towns and cities on the west coast of Vancouver Island, such as Tofino and Ucluelet, are at risk for a sudden, earthquake initiated, 1–2 m subsidence. San Andreas Fault connection Studies of past earthquake traces on both the northern San Andreas Fault and the southern Cascadia subduction zone indicate a correlation in time which may be evidence that quakes on the Cascadia subduction zone may have triggered most of the major quakes on the northern San Andreas during at least the past 3,000 years or so. The evidence also shows the rupture direction going from north to south in each of these time-correlated events. The 1906 San Francisco earthquake seems to have been a major exception to this correlation, however, as it was not preceded by a major Cascadia quake. Earthquake timing The last known great earthquake in the northwest was the 1700 Cascadia earthquake, years ago. Geological evidence indicates that great earthquakes (> magnitude 8.0) may have occurred sporadically at least seven times in the last 3,500 years, suggesting a return time of about 500 years. Seafloor core evidence indicates that there have been forty-one subduction zone earthquakes on the Cascadia subduction zone in the past 10,000 years, suggesting a general average earthquake recurrence interval of only 243 years. Of these 41, nineteen have produced a "full margin rupture", wherein the entire fault opens up. By comparison, similar subduction zones in the world usually have such earthquakes every 100 to 200 years; the longer interval here may indicate unusually large stress buildup and subsequent unusually large earthquake slip. There is also evidence of accompanying tsunamis with every earthquake. One strong line of evidence for these earthquakes is convergent timings for fossil damage from tsunamis in the Pacific Northwest and historical Japanese records of tsunamis. The next rupture of the Cascadia Subduction Zone is anticipated to be capable of causing widespread destruction throughout the Pacific Northwest. Forecasts of the next major earthquake Prior to the 1980s, scientists thought that the subduction zone did not generate earthquakes like other subduction zones around the world, but research by Brian Atwater and Kenji Satake tied together evidence of a large tsunami on the Washington coast with documentation of an orphan tsunami in Japan (a tsunami without an associated earthquake). The two pieces of the puzzle were linked, and they then realized that the subduction zone was more hazardous than previously suggested. In 2009,