Geoscience Reference
In-Depth Information
Landslides and earthquakes are often intimately related in seismically active
regions. Such is the case in New Zealand where the long-term history of land-
slides can also be used to infer the nature of the earthquake hazard. Likewise,
landslides and tsunamis are related in some locations such as the Canary Islands.
Here, side-scan sonar images of prehistoric massive slides now beneath the ocean
surface show that these events would probably have created massive tsunamis.
Dendrochronology has proved useful for reconstructing the frequency of many
natural extreme events and landslides are no exception. Scars from landslide
impacts and tilted stems help to identify the precise year that these events
occurred. Apart, from tree rings, standard geological dating techniques proba-
bly do not provide the resolution required to determine detailed frequencies
of landslide events. As such it is difficult to identify as yet whether landslides
show any clustering over time. But like earthquakes, the prehistoric record cer-
tainly provides a good indication of the magnitude of the events possible in an
area and, therefore, provides an invaluable aid to the assessor of risks from this
natural hazard.
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