Future earthquakes

Abstract

While significant progress toward earthquake prediction has occurred in the past four years, the current guarded optimism for continued progress reflects in part revised goals and new definitions. First, recognition [e.g., Evcrndcn, 1982] of the failures of the search during the 1970s for a reliable readilyobservable earthquake precursor has reemphasized the need to understand the fundamental physics of the earthquake generation process [e.g., Stuart, 1984/85] and brought acceptance of a probabilistic rather than a deterministic approach to earthquake prediction. That is, we now accept the notion that earthquake predictions must be couched in terms of probability gain and likelihood estimates. Second, a prediction terminology [Wallace et al., 1984] has been largely adopted that separates and expands •he tasks into long-term earthquake potential (no specific time window) and long-term prediction (time windows. of a few years to a few decades}, where progress has been significant, and intermediate-term prediction (time windows of a few weeks to a few years} and short-term prediction (time windows up to a few weeks}, where progress has lagged. In the 1970s, earthquake prediction usually was taken to mean a deterministic short-term or intermediate-term warning; now, probabilistic estimates of earthquake potential [e.g., Lindh, 1953; Sykes and N&henko, 1984] are accepted as the most reasonable and valid form for expressing the likelihood of a future earthquake and its hazards, as well as the uncertainties. Long-term earthquake potential and long-term earthquake prediction. Although there are differences in the use of the term 'seismic gap' [e.g., Habermann et al., 1983], for our purposes a seismic gap is a segment of a plate boundary that has not re-centl¾ ruptured so that a future shock is anticipated there. The continued successful use of the notion of seismic gaps to anticipate the size and location of large plate boundary-rupturing shocks (e.g., see Nithenko [1985] and the gap-filling 1985 central Chile M = 7.8 shock} is evidence that a methodology for the long-term prediction of at least some large interplate shocks is available. In recent years, attention has been focused on a number of as-yet-unfilled seismic gaps in the United States. On the Pacific-North American plate boundary in Alaska, future large shocks are considered likely along the Shumagin, Yakataga, and Adak sections [e.g., Shearer, 1986; Hags and Gori, 1986], although there is some evidence that little shear strain is accumulating in the crust near the Shumagin section so that a great thrust shock may not occur there [Savage and oeisowtki, 1986a]. Although no large historic shocks have occurred alongthe Washington and Oregon coasts, there is concern that the subducting Juan de Fuca plate could be the source of a great earthquake in the Pacific Northwest [e.g., Heston and Kanamori, 1984]. Similarly, there is concern that a magnitude 7 shock could rupture the historically quiet White Mountain This paper is not subject to U.S. copyright.Published in...

The limits of self-similarity

“…Thus, we cannot know, on the strength of the data alone, whether there is a 63-year fundamental earth rhythm in southern Kanto which is likely to be repeated indefinitely or not. Such an assumption underlies, for example, the prediction of the Parkfield, California earthquakes (Bakun, 1987). If one assumed a self-exciting model, no underlying infinite rhythm would exist, and all one could reasonably state about the date of the next earthquake is that it will depend on the dates of the preceding shocks in some complicated way.…”