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[SSS05-P22] Coriolis Force could modify a Principal Strain Axis of Focal Mechanism
Keywords: Colriolis Force, focal mechanism, Chishima Trench Area, Okinawa Trough, CMT solution
Any moving materials might be affected by Coriolis Force toward right orthogonally to the course on northern hemisphere. Coriolis Force is increased with latitude and speed of the motion, and decreased with the friction.
CMT solutions from JMA are representing the time, location, and magnitude of initial breakage as Initial Motion Hypocenter and main destruction as Centroid Moment Tensor Hypocenter. .
Speed of breakage can be calculated from the time and location of Initial Motion and CMT. The speed of the breakage is in order of km/s, enough high for Coriolis Force.
Azimuths of principal strain axes of the CMT are parallel to Euler latitude lines of the relative Plate Motion of Pacific to North America PC-NA (Figs, 1 and 2: left upper epicenter map), and Philippine Sea to South China PH-SC (Figs. 3 and 4: left epicenter map).
The outlines of trench axis have arc shape, which can be treated as small circle chain on sphere surface. We can calculate the position of small circle center, using ocean floor topographic map Etopo2, based on constancy of distance from the center to the trench axis. We can use a coordinate system with distance and direction from the small circle center for positions in the trench area within the small circle division.
Trench dip direction changes linearly with the direction from small circle center in the coordinate system., however, changes in direction of relative Plate motion are much smaller. Direction of Plate motion is drawn as broken line in diagram referring trench dip direction as center line. We use the diagram for the analysis of dip azimuth of principal axis of strain. In the case that Plate motion relating to form the trench, the direction of Plate motion is drawn as broken line around reference center line (purple line in Figs. 1-4).
Hypocenters of normal fault type of focal Mechanism are located in the surficial part and reverse fault type in the deeper part of bending Slab; and reverse fault type in the surficial part and normal fault type in the deeper part of unbending Slab.
The compressional strain with Plate parallel azimuth for reverse fault type is accumulated by buckling of Slab. The compressional strain with Plate anti-parallel azimuth is accumulated by shearing along frictional Slab surface.
Compressional strain should be accumulated and released in enclosed system with large friction, however, tensional strain is accumulated in expanding system and released from other side just after the breakage with less friction.
The effect of Coriolis Force might be suppressed by the friction on 391compressional axes of reverse fault type, and the dip azimuths are kept in the original Plate parallel.
Chishima Trench Area (44.7N+-1.8)+12+-31 (in degree).
Dip Azimuths of principal tensional Strain axes of 118 and 68 normal fault type are significantly rotated clockwise.
Chishima Trench Area (50.3N+-1.6) +54+-35,
Okinawa Trough (27.3N+-2.0) +32+-21.
The amount of the clockwise rotations on the tensional axis of normal fault type focal mechanism with less friction are comparable to latitude, verify that Coriolis Force could modify the focal processes.
CMT solutions from JMA are representing the time, location, and magnitude of initial breakage as Initial Motion Hypocenter and main destruction as Centroid Moment Tensor Hypocenter. .
Speed of breakage can be calculated from the time and location of Initial Motion and CMT. The speed of the breakage is in order of km/s, enough high for Coriolis Force.
Azimuths of principal strain axes of the CMT are parallel to Euler latitude lines of the relative Plate Motion of Pacific to North America PC-NA (Figs, 1 and 2: left upper epicenter map), and Philippine Sea to South China PH-SC (Figs. 3 and 4: left epicenter map).
The outlines of trench axis have arc shape, which can be treated as small circle chain on sphere surface. We can calculate the position of small circle center, using ocean floor topographic map Etopo2, based on constancy of distance from the center to the trench axis. We can use a coordinate system with distance and direction from the small circle center for positions in the trench area within the small circle division.
Trench dip direction changes linearly with the direction from small circle center in the coordinate system., however, changes in direction of relative Plate motion are much smaller. Direction of Plate motion is drawn as broken line in diagram referring trench dip direction as center line. We use the diagram for the analysis of dip azimuth of principal axis of strain. In the case that Plate motion relating to form the trench, the direction of Plate motion is drawn as broken line around reference center line (purple line in Figs. 1-4).
Hypocenters of normal fault type of focal Mechanism are located in the surficial part and reverse fault type in the deeper part of bending Slab; and reverse fault type in the surficial part and normal fault type in the deeper part of unbending Slab.
The compressional strain with Plate parallel azimuth for reverse fault type is accumulated by buckling of Slab. The compressional strain with Plate anti-parallel azimuth is accumulated by shearing along frictional Slab surface.
Compressional strain should be accumulated and released in enclosed system with large friction, however, tensional strain is accumulated in expanding system and released from other side just after the breakage with less friction.
The effect of Coriolis Force might be suppressed by the friction on 391compressional axes of reverse fault type, and the dip azimuths are kept in the original Plate parallel.
Chishima Trench Area (44.7N+-1.8)+12+-31 (in degree).
Dip Azimuths of principal tensional Strain axes of 118 and 68 normal fault type are significantly rotated clockwise.
Chishima Trench Area (50.3N+-1.6) +54+-35,
Okinawa Trough (27.3N+-2.0) +32+-21.
The amount of the clockwise rotations on the tensional axis of normal fault type focal mechanism with less friction are comparable to latitude, verify that Coriolis Force could modify the focal processes.