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[HDS06-08] Tsunami and Megathrust earthquake disaster prevention warnings: Real-time monitoring of the genesis processes with Physical Wavelets
Keywords:Megathrust earthquake genesis, Tsunami genesis, Megathrust earthquake disaster prevention warnings, Tsunami disaster prevention warnings, Physical Wavelets
Japan's seismograph [1] and GPS [2] networks have a comprehensive record of earthquakes (EQs). A mathematical tool named Physical Wavelets (PWs) can describe the processes leading to megathrust and significant EQs with the record, allowing for accurate prediction of their focuses, fault movements, sizes, and rupture times, up to three months in advance, with time accuracies within a day [3-6]. The 2011 Tohoku EQ provides an example of how the PWs can provide a tsunami disaster prevention warning in the last three months before the event [4,6]. However, there are still challenges to effectively informing societal decisions [4,7,8].
Tsunami warning
The GPS stations of a subduction zone are in Fig. 1, whose relative position changes are non-differentiable displacements. Denoting the geographic axis c by E (eastward), N (northward), and h (upward) in (E, N, h), the displacement time history is {c}={d (c, 0 ), ., d (c, j ), .}. The j is the time in days. The cross-correlation of PWs with {c} defines noise-free displacement D (c, t), velocity V (c, t), and acceleration A (c, t) at time t. The paths in D (c, t)-V (c, t) and D (c, t)-A (c, t) plane show the 2011 Tohoku EQ genesis of 15 months, having the last 3 months of disaster prevention warning [4,6].
A schematic cross-section at the dotted line in Fig. 1b is Fig. 2, having stations 1, 2, and 3 referred to as the east coast E, TOP, and the west coast W, respectively. The schematics of (a) - (c) show the megathrust EQ genesis process [4].
(a) The fault (200×500 km) had coupled the counter-movements of two plates at the subduction zone, generating movements of 1.5 mm/y up on the west coast and 6 mm/y down on the east coast. The regular slow deformation with A (E, t) > 0 (eastward) began an initial bulge deformation on the west coast by changing A (E, t) < 0 (westward) in Jan 2010. The change in the east coast and TOP began in Jun and Oct 2010. The initial phase subsided on the east coast by 2.8 m, 1.5 mm on TOP, and 1 mm on the west coast by June. The initial phase had a uniformly increasing lifting force (A (h, t)>0) only on the east coast. The east coast subsidence was a pre-transition process from regular to bulge-bending deformation that compressed Tohoku by 18.4mm (W) and 13.2mm (E) by 11 Mar 2011. The initial phase had a uniformly increasing lifting force (A (h, t)>0) only on the east coast.
(b) In Jun 2010, the bulge-bending began a further linear subsidence of 3.3 mm on the east coast, compressing the fault to pull down the subducting plate in Jul 2010. The pulling speed became the highest westward V (E, t) = −0.69 mm/day on 22 Dec 2010, 3 times that on 11 Jul. The east coast had an average A (h, t) of 8.99×10–5 mm/day2, about 100 times that in the initial phase.
(c) The final phase is the east coast linear upheaval of 1.2 mm, which began in Nov 2010. The upheaval decelerated V (E, t) to zero on 25 Feb and reversed the westward movement to + 0.06 mm/day on 8 Mar 2011, generating the M9 EQ and a tsunami on 11 Mar 2011. The last 3-month abnormal oceanic plate motion is the Tsunami warning.
Detecting abnormal motion
The subducting oceanic plate's {c}, recorded at GPS stations in the Northwest Pacific Ocean, is under the lunar synodic tidal force loading (30-day period). The east coast bulge pulling is a new external force to the tidal loading, gradually changing the amplitudes and phases of the periodic loading to the plate motion. The paths of D (E, t)-V (E, t) and D (E, t)-A (E, t) with PW (E, t)=V (E, t)×A (E, t) automatically detect the abnormal oceanic plate motion as a Tsunami warning.
