The magnitude-7.3 main temblor in Kumamoto Prefecture on April 16 caused an area near the Nakadake crater of Mount Aso in the prefecture to sink by about 20 centimeters, the Geospatial Information Authority of Japan (GSI) said.
Noting that the Futagawa fault zone that triggered the temblor is believed to end around the western part of Mount Aso, GSI senior researcher Satoshi Fujiwara said, "The quake undoubtedly had some impact on the sinking, but I'm not sure whether there is any connection with volcanic activity."
GSI analyzed observation data, including data from the Japan Aerospace Exploration Agency's Daichi-2 satellite, and found the western part of Mount Aso had sunk following the quake. An area around the crater had sunk by approximately 20 centimeters and at least one area in the western part ended up about 30 centimeters lower.
The eastern edge of the Futagawa fault zone ends around the western part of the mountain. Experts say they cannot confirm that the zone further stretches eastward.
GSI found the northern side of the Futagawa fault zone had moved up to 1.5 meters to the east and its southern side had shifted at least 70 centimeters toward the west following the quake.