A change in fault-plane orientation between foreshocks and aftershocks of the Galway Lake earthquake, ML = 5.2, 1975, Mojave Desert, California
G. S. Fuis, A.G. Lindh
1979, Tectonophysics (52) 601-602
A marked change is observed in P/SV amplitude ratios, measured at station TPC, from foreshocks to aftershocks of the Galway Lake earthquake. This change is interpreted to be the result of a change in fault-plane orientation occurring between foreshocks and aftershocks.The Galway Lake earthquake, ML= 5.2, occurred on June 1, 1975. The first-motion...
Marine terrace deformation, San Diego County, California
P.A. McCrory, K. R. Lajoie
1979, Tectonophysics (52) 407-408
The NW—SE trending southern California coastline between the Palos Verdes Peninsula and San Diego roughly parallels the southern part and off-shore extension of the dominantly right-lateral, strike-slip, Newport—Inglewood fault zone. Emergent marine terraces between Newport Bay and San Diego record general uplift and gentle warping on the northeast side of...
Deep structure under Yellowstone National Park U.S.A.: A continental "hot spot"
H. M. Iyer
1979, Tectonophysics (56) 165-197
In order to understand the origin of long-lived loci of volcanism (sometimes called “hot spots”) and their possible role in global tectonic processes, it is essential to know their deep structure. Even though some work has been done on the crustal, upper-mantle, and deep-mantle structure under some of these “hot...
The petrogenesis and trace-element geochemistry of intermediate lavas from Humphreys Peak, San Francisco volcanic field, Arizona
K.J. Wenrich-Verbeek
1979, Tectonophysics (61) 103-129
The San Francisco Mountain lavas exposed in the upper portion of the southeast slope of Humphreys Peak are composed of three petrographically distinct types: (1) a lower series of hornblende pyroxene andesites; (2) a group of hypersthene dacites; and (3) an upper series of olivine andesites. These rocks have been...
Elastic expansion of the lithosphere caused by groundwater withdrawal in south-central Arizona
T.L. Holzer
1979, Tectonophysics (52) 304-304
Relative crustal uplift observed from 1948–1949 to 1967 in the Lower Santa Cruz River Basin in south-central Arizona is attributed at least in part to elastic expansion of the lithosphere induced by the removal, and subsequent loss by evapo transpiration, of 4.35 × 1013 kg of groundwater from alluvium. The area...
Changes in rate of fault creep
P. Harsh
1979, Tectonophysics (52) 519-519
Aseismic slip or fault creep is occurring on many faults in California. Although the creep rates are generally less than 10 mm/yr in most regions, the maximum observed rate along the San Andreas fault between San Juan Bautista and Gold Hill in central California exceeds 30 mm/yr. Changes in slip...
Evidence for the recurrence of large-magnitude earthquakes along the Makran coast of Iran and Pakistan
W.D. Page, J. N. Alt, L.S. Cluff, George Plafker
1979, Tectonophysics (52) 533-547
The presence of raised beaches and marine terraces along the Makran coast indicates episodic uplift of the continental margin resulting from large-magnitude earthquakes. The uplift occurs as incremental steps similar in height to the 1–3 m of measured uplift resulting from the November 28, 1945 (M 8.3) earthquake at Pasni and...
Earthquakes and fault creep on the northern San Andreas fault
R. Nason
1979, Tectonophysics (52) 604-604
At present there is an absence of both fault creep and small earthquakes on the northern San Andreas fault, which had a magnitude 8 earthquake with 5 m of slip in 1906. The fault has apparently been dormant after the 1906 earthquake. One possibility is that the fault is ‘locked’...
Strain pattern represented by scarps formed during the earthquakes of October 2, 1915, Pleasant Valley, Nevada
R. E. Wallace
1979, Tectonophysics (52) 599-599
The pattern of scarps developed during the earthquakes of October 2, 1915, in Pleasant Valley, Nevada, may have formed as a result of a modern stress system acting on a set of fractures produced by an earlier stress system which was oriented differently. Four major scarps developed in a right-stepping,...
Dislocation modeling of creep-related tilt changes
S. McHugh, M.J.S. Johnston
1979, Tectonophysics (52) 520-520
Tilt changes associated with 1–5 mm of fault creep have been detected at several different locations on the San Andreas fault on tiltmeters within 500 m of the creep observation point. The creep-related tilts have amplitudes of ≤ 0̌.5 μrad and durations...
Preliminary results from comparisons of redundant tiltmeters at three sites in central California
C.E. Mortensen, M.J.S. Johnston
1979, Tectonophysics (52) 85-86
The U.S. Geological Survey has been operating a network of shallow-borehole tiltmeters in central California since June 1973. At six sites redundant instruments have been installed as a check on data coherency. These include the Sage Ranch, Tres Pinos, New Idria, Aromas,...
Early 20th-century uplift of the northern Peninsular Ranges province of southern California
Spencer H. Wood, Michael R. Elliott
1979, Tectonophysics (52) 249-265
Repeated leveling in the northern Peninsular Ranges province identifies an early 20thcentury episode of crustal upwarping in southern California. The episodic vertical movement is broadly bracketed between 1897 and 1934, and the main deformation is bracketed within 1906–1914 and involved regional up-to-the-northeast tilting of the Santa Ana block of as...
Monitoring massive fracture growth at 2-km depths using surface tiltmeter arrays
M.D. Wood
1979, Tectonophysics (52) 643-643
Tilt due to massive hydraulic fractures induced in sedimentary rocks at depths of up to 2.2 km have been recorded by surface tiltmeters. Injection of fluid volumes up to 4 · 105 liters and masses of propping agent up to 5 · 105 kg is designed to produce fractures approximately 1 km...
