As a follow up to the presentation, the panelists graciously offered to answer a range of questions that were submitted by and voted on by the attending CHRN members. Below are the five questions that were voted the most relevant or interesting to the members.
1. What can we learn from Japan about coastal community recovery after a subduction zone earthquake? In particular, are there abandoned zones that are subsided?
Carrie– I recently took some time to read about the post-earthquake and tsunami recovery, which I did not know very much about. I had seen reports that characterized the recovery as both remarkably quick, and also slow and still underway. I sent an email to Dr. Lori Dengler, emeritus professor from Humboldt State University, who has done a lot of outreach work on tsunami hazards, and also participated in post-2011-tsunami surveys in Japan, to ask for further information, and here is her response:
“Recovery in Japan has been complex and varies from community to community. Every community has changed its land use policies as a result of the tsunami – subsidence is only a small part of the equation. I know most about what happened in Rikuzentakata in Iwate prefecture but I expect other cities have had similar experiences.
- All of these cities and communities have permanently lost population. Rikuzentakata had about 24,000 people before and is at about 16,000 now.
- The city and surroundings have been completely rezoned. No residences are within the inundation zone. In order to make land available for homes, they cut off the tops of mountains creating flat areas at high elevation to build homes.
- The residue from the mountain and hill tops has been used to fill and raise the ground https://www.japantimes.co.jp/news/2017/03/07/national/tsunami-hit-rikuzentakata-rebuilding-high-ground-hoping-thrive-anew/#.WxmxOunT_TM The new business center of the town is being built on this raised ground. The land is still within the 2011 inundation area, but less vulnerable and close enough to higher ground [making evacuation out of the area easier].
- Lower areas are reserved for the memorial park and for farmland. The area was not much of a farming center before and even less so now.
Short answer is – every bit of land has been modified and the new towns look nothing like the old ones.”
Lori is available to answer further questions the group may have, and her email address is lori.dengler@humboldt.edu.
Ann – The Integrated Research Institute of Disaster Sciences (IRIDeS) at Tohoku University also conducts research on recovery from 3.11 and is developing a digital archive (see http://shinrokuden.irides.tohoku.ac.jp/ ). Tohoku University partners with the UW in the UW-TU Academic Open Space, and many of the researchers who have spoken in UW-TU events to date are from IRIDeS.
2. Are there any conversations happening with google maps for emergency evacuation?
Daniel– This question is on the cutting edge of what technology may be capable of today. It is possible to incorporate evacuation maps and routing into map services like Google (assuming they play ball). However, for a local source event it is highly likely that the cell network will be compromised and access to services will be limited. This would be a great idea for distant source evacuations and I will pass it on to EMD to look into.
3. Is there subsidence occurring in northern WA? I noticed in your slide that the bulk of the research is from Copalis to the Columbia.
Carrie– Currently the northern part of the WA coastline is rising. Geodetic arrays show that northwest WA is rising at about 3 mm/yr, and that may explain why there are so few tidal marshes along that stretch of coast, but instead rocky coastline. Areas that are rising are above “locked” portions of the plate interface at depth, and will subside during the next subduction zone earthquake when the crust deforms following a slip.
Daniel– All of Washington’s coastline will subside by some amount in the next subduction zone earthquake. The amount depends largely on the size of the earthquake and/or the places with greatest slip.
4. What are the existing tsunami alerts implemented for general public in Washington (ie. cell phone alerts, alarms, radio, and media)?
Carrie – The National Tsunami Warning Center pushes information to a variety of sources in the event of a tsunami. They send info the NOAA Weather Wire, which gets pushed to NOAA weather radio, State Emergency Managers, and the Coast Guard. Data is also sent to local emergency managers, the media, and other Federal entities.
National Weather Service forecast offices will send out wireless emergency alerts (WEA) and activate the Emergency Alert System (EAS). WEA are alerts that you’ll get automatically if you are in an area with a tsunami warning, and these come to your phone like Amber alerts. On some phones you need to enable these.
The state Emergency Management Division will turn on the tsunami sirens upon receiving a tsunami warning from the National Tsunami Warning Center if a tsunami will arrive within three hours. They are most likely to be activated with adequate warning time in the event of a trans-Pacific tsunami.
There are other ways to get alerts as well. Tsunami.gov website shows current tsunami status. This site also has information about the variety of messages you can subscribe to: https://www.tsunami.gov/?page=productRetrieval One interesting thing I learned is that Twitter may be the fastest source of information on tsunami warnings. For information on receiving SMS info via Twitter, see tsunami.gov.
The WA Emergency Management Division page summarizes a lot of this information and the differences between warnings/watches/advisories at: https://mil.wa.gov/static/78/tsunami
There is a lot of redundancy in the alerting systems, which is good. I can put people in contact with those who can provide further information.
Don’t forget that the most urgent tsunami alert is strong ground shaking, which is your best indicator to move to high ground! Don’t wait for an official warning if you are on the coast, since you may have only 15-20 minutes before the tsunami arrives. Get to high ground or as far inland as possible.
Daniel– To add to Carrie’s response and clarify, the WEA alert system for cell phones is automatically enabled on all compatible smartphones. You would have to manually opt out, not have a WEA enabled phone, or your carrier chooses to opt out of the system (all major carriers participate presently) to not receive the alerts if you are in the alert area.
Another source of alerts are a reverse 911 calling system that is in use in certain counties. Interested persons should contact their county Emergency Management to see what system the county may have and how to opt in to the service.
5. How do you validate your maps? Measurements? Deposits?
Daniel– These maps are models of tsunami inundation from a hypothetical source and they would be difficult to validate in any physical manner. The numerical models have been put through a rigorous benchmarking process by the national tsunami mitigation program (NTHMP) and peer reviewed. The greatest source of uncertainty from the models is in the earthquake scenario. For this reason we use the L1 model which has been shown to encompass 95% of inundation hazard from studies in Oregon. See this paper for a detailed breakdown of Cascadia scenarios: http://activetectonics.coas.oregonstate.edu/paper_files/SP-43_print.pdf
If you are interested in learning more about these questions and answers, please email Sara Brostrom at bros461@ecy.wa.gov. Additionally, please check out the meeting notes for more details about the 2017-2018 CHRN meeting.
