Geography Reference
In-Depth Information
submerged Lomonosov Ridge, New Siberian Islands, Sakhalin Island,
Hokkaido and the north-eastern part of Honshu Island. The Japan-Sea
lineament, in turn, is an element of the Antarctic super-lineament being a
planetary meridian seam [46]. In addition, the Fukushima map images local
seismic structures within the linear trend of the largest events for the past
decade (No. 1 in Figure 16); a response to these events 200 km to the south
(No. 3 in Figure 16); an inner zone of weak volcanic activity in the form of a
ring within the location of Aizu-Wakamatsu (No. 2 in Figure 16); a deep
active zone (No. 4 in Figure 16); and a swarm (No. 5 in Figure 16) near the
Pacific coast on the Ibaraki-Fukushima prefectural border (a sequence of
shallow normal-slip earthquakes [47]), including the
M
s
=7.0 earthquake of
April 11, 2011. This is an example visualization analysis of primary
information on seismicity in a selected area, with the Fukushima-EEDB
procedures (Figure 16).
The revealed linear pattern of great earthquakes (
M
s
>= 7), including the
M
= 9.0 Tohoku event, appears to be the most interesting result (No.1 in
Figure 16; Figure 17a). In the map of Takashi NAKATA et al. [48], there are
northeast- and north-striking tectonic elements in the area, which align with
global structures. However, the orientations of some tectonic structures
(stepwise displacement of an eroded anticlinal ridge, as well as a bend in the
orientation of the Japan trench (Figure 17a) and faults along it, prompt the
existence along 38°N of an ancient fault or another structure, which has shown
up as a lineament with a high seismic potential through the past decade.
Figure 16.
M
s
>= 3.5 seismicity (13,742 events) near the Fukushima coast, since 2003.
