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Estimates of long‐term probabilities for future great earthquakes in the Aleutians
Author(s) -
Jacob Klaus H.
Publication year - 1984
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl011i004p00295
Subject(s) - geology , seismology , conditional probability , seismic zone , probability distribution , distribution (mathematics) , induced seismicity , statistics , mathematics , mathematical analysis
We compute probabilities for future great earthquakes in the Aleutian arc. Probability distributions are fitted to recurrence periods of great Aleutian events (M w ≥ 7.8) since 1788. Given a probability distribution and date of the last great earthquake in each arc segment, time‐dependent conditional probabilities are determined for future periods of interest. We obtain for the next two decades high probabilities (99 to 30%) for great earthquakes in the Shumagin, Yakataga, Unalaska and Kommandorski seismic gaps. These probabilities are higher than for any other assessed region of the U.S. believed to be capable of great earthquakes. Low probabilities (17 to 9%) are found for segments that ruptured most recently in 1965, 1964 and 1957. Recurrence periods for great earthquakes measure on average about 80 years but vary substantially. Whether recurrence periods for great Aleutian earthquakes follow a normal, log‐normal or any other probability distribution is not resolved because in most arc segments the known seismic record embraces at best one or two recurrences. The resulting uncertainty affects the magnitude of estimated probabilities, especially in seismic gaps that have not ruptured for a long time. In some instances a normal distribution yields a three times higher probability than the corresponding log‐normal distribution.