Tsunami Warning
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Over the past few years, several attempts have been performed to find alternative “chemical proxies” in order to discriminate “tsunami backwash deposits” from “typical marine sediments”. A wide range of statistical tools has been selected... more
Over the past few years, several attempts have been performed to find alternative “chemical proxies” in order to discriminate “tsunami backwash deposits” from “typical marine sediments”. A wide range of statistical tools has been selected in order to investigate the sediments and/or terrestrial soils transportation mechanism during the tsunami inundation period by using several types of chemical tracers. To relate the physical and chemical characteristics of Typical Marine Sediments (TMS),Tsunami Backwash Deposits (TBD), Onshore Tsunami Deposits (OTD) and Coastal Zone Soils (CZS) with their synchrotron radiation based micro-X-ray Fluorescence (μ-SXRF) spectra, the μ- SXRF spectra were built in the appropriate selected spectra range from 3,000 eV to 8,000 eV. Further challenges were considered by using the first-order derivative μ-SXRF spectra coupled with Probability Distribution Function (PDF), Hierarchical Cluster Analysis (HCA) and Principal Component Analysis (PCA) in order to investigate the elemental distribution characteristics in various types of terrestrial soils and marine sediments. Dendrographic classifications and multi-dimensional plots of principal components (i.e. bi-polar and three dimensional plots) could indicate the impacts of terrestrial soils and/or marine sediments transport on onshore and/or offshore during the tsunami inundation period. Obviously, these advanced statistical analyses are quite useful and provide valuable information and thus shed new light on the study of paleotsunami.
The Honshu, Japan earthquake of 11th March 2011, caused severe hazard in Japan and neighboring countries. It revealed the need and importance of warning system for Tsunami generation to minimize the casualties. Seismograms of the Honshu... more
The Honshu, Japan earthquake of 11th March 2011, caused severe hazard in Japan and neighboring countries. It revealed the need and importance of warning system for Tsunami generation to minimize the casualties. Seismograms of the Honshu earthquake event (recorded by broadband seismograms, being operated in the NW Himalaya by Wadia Institute of Himalayan Geology, Dehradun) are used for quick prediction of tsunami. The frequency content of these seismo-
grams is studied and energy content in high frequencies is calculated, which is used to give tsunami warning. It is observed that wavelet coefficients for frequencies greater than 0.33 Hz tsunamigenic earthquakes do not show significant energy in the spectrum. However, significant energy is found in wavelet spectrum of non tsunamigenic earthquake. In this paper we present the wavelet analysis on the Honshu, Japan earthquake of 11th March, 2011. Some other global tsunamigenic and non-tsunamigenic events are also analyzed for test and comparison purpose of the methodology used.
grams is studied and energy content in high frequencies is calculated, which is used to give tsunami warning. It is observed that wavelet coefficients for frequencies greater than 0.33 Hz tsunamigenic earthquakes do not show significant energy in the spectrum. However, significant energy is found in wavelet spectrum of non tsunamigenic earthquake. In this paper we present the wavelet analysis on the Honshu, Japan earthquake of 11th March, 2011. Some other global tsunamigenic and non-tsunamigenic events are also analyzed for test and comparison purpose of the methodology used.
- by Sachin Kumar Sengar and +1
- •
- Earthquake, Tsunami Warning
"The Great East Japan moment magnitude (Mw) 9.0 earthquake occurred at 14:46 (Japanese Standard Time) on March 11th 2011. Significant seabed displacement generated thesubsequent tsunami, which caused significant damage in Iwate, Miyagi,... more
"The Great East Japan moment magnitude (Mw) 9.0 earthquake occurred at 14:46 (Japanese Standard Time) on March 11th 2011. Significant seabed displacement generated thesubsequent tsunami, which caused significant damage in Iwate, Miyagi, Fukushima and Ibaraki Prefectures. As a result of this event over 19,000 people are dead or missing, with over 295,000 collapsed buildings along 600 km of affected coastline.
