Geology topics

N.E. King

Publications and source records attributed to N.E. King.

8 recordsLinked to original sources

USGS2012

Strain‐rate profile across the Elsinore, San Jacinto, and San Andreas Faults near Palm Springs, California, 1973‐81

A profile of the strain accumulation rate along a line trending N50°E across the subparallel Elsinore, San Jacinto, and San Andreas faults near Palm Springs, California, has been constructed from trilateration surveys in the 1973‐81 interval. The strain accumulation is principally right‐lateral shear across a vertical plane parallel to fault strike (N40°W). The strain rate profile for that component exhibits two clearly resolved maxima, one centered on the San Jacinto fault (γ max = 0.35 ± 0.02 µrad/a) and the other on the San Andreas fault (γ max = 0.40 ± 0.02 µrad/a); no maximum is associated with the Elsinore fault. This result clearly implies that slip at depth on both the San Andreas and San Jacinto faults is loading the shallower sections of these faults, and that eventually rupture can be expected on both.

California↗

USGS2012

Strain accumulation along the Laguna Salada Fault, Baja California, Mexico

Strain accumulation observed over the 1978–1991 interval in a 30×100 km aperture trilateration network spanning the Laguna Salada fault is described by the principal strain rates 0.101±0.012 strain/yr N80°E±2° and −0.021±0.012 strain/yr N10°W±2°, extension reckoned positive. These strain accumulation rates have been corrected to remove coseismic effects of the nearby 1979 Imperial Valley ( = 6.5), 1980 Victoria (Baja California) ( = 6.4), 1987 Superstition Hills ( = 6.5), and 1987 Elmore Ranch ( = 5.9) earthquakes. The observed strain rates indicate extension at a rate of about 0.08 strain/yr perpendicular to the trend (N35°W) of the Salton trough as well as a right‐lateral tensor shear strain rate 0.05 strain/yr across it. The extension perpendicular to the trough is observed neither farther north near the Salton Sea nor farther south across the Gulf of California. However, Holocene slip on the Laguna Salada fault, about equal parts right‐lateral and normal slip, is consistent with the observed strain accumulation. A simple dislocation model intended to explain the observed strain accumulation as a product of slip at depth on the Laguna Salada fault would require that the fault be listric.

California↗

USGS2012

Strain accumulation in southern California, 1973-1980

Frequent surveys of seven trilateration networks in southern California over the interval 1973–1980 suggest that a regional increment in strain may have occurred in 1978–1979. Prior to 1978 and after late 1979 the strain accumulation has been predominantly a uniaxial north-south compression. This secular trend was interrupted sometime in 1978–1979 by an increment in both north-south and east-west extension in five of the seven networks. The onset of this change appears to have occurred first in the networks farthest south. The changes occurred without any unusual seismicity within the networks, but the overall seismicity in southern California was unusually low prior to and has been unusually high since the occurrence. The average principal strain rates for the seven networks in the 1973–1980 interval are 0.17 μstrain/yr north-south contraction and 0.08 μstrain/yr east-west extension. Although the observed increment in strain could be related to unidentified systematic error in the measuring system, a careful review of the measurements and comparisons with three other measuring systems reveal no appreciable cumulative systematic error.

Journal of Geophysical Research Solid Earth↗

USGS2012

Regional deformation near Palmdale, California, 1973-1983 (USA)

The Tehachapi trilateration network spans the intersection of the San Andreas and Garlock faults in southern California in the “Big Bend” region of the San Andreas fault. Analysis of data from 1973–1983 shows strain differences between the northwest and southeast regions of the network and slip at depth on both faults. The Palmdale network, spanning the San Andreas fault entirely within the Tehachapi network, showed increases of about 1 μstrain in both east‐west and north‐south extension in late 1979. The Tehachapi strains also jumped at this time, but the magnitude of the increase was only about one third that of Palmdale. The principal strain rates for Tehachapi over the time interval 1973–1983 are μstrain/yr and μstrain/yr, with the 1 axis directed N76°E. Strains were also computed for two subregions. The principal strain rates for the southeast Tehachapi region are μstrain/yr and μStrain/yr, with the 1 axis directed N73°E. This result differs significantly from the principal strain rates at Palmdale ( μstrain/yr, μstrain/yr, with the 1 axis directed N71°E). For the northwest Tehachapi region, μstrain/yr and μstrain/yr, with the 1 axis directed N93°E.