Fault-crossing P delays, epicentral biasing, and fault behavior in central California
S.M. Marks, C. G. Bufe
1979, Tectonophysics (52) 600-600
The P delays across the San Andreas fault zone in central California have been determined from travel-time differences at station pairs spanning the fault, using off-fault local earthquake or quarry blast sources. Systematic delays as large as 0.4 sec have been observed for paths crossing the fault at depths of...
Quaternary crustal deformation along a major branch of the San Andreas fault in central California
G. E. Weber, K. R. Lajoie, J.F. Wehmiller
1979, Tectonophysics (52) 378-379
Deformed marine terraces and alluvial deposits record Quaternary crustal deformation along segments of a major, seismically active branch of the San Andreas fault which extends 190 km SSE roughly parallel to the California coastline from Bolinas Lagoon to the Point Sur area. Most of this complex fault zone lies offshore...
Earthquake recurrence on the Calaveras fault east of San Jose, California
Charles G. Bufe, Philip W. Harsh, Robert O. Burford
1979, Tectonophysics (52) 603-603
Occurrence of small (3 ⩽ ML < 4) earthquakes on two 10-km segments of the Calaveras fault between Calaveras and Anderson reservoirs follows a simple linear pattern of elastic strain accumulation and release. The centers of these independent patches of earthquake activity are 20 km apart. Each region is characterized by a...
Anomalously high uplift rates along the Ventura-Santa Barbara coast, California-tectonic implications
J.F. Wehmiller, A. Sarna-Wojcicki, R. F. Yerkes, K. R. Lajoie
1979, Tectonophysics (52) 380-380
The NW—SE trending segments of the California coastline from Point Arena to Point Conception (500 km) and from Los Angeles to San Diego (200 km) generally parallel major right-lateral strike-slip fault systems. Minor vertical crustal movements associated with the dominant horizontal displacements along these fault systems are recorded in local...
Geology and tectonic development of the continental margin north of Alaska
Arthur Grantz, Stephen Eittreim, David A. Dinter
1979, Tectonophysics (59) 263-291
The continental margin north of Alaska, as interpreted from seismic reflection profiles, is of the Atlantic type and consists of three sectors of contrasting structure and stratigraphy. The Chukchi sector, on the west, is characterized by the deep late Mesozoic and Tertiary North Chukchi basin and the Chukchi Continental Borderland....
Coal depositional models in some Tertiary and Cretaceous coal fields in the U.S. Western Interior
R. M. Flores
1979, Organic Geochemistry (1) 225-235
Detailed stratigraphic and sedimentological studies of the Tertiary Tongue River Member of the Fort Union Formation in the Powder River Basin, Wyoming, and the Cretaceous Blackhawk Formation and Star Point Sandstone in the Wasatch Plateau, Utah, indicate that the depositional environments of coal played a major role in controlling coal...
Seismic refraction study of the continental edge off the eastern United States
R. E. Sheridan, J. A. Grow, John C. Behrendt, K.C. Bayer
1979, Tectonophysics (59) 1-26
Three long, strike-parallel, seismic-refraction profiles were made on the continental shelf edge, slope and upper rise off New Jersey during 1975. The shelf edge line lies along the axis of the East Coast Magnetic Anomaly (ECMA), while the continental rise line lies 80 km seaward of the shelf edge. Below...
The gravity field of the U.S. Atlantic continental margin
John A. Grow, C.O. Bowin, Deborah R. Hutchinson
1979, Tectonophysics (59) 27-52
Approximately 39,000 km of marine gravity data collected during 1975 and 1976 have been integrated with U.S. Navy and other available data over the U.S. Atlantic continental margin between Florida and Maine to obtain a 10 mgal contour free-air gravity anomaly map. A maximum typically ranging from 0 to +70...
Earliest Phanerozoic or latest Proterozoic fossils from the Arabian Shield
P. Cloud, S.M. Awramik, K. Morrison, D.G. Hadley
1979, Precambrian Research (10) 73-93
We report here the first biologically definable fossils from pre-Saq (pre-Middle Cambrian) rocks of the Arabian Shield. They include the distinctive helically coiled tubular filaments of the oscillatorialean blue-green alga Obruchevella parva as well as two size classes of spheroidal unicells of uncertain affinity. Also present is the conical stromatolite Conophyton and unidentified stromatolites....
CDP seismic sections of the western Beaufort continental margin
Stephen Eittreim, Arthur Grantz
1979, Tectonophysics (59) 251-262
The continental rise, slope, and shelf in the Beaufort Sea off northern Alaska were surveyed with 5600 km of common-depth-point (CDP) seismic data by the U.S. Geological Survey in 1977. The lower continental rise consists of a wedge of at least 4.5 km of low-velocity, generally flat-lying, parallel-bedded sediments. Slump-related...
Anomalous topography on the continental shelf around Hudson Canyon
H.J. Knebel
1979, Marine Geology (33) 67-75
Recent seismic-reflection data show that the topography on the Continental Shelf around Hudson Canyon is composed of a series of depressions having variable spacings (< 100 m to 2 km), depths (1–10 m), outlines, and bottom configurations that give the sea floor an anomalous “jagged” appearance in profile. The acoustic...
Effects of oil transferred from incubating gulls to their eggs
Kirk A. King, C.A. LeFever
1979, Marine Pollution Bulletin (10) 319-321
No. 2 fuel oil, or water, was applied to the breast feathers of incubating laughing gulls trapped at their nest site on an island colony in Texas. Gulls were released after treatment and allowed to incubate their eggs for 5 days. Oil was transferred from the feathers of incubating adults...
