Prediction of Strong Ground Motion with “Recipe”
Kojiro Irikura
Kyoto University and Aichi Institute of Technology
4-3-2, Itachibori, Nishi-ku, Osaka 550-0012, Japan

Summary
A recipe for estimating strong ground motions from specific earthquakes is proposed based on source
characteristics from the waveform inversion using strong motion data. Main features of the source
model are characterized by two kinds of parameters, which we call: outer and inner fault parameters.
The outer fault parameters are to outline the overall pictures of the target earthquakes such as entire
source area and seismic moment The inner fault parameters are parameters characterizing fault
heterogeneity inside the fault area. Further, other fault parameters are considered to complete thesource model such as the starting point and propagation pattern of the rupture. The seismic hazard
maps for future large earthquakes with high probability of occurrence potential are made following theidea of the recipe proposed here by two governmental organizations, the Head Quarter of Earthquake
Research Center and Central Disaster Prevention Council in Japan.

1. Introduction
From recent developments of the waveform
inversion analyses for estimating rupture processusing strong motion data during large earthquakes,
we have understood that strong ground motion isrelevant to slip heterogeneity inside the source
rather than average slip in the entire rupture area.
Asperities are characterized as regions that havelarge slip relative to the average slip on the rupturearea, based on slip distributions estimated from thesource inversion (Somerville et al. , 1999). Then,the asperity areas as well as total rupture areas scalewith seismic moment. We examined that strong
motion generation areas approximately coincidewith the asperity areas where stresses are largely
released (Miyake et al., 2003). Based on the scaling
relationships, the source model for the prediction ofstrong ground motions is characterized by two
kinds of parameters, outer and inner fault
parameters. The outer fault parameters areconventional parameters such as rupture area andseismic moment to outline the overall pictures ofthe source fault. The inner fault parameters aredefined as slip heterogeneity inside the source, areaof asperities, and stress drop on each asperity. We
developed a recipe for predicting strong groundmotions, which is to characterize the source modelfor the future large earthquakes based on geologicaland geomorphological surveys.

Japan is based on the 1999 fundamental mission
statement governing earthquake research over the nextten years as “The promotion of earthquake research –comprehensive basic policies for the promotion ofseismic
research
throughtheobservation,measurement, and survey of earthquakes –“,established by the Headquarters for Earthquake
Research Promotion (Director: Ministry of Education,

2. Strong Motion Prediction Program in Japan

Fig. 1. Probability of suffering strong motion morethan seismic intensity 6- within 30 years from 2005
AD (Earthquake Research Committee, 2005).

The basic policy for defining the seismic hazard inCulture, Sports, Science, and Technology). It initiatedthe creation of seismic hazard maps by promoting thesurvey of active faults, long-term evaluation ofoccurrence potentials and prediction of strong groundmotion.
There were established two subcommittees underthe Headquarter. One is for long term evaluation ofearthquakes. The other is for strong motion evaluationthat started in 1998 to make the seismic hazard maps
from two different approaches, probabilistic anddeterministic.
The probabilistic seismic hazard map is shown as
the predicted likelihood of a ground motion level suchas PGA, PGV, and seismic intensity occurring in agiven area within a set period of time shown in Fig. 1.
It provides important information for land planning,
design standards of structures and people’senlightening as to seismic risks.
The deterministic seismic hazard map is shown as

the distribution of the ground motion level predicted
for individual specific earthquakes assuming theirfault models. The strong ground motions at specificsites near each source fault are estimated as time
history, based on the recipe characterizing the sourceand numerical simulation considering the 3-Dstructures from the source to the target sites. Suchtime histories of the ground motions are useful for
nonlinear dynamic analysis of structures, which isneeded to design earthquake-resistant buildings andcritical structures such as bridges, lifelines, electric
power plants, and so on.
The Central Disaster Prevention Council belonging
to the Cabinet Office also made seismic hazard maps
for the Tokai, Tonankai and Nankai earthquakes
shown as Fig. 2, which are feared likely to occur
within the next half century. They made damage andcausality estimates to determine disaster management
plans for those earthquakes.

Fig. 2. Seismic intensity map from three earthquakes, Tokai, Tonankai, and Nankai earthquakes continuouslygenerated (Central Disaster Prevention Council, 2003).

References
Miyake H, Iwata T, Irikura K. (2003). “Source
characterization for broadband ground motion
simulation: Kinematic heterogeneous source modeland strong motion generation area.” Bull. Seism.
Soc. Am., 93: 2531-2545.

Somerville, P. G., K. Irikura, R. Graves, S. Sawada, D.
Wald, N. Abrahamson, Y. Iwasaki, T. Kagawa, N.
Smith, A. Kowada (1999). “Characterizing crustal
earthquake slip models for the prediction of strong
ground motion”, Seism. Res. Lett., 70, 59-80.