Reconnaissance-level analysis of evacuation preparedness and actions related to thetsunami has been carried out using semi-structured interviews with local disaster prevention officials and emergency services officials. Interviews were carried out in Tarō Town, Kamaishi City, Ōfunato City (Iwate Prefecture) and Kesennuma City, Minami-Sanriku Town, Ishinomaki City and Natori City (Miyagi Prefecture). The interviews covered tsunami
awareness, observations and response to natural and informal warnings; style and derivation of evacuation maps; official warning timing and dynamics; evacuation timing, mechanisms and issues; and vertical evacuation buildings – availability, designation, public awareness, utilisation, relationship to maps, and post-event review. The report also presents examples of
hazard and evacuation maps and signs employed in the Tōhoku region.
Experiences in Tōhoku during this event are relevant to tsunami mitigation activities in the State of Washington and in New Zealand, which co-funded this research. These areas have
local earthquake and tsunami risk posed by the Cascadia Subduction Zone and the offshore Hikurangi subduction margin, respectively. This report provides recommendations for further
development of tsunami mitigation activities in these areas, based on findings from the interviews.
Overall there was a 96% survival rate of those living in the inundated area of the municipalities visited. This can be attributed to mostly effective education and evacuation procedures. Schools education, hazard maps and exercises appear to be the most common forms of education. Community involvement in planning of evacuation maps, routes and buildings is common, with many places conducting regular community-level exercises. Hazard and evacuation maps lacked consistency and both maps and safe locations were generally designed for a tsunami height that under-represented the worst case scenario.
The natural warning of long ground shaking (reported as more than two minutes, and often more than three) was widely agreed as enough by itself to have triggered evacuation. Sea walls reduced effective observation of the natural warning of unusual ocean behaviour in many places, and fostered a false sense of security in some locations.
Although an early warning system is often seen publicly as key infrastructure in enhancing tsunami resilience, the expectation of official warnings (and their content) may have slowed the time taken for people to initiate evacuation in Tōhoku, compared to if there had been total reliance on natural warnings. Exposure to previous false ‘major tsunami’ warnings apparently led to complacency in this event, despite this earthquake feeling much larger than anything previously experienced. The philosophy of tsunami tendenko was shown to be a positive education tool which promoted immediate self-evacuation and save many lives.
Peoples’ movements during and after evacuation reveal that many people died unnecessarily due to delayed evacuation or non-evacuation as a result of social or parental responsibility, lack of education or scepticism of warnings. Widespread use of motor vehicles caused traffic congestion in some areas, when walking, running or cycling would have been much more effective and saved lives.
Many people returned to the evacuation zone too early in some places because they had not seen the wave arrive at the expected time given in official warnings, or because they
expected no more waves to arrive. It is critical that people have the awareness that the first wave may come later than estimated by rapid scientific analysis, and the largest wave may
not be the first.
The evacuation strategy in place at March 11th 2011 was appropriate in that it sent people to safe locations, used maps and community involvement and was regularly exercised in many
places. Some evacuation centres were not located far enough inland or on high enough ground because they were not designated using the worst-case tsunami inundation.
There was extensive effective use of both designated and informal vertical evacuation buildings. The most important considerations for effective use are sufficient height (in relation to expected inundation depth), reinforced concrete construction, community engagement, owner agreement, signage, 24-hour access and evacuee welfare. More than one building owner considered use of their building in evacuation as corporate social responsibility. To enhance evacuee safety it is prudent to minimise the opportunities for spilled accelerants such as oil, and debris such as logs in tsunami-prone locations."
