<P> However, some underlying assumptions about seismic gaps are now known to be incorrect . A close examination suggests that "there may be no information in seismic gaps about the time of occurrence or the magnitude of the next large event in the region"; statistical tests of the circum - Pacific forecasts shows that the seismic gap model "did not forecast large earthquakes well". Another study concluded that a long quiet period did not increase earthquake potential . </P> <P> 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 . 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 . </P> <P> M8 gained considerable attention when the 2003 San Simeon and Hokkaido earthquakes occurred within a TIP . In 1999, Keilis - Borok's group published a claim to have achieved statistically significant intermediate - term results using their M8 and MSc models, as far as world - wide large earthquakes are regarded . However, Geller et al. are skeptical of prediction claims over any period shorter than 30 years . A widely publicized TIP for an M 6.4 quake in Southern California in 2004 was not fulfilled, nor two other lesser known TIPs . 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). It concluded that "RTP is not significantly different from a naïve method of guessing based on the historical rates (of) seismicity ." </P> <P> 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 . In other words, a plot of the cumulative number of foreshocks gets steeper just before the main shock . </P>

What earthquake pattern have scientists observed in california
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