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Rupture Probability Map of Major Active Faults in Japan
- Calculating the Probability of Activity over the next Thirty Years -

( Translation of the AIST press release dated October 18, 2005)

Key Points
  1. Colour-coded map showing probability of activity in major active faults in Japan over the next thirty years
  2. Evaluation based on pro-active use of the latest research results
  3. Expected to contribute toward advances in earthquake prediction

Synopsis

The National Institute of Advanced Industrial Science and Technology (AIST) published a nation-wide map that uses colours to show the probability of activity in major active faults within the next thirty years.  The map is based on research done by AIST and other organizations on the history of active faults and serves to summarize the data into segments of activity.  This data can be used to objectively assess the possibility of future activity in Japan’s active faults.

In this map, the faults are divided into behavioral segments, allowing evaluations to be made based on the latest research.  Mid range values were used to represent data that was given in ranges rather than specific figures, and empirical formulas were used to calculate values when data was not available for a particular fault.  Because of this, it was possible to summarize the probability of future activity with a single, representative value for each segment.

AIST has made the data represented in this map available to the public through an online active fault database which will be updated regularly.  In addition, they intend to transform the information in the database into GIS and include other kinds of geographic information.

Figure

Figure : Detail of the Rupture probability map of major active faults in Japan
Probabilities are shown by colour-coded behavioral segments.
The red lines indicate a 3% or greater chance of activity in a particular segment within the next 30 years.
The thick lines indicate an average activity interval of less than 3000 years for a particular segment.

Background

Since the Kobe Earthquake in January 1995, a great deal of attention has been placed on active faults that cause strong inland earthquakes.  The Headquarters for Earthquake Research Promotion has been a leading force in investigating the major active faults in Japan.  Based on these investigations, the Headquarters' Earthquake Research Committee published a long-term assessment of earthquakes caused by active faults.  At AIST, research on active faults has been continuing since the 1970s (initially by the Geological Survey of Japan, a precursor to the current AIST), and the organization has recently been serving as the nation's predominant data center for information on active faults.

History of the Research

AIST has been engaged in investigating major fault lines while also co-operating with other organizations on the creation of an active fault database in line with the policies of the Headquarters for Earthquake Research Promotion.  Research is also being done to enhance assessment of the active faults that cause earthquakes.  The active fault map combines the information collected in the database with the latest assessment methods.

Explanation of the Research

Assessment methods based on AIST's research results were used to create this map.  Faults throughout the country were divided into approximately 550 behavioral segments, and the probability of future activity was calculated for 290 of those segments.  The latest model was used to assess the probability, taking into account both the possibility of activity within a single fault causing an earthquake and the collective activity of a number of faults causing a larger-scale earthquake.

It is necessary to note that this map indicates the probability of activity within a particular segment, but it does not directly predict the probability of an earthquake happening or the scale of such a quake.  Furthermore, this map is one prototype based on the latest research results, but it may differ from the active fault assessment performed by the Headquarters for Earthquake Research Promotion.