10:45 AM - 12:15 PM
[SSS11-P01] Yamato Bank aSeismic Area in Wadati Plane of Japan Seismic Belt and relation to 2011 March 11 M9.0
Keywords:Seismic Belt, Wadati, Yamato Bank , Arc shape of Trench axis , Execess and Shortage of Slab Area , 2011 March 11 M9.0
All hypocenters of Japanese Island Arcs have been classified, based on 4786 Centroid Moment Tensor CMT solutions released from Meteorological Agency JMA. 13 "Hyper Seismic Belt", 38 "Seismic Belt", and 169 "Seismic Division" have been defined. The hypocenters related to Pacific Slab decending along Chishima, Japan , and Izu Trenchs, for example, are belonging to "Wadati Hyper Seismic Belt Wdti", which are composed with "Chishima Plane Seismic Belt WdtiC", "Japan Plane Seismic Belt WdtiJ" and "Izu Wing Seismic Belt WdtiWingI". WdtiJ is composed of 10 Seismic Divisions, named as "Soya Soy", "Rumoi Rm", "North Arc AcN", "Skhalin Skh", "PreMorie Pmr", "Vladivostok Vlad", "Japan Basin Jsb", "Oshima Osm", "Central Arc AcC", and "Wakasa Wks".
The classification has been extended for hypocenters of 12816 solusions of JMA Initial Motion & 12625 JMA Catalog of Seismic Intensity Distribution with Seno & Eguchi (1983), and systematically covered on seismic activities of Japanes Island Arcs for more than hundred years.
"Wadati Hyper Seismic Belt Wdti" is named after Wadati (1935) which was the first report on the deep seismic plane. The activities of "Wdti" had three peaks of 1930s, 1970s, and 1990s to 2010s. The peaks can be recognised as a steep slope of cumulative curve on area of seismic fault slip. Wadati (1935) was observed the 1930s activities and reported.
Because the principal strain axes of "WdtiJ" have a trend paralle to the direction of relative motion of Pacifc Plate to North American Plate, the Plate motion might control the seismic activities.
The focal depths of the "WdtiJ" have wide range from shallow of "AcN" & "AcC" to deeper than the upper boundary of Lower Mantle of "Vlad" Seismic Division.
The hypocenters of "WdtiJ" are positive imformation on the exisistence of descending Pacific Slab from Japan Trench. However there is seismic void area on the central part of "WdtiJ ", locating on "Yamato Bank" in the central Japan Sea, named as "Yamato Bank aSeismic area". The absence of hypocenters in the "Yamato Bank aSeismic Area" is certified also by hypocenters in JMA Catalog of Seismic Intensity Distribution.
The shapes of trench axis outlines are bent as arc. The arc shape is expressed as small circle on spherical surface in spherical geometory. There is a center of equidistance to trench axis for a small circle. Japan Trench is composed with three arcs of Erimo, Mogami and Kashima. The centers of the small circles locate on ocean side for possitive polarity of Erimo and Kashima, and on island arc side for negative polarity of Mogami.
The oceanic descending Slab might have excess area from positive arc, and shortage area from negative arc of trench axis, like as tablecloth. The negative Mogami Slab with shortage has to be splited or to get supplement from both neighbors of positive Erimo and Kashima Slabs to descend. "Yamato Bank aSeismic Area" locates on the continental side of negative Mogami small circle center.
The distributions of Seismic Intensity on the hypocenters of "Vlad", whose seismic wave pass through "Yamato Bank aSeismic Area" to Japanies seismic stations, have not any anormally in attenuation. It means that "Yamato Bank aSeismic Area" is a part of Slab with normal attenuation and strain under the limit of rupture, as ocean floor.
