NCKU research team develops tsunami warning system
Tainan, Taiwan, December 16, 2013
Using the fact that the tsunami induced atmospheric disturbance waves propagating four times faster than those on sea surface, a Tainan-based research team led by Drs. Chien-Hung Lin and Chia-Hung Chen of National Cheng Kung University (NCKU) and Jann-Yenq Liu of National Central University (NCU) has developed an Ionospheric Tsunami Warning system that could provide early warning for tsunamis occurred 200 km away from the land.
Using both ground-based GPS receivers and ionosphere space weather model, the team showed a plot of warning assuming the tsunamis may occur at fault zones around Taiwan.
It is possible to warn a coming tsunami by looking at the waves propagating in the space of 300 km altitude, according to the team.
Lin said, the plot shows that the leading time for warning is zero for tsunamis occur 201.9 km away, 10 minutes for those occur 370.15 km away, and 20 minutes for 538.40 km away from Taiwan. “The further away the tsunami occurs the longer leading time we’d have.”
Take Japan Tohoku earthquake in 2011as example, Lin pointed out that the tsunami arrived Taiwan coast around 4 hours after the earthquake through sea surface; however, it took only 1.5 to arrive ionosphere above Taiwan and was clearly detected by GPS stations, giving a 2.5-hour leading time.
According to NCKU President, Hwung-Hweng Hwung, who is a hydraulic expert, there were six recorded tsunamis striking Taiwan and chances for another tsunami remain. The tsunami warning system for Japan gives 10 seconds of leading time and it will be much more secured if we have a few minutes of leading time.
The team proposed that setting up the GPS receivers around the Taiwan coast as the tsunami warning system could be very helpful.
The Earth’s ionosphere locates around 100 - 800 km altitude filling with plasma that has equal positive and negative charged particles.
The ionosphere is a thin layer over the surface of the Earth, according to Chen. This thin layer, however, affects the electromagnetic waves transmitted by global positioning system (GPS) due to its high conductivity.
For precise positioning, ionospheric plasma delays the transmitted GPS signals and results in major error in positioning, Chen added. Usefulness of GPS signal delay due to ionosphere is well demonstrated for the study of seismic and tsunami activities.
Currently, tide gauge and Deep-ocean Assessment and Reporting of Tsunamis (DART) are applied to detect the upcoming tsunami as a warning system; however, tide gauge and DART are very expensive and requires scheduled maintenance.
On the other hand, the GPS receivers can detect the ionospheric disturbances induced by tsunamis for a wider range. Moreover, the relatively low-cost two-frequency GPS receiver could be densely setup.
Chen said that a tsunami could be triggered by the movement of the Earth’s plates during an earthquake. The earthquake and tsunami waves will be transport along the Earth’s surface and vertical displacements due to these waves in ground and sea surfaces will produce acoustic waves propagating upward to the atmosphere and ionosphere.
Once the acoustic waves arrive ionosphere, they could travel horizontally away from the epicenter with velocity four times faster than tsunami, Chen revealed.
These are the so-called seismo-traveling ionospheric disturbances (STID). The STID has inference not only to the GPS navigation, but also to the satellite communications.
It was the very first time for scientists to observe such clearest and strongest tsunami-induced STID seen during 11 March 2011 Japan Tohoku by dense ground-based GPS receiver networks.
The team used high dense GPS receivers along Japan and Taiwan and detected the signal of STID after the earthquake. The concentric structures of ionospheric disturbances induced by the tsunami waves were found.
From the propagation times of ionospheric disturbances and tsunami waves, it is found that the ionospheric disturbances arrived Taiwan around 1.5 hours after the earthquake onset while the tsunami waves arrived Taiwan around 4 hours after the earthquake onset, which means there is a 2.5-hour of leading time for warning.
Enditem/
Using the fact that the tsunami induced atmospheric disturbance waves propagating four times faster than those on sea surface, a Tainan-based research team led by Drs. Chien-Hung Lin and Chia-Hung Chen of National Cheng Kung University (NCKU) and Jann-Yenq Liu of National Central University (NCU) has developed an Ionospheric Tsunami Warning system that could provide early warning for tsunamis occurred 200 km away from the land.
Using both ground-based GPS receivers and ionosphere space weather model, the team showed a plot of warning assuming the tsunamis may occur at fault zones around Taiwan.
It is possible to warn a coming tsunami by looking at the waves propagating in the space of 300 km altitude, according to the team.
Lin said, the plot shows that the leading time for warning is zero for tsunamis occur 201.9 km away, 10 minutes for those occur 370.15 km away, and 20 minutes for 538.40 km away from Taiwan. “The further away the tsunami occurs the longer leading time we’d have.”
Take Japan Tohoku earthquake in 2011as example, Lin pointed out that the tsunami arrived Taiwan coast around 4 hours after the earthquake through sea surface; however, it took only 1.5 to arrive ionosphere above Taiwan and was clearly detected by GPS stations, giving a 2.5-hour leading time.
According to NCKU President, Hwung-Hweng Hwung, who is a hydraulic expert, there were six recorded tsunamis striking Taiwan and chances for another tsunami remain. The tsunami warning system for Japan gives 10 seconds of leading time and it will be much more secured if we have a few minutes of leading time.
The team proposed that setting up the GPS receivers around the Taiwan coast as the tsunami warning system could be very helpful.
The Earth’s ionosphere locates around 100 - 800 km altitude filling with plasma that has equal positive and negative charged particles.
The ionosphere is a thin layer over the surface of the Earth, according to Chen. This thin layer, however, affects the electromagnetic waves transmitted by global positioning system (GPS) due to its high conductivity.
For precise positioning, ionospheric plasma delays the transmitted GPS signals and results in major error in positioning, Chen added. Usefulness of GPS signal delay due to ionosphere is well demonstrated for the study of seismic and tsunami activities.
Currently, tide gauge and Deep-ocean Assessment and Reporting of Tsunamis (DART) are applied to detect the upcoming tsunami as a warning system; however, tide gauge and DART are very expensive and requires scheduled maintenance.
On the other hand, the GPS receivers can detect the ionospheric disturbances induced by tsunamis for a wider range. Moreover, the relatively low-cost two-frequency GPS receiver could be densely setup.
Chen said that a tsunami could be triggered by the movement of the Earth’s plates during an earthquake. The earthquake and tsunami waves will be transport along the Earth’s surface and vertical displacements due to these waves in ground and sea surfaces will produce acoustic waves propagating upward to the atmosphere and ionosphere.
Once the acoustic waves arrive ionosphere, they could travel horizontally away from the epicenter with velocity four times faster than tsunami, Chen revealed.
These are the so-called seismo-traveling ionospheric disturbances (STID). The STID has inference not only to the GPS navigation, but also to the satellite communications.
It was the very first time for scientists to observe such clearest and strongest tsunami-induced STID seen during 11 March 2011 Japan Tohoku by dense ground-based GPS receiver networks.
The team used high dense GPS receivers along Japan and Taiwan and detected the signal of STID after the earthquake. The concentric structures of ionospheric disturbances induced by the tsunami waves were found.
From the propagation times of ionospheric disturbances and tsunami waves, it is found that the ionospheric disturbances arrived Taiwan around 1.5 hours after the earthquake onset while the tsunami waves arrived Taiwan around 4 hours after the earthquake onset, which means there is a 2.5-hour of leading time for warning.
Enditem/
Click Num:
Share
