[S-CG53] Science of slow earthquakes: Toward unified understandings of whole earthquake process

[SCG53-15] 東海地方の重力の時間変化とスロースリップとの関係

*田中 愛幸⁵、鈴木 岳人²、今西 祐一¹、大久保 修平¹、新林 張³、安藤 美和子¹、渡邉 篤志¹、加藤 知瑛⁴、大森 秀一⁴、平岡 喜文⁴ (1.東京大学地震研究所、2.青山学院大学、3.中国地震局、4.国土交通省国土地理院、5.東京大学)

キーワード：重力、スロー地震、間隙弾性、スロースリップ、沈み込み帯、水

The water in Earth’s mantle is closely related with plate subduction and volcanism. Recent studies revealed that the mantle wedge corner at approximately 30 km depth holds high-pressure water, where many slow earthquakes occur. To quantify how such water behaves during slow earthquakes helps us understand the mechanisms of these earthquakes and (eventually) a part of the long-term water cycle between the interior and surface of the Earth. However, little evidence has thus far been reported on the transient flows of such deep water. Here, we report anomalous, negative mass anomalies during two recent long-term slow slip events in the Tokai area in Japan, which were detected by absolute gravity measurements over 20 years. We present a poroelastic fluid flow model assuming a localized deformation within the fault fracture zone. The model can reproduce the gravity change with a permeability range between those suggested by laboratory experiments and numerical simulations of slow earthquakes.