SEE ALSO: Tsunami Vertical Evacuation Buildings - Lessons for International Preparedness Following the 2011 Great East Japan Tsunami, Journal of Disaster Research; http://www.fujipress.jp/finder/xslt.php?mode=present&inputfile=DSSTR000700070005.xml (requires free registration to access paper)
Reconnaissance-level analysis of evacuation preparedness and actions related to thetsunami has been carried out using semi-structured interviews with local disaster prevention officials and emergency services officials. Interviews were carried out in Tarō Town, Kamaishi City, Ōfunato City (Iwate Prefecture) and Kesennuma City, Minami-Sanriku Town, Ishinomaki City and Natori City (Miyagi Prefecture). The interviews covered tsunami
awareness, observations and response to natural and informal warnings; style and derivation of evacuation maps; official warning timing and dynamics; evacuation timing, mechanisms and issues; and vertical evacuation buildings – availability, designation, public awareness, utilisation, relationship to maps, and post-event review. The report also presents examples of
hazard and evacuation maps and signs employed in the Tōhoku region.
Experiences in Tōhoku during this event are relevant to tsunami mitigation activities in the State of Washington and in New Zealand, which co-funded this research. These areas have
local earthquake and tsunami risk posed by the Cascadia Subduction Zone and the offshore Hikurangi subduction margin, respectively. This report provides recommendations for further
development of tsunami mitigation activities in these areas, based on findings from the interviews.
Overall there was a 96% survival rate of those living in the inundated area of the municipalities visited. This can be attributed to mostly effective education and evacuation procedures. Schools education, hazard maps and exercises appear to be the most common forms of education. Community involvement in planning of evacuation maps, routes and buildings is common, with many places conducting regular community-level exercises. Hazard and evacuation maps lacked consistency and both maps and safe locations were generally designed for a tsunami height that under-represented the worst case scenario.
The natural warning of long ground shaking (reported as more than two minutes, and often more than three) was widely agreed as enough by itself to have triggered evacuation. Sea walls reduced effective observation of the natural warning of unusual ocean behaviour in many places, and fostered a false sense of security in some locations.
Although an early warning system is often seen publicly as key infrastructure in enhancing tsunami resilience, the expectation of official warnings (and their content) may have slowed the time taken for people to initiate evacuation in Tōhoku, compared to if there had been total reliance on natural warnings. Exposure to previous false ‘major tsunami’ warnings apparently led to complacency in this event, despite this earthquake feeling much larger than anything previously experienced. The philosophy of tsunami tendenko was shown to be a positive education tool which promoted immediate self-evacuation and save many lives.
Peoples’ movements during and after evacuation reveal that many people died unnecessarily due to delayed evacuation or non-evacuation as a result of social or parental responsibility, lack of education or scepticism of warnings. Widespread use of motor vehicles caused traffic congestion in some areas, when walking, running or cycling would have been much more effective and saved lives.
Many people returned to the evacuation zone too early in some places because they had not seen the wave arrive at the expected time given in official warnings, or because they
expected no more waves to arrive. It is critical that people have the awareness that the first wave may come later than estimated by rapid scientific analysis, and the largest wave may
not be the first.
The evacuation strategy in place at March 11th 2011 was appropriate in that it sent people to safe locations, used maps and community involvement and was regularly exercised in many
places. Some evacuation centres were not located far enough inland or on high enough ground because they were not designated using the worst-case tsunami inundation.
There was extensive effective use of both designated and informal vertical evacuation buildings. The most important considerations for effective use are sufficient height (in relation to expected inundation depth), reinforced concrete construction, community engagement, owner agreement, signage, 24-hour access and evacuee welfare. More than one building owner considered use of their building in evacuation as corporate social responsibility. To enhance evacuee safety it is prudent to minimise the opportunities for spilled accelerants such as oil, and debris such as logs in tsunami-prone locations."
SEE ALSO: Tsunami Vertical Evacuation Buildings - Lessons for International Preparedness Following the 2011 Great East Japan Tsunami, Journal of Disaster Research; http://www.fujipress.jp/finder/xslt.php?mode=present&inputfile=DSSTR000700070005.xml (requires free registration to access paper)
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