Magnitude 5.8 earthquake — Toride, Japan
Developed over time first seen 2 months ago
A magnitude 5.8 earthquake was recorded near Toride in Ibaraki Prefecture, Japan, at 17:00 UTC on 22 August, equivalent to about 02:00 on 23 August local time. The US Geological Survey placed the event roughly 4 km north-north-west of Toride and at considerable depth. Japan’s Meteorological Agency assessed the same earthquake at preliminary magnitude 5.9, with an epicentre in southern Ibaraki and a depth of about 68–70 km. Shaking was felt across the Tokyo region, with a maximum Japanese seismic intensity of lower 5 reported in parts of Ibaraki, Saitama, Chiba and Tokyo.
Authorities said there was no tsunami risk. According to reports citing prefectural officials, 23 people were injured across Saitama, Kanagawa, Chiba and Ibaraki, largely in falls or collisions with furniture and doors after people were woken by the overnight shaking. Most injuries were described as minor, although one elderly woman in Yokohama reportedly sustained a serious hip injury after falling from her bed. Early estimates and reported depths may differ between monitoring agencies because they use separate seismic networks and assessment methods.
- USGS recorded a magnitude 5.8 earthquake near Toride, Japan.
- The quake shook the Tokyo region around 02:00 local time on 23 August.
- No tsunami was expected; 23 injuries were reported, mostly minor.
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Japan sits on the Pacific "Ring of Fire", a zone where several tectonic plates meet, making earthquakes a routine part of life there. Ibaraki Prefecture, north-east of Tokyo, and the wider Kanto region including Tokyo, Saitama and Chiba, are densely populated areas that regularly experience tremors, so the country has strict building codes and well-established emergency procedures.
Earthquake strength is measured in two different ways that can cause confusion: magnitude, which describes the total energy released, and local seismic intensity, which describes how strongly the shaking is felt in a particular place. Agencies such as the US Geological Survey and Japan's own Meteorological Agency often report slightly different magnitude and depth figures for the same quake, because they use separate monitoring networks and calculation methods.
A quake's depth matters because deeper earthquakes, like this one, tend to spread their shaking over a wider surface area but with less intensity at the surface than shallow ones of similar magnitude. Tsunamis are a major concern with undersea earthquakes near Japan, given the country's history of destructive waves, so any official assessment of tsunami risk is a key piece of information in the immediate aftermath of a quake.