The State of Washington has been reminded that we are in a high-risk area for earthquakes. Olympia and Tacoma took the majority of the brunt of this earthquake, leaving Redmond and the other Eastside cities with minor damage. There is still concern surrounding the shallow fault that runs through downtown Seattle and the Eastside following I-90. One might believe that once you are outside you are on solid ground, but this isn t always the case. A significant worry is that during a shallow earthquake, area with loose soil will experience liquefaction, compounding the damage caused already by the shaking.
Liquefaction occurs when an earthquake turns underground sediments to quicksand.
This phenomenon happened in the 1964 Alaska earthquake in an Anchorage neighborhood. When the soil liquefied, many of the homes disappeared or were totally destroyed. We can expect continued flooding because human activities increase flooding. Paving roads and parking lots reduces water infiltration into the soil and increases the rate of runoff into streams and lakes. Clearing land for agriculture and filling cities with buildings also increase water discharge after a storm.