SECONDARY EARTHQUAKE HAZARDS

Very often earthquakes are the cause of secondary hazards. The factors of the earthquakes’ impact on other natural processes are the following: 1) vertical movement of crustal blocks; 2) shaking; 3) ground properties alteration; 4) longitudinal and rotational waves. The first factor is necessary for emergence of tsunamis, seiches, and internal waves. We know that far not each submarine earthquake generates tsunami. For that, vertical movement of sea bed and certain depth of the earthquake center are necessary. Submarine earthquakes are the most frequent cause of tsunamis, and especially strong ones. The role of submarine earthquakes in creation of internal waves and seiches is of minor importance. The shakes are important factor of awakening of slope processes. This factor is important for emergence of rock and ice falls, landslides, submarine landslides, taluses, rock streams, avalanches. Quite often slope processes caused by shaking are the most dimensioned. Ground properties alteration impacts on other natural processes through ground liquefaction. Vibration transforms ground from solid to viscous semi-fluid condition which resembles quick sand. Above all, this factor is important for mudflows; it is also of some importance for landslides. The impact on volcanic eruptions lies in exposure of one and closing of other cracks in rocks, proportionally to the distribution of impulses of extension-compression through those cracks.