Parkfield is a small community in Monterey County, California. As of the 2000 census the Zip Code in which the town is located (93452) had a total population of 470. Various sources list the population of Parkfield as between 18 and 37. Some sources, however, list the population as 900.
Parkfield is located at 35.899N, 120.431W1. Its elevation is 1,530 feet.
The town itself is located in the central coastal range in Central California. Mining used to be a prosperous activity in this community, but the mines were exhausted below economic recovery levels and the industry moved elsewhere. Today, it is a small town of about 900 people who are mostly ranchers and farmers or merchants supporting these activities. There is a small tourism industry in the town that basis itself on the prospect of earthquakes (see the geology section below). The Parkfield slogan is, "Eat here when it happens, Sleep here when it happens."
Geology
Parkfield lies along the San Andreas Fault that is highly geologically active. Parkfield traditionally has an earthquake of 6 or greater magnitude every 22 years. In 1985, the US Geological Survey predicted that there would be a major earthquake in this community in 1993, but no such earthquake came until September 28, 2004 when a mgnitude 6.0 earthquake struck at 10:15 am Pacific Daylight Time.
Parkfield is the most closely observed earthquake zone in the world. Scientists measure the strain in rocks, heat flow, and geomagnetism constantly around Parkfield. The observance of the San Andreas fault in Parkfield will hopefully help scientists understand earthquakes and maybe some day predict major earthquakes along the San Andreas fault and across the world.
Since 1985, the US Geological Society (USGS) has been working on The Parkfield Experiment, a long-term research project on the San Andreas fault. "The experiment's purpose is to better understand the physics of earthquakes - what actually happens on the fault and in the surrounding region before, during and after an earthquake"
The reason that earthquakes occur so regularly here is that it lies about midway on a fault segment between a locked segment to the south (last major earthquake 1883) and a creeping segment to the north where two tectonic plates are continuously moving without major earthquakes. As the earthquake was eleven years overdue it lends some credence to the folk saying "a watched pot never boils". The additional time did offer the opportunity to add improvements in instrumentation as the technology was further developed, including the recent drilling of a deep hole for insertion of instruments.
Taken from USGS site for 120W, 36N (click for current and recent activity)
Substatial (5.0) aftershocks continue on a Northwesterly progression, each further from the principle shock.
Excerpt of earthquake list - only magnitude 3.0 and greater (reverse chronological order)
Mag Date Time Location Depth General ___location WP Editor Notes 5.0 2004/09/30 11:54:28 35.984N 120.550W 10.1 14 km ( 9 mi) NW of Parkfield (Large aftershock 25 km NW from intial) 3.5 2004/09/29 22:02:27 35.953N 120.506W 9.7 9 km ( 6 mi) NW of Parkfield ----- following are shown on map above 4.5 2004/09/29 10:12:06 35.952N 120.492W 10.2 8 km ( 5 mi) NW of Parkfield 5.0 2004/09/29 10:10:04 35.953N 120.502W 11.5 9 km ( 5 mi) NW of Parkfield (Large aftershock 20km NW from intial) 3.1 2004/09/29 09:11:51 36.139N 120.207W 7.8 12 km ( 7 mi) SW of Huron 3.2 2004/09/29 02:04:07 36.644N 120.880W 0.0 27 km (17 mi) ENE of Pinnacles 3.4 2004/09/28 18:53:35 35.893N 120.446W 5.8 1 km ( 1 mi) WSW of Parkfield 3.0 2004/09/28 12:59:27 35.903N 120.449W 6.2 2 km ( 1 mi) W of Parkfield 4.0 2004/09/28 12:31:27 35.839N 120.387W 9.3 8 km ( 5 mi) SSE of Parkfield 3.1 2004/09/28 12:23:39 35.830N 120.379W 6.6 9 km ( 6 mi) SSE of Parkfield 3.6 2004/09/28 10:35:17 35.947N 120.489W 10.2 7 km ( 5 mi) NW of Parkfield 3.7 2004/09/28 10:33:55 35.817N 120.359W 7.1 11 km ( 7 mi) SE of Parkfield 3.2 2004/09/28 10:29:41 35.829N 120.369W 9.4 10 km ( 6 mi) SE of Parkfield 3.3 2004/09/28 10:29:22 35.836N 120.380W 9.0 8 km ( 5 mi) SSE of Parkfield 3.4 2004/09/28 10:29:15 35.852N 120.401W 5.3 6 km ( 4 mi) SSE of Parkfield 4.7 2004/09/28 10:24:15 35.806N 120.349W 6.7 13 km ( 8 mi) SE of Parkfield 3.0 2004/09/28 10:22:22 35.910N 120.458W 6.6 3 km ( 2 mi) WNW of Parkfield 4.1 2004/09/28 10:22:18 35.840N 120.388W 5.6 8 km ( 5 mi) SSE of Parkfield 5.0 2004/09/28 10:19:06 35.855N 120.411W 8.6 5 km ( 3 mi) SSE of Parkfield (Principle aftershock 6km to NW from initial) 6.0 2004/09/28 10:15:24 35.815N 120.374W 7.9 11 km ( 7 mi) SSE of Parkfield (MAIN SHOCK) 3.4 2004/09/26 19:00:06 36.160N 120.662W 5.5 27 km (17 mi) NE of San Ardo 3.7 2004/09/26 08:54:05 36.155N 120.654W 5.0 27 km (17 mi) W of Coalinga