Various heuristically derived algorithms have been developed for predicting earthquakes. Probably the most widely known is the M8 family of algorithms (including the RTP method) developed under the leadership of Vladimir Keilis-Borok. M8 issues a "Time of Increased Probability" (TIP) alarm for a large earthquake of a specified magnitude upon observing certain patterns of smaller earthquakes. TIPs generally cover large areas (up to a thousand kilometers across) for up to five years.[84] Such large parameters have made M8 controversial, as it is hard to determine whether any hits that happened were skillfully predicted, or only the result of chance.
M8 gained considerable attention when the 2003 San Simeon and Hokkaido earthquakes occurred within a TIP.[85] But a widely publicized TIP for an M 6.4 quake in Southern California in 2004 was not fulfilled, nor two other lesser known TIPs.[86] A deep study of the RTP method in 2008 found that out of some twenty alarms only two could be considered hits (and one of those had a 60% chance of happening anyway).[87] It concluded that "RTP is not significantly different from a naïve method of guessing based on the historical rates [of] seismicity."[88]
Accelerating moment release (AMR, "moment" being a measurement of seismic energy), also known as time-to-failure analysis, or accelerating seismic moment release (ASMR), is based on observations that foreshock activity prior to a major earthquake not only increased, but increased at an exponential rate.[89] In other words, a plot of the cumulative number of foreshocks gets steeper just before the main shock.
Following formulation by Bowman et al. (1998) into a testable hypothesis,[90] and a number of positive reports, AMR seemed promising[91] despite several problems. Known issues included not being detected for all locations and events, and the difficulty of projecting an accurate occurrence time when the tail end of the curve gets steep.[92] But rigorous testing has shown that apparent AMR trends likely result from how data fitting is done,[93] and failing to account for spatiotemporal clustering of earthquakes.[94] The AMR trends are therefore statistically insignificant. Interest in AMR (as judged by the number of peer-reviewed papers) has fallen off since 2004.[95]
The occurrence of foreshocks has long been thought to be the most promising avenue in predicting earthquakes. A foreshock is a smaller earthquake that can strike minutes or days before a larger one. Because the rupture process for the earthquakes is still not completely clear, foreshock occurrence may give clues into an earthquake-triggering process. In the Non-Critical Precursory Accelerating Seismicity Theory (N-C PAST), foreshocks happen because of the constant buildup of pressure along the fault lines.[96] This theory is given weight due to seismic measurements. This had led to the conclusion for some scientists that foreshocks are a precursor to a larger event, and should be further studied and considered in earthquake prediction.