Evaluation for Short-Term and Annual Prediction of Earthquakes (ESTAPE)


Mathematical Formulation of ESTAPE

 

Using  Look-up Tables to Calculate ESTAPE

 

Using Look-up Graphs to Calculate ESTAPE 

 

Summary of ESTAPE scores

 

To evaluate the practical results of prediction research, the UN Global Programme -IPASD developed ESTAPE, the Evaluation for Short-Term and Annual Prediction of Earthquakes. ESTAPE provides city administrators and public safety officials with a simple tool to evaluate earthquake predictions so as to distinguish which information should be taken into account in preparing their communities for natural disasters.

How ESTAPE Works

Fundamental Premise:  Any prediction, to be evaluated by ESTAPE, must have been made before the predicted event. In order to ensure the soundness of an ESTAPE evaluation score, the following information need to be on record: (a) the date on which and (b) the agency to which the prediction is submitted and/or accepted, (c) a listing of the method(s) used to generate the prediction, and (d) the name of the individual or group that calculates the ESTAPE score. Adherence to these procedural prerequisites assures a level of confidence in the ESTAPE score.

Key Inputs: ESTAPE is based on three key elements that are typically used to describe earthquakes: (1) magnitude, (2) time and (3) location. ESTAPE looks at the error (misfit) of the elements between the predicted natural event and the actual earthquake.

Scoring of Predictions: If the prediction is completely accurate, i.e. the magnitude time and location of the actual earthquake have values that match those predicted, a 100% score is attributed to each element, giving an overall combined score of 100%. Anything less than a perfect match in any of the elements is scored according to the degree of "error" or "misfit" using the tables ESTAPE-S and ESTAPE-A.

ESTAPE-S (Chu and Col, 1999: Table 1a; United Nations, 1998: Appendix 1) is used to evaluate short-term predictions of earthquakes. Short-term typically implies several weeks to several days before an event. ESTAPE-A (Chu and Col, 1999: Table 2a; United Nations, 1998: Appendix 1) is used to evaluate annual predictions. As long as the forecasted seismic event occurs within one year of the date of submission of the prediction, the score for the time element of an annual prediction is 100%. We note here that ESTAPE scores for short-term predictions are very time sensitive, whereas by comparison, the scoring of annual predictions is much less time-sensitive. For this reason, overall scores for the two types of prediction categories (short-term and annual) are not comparable.

The Strengths of ESTAPE

The ESTAPE approach creates an open environment where any individual can independently evaluate the practical results of prediction research. ESTAPE focuses on providing scientific information in a format that is easy to understand and usable by public officials and members of civil society. In its essence, ESTAPE provides a "yardstick" to measure earthquake prediction reports.

For example, the information contained in the short-term prediction that contributed to the successful early warning for the Qinglong County community of nearly a half-million people during the magnitude M7.8 Tangshan earthquake has an overall ESTAPE score of just over 60%. Thus, information associated with scores of 60% or greater is socially useful.

In the more recent successful early warning for a series of larger than magnitude 6 earthquakes in Jiashi County in western China (Li and Kerr, 1997}, the overall ESTAPE score for the multidisciplinary prediction effort by UNGP-IPASD scientists is 88%. This result is encouraging, for it indicates that by combining a number of different approaches to earthquake prediction, the resulting forecast is more likely to reflect the real situation.

Single predictions can be assessed by ESTAPE for accuracy. Even more potent and revealing is the comprehensive analysis of prediction records that span years of forecasting work using different methodologies. Public administrators can assess these catalogues of past predictions using ESTAPE to see which forecasting technologies have the best record for anticipating earthquakes. The practical benefit of such a screening is that officials and individuals can then choose to act on the information provided, by the more reliable of methodologies.

As an example of a prediction catalogue, crustal stress experts in China who have officially submitted their predictions to the Chinese Seismological Bureau during the last three decades tabulated the ESTAPE scores of more than 175 short-term earthquake predictions made over these years.  Those data showed that the crustal stress method was socially useful (overall ESTAPE-S scores of 60% or more) for one out of every three earthquakes.

For public administrators, annual forecast(s) from methodologies screened by ESTAPE can provide these officials with lead time to set up local earthquake offices, conduct disaster education campaigns and raise public awareness to the importance of networking and communicating changes in the natural environment. Short-term forecasting technologies would also be implemented in the region of concern and lay- monitoring equipment installed with the training of local observers. All of the information gathered through these activities, when integrated into a comprehensive disaster plan, can play a significant role in mitigating the impact of large and sudden natural disasters such as earthquakes.