Geodetic applications of laser ranging

1977 ◽  
Vol 284 (1326) ◽  
pp. 529-536 ◽  
Keyword(s):  
High Altitude ◽  
San Andreas Fault ◽  
Plate Motion ◽  
Laser Ranging ◽  
Northern California ◽  
San Andreas ◽  
Lageos Satellite ◽  
Made In

The measurement of intersite distances with laser ranging to satellites has been demon­strated during the last few years for distances of several hundred to several thousand kilometres with precisions of a few tens of centimetres. These techniques are now being tested across the San Andreas fault in California where it is hoped plate motion will be observable after several years of measurements. The first measurements, between sites in southern and northern California, were made in 1972 and repeated again in 1974 with agreement between the baselines for each of the two years at the 10 cm level. The next measurements are planned for the summer of 1976. The results of these and related experiments will be described together with simulations of the projected capability using the high altitude Lageos satellite. General plans for future experiments will be described.

Microearthquake seismicity and tectonics of Coastal Northern California

1970 ◽  
Vol 60 (5) ◽  
pp. 1669-1699 ◽  
Author(s):  
Leonardo Seeber ◽  
Muawia Barazangi ◽  
Ali Nowroozi
Keyword(s):  
High Frequency ◽  
Fault Plane ◽  
San Andreas Fault ◽  
High Gain ◽  
Strike Slip ◽  
Fault System ◽  
Northern California ◽  
Fault Plane Solutions ◽  
Sharp Bend ◽  
San Andreas

Abstract This paper demonstrates that high-gain, high-frequency portable seismographs operated for short intervals can provide unique data on the details of the current tectonic activity in a very small area. Five high-frequency, high-gain seismographs were operated at 25 sites along the coast of northern California during the summer of 1968. Eighty per cent of 160 microearthquakes located in the Cape Mendocino area occurred at depths between 15 and 35 km in a well-defined, horizontal seismic layer. These depths are significantly greater than those reported for other areas along the San Andreas fault system in California. Many of the earthquakes of the Cape Mendocino area occurred in sequences that have approximately the same magnitude versus length of faulting characteristics as other California earthquakes. Consistent first-motion directions are recorded from microearthquakes located within suitably chosen subdivisions of the active area. Composite fault plane solutions indicate that right-lateral movement prevails on strike-slip faults that radiate from Cape Mendocino northwest toward the Gorda basin. This is evidence that the Gorda basin is undergoing internal deformation. Inland, east of Cape Mendocino, a significant component of thrust faulting prevails for all the composite fault plane solutions. Thrusting is predominant in the fault plane solution of the June 26 1968 earthquake located along the Gorda escarpement. In general, the pattern of slip is consistent with a north-south crustal shortening. The Gorda escarpment, the Mattole River Valley, and the 1906 fault break northwest of Shelter Cove define a sharp bend that forms a possible connection between the Mendocino escarpment and the San Andreas fault. The distribution of hypocenters, relative travel times of P waves, and focal mechanisms strongly indicate that the above three features are surface expressions of an important structural boundary. The sharp bend in this boundary, which is concave toward the southwest, would tend to lock the dextral slip along the San Andreas fault and thus cause the regional north-south compression observed at Cape Mendocino. The above conclusions support the hypothesis that dextral strike-slip motion along the San Andreas fault is currently being taken up by slip along the Mendocino escarpment as well as by slip along northwest trending faults in the Gorda basin.

scholarly journals The San Andreas Fault Paleoseismic Record at Elizabeth Lake: Why are There Fewer Surface-Rupturing Earthquakes on the Mojave Section?

2021 ◽  
Author(s):  
Sean P. Bemis ◽  
Kate Scharer ◽  
James F. Dolan
Keyword(s):  
San Andreas Fault ◽  
Active Faults ◽  
Structural Complexity ◽  
Plate Motion ◽  
Fault System ◽  
San Andreas ◽  
Time Period ◽  
Earthquake Ruptures ◽  
Major Fault ◽  
Restraining Bend

ABSTRACT The structural complexity of active faults and the stress release history along the fault system may exert control on the locus and extent of individual earthquake ruptures. Fault bends, in particular, are often invoked as a possible mechanism for terminating earthquake ruptures. However, there are few records available to examine how these factors may influence the along-fault recurrence of earthquakes. We present a new paleoearthquake chronology for the southern San Andreas fault at Elizabeth Lake and integrate this record with existing paleoearthquake records to examine how the timing and frequency of earthquakes vary through a major restraining bend. This restraining bend features a mature, throughgoing right-lateral strike-slip fault, two major fault intersections, proposed subsurface fault dip changes, and a >200  km long section of fault misaligned with the regional plate motion. The Frazier Mountain, Elizabeth Lake, Pallett Creek, Wrightwood, and Pitman Canyon paleoseismic sites are located on this relatively linear surface trace of the San Andreas fault between fault bends. Our paleoseismic investigations at Elizabeth Lake document 4–5 earthquakes, since ∼1100  C.E., similar to the number of earthquakes recorded at Pallett Creek. In contrast, the Frazier Mountain and Wrightwood sites each record 8–9 earthquakes during this same time period. Differences in earthquake frequency demonstrate that fewer earthquakes rupture the central portion of the restraining bend than occur near the fault bends and intersections. Furthermore, the similarity of earthquake records from the Bidart Fan paleoseismic site northwest of the restraining bend and the Frazier Mountain paleoseismic site suggests that the broad, 30° curve of the Big Bend section of the San Andreas fault exerts less influence on fault rupture behavior than the 3D geometry of the Mojave sections of the fault.

Geomorphology, denudation rates, and stream channel profiles reveal patterns of mountain building adjacent to the San Andreas fault in northern California, USA

2017 ◽  
Vol 129 (5-6) ◽  
pp. 732-749 ◽  
Author(s):  
Stephen B. DeLong ◽  
George E. Hilley ◽  
Carol S. Prentice ◽  
Christopher J. Crosby ◽  
Intan N. Yokelson
Keyword(s):  
San Andreas Fault ◽  
Northern California ◽  
Stream Channel ◽  
Mountain Building ◽  
Denudation Rates ◽  
San Andreas

Seismicity of northern California and western Nevada

1964 ◽  
Vol 54 (2) ◽  
pp. 845-850
Author(s):  
Mansour Niazi
Keyword(s):  
Fault Zone ◽  
Frequency Distribution ◽  
Seismic Activity ◽  
San Andreas Fault ◽  
Seismic Energy ◽  
Northern California ◽  
Time Intervals ◽  
San Andreas ◽  
Strain Release ◽  
Surface Creep

abstract Nearly 1500 recent northern California and western Nevada earthquakes of magnitude 2 and above have been used to study aspects of the seismicity of the region. In an area covering 512 degrees of latitude by 8 degrees of longitude, each square degree was subdivided into 16 approximately equal quadrilateral blocks. The seismic energy and associated strain release in each block were computed for time intervals up to five years. The computed representations of strain release for each year are contoured to define the distribution of seismic zones in the area and to give a dynamic measure of thier variation. The observed surface creep along the San Andreas fault at the Vineyard seismographic station is compared with the intensity of the seismic activity in the immediate neighborhood of the fault zone. The frequency distribution of earthquakes of different magnitude is discussed.

Sign in / Sign up

Export Citation Format

Share Document