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This chapter focuses on the use of information about earthquakes and earthquake-induced landslides, volcanic eruptions, and tsunamis (ocean waves caused by earth movement) to improve development planning in Latin America and the Caribbean.For each hazard the chapter presents physical characteristics, information sources, data available for determining the threat posed, and mitigation measures; Chapter 10 provides a more detailed discussion of landslides.The earlier geologic hazard mitigation is incorporated into the development planning process, the more effective it is. Furthermore, it must be available at the right time, since integrated development planning, if it is to be efficient, operates on a tight schedule.
Estimates of an occurrence of a given hazardous event are probabilistic, based on consideration of the magnitude of an event and its occurrence in time and space.
Other measures-duration, areal extent, speed of onset, geographic dispersion, frequency-can be anticipated with even less precision.
(In a few areas where known hazards exist, e.g., Nevado del Ruiz, Mt. Helens and the San Andreas Fault, instrumentation has been installed which can give an indication of impending activity.) Tsunamis travel great distances over the open ocean; one triggered off the cost of Peru might hit the coast of Japan 18 hours later, giving reasonable warning time, but the same tsunami would hit the coast of Peru with almost no warning at all.
In addition to speed of onset, geologic hazards also tend to have impacts covering large areas.
Friction produces stress and temperature increases; the subducted rock melts and expands, causing additional stress and upward movement of the magma.