Preliminary structure contour map of the Sacramento Valley, California, showing major late Cenozoic structural features and depth to basement

Harwood, David S.; Helley, E.J.

doi:10.3133/ofr82737

Cited by 8 publications

(11 citation statements)

References 6 publications

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“…In terms of individual structures within the CRSB boundary zone the Midland fault, possibly the only observed fault that may form part of the boundary, does not appear to be seismically active, at least during this time period. This is consistent with the geologic data that suggest no offsets of deposits younger than early Oligocene [Harwood and Helley, 1982]. The Capay Valley and Dunnigan Hills faults, the latter of which may be similar to the faults beneath the anticlines in the southern San Joaquin Valley, may be seismogenic based upon the observed seismicity.…”

Section: In the Southernmost Portion Of The Central Crsb Boundary Zonsupporting

confidence: 90%

Contemporary seismicity and tectonics of the northern and central coast ranges‐Sierran Block Boundary Zone, California

Wong¹,

Ely²,

Kollmann³

1988

J. Geophys. Res.

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Beneath the physiographic boundary between the Coast Ranges and the Great Valley, a fundamental tectonic boundary exists between the Coast Ranges province and the Sierran block. Recent geophysical studies have revealed the Coast Ranges‐Sierran block (CRSB) boundary zone to be a complex region of compressional tectonics wherein wedges of comparatively ductile Franciscan Complex of the Coast Ranges have overridden the competent Sierran block basement and peeled up the overlying sediments of the Great Valley Sequence. The boundary zone was the probable source of the two 1892 Winters earthquakes (ML 6–7) and the 1983 Coalinga earthquake (ML 6.7). We evaluated the seismicity within the northern and central portions of the zone from Red Bluff south to San Luis reservoir for the period 1969–1985. Seismicity was spatially diffuse; most of the earthquakes occurred in somewhat isolated concentrations within the upper crust. A low activity level, temporal clustering, and episodic behavior also characterized this seismicity. The largest earthquake in the boundary zone was a ML 4.2 event near Madison; 20 events exceeded ML 3.0. In a few cases the seismogenic sources appear to be eastward dipping, high‐angle reverse faults, although some right‐slip, north trending faults also appear to be seismogenic. In comparison, the Coalinga and 1985 Kettleman Hills main shocks in the southern portion of the zone appeared to involve gently westward dipping thrust faults, although aftershocks also occurred on moderately to steeply dipping reverse faults. Fault plane solutions along the zone exhibited a tectonic stress field of NE to E trending compression, normal to the boundary. Such compression may be a consequence of one or a combination of several influences: (1) the westward movement of the Sierran block against the Coast Ranges due to late Cenozoic crustal extension in the Great Basin, (2) slightly convergent motion between the Pacific and North American plates, and (3) fault‐normal crustal compression due to the low shear strength of the San Andreas fault. The tectonic deformation manifested by the Coalinga and recent moderate‐sized earthquakes in the southern zone appears to be occurring along the full extent of the boundary albeit at varying rates for different segments. Thus the potential for large earthquakes may exist along segments of the CRSB boundary and the 1892 main shock may represent a characteristic earthquake for that portion of the zone.

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Section: In the Southernmost Portion Of The Central Crsb Boundary Zonsupporting

confidence: 90%

Contemporary seismicity and tectonics of the northern and central coast ranges‐Sierran Block Boundary Zone, California

Wong¹,

Ely²,

Kollmann³

1988

J. Geophys. Res.

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“…Petrographic work on basement samples (largely thin sections) was carried out by May and Hewitt (1948) over the whole Great Valley and by Williams and Curtis (1977) in the vicinity of Sutter Butte and Ross (1979) in the southeastern San Joaquin Valley. Later reconsideration of basement rock types included work by Harwood (Harwood and Helley, 1987). In the course of the present compilation, 110 of the thin sections collected by May and Hewitt and preserved by the California Academy of Sciences were reexamined by petrologists M.C.…”

Section: Basement Rock Typesmentioning

confidence: 99%

“…Smith (1964) compiled a map at a scale of 1:500,000 of about 250 basement wells and demonstrated a simple, west-dipping basement surface beneath the eastern half of the Great Valley. Maps at a scale of 1:250,000 were prepared of the basement surface in the northern San Joaquin Valley and in the Sacramento Valley by Bartow (1983) and Harwood and Helley (1987), respectively, using essentially the same well data as are used herein.…”

Section: Drill Holesmentioning

confidence: 99%

The surface of crystalline basement, Great Valley and Sierra Nevada, California: A digital map database

Wentworth¹,

Fisher²,

Levine³

et al. 1995

Open-File Report

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“…From Red Bluff to the northern end of the valley, late Cenozoic structural features strike east-northeast, nearly orthogonal to the Chico monocline and other north-trending structures located south of the map area (Harwood and Helley, 1982). The change from north-and northwest-striking structures to east-northeast-trending structures occurs at the Red Bluff fault, which trends about N.40°E.…”

Section: Structural Analysis Of the Sacramento Valleymentioning

confidence: 91%

“…The northwesttrending zone of short fault segments located southeast of Red Bluff marks the northern half of the Chico monocline (Harwood and others, 1981). The monocline is a southwest facing flexure draped over a steeply east-dipping, highangle reverse fault that offsets basement rocks about 400 m up-to-the east (Harwood and Helley, 1982;in press). The monocline formed between 1.0 and 2.5 m.y.…”

Section: Structural Analysis Of the Sacramento Valleymentioning

confidence: 99%

Preliminary geologic map of the Red Bluff 1:100,000 Quadrangle, California

Blake¹,

Harwood²,

Helley³

et al. 1984

Open-File Report

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Preliminary structure contour map of the Sacramento Valley, California, showing major late Cenozoic structural features and depth to basement

Cited by 8 publications

References 6 publications

Contemporary seismicity and tectonics of the northern and central coast ranges‐Sierran Block Boundary Zone, California

Contemporary seismicity and tectonics of the northern and central coast ranges‐Sierran Block Boundary Zone, California

The surface of crystalline basement, Great Valley and Sierra Nevada, California: A digital map database

Preliminary geologic map of the Red Bluff 1:100,000 Quadrangle, California

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