In the past week, the eastern coast of Chiba Prefecture has been rocked by a series of earthquakes, including a magnitude 5.3 quake last Friday morning. Japan’s Meteorological Agency (JMA) has advised citizens to be on alert, warning that more tremors are expected in the coming days. The reason for this increase in shaking is reportedly due to a phenomenon known as “slow slip” in tectonic plates off the coast. According to the Geospatial Information Authority, between May 1996 and June 2018, this phenomenon was observed off the Boso Peninsula on six occasions.

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A Significant Increase in Seismic Activity  

There has been a significant increase in seismic activity off the eastern coast of Chiba Prefecture in the past week. The JMA said that between Monday and Sunday evening, the region experienced a total of 31 quakes with a seismic intensity (shindo) of 1 or higher on the country’s scale of zero to 7. Three of those quakes measured 4 on the shindo scale. As well as the magnitude 5.3 quake on Friday morning, there was also a magnitude 4.9 quake on Thursday evening and a magnitude 5.0 quake in the early hours of Saturday.   

The JMA’s seismic intensity guide states that shindo 4 earthquakes can lead to, “strong shaking of houses and buildings, overturning of unstable objects, and spilling of liquids out of vessels.” It can also be “felt by people walking outdoors.” The scale goes from zero, shocks that are too weak to be felt by humans and registered only by seismologists, to 7, which is described as “very disastrous,” leading to the “collapse of more than 30% of all houses, intense landslides, large fissures in the ground, and faults.”  

Preparation for an Earthquake 

For those who are unprepared for an earthquake, here’s Tokyo Weekender‘s guide on what to do before, during and after a big quake.  

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