Abstract

We present the well-documented case of a 2 · 106 m3 rockslide that was recorded by seismographs to distances of several hundred kilometers and might have entered the Canadian catalog as a bona fide earthquake except for independent knowledge to the contrary. Motivated by the observation of this event, we reexamined the seismograms associated with the 1965 Hope slide in British Columbia, the largest known historical landslide in the Canadian Cordillera, and conclude that these seismograms were the signatures of two rockslides, and not of hypothetical tectonic earthquake triggers as previously suggested (Mathews and McTaggart, 1969; Wetmiller and Evans, 1989). These events raise the general question of differentiation between seismic signals from landslides and true earthquakes. We suggest an LP/SP discriminant as the most obvious, although a resolvable mechanism solution may be even more convincing. Efficiency of energy conversion from potential to seismic is also a diagnostic aid and correlates well with the slope of the slide detachment surface.

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