Conditional Probabilities for Large Events Estimated by Small Earthquake Rate

Yi Hsuan Wu, Chien Chih Chen, Hsien Chi Li

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


We examined forecasting quiescence and activation models to obtain the conditional probability that a large earthquake will occur in a specific time period on different scales in Taiwan. The basic idea of the quiescence and activation models is to use earthquakes that have magnitudes larger than the completeness magnitude to compute the expected properties of large earthquakes. We calculated the probability time series for the whole Taiwan region and for three subareas of Taiwan—the western, eastern, and northeastern Taiwan regions—using 40 years of data from the Central Weather Bureau catalog. In the probability time series for the eastern and northeastern Taiwan regions, a high probability value is usually yielded in cluster events such as events with foreshocks and events that all occur in a short time period. In addition to the time series, we produced probability maps by calculating the conditional probability for every grid point at the time just before a large earthquake. The probability maps show that high probability values are yielded around the epicenter before a large earthquake. The receiver operating characteristic (ROC) curves of the probability maps demonstrate that the probability maps are not random forecasts, but also suggest that lowering the magnitude of a forecasted large earthquake may not improve the forecast method itself. From both the probability time series and probability maps, it can be observed that the probability obtained from the quiescence model increases before a large earthquake and the probability obtained from the activation model increases as the large earthquakes occur. The results lead us to conclude that the quiescence model has better forecast potential than the activation model.

Original languageEnglish
Pages (from-to)183-196
Number of pages14
JournalPure and Applied Geophysics
Issue number1
StatePublished - 1 Jan 2016


  • Gutenberg–Richter relation
  • Probabilistic forecasting
  • ROC test
  • seismic activation
  • seismic quiescence
  • Taiwan seismicity


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