Geology topics

G. Carver

Publications and source records attributed to G. Carver.

3 recordsLinked to original sources

USGS2004

Geotechnical reconnaissance of the 2002 Denali fault, Alaska, earthquake

The 2002 M7.9 Denali fault earthquake resulted in 340 km of ruptures along three separate faults, causing widespread liquefaction in the fluvial deposits of the alpine valleys of the Alaska Range and eastern lowlands of the Tanana River. Areas affected by liquefaction are largely confined to Holocene alluvial deposits, man-made embankments, and backfills. Liquefaction damage, sparse surrounding the fault rupture in the western region, was abundant and severe on the eastern rivers: the Robertson, Slana, Tok, Chisana, Nabesna and Tanana Rivers. Synthetic seismograms from a kinematic source model suggest that the eastern region of the rupture zone had elevated strong-motion levels due to rupture directivity, supporting observations of elevated geotechnical damage. We use augered soil samples and shear-wave velocity profiles made with a portable apparatus for the spectral analysis of surface waves (SASW) to characterize soil properties and stiffness at liquefaction sites and three trans-Alaska pipeline pump station accelerometer locations. ?? 2004, Earthquake Engineering Research Institute.

Earthquake Spectra↗

USGS2004

Surface rupture on the Denali fault interpreted from tree damage during the 1912 Delta River Mw 7.2–7.4 earthquake: Implications for the 2002 Denali fault earthquake slip distribution

During the 3 November 2002 Denali fault earthquake, surface rupture propagated through a small, old-growth forest in the Delta River valley and damaged many trees growing on the fault. Damage was principally the result of fault offset of tree roots and tilting of trees. Some trees were split by surface faults that intersected the base of their trunks or large taproots. A few trees appear to have been damaged by strong shaking. Many of the older trees damaged in 2002 were deformed and scarred. Some of these scarred trees exhibit past damage indicative of surface faulting and have abrupt changes in their annual ring patterns that coincide with the past damage. Annual ring counts from several of these older scarred trees indicate the damage was caused by surface rupture on the Denali fault in 1912. The only earthquake of sufficient magnitude that fits the requirements for timing and general location as recorded by the damaged trees is a widely felt Ms 7.2-7.4 earthquake on 6 July 1912 informally referred to as the 1912 Delta River earthquake. Seismologic data and intensity distribution for the 1912 Delta River earthquake indicate that its epicenter was within 60-90 km of the Delta River and that rupture probably propagated toward the west. Inferred fault length, displacement, and rupture direction suggest the 1912 rupture was probably largely coincident with the western, lower slip section of the 2002 rupture.

Alaska↗

USGS1993

The Cape Mendocino, California, earthquakes of April 1992: Subduction at the triple junction

The 25 April 1992 magnitude 7.1 Cape Mendocino thrust earthquake demonstrated that the North America—Gorda plate boundary is seismogenic and illustrated hazards that could result from much larger earthquakes forecast for the Cascadia region. The shock occurred just north of the Mendocino Triple Junction and caused strong ground motion and moderate damage in the immediate area. Rupture initiated onshore at a depth of 10.5 kilometers and propagated up-dip and seaward. Slip on steep faults in the Gorda plate generated two magnitude 6.6 aftershocks on 26 April. The main shock did not produce surface rupture on land but caused coastal uplift and a tsunami. The emerging picture of seismicity and faulting at the triple junction suggests that the region is likely to continue experiencing significant seismicity.

California↗