Induced seismicity in Basel
The largest event prompted concern from local residents. The six borehole seismometers installed near the Basel injection well to monitor the natural background seismicity and the geothermal stimulation recorded more than 13,500 potential events connected with the geothermal project, from which 3,124 were of sufficient quality to permit [hypocenter] determinations in the period 2–12 December 2006, which spanned the main stimulation and the decline in the event rate. During the post-stimulation period from 13 December 2006 onward, a further 350 locatable events were detected up to 2 May 2007, by which time events were occurring sporadically at around one per day. In all, locations for more than 3,500 events were determined.
1949 Olympia earthquake
The 1949 Olympia earthquake occurred on April 13 at with a moment magnitude of 6.7 and a maximum Mercalli Intensity of VIII ("Severe"). The shock was located in the area between Olympia and Tacoma, and was felt throughout the state, as well as parts of Oregon, British Columbia, Idaho, and Montana. It is the largest recorded earthquake to occur in the Puget Sound region of Washington. Eight people were killed, a minimum of 64 people were injured, and the total damage is estimated at $25 million.