. An aftershock sequence ends as soon as the frequency of quakes is as low as it was prior to the mainshock. Therefore the February 13th 2021 earthquake can be defined as an aftershock of the 2011 Tohoku earthquake. It did not nupture the megathrust but a fault within the slab, that has experienced additional stress after the Tohoku quake. 

Event Characteristics
Latitude 37.78 °N
Longitude 141.57 °E
Date & Time Feb. 13, 2021, 2:07 p.m.
Magnitude Mw 7.1
Depth 70 km
Last Update 2021-02-13
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