Earthquake forecast models for inland Japan based on the G-R law and the modified G-R law

Fuyuki Hirose,Kenji Maeda

doi:10.5047/eps.2010.10.002

Abstract

The frequency-magnitude distribution expressed by the Gutenberg-Richter (G-R) law is the basis of a simple method to forecast earthquakes. The frequency-magnitude distribution is sometimes approximated by the modified G-R law, which imposes a maximum magnitude. In this study we tested three earthquake forecast models: Cbv (the Constant b-value model) based on only the G-R law with a spatially constant b-value, Vbv (the Variable b-value model) based on only the G-R law with regionally variable b-values, and MGR (the Modified G-R model) based on the modified G-R or G-R law (chosen according to Akaike Information Criterion) with regionally variable b-values. We also incorporated aftershock decay and minimum limits of expected seismicity in these models. Comparing the results of retrospective forecasts by the three models, we found that MGR was almost always better than Vbv; Cbv was better than Vbv for short-term (one year) forecasts; little difference between MGR and Cbv for short-term forecasts; and MGR and Vbv tended to be better than Cbv for long-term (three years or longer) forecasts. We propose the use of MGR in the earthquake forecast testing experiment by the Collaboratory for the Study of Earthquake Predictability for Japan.

Highlights

An earthquake forecast testing experiment was started by the Collaboratory for the Study of Earthquake Predictability (CSEP) for Japan on November 1, 2009 (Nanjo et al, 2009)
Because the b-value varies spatially (e.g., Wiemer and Wyss, 1997; Hirose et al, 2002a, b; Schorlemmer et al, 2005), we made an earthquake forecast model using b-values estimated for each region to capture the regionality of seismicity, which we call the Vbv model
This paper reports the results of comparison of retrospective forecasts made using the MGR, Vbv, and Cbv models

Summary

Introduction

An earthquake forecast testing experiment was started by the Collaboratory for the Study of Earthquake Predictability (CSEP) for Japan on November 1, 2009 (Nanjo et al, 2009). The Gutenberg-Richter (G-R) law (Gutenberg and Richter, 1944) is the basis of a simple method to predict earthquakes (e.g., Earthquake Research Committee, 2006; Wiemer and Schorlemmer, 2007). The Earthquake Research Committee (2006), for example, estimated nationwide occurrence probabilities for earthquakes in Japan whose location cannot be predefined. They used the G-R law with a spatiotemporally constant b-value, which we call the Cbv (constant b-value) model here. Because the b-value varies spatially (e.g., Wiemer and Wyss, 1997; Hirose et al, 2002a, b; Schorlemmer et al, 2005), we made an earthquake forecast model using b-values estimated for each region to capture the regionality of seismicity, which we call the Vbv (variable b-value) model

Methods

Results

Discussion

Conclusion