[SGL29-P05] A challenge to detect mud volcano activities in an ocean area using DONET1 in the Kumano Basin, central Japan
Keywords:Mud Volcano, seismic signal, DONET
DONET (Dense Oceanfloor Network system for Earthquakes and Tsunamis) is a submarine cabled real-time seafloor observation infrastructure which is designed for precise monitoring of earthquakes and tsunamis in the Nankai area. The system is constructed by 2 loops of observatories, developed in the western Kumano Basin (DONET1) and off-Shikoku area (DONET2). MVs in the Kumano Basin locate within areas of observatories connected to node A and D of the DONET1. We just start challenge to detect signals of MV’s activity into the DONET data.
Seismic signals related to MVism are considered as a result of subseafloor intrusion and emission of gas bubbles into water. We searched suspected-MV-related signals in data from differential pressure gauge, DONET, using an information provided by Prof. Obara, ERI, Univ. of Tokyo. Prof. Obara’s data show a seismic event occurred at seafloor in Sagami Bay in December 2001 detected by on-land seismometers. The characteristics we are seeking for into DONET data is as follows:
- Data having a peak at 5~6 Hz
- Duration of data is at least 10~20 minutes
- Data having strongest signals at around A and D nodes of DONET1 where closely exists to the known MVs
- Data having a square shape, meaning steady strength during its duration (data do not show spindle-shape)
There are many events detecting Earthquakes within the data from DONET, but there are less number of events which show features mentioned above. For examples, such feature has detected only 2 times during January 2017. As for a timing of ~1 week before and after the large Earthquake occurred at SE off-Kii peninsula (M6.1) in 2016 April 1st, we cannot find notable features. It may be because the MV activity behind of high-level of seismic signals, and/or no MV activities relate to the event. Further inspection and discussion beyond research fields is absolutely needed.