Fig. 7
From: Visualizing heterogeneities of earthquake hypocenter catalogs: modeling, analysis, and compensation
Correction of the epicenter locations determined by the local MSAS array for global earthquakes. Epicenter locations (gray disks) for earthquakes determined by MSAS; a earthquakes occurring in 1984–1988 and c earthquakes occurring in 1989–1992. The geographical world map is drawn by a polar coordinate system whose center is the location of the MSAS origin in central Japan. Black disks in a indicate USGS locations and b difference of epicenter locations of the same earthquake. An arrow indicates the shift from the MSAS location to the USGS location, provided that the differences of epicentral distance and azimuth are within 2o and 25o, respectively. These are used to minimize by the sum of least squares under a smoothness constraint (see text). The black disks in c are compensated locations from the MSAS data (gray disks) in c by the estimated bias functions f and g, shown in d and e, respectively. Contour plots in the panels d and e show the bias functions f for epicentral distance and g for azimuth in Eqs. (10) and (11), respectively, which are estimated using the data during 1984–1988 in Fig. 7a. The function f varies from − 3.5° to 2.5° in the angular distance, and the contour interval is 0.5°. The function g varies from − 45.0° to 50.0°, and the contour interval is 5.0°. Areas of negative function values are white