Directions: Read the following passage carefully and then translate
the underlined sentences into Chinese and write your translation on the ANSWER
SHEET.
Tsunamis are impulsively generated sea waves by a disturbance
to or near the ocean. 21. Earthquakes, submarine volcanic
explosions, landslides and the detonation of nuclear devices near the sea can
give rise to such destructive sea waves. By far the most destructive tsunamis
are generated from large shallow-focus earthquakes with an epicenter or fault
line near or in the ocean. Vertical displacements of the earth’s crust along the
rupture resulting from the ocean. Vertical displacements of the earth’s crust
along the rupture resulting from such earthquakes can generate destructive
tsunami waves which can travel across an ocean spreading destruction across
their path. Similar displacements of the ocean floor can also be produced by
volcanic eruptions and submarine avalanches or landslides. However, these
sources are considered as point sources and, although the tsunami waves
generated can be very destructive locally, the energy of the waves is rapidly
dissipated as they travel across the ocean. To forecast tsunamis and
determine terminal run-up and destructiveness, one must be able to evaluate the
parameters of the tsunami source mechanism in real time, often, from inadequate
date. 22. Tsunami source mechanism analysis is difficult given the time
constraints of a warning situation. It will suffice to say that forecasting the
run-up and potential destructiveness of a tsunami at a distant shore will depend
greatly on determining the seismic parameters of the source location such as
magnitude of the earthquake, its depth, its orientation, the length of the fault
line, the size of the crustal displacements, and depth of the water. 23.
Refraction(折射) and diffraction(衍射) processes will affect the energy and
height of the tsunami waves as they travel across the ocean. These effects must
also be determined. Finally, terminal height, run-up, and inundation of the
tsunami at a point of impact will depend upon the energy forcusing effect, the
travel path of the waves, the coastal configuration, and the offshore
bathymetry, only to name a few. Tsunami run-up is the
vertical distance between the maximum height reached by the water on shore and
the mean-sea-level surface. 24. Contrary to meteorological predictions,
tsunami run-up, the final product of earthquake and tsunami investigations is
not possible to forecast with a great degree of accuracy. The reason for this
inadequacy is that the Tsunami Warning System works in a real time frame of
short duration, often with inadequate date and information. Problems of
communication and lack of sufficient station density, often complicate the
process. Forecasting tsunamis requires adequate understanding of the
phenomenon, good and expeditious collection of earthquake and sea level date,
and accruate and expeditious assessment and interpretation of this data.