November 30th, 2018 will not be forgotten anytime soon in the minds of Alaskans. A 7.2 magnitude earthquake centered just south of Big Lake, Alaska shook south central Alaska with significant damage to infrastructure, homes, businesses, and lake ice. Taking this opportunity to see what type of damage occurs to lake ice during such a large magnitude earthquake, we headed out to explore local lakes. Here are our observations and suggestions if you have happen to get caught on the ice during a major earthquake event.
The majority of severe damage occurs along the shoreline where the lake ice meets the ground along the lakes edge. I would always tell clients while we are ice fishing, if we experience an earthquake, quickly and safely move to shore. This is no longer a valid suggestion and I will advise against it. The section of shoreline ice that was destroyed was out far enough that the depth of water is now a serious risk consideration should someone enter the water at that point. The ice was damage in small and medium fragments while some large chunks of ice were pushed onto shore. Along the shoreline during a major earthquake is the most hazardous location!!! Do not attempt to run off the ice towards the shoreline during a major earthquake!!!
While the shoreline ice was extremely damaged, much of the larger lakes (Finger and Big) main lake ice was mostly in tact although fractured in locations. The earthquake creates a wave under the ice, moving as such until it is stopped by the shoreline. Having stood on the lake two days later with a 5.1 magnitude earthquake, it was obvious that while the ice is moving, it is not moving violently enough to cause someone to fall. If you find yourself on the ice during a major earthquake, stay low, stay balanced and watch for fractures in the ice. Move away from the fractures and center yourself on the sheet of ice until the earthquake has subsided. Once the earthquake has stopped, quickly collect your gear and make your way towards shore very carefully identifying faults in the ice. Stay as centered as you can and avoid sections that have multiple cracks intersecting. As you approach the shoreline, observe where the damage is most or less significant and choose your exit wisely. If you feel exit off the lake is not possible and you are unsure of water depth, do not risk it, call local authorities to assist with an on the ice rescue.
While the main lake ice on the larger lakes seemed to fair well compared to the shoreline it's comparison to smaller lakes in not equivalent. Smaller lakes seemed to fracture more significantly throughout the entirety of the lake rather then just along the shoreline. Perhaps there is less of a surface area of ice to absorb the energy of the earthquake. Less surface area, more prone to damage. The same rule applies with actions you take during the earthquake if you find yourself on a smaller body of water. Hold tight, stay low, and watch for fractures. As the ice fractures move yourself towards the center of the ice sheet and prepare for more fractures. Once the earthquake has stopped, quickly and smartly, attempt to exit the lake being very observant of the ice conditions as they lay ahead. If you ever have a doubt about reaching shore, stop. It's not worth the risk.
When you are on the ice in an earthquake prone area it would be wise to carry some safety items. Personal recovery can be greatly assisted with throw ropes, ice spikes, and of course a cell phone. Some companies make ice suits with built in flotation that would allow someone, who enters the water, to remain on the surface without struggle. There are numerous safety videos on the web that demonstrate how to overcome the initial cold shock and self extraction should you enter the water without a flotation device, watch them. However, the most important piece of safety equipment is a buddy. Always travel on the ice with someone, there is safety in numbers.
As we move deeper into winter and the ice gets thicker continue to plan for a large earthquake. I can assure you, I will no longer be parking a vehicle on the ice in close proximity to other vehicles. I will not have any reservations about driving on the ice as a sheet of 20 inch ice can support the weight of any vehicle just fine. However, exit from the lake in vehicle will require a lot more caution, risk assessment, and responsible decision making. Don't let the earthquake control your winter activities on the ice, just prepare for the worse in case another big shake has an untimely appearance. We were on the ice the day after the earthquake with no worries but plenty of cautious decisions and risk mitigations. I hope your days ahaead are filled with good fishing and better catching!!!