15:30 〜 15:45
[HCG21-01] T-phases from events to the west of Sofugan on October 8, 2023
★Invited Papers
キーワード：T波、ハイドロフォン、フロート
During 2.5 hours from 18:58(UTC) on October 8, there were 15 earthquakes with mb 4.3–5.4 to the west of Sofugan according to the earthquake catalog of U. S. Geological Survey. Among them 13 earthquakes from 2nd to 14th generated strong T-phases. We collected seismic waveform data at stations MRA01 and S1N10 from seafloor cable observation systems DONET, and S-net, respectively and island stations AOG from F-net, OGS from Pacific21 network that can be obtained from Incorporated Research Institutions for Seismology. We also collected hydrophone waveform data of two stations H11N1 and H11S1 from International Monitoring System at Wake Island and two MERMAID floats P0057 and T0100 that were drifting approximately 480 km south and 90 km north-northeast of Sofugan, respectively. MERMAID is an autonomous robotic float equipped with a hydrophone and drifts passively at 1,500 –2,000 m depth until an earthquake signal is detected. If this is identified as a strong P wave, the MERMAID ascends at speed of 10 cm/s for transmission of the recorded waveform within time window of a hundred seconds before and after the P wave arrival as well as its global positioning system coordinates at the surface.
These stations distribute around Sofugan to achieve good azimuthal coverage so that the locations of the T-phase sources can be accurately determined. We relocated the T-phase sources using differential traveltimes between every two stations of each event measured by picking the peak on envelope function of waveform band-pass filtered between 4 and 8 Hz. Most of the relcated events are concentrated within a circle with a diameter of 10 km in the Sofu seamount extending west from Sofugan. In my talk, I will show the charactristics of each record.
These stations distribute around Sofugan to achieve good azimuthal coverage so that the locations of the T-phase sources can be accurately determined. We relocated the T-phase sources using differential traveltimes between every two stations of each event measured by picking the peak on envelope function of waveform band-pass filtered between 4 and 8 Hz. Most of the relcated events are concentrated within a circle with a diameter of 10 km in the Sofu seamount extending west from Sofugan. In my talk, I will show the charactristics of each record.