This week PBS’ NewsHour had a feature on a little known earthquake phenomenon known as liquefaction, using Oregon as an example of the dangers. It just happened to air after a 5.9 quake off the Oregon coast, and brings to light serious concerns.
Each year at some point we typically face the risk of landslides in Western Oregon due to saturated soil from our intense rain. Besides the rain, this is because most of the significantly populated areas are in flood plain areas where the soil is light and weak, a sandy substance with few large rocks or other anchors. The rivers that attracted us with such beauty and access to transportation, and the fertile farm lands that benefit from flood plain soils place us in a risky position.
When a significant earthquake happens this soil receives stress from the shaking which, when saturated, can allow water to fill in gaps. The water increases in pressure and needs somewhere to go, with ‘up’ towards the surface often being an answer. What was once a fairly firm and stable ground to stand on can quickly become quicksand. Buildings would sink and possibly collapse, cars could get stuck, landslides become prevalent, and many bridges could be destroyed as their foundation moves – likely leaving coastal communities, suffering possible tsunami damage, isolated. This is soil liquefaction.
Earlier this week I mentioned the 2011 Christchurch earthquake as an example for the risk of aftershocks, and it also has some of the prime examples for the dangers of liquefaction. In addition to the previously listed dangers, underground utilities (like water and sewer) were significantly damaged. Tens of thousands of portable toilets had to be brought in, and mobile water purification machinery.
For more information about the dangers and preparations to our area, take a peak at the video above.