California↗

USGS2007

Space geodetic observation of expansion of the San Gabriel Valley, California, aquifer system, during heavy rainfall in winter 2004-2005

[1] Starting early in 2005, the positions of GPS stations in the San Gabriel valley region of southern California showed statistically significant departures from their previous behavior. Station LONG moved up by about 47 mm, and nearby stations moved away from LONG by about 10 mm. These changes began during an extremely rainy season in southern California and coincided with a 16-m increase in water level at a nearby well in Baldwin Park and a regional uplift detected by interferometric synthetic aperture radar. No equivalent signals were seen in GPS station position time series elsewhere in southern California. Our preferred explanation, supported by the timing and by a hydrologic simulation, is deformation due to recharging of aquifers after near-record rainfall in 2004–2005. We cannot rule out an aseismic slip event, but we consider such an event unlikely because it requires slip on multiple faults and predicts other signals that are not observed.

Journal of Geophysical Research B: Solid Earth↗

USGS1994

The co-seismic slip distribution of the Landers earthquake

We derived a model for the co-seismic slip distribution on the faults which ruptured during the Landers earthquake sequence of 28 June 1992. The model is based on the inversion of surface geodetic measurements, primarily vector displacements measured using the Global Positioning System ( GPS ). The inversion procedure assumes that the slip distribution is to some extent smooth and purely right-lateral strike slip. For a given fault geometry, a family of solutions of varying smoothness can be generated. We choose the optimal model from this family based on cross-validation, which measures the predictive power of the data, and the trade-off of misfit and roughness. Solutions which give roughly equal weight to misfit and smoothness are preferred and have certain features in common: (1) there are two main patches of slip, on the Johnson Valley fault, and on the Homestead Valley, Emerson, and Camp Rock faults; (2) virtually all slip is in the upper 10 to 12 km; and (3) the model reproduces the general features of the geologically measured surface displacements, without prior constraints on the surface slip. In all models, regardless of smoothing, very little slip is required on the fault that represents the Big Bear event, and the total moment of the Landers event is 9 · 10 19 N-m. The nearly simultaneous rupture of multiple distinct faults suggests that much of the crust in this region must have been close to failure prior to the earthquake.

California↗

USGS1981

Strain on the San Andreas fault near Palmdale, California: Rapid, aseismic change

Frequently repeated strain measurements near Palmdale, California, during the period from 1971 through 1980 indicate that, in addition to a uniform accumulation of right-lateral shear strain (engineering shear, 0.35 microradian per year) across the San Andreas fault, a 1-microstrain contraction perpendicular to the fault that accumulated gradually during the interval 1974 through 1978 was aseismically released between February and November 1979. Subsequently (November 1979 to March 1980), about half of the contraction was recovered. This sequence of strain changes can be explained in terms of south-southwestward migration of a slip event consisting of the south-southwestward movement of the upper crust on a horizontal detachment surface at a depth of 10 to 30 kilometers. The large strain change in 1979 corresponds to the passage of the slip event beneath the San Andreas fault.

California↗

USGS1977

Relation between earthquakes, weather, and soil tilt

Two years of local earthquake, temperature, and rainfall data taken near a tiltmeter site were used in a study of the numerical relation between these phenomena and the recorded tilt response. A least-squares shaping and predictive error filter approach was used. The relations were ranked in part according to the root mean square (r.m.s.) error of fit across the entire sample space. The tilt data with an annual range of tilt of approximately 10 microradians were fitted to the combined weather data of temperature and rainfall with a 0.75-microradian r.m.s. error. The best fit of earthquakes to these same tilt data is the subclass of events with magnitude (M) > 2.5 within 30 kilometers of the tilt site. The filter that mapped earthquakes to tilt yielded a 1.03-microradian r.m.s. error. The most unusual tilt anomaly over the entire 2-year period has the best fit of rainfall to the data for any single month of the entire data set. This unusual anomaly was the basis of an erroneously predicted earthquake (M ∼ 5). These data indicate that if there are premonitory earthquake signals, they are buried in local meteorlogical noise. Separating an earthquake anomaly from the response to surface phenomena becomes more difficult as the earthquake anomaly lead time approaches the rise time of the soil to weather and seasonal variations.

Science↗