[SMP39-07] Push out and Phase Transition of Mantle under the Izu Slab, recorded on CMT solutions of JMA
Keywords: Izu Slab, Mantle Phase Transition, Wing Subduction, Push out Mantle, accompanied Mantle, Centrol Moment Tensor Solution of Japan Meteorological Agency
1. Anomalous distribution in seismic intensity on M6.6 in 2019/7/28.
The epicenter of CMT was located on the axis of Nankai Trough off Mie Pref. of central Japan with depth 393km, however, the seismic intensities were less than 1 in Mie but the maximum 4 was recorded in Miyagi Pref. of northeast Japan, The anomalous distribution indicates the existence of less attenuate Slab, consistent with hypocenter distribution.
2. Polymorph of seismicity in the Izu, Ogasawara & Mariana Slab
The hypocenter distribution has polymorph with subduction types of low gradient Wing , vertical & recumbent. The earthquake with anomalous seismic intensity was happened on the base of the low gradient Wing.
3. Wing Subduction and Push out Mantle
The root of Wing is high seismicity with mainly reverse fault type and the tip of wing with strike slip fault type. The difference could be explained with pushing up strain to reduce the gradient of Slab. The hypocenters of low gradient Wings are concentrated above 410km in north and 550km in south of Hachijo Island.
4. Phase Transition of push out Mantle
The depths 410km and 550km of the Wings are well corresponding to α/β and β/γ phase transition in Mantle Transition Zone. The Wings should be related with the phase transition of the Mantle. The accompanied Mantle umder the ocean floor should be interrupted by descending Slab along trench axis and push out to continue the Plate Motion. The phase transitions of α/β and β/γ are progress more under higher pressure and lower temperature. Push out cool Mantle under the terminal of Slab could be transited than Slab for the depth. The terminal of Slab might be float on the transited Mantle with higher density and form Wings.
5. Changes in Push out Mantle recorded on Seismicity of Wing
The seismicity of the Wings have been observed for the last hundred years with seismometer of JMA. We can trace back the strength of the push out Mantle as the seismicity of the Wings. The time series of the seismicity are not in phase but reversed phase.. The phase should have influence on seismic and volcanic activities of Japanese Island Arcs.
The epicenter of CMT was located on the axis of Nankai Trough off Mie Pref. of central Japan with depth 393km, however, the seismic intensities were less than 1 in Mie but the maximum 4 was recorded in Miyagi Pref. of northeast Japan, The anomalous distribution indicates the existence of less attenuate Slab, consistent with hypocenter distribution.
2. Polymorph of seismicity in the Izu, Ogasawara & Mariana Slab
The hypocenter distribution has polymorph with subduction types of low gradient Wing , vertical & recumbent. The earthquake with anomalous seismic intensity was happened on the base of the low gradient Wing.
3. Wing Subduction and Push out Mantle
The root of Wing is high seismicity with mainly reverse fault type and the tip of wing with strike slip fault type. The difference could be explained with pushing up strain to reduce the gradient of Slab. The hypocenters of low gradient Wings are concentrated above 410km in north and 550km in south of Hachijo Island.
4. Phase Transition of push out Mantle
The depths 410km and 550km of the Wings are well corresponding to α/β and β/γ phase transition in Mantle Transition Zone. The Wings should be related with the phase transition of the Mantle. The accompanied Mantle umder the ocean floor should be interrupted by descending Slab along trench axis and push out to continue the Plate Motion. The phase transitions of α/β and β/γ are progress more under higher pressure and lower temperature. Push out cool Mantle under the terminal of Slab could be transited than Slab for the depth. The terminal of Slab might be float on the transited Mantle with higher density and form Wings.
5. Changes in Push out Mantle recorded on Seismicity of Wing
The seismicity of the Wings have been observed for the last hundred years with seismometer of JMA. We can trace back the strength of the push out Mantle as the seismicity of the Wings. The time series of the seismicity are not in phase but reversed phase.. The phase should have influence on seismic and volcanic activities of Japanese Island Arcs.