[1] https://www.hinet.bosai.go.jp/?LANG=en
[2] https://mekira.gsi.go.jp/index.en.html
[3] Takeda, F. (2015) https://patents.google.com/patent/JP5798545B2/ja
[4] Takeda, F. (2021) https://doi.org/10.48550/arXiv.2107.02799
[5] Takeda, F. (2022) https://doi.org/10.48550/arXiv.2201.02815
[6] Takeda, F. (2022) https://doi.org/10.48550/arXiv.2208.09486
[7] https://www.tec21.jp
[8] https://www.epi21.org
Tsunami warning
The GPS stations of a subduction zone are in Fig. 1, whose relative position changes are non-differentiable displacements. Denoting the geographic axis c by E (eastward), N (northward), and h (upward) in (E, N, h), the displacement time history is {c}={d (c, 0 ), ., d (c, j ), .}. The j is the time in days. The cross-correlation of PWs with {c} defines noise-free displacement D (c, t), velocity V (c, t), and acceleration A (c, t) at time t. The paths in D (c, t)-V (c, t) and D (c, t)-A (c, t) plane show the 2011 Tohoku EQ genesis of 15 months, having the last 3 months of disaster prevention warning [4,6].
A schematic cross-section at the dotted line in Fig. 1b is Fig. 2, having stations 1, 2, and 3 referred to as the east coast E, TOP, and the west coast W, respectively. The schematics of (a) - (c) show the megathrust EQ genesis process [4].
(a) The fault (200×500 km) had coupled the counter-movements of two plates at the subduction zone, generating movements of 1.5 mm/y up on the west coast and 6 mm/y down on the east coast. The regular slow deformation with A (E, t) > 0 (eastward) began an initial bulge deformation on the west coast by changing A (E, t) < 0 (westward) in Jan 2010. The change in the east coast and TOP began in Jun and Oct 2010. The initial phase subsided on the east coast by 2.8 m, 1.5 mm on TOP, and 1 mm on the west coast by June. The initial phase had a uniformly increasing lifting force (A (h, t)>0) only on the east coast. The east coast subsidence was a pre-transition process from regular to bulge-bending deformation that compressed Tohoku by 18.4mm (W) and 13.2mm (E) by 11 Mar 2011. The initial phase had a uniformly increasing lifting force (A (h, t)>0) only on the east coast.
(b) In Jun 2010, the bulge-bending began a further linear subsidence of 3.3 mm on the east coast, compressing the fault to pull down the subducting plate in Jul 2010. The pulling speed became the highest westward V (E, t) = −0.69 mm/day on 22 Dec 2010, 3 times that on 11 Jul. The east coast had an average A (h, t) of 8.99×10–5 mm/day2, about 100 times that in the initial phase.
(c) The final phase is the east coast linear upheaval of 1.2 mm, which began in Nov 2010. The upheaval decelerated V (E, t) to zero on 25 Feb and reversed the westward movement to + 0.06 mm/day on 8 Mar 2011, generating the M9 EQ and a tsunami on 11 Mar 2011. The last 3-month abnormal oceanic plate motion is the Tsunami warning.
Detecting abnormal motion
The subducting oceanic plate's {c}, recorded at GPS stations in the Northwest Pacific Ocean, is under the lunar synodic tidal force loading (30-day period). The east coast bulge pulling is a new external force to the tidal loading, gradually changing the amplitudes and phases of the periodic loading to the plate motion. The paths of D (E, t)-V (E, t) and D (E, t)-A (E, t) with PW (E, t)=V (E, t)×A (E, t) automatically detect the abnormal oceanic plate motion as a Tsunami warning.
[1] https://www.hinet.bosai.go.jp/?LANG=en
[2] https://mekira.gsi.go.jp/index.en.html
[3] Takeda, F. (2015) https://patents.google.com/patent/JP5798545B2/ja
[4] Takeda, F. (2021) https://doi.org/10.48550/arXiv.2107.02799
[5] Takeda, F. (2022) https://doi.org/10.48550/arXiv.2201.02815
[6] Takeda, F. (2022) https://doi.org/10.48550/arXiv.2208.09486
[7] https://www.tec21.jp
[8] https://www.epi21.org