(1) Strong ground vibration. Because seismic waves reach the
coast before tsunamis, they must leave the coast quickly and
move to inland heights.
(2) Abnormal seawater retreat or rose suddenly. The seawater
retreats first before the tsunami arrives at the coasts, which
is a bit like ebb tide, but the sea water retreats further, many
marine animals such as fish and shrimp are often left in the
shallows when sea water recedes abnormally. At this time we must
not go to pick up fish or watch the fun, must quickly leave the
coast, move to the inland high places. Unlike normal high tides,
tsunami waves are very regular, with high waves like a wall.
Escape at the sight of such a wave.
(3) A low-frequency roar will occur before the tsunami arrives.
Unlike normal waves, strange low-frequency waves (roars) heard
at the seaside should be evacuated immediately to safe heights.
(4) Ships in shallow waters suddenly bumps violently up and down.
(5) In the shallow waters not far from the coast, the sea suddenly
turns white and a long bright wall of water appears in front of it.
(6)The sea suddenly retreated far away from the beach, and the beach
looks much larger than usual, with a large area of bare sand.
(7)Animals behave strangely: they may suddenly leave, gather in
groups, or enter places where they usually don't go.
Tsunami Warning and Forecasting(1)
Tsunami is predictable.
The tsunami is so powerful that early warning is very important in
order to win the time of early evacuation and reduce casualties
and property losses. Seismic waves travel along the earth's crust
much faster than tsunami wave, providing valuable time for tsunami
prediction in advance. The Global Tsunami Warning System Coordination
Group was established in 1964. Tsunami warning systems are well
developed in the Pacific Ocean due to the frequent occurrence of
tsunamis. In 1965, 26 countries and regions cooperated to establish
the Pacific Tsunami Warning Center (PTWC) in Hawaii (Fig. 5-2).
Once an earthquake occurs in the ocean from the seismograph, PTWC
can calculate the time when the tsunami arrives in all parts of
the Pacific Ocean and give an early warning, China joined the Pacific
Tsunami Prediction Center in 1983. The Pacific Tsunami Warning Center
has nearly 100 monitoring stations in the Pacific Ocean, which can
monitor sea level fluctuations, the occurrence and intensity of tsunamis
at any time. Monitoring stations are connected by satellites, cables
and early warning systems, and early warning centers are connected to
huge seismic monitoring networks that can observe the earthquakes may
cause tsunamis in the first time, so as to send out warnings in time.
Figure 5-2 Pacific Tsunami Forecasting Center
Since there are few tsunamis in the history of the Indian Ocean
and there has been no tsunami in the past 100 years, no country has
participated in the tsunami warning system, the Indian Ocean tsunami
in 2004 caused heavy casualties and had no early warning system.
Fifteen minutes after the earthquake, the Pacific tsunami warning
center issued early warning information to countries participating
in the joint warning system. The Indian Ocean countries did not join
the system, so they did not receive early warning information.