Abstract
We conducted an urgent field survey at the Sendai Plain to measure the run-up heights and inundation distances of the 2011 Tohoku-oki tsunami. We used GPS measurements because of the remarkably long inundation distances (ca. 5.4 km). We established an accurate measurement scheme using the far electric reference points (about 350 km). Using this method, we quickly measured 69 run-up heights within 3 days. The tsunami run-up heights and inundation distances varied mainly according to the local topography, ranging from 9.6 m at 0.4 km to 0.2 m at 5.4 km, respectively. Furthermore, artificial structures and topography played an important role in constraining the inundation limit. Our observations are important for future analyses using aerial and satellite imagery and numerical modeling in the area because the maximum inundation area might be underestimated in the images as a result of the subtle traces of the tsunami inundation, which were difficult to identify in the field. However, results show that numerical modeling might not reproduce minor inundation beyond the highway without sufficiently high-resolution topographic data because data for the modeling are usually rough, and the highway, small channels, and street gutters, which played an important role in local inundation, are too small a resolution to be recognized in the model.
Highlights
An earthquake of magnitude 9.0 occurred off the Pacific coast of Tohoku, Japan on March 11, 2011 (e.g. Hirose et al, 2011)
Tsunami inundation in the Sendai Plain is generally classified into areas of three types from north to south (Fig. 1, Table 1): (1) inundation in the urban city at the Tagajo and Shichigahama near the Sendai Port; (2) inundation in the very wide and flat plain at Sendai, Natori, Iwanuma, and Watari plus north of Yamamoto, and (3) inundation in the narrow plain at Yamamoto. 4.1 Area 1
One important result of our study is that we established a scheme of quick and accurate measurement of the run-up heights at the remarkably long tsunami inundation area using GPS instruments
Summary
An earthquake of magnitude 9.0 occurred off the Pacific coast of Tohoku, Japan on March 11, 2011 (e.g. Hirose et al, 2011). An earthquake of magnitude 9.0 occurred off the Pacific coast of Tohoku, Japan on March 11, 2011 A large tsunami (designated hereinafter as the 2011 Tohoku-oki tsunami) struck the Pacific coast of eastern Japan After late March, the joint survey group conducted many field surveys to measure the run-up height, flow depth (= inundation depth), and inundation area of the tsunami along the Pacific coast of eastern Japan. More than 5,000 data points have been collected (The 2011 Tohoku Earthquake Tsunami Joint Survey Group (TETJSG), 2011). Such extensive research clarified that the maximum run-up height of the tsunami The 2011 Tohoku-oki tsunami is characterized by its remarkably long inundation distance, especially at the Copyright c The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB
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