Megaquake M9.0 of 2011 March 11 on Seismic Division "Heisei off Tohoku Arc oAcJHs" released strain as the seismic fault slip area comparable with area of relative Plate motion for several hundred years. The cumulative area of seismic fault slips in the Japan Trench Region for the last hundred yeras, excepting the Megaquake M9.0 is comparative to relative Plate motion. These facts mean that there are tow ways to strage the strain of Plate motion. Hyocenter of the Megaquake and "Yamato Bank aSeismic Area" locate on almost same Euler Latitude of Plate motion. The directions of the principal strain axes of "WdtiJ" were changed like as to slacken the reins after the Megaquake. The seismicites of northeast margin of "aSeismic Area" were activated from 2006 to 2014 clossing the 2011 Megaquake. The facts indicate the relation of Megaquake and the "aSeismic Area".
The classification has been extended for hypocenters of 12816 solusions of JMA Initial Motion & 12625 JMA Catalog of Seismic Intensity Distribution with Seno & Eguchi (1983), and systematically covered on seismic activities of Japanes Island Arcs for more than hundred years.
"Wadati Hyper Seismic Belt Wdti" is named after Wadati (1935) which was the first report on the deep seismic plane. The activities of "Wdti" had three peaks of 1930s, 1970s, and 1990s to 2010s. The peaks can be recognised as a steep slope of cumulative curve on area of seismic fault slip. Wadati (1935) was observed the 1930s activities and reported.
Because the principal strain axes of "WdtiJ" have a trend paralle to the direction of relative motion of Pacifc Plate to North American Plate, the Plate motion might control the seismic activities.
The focal depths of the "WdtiJ" have wide range from shallow of "AcN" & "AcC" to deeper than the upper boundary of Lower Mantle of "Vlad" Seismic Division.
The hypocenters of "WdtiJ" are positive imformation on the exisistence of descending Pacific Slab from Japan Trench. However there is seismic void area on the central part of "WdtiJ ", locating on "Yamato Bank" in the central Japan Sea, named as "Yamato Bank aSeismic area". The absence of hypocenters in the "Yamato Bank aSeismic Area" is certified also by hypocenters in JMA Catalog of Seismic Intensity Distribution.
The shapes of trench axis outlines are bent as arc. The arc shape is expressed as small circle on spherical surface in spherical geometory. There is a center of equidistance to trench axis for a small circle. Japan Trench is composed with three arcs of Erimo, Mogami and Kashima. The centers of the small circles locate on ocean side for possitive polarity of Erimo and Kashima, and on island arc side for negative polarity of Mogami.
The oceanic descending Slab might have excess area from positive arc, and shortage area from negative arc of trench axis, like as tablecloth. The negative Mogami Slab with shortage has to be splited or to get supplement from both neighbors of positive Erimo and Kashima Slabs to descend. "Yamato Bank aSeismic Area" locates on the continental side of negative Mogami small circle center.
The distributions of Seismic Intensity on the hypocenters of "Vlad", whose seismic wave pass through "Yamato Bank aSeismic Area" to Japanies seismic stations, have not any anormally in attenuation. It means that "Yamato Bank aSeismic Area" is a part of Slab with normal attenuation and strain under the limit of rupture, as ocean floor.
Megaquake M9.0 of 2011 March 11 on Seismic Division "Heisei off Tohoku Arc oAcJHs" released strain as the seismic fault slip area comparable with area of relative Plate motion for several hundred years. The cumulative area of seismic fault slips in the Japan Trench Region for the last hundred yeras, excepting the Megaquake M9.0 is comparative to relative Plate motion. These facts mean that there are tow ways to strage the strain of Plate motion. Hyocenter of the Megaquake and "Yamato Bank aSeismic Area" locate on almost same Euler Latitude of Plate motion. The directions of the principal strain axes of "WdtiJ" were changed like as to slacken the reins after the Megaquake. The seismicites of northeast margin of "aSeismic Area" were activated from 2006 to 2014 clossing the 2011 Megaquake. The facts indicate the relation of Megaquake and the "aSeismic Area".