Images

A brain coral boulder eight feet in diameter stands 750 feet inland in the British Virgin Islands. Geologists say that the coral was brought ashore, probably alive, by an unusual tsunami or storm between the years 1200 and 1480.

Damage to the brick exterior of the downtown Napa Post Office. Photo take September 11, 2014

Increased flow over rock riffle in Sonoma Creek seen after South Napa Earthquake of August 24, 2014.

Location: Sonoma Creek downstream of the Agua Caliente Road Bridge, Sonoma County, California.

USGS summer geology interns Alexandra Pickering and Nikita Avdievitch collecting topographic data with a three-dimensional laser scanner on August 26. Surface rupture from the 2014 South Napa Earthquake is visible in the foreground

Surface rupture in soil near the intersection of state Highway 12 and Cuttings Wharf Road in Napa, CA on August 24, 2104

Surface rupture across Los Carneros Ave just northwest of South Ave in Napa County, CA. Photo taken by USGS from California Highway Patrol helicopter on August 24, 2014

Surface rupture across State Highway 12 at Cuttings Wharf Road - Photo taken by USGS from California Highway Patrol helicopter on August 24, 2014

Damage to a building in downtown Napa, CA caused by the South Napa earthquake. Photo taken by USGS from California Highway Patrol helicopter on August 24, 2014

USGS volunteer Whitney DeLong and geology intern Alexandra Pickering collecting topographic data with a three-dimensional laser scanner along Cuttings Wharf Road in Napa County, CA on August 26, 2014. In the background are engineers inspecting the earthquake surface rupture where is passes through a horse paddock.

Right-lateral displacement of centerline on Redwood Rd of 2.4 cm along a secondary rupture strand, near the north end of the fault rupture.

Right-lateral offset of vineyard row of nearly 40 cm. Photo taken on the main fault rupture near Buhman Rd.

Pavement buckling and tented sidewalk resulting from ~14 cm of compression on Sandybrook Ln., north end of main rupture.

Damaged unreinforced masonry building on Main St. in Napa Downtown.

Small displacement ground cracks along main rupture near Cuttings Wharf Rd., south of Hwy. 12, taken the day of the earthquake. Displacement in this area grew to ~20 cm right-lateral by Monday, 8/25, due to afterslip.

Left-stepping en echelon fractures characteristic of right-lateral fault displacement at the ground surface. Total fault slip measured near this location was 40-46 cm. Photo taken on main rupture strand near Buhman Rd.

Right lateral offset of Browns Valley Rd. centerline, on a secondary fault strand.

Driveway buckling across secondary fault strand at Browns Valley Rd. 

Continuous "mole-track" running parallel to the strike of the fault indicates some E-W compression in addition to right-lateral faulting. Photo taken near Buhman Rd.

USGS scientists Robert Sickler (left) and Rufus Catchings (right) carrying an auger to a drill hole for seismic survey.

USGS scientists Robert Sickler (below) and Rufus Catchings (standing) attaching a section of an auger bit in order to drill a hole for a seismic survey.

Warren Hall on California State University East Bay's Hayward campus is scheduled to be demolished Aug. 17, 2013 for seismic safety reasons. The landmark building's implosion will produce energy similar to a small earthquake that can be used to study and map the nearby Hayward Fault. In partnership with the university, U.S.