Geologic Hazards on Whidbey Island February 21, 2018 active fault Chuckanut sandstone +6 earthquake geologic hazards field trip glaciation landslide liquefaction Northwest Geological Society Puget Sound tsunami Whidbey Island active fault Chuckanut sandstone earthquake geologic hazards field trip glaciation landslide liquefaction Northwest Geological Society Puget Sound tsunami Whidbey Island