The fault distance is referred to in NIED’s definition.
In the figure, the empirical attenuation relation by Si and
Midorikawa (2000), with a moment magnitude of 6.8, is also illustrated. The empirical relation goes through the center of
the recorded values. This means that the earthquake produced
average groundmotion. However, in a very short range, the
discrepancy between the recorded value sand the empirical
ones is very large. Several PGA values exceed the gravity unit
(e.g., 980cm/s2) in the short range. The largest PGA is
obtained at Ichinoseki-Nishi Station (IWTH25), which is the
closest station to the hypocenter (Fig. 3). APGA value of
3866 cm/s2 was obtained for the vertical component, which is
a world record of PGA. This ground motion will be discussed
later in the chapter. The largest horizontal PGA value of
2449cm/s2 was obtained at AKTH04.