The Central California earthquakes of May 16, 1933, and June 7, 1934

1935 ◽  
Vol 25 (3) ◽  
pp. 223-246 ◽  
Author(s):  
Perry Byerly ◽  
James T. Wilson
Keyword(s):  
Travel Time ◽  
Earth’S Crust ◽  
Coast Range ◽  
Owens Valley ◽  
P Waves ◽  
Central California ◽  
Earth's Crust ◽  
Great Valley

Abstract Isoseismalsare drawn and field intensities listed for the Niles earthquake of May 16, 1933. The epicenter is placed at 37° 38′ N, 121° 57′ W. Isoseismals are drawn and field intensities listed for the Parkfield earthquakes of June 7, 1934. The epicenter of the shock at 8h 48mp.m. (P.S.T.) is placed at 35° 56′ N, 120° 29′ W. The epicenter of the shock at 8h 30m is placed about 4 km. north of this. Travel-time curves are drawn for each of these three shocks. It is shown that the Owens Valley stations, Tinemaha and Haiwee, did not record the normal P (v = 8.0 km/sec., ca.) for any of these earthquakes. It is concluded that there exists some barrier to these waves under the Great Valley of California (or possibly under the Sierra), which prevents their observation at stations so close to the valley as Tinemaha and Haiwee when the source is in the Coast Range region. The interpretation of the data of difficult, but there is some evidence for identifying P waves traveling through three successive layers of the earth's crust. A tentative computation of this structure is made.

Near earthquakes in Central California*

1939 ◽  
Vol 29 (3) ◽  
pp. 427-462 ◽  
Author(s):  
Perry Byerly
Keyword(s):  
Least Squares ◽  
Travel Time ◽  
Sierra Nevada ◽  
Accurate Determination ◽  
Depth Of Focus ◽  
Surface Layers ◽  
P Waves ◽  
Central California ◽  
The Waves

Summary Least-squares adjustments of observations of waves of the P groups at central and southern California stations are used to obtain the speeds of various waves. Only observations made to tenths of a second are used. It is assumed that the waves have a common velocity for all earthquakes. But the time intercepts of the travel-time curves are allowed to be different for different shocks. The speed of P̄ is found to be 5.61 km/sec.±0.05. The speed for S̄ (founded on fewer data) is 3.26 km/sec. ± 0.09. There are slight differences in the epicenters located by the use of P̄ and S̄ which may or may not be significant. It is suggested that P̄ and S̄ may be released from different foci. The speed of Pn, the wave in the top of the mantle, is 8.02 km/sec. ± 0.05. Intermediate P waves of speeds 6.72 km/sec. ± 0.02 and 7.24 km/sec. ± 0.04 are observed. Only the former has a time intercept which allows a consistent computation of structure when considered a layer wave. For the Berkeley earthquake of March 8, 1937, the accurate determination of depth of focus was possible. This enabled a determination of layering of the earth's crust. The result was about 9 km. of granite over 23 km. of a medium of speed 6.72 km/sec. Underneath these two layers is the mantle of speed 8.02 km/sec. The data from other shocks centering south of Berkeley would not fit this structure, but an assumption of the thickening of the granite southerly brought all into agreement. The earthquakes discussed show a lag of Pn as it passes under the Sierra Nevada. This has been observed before. A reconsideration of the Pn data of the Nevada earthquake of December 20, 1932, together with the data mentioned above, leads to the conclusion that the root of the mountain mass projects into the mantle beneath the surface layers by an amount between 6 and 41 km.

Seismic wave travel times from nuclear explosions

1958 ◽  
Vol 48 (4) ◽  
pp. 377-398
Author(s):  
Dean S. Carder ◽  
Leslie F. Bailey
Keyword(s):  
Travel Time ◽  
Travel Times ◽  
Strong Variation ◽  
Time Data ◽  
Owens Valley ◽  
Central California ◽  
Nuclear Explosions ◽  
Travel Time Data ◽  
The Pacific ◽  
Wave Travel

Abstract A large number of seismograph records from nuclear explosions in the Nevada and Pacific Island proving grounds have been collected and analyzed. The Nevada explosions were well recorded to distances of 6°.5 (450 mi.) and weakly recorded as far as 17°.5, and under favorable circumstances as far as 34°. The Pacific explosions had world-wide recording except that regional data were necessarily meager. The Nevada data confirm that the crustal thickness in the area is about 35 km., with associations of 6.1 km/sec. speeds in the crust and 8.0 to 8.2 km/sec. speeds beneath it. They indicate that there is no uniform layering in the crust, and that if higher-speed media do exist, they are not consistent; also, that the crust between the proving grounds and central California shows a thickening probably as high as 70 or 75 km., and that this thickened portion may extend beneath the Owens Valley. The data also point to a discontinuity at postulated depths of 160 to 185 km. Pacific travel times out to 14° are from 4 to 8 sec. earlier than similar continental data partly because of a thinner crust, 17 km. or less, under the atolls and partly because speeds in the top of the mantle are more nearly 8.15 km/sec. than 8.0 km/sec. More distant points, at 17°.5 and 18°.5, indicate slower travel times—about 8.1 km/sec. A fairly sharp discontinuity at 19° in the travel-time data is indicated. Travel times from Pacific sources to North America follow closely Jeffreys-Bullen 1948 and Gutenberg 1953 travel-time curves for surface foci except they are about 2 sec. earlier on the continent, and Arctic and Pacific basin data are about 2 sec. still earlier. The core reflection PcP shows a strong variation in amplitude with slight changes in distance at two points where sufficient data were available.

Channel P waves IIgin the Earth's crust

1956 ◽  
Vol 37 (6) ◽  
pp. 754 ◽  
Author(s):  
F. Press ◽  
B. Gutenberg
Keyword(s):  
Earth’S Crust ◽  
P Waves ◽  
Earth's Crust

An observational determination of the variation of the angle of incidence of P waves with epicentral distance

1961 ◽  
Vol 51 (2) ◽  
pp. 269-276
Author(s):  
Otto Nuttli ◽  
John D. Whitmore
Keyword(s):  
Epicentral Distance ◽  
Crustal Thickness ◽  
Earth’S Crust ◽  
P Wave ◽  
Angle Of Incidence ◽  
P Waves ◽  
Wave Data ◽  
Earth's Crust ◽  
Alaska Earthquake

Abstract Apparent angles of incidence of the P wave were obtained from the seismograms of the Galitzin-Wilip instruments at Florissant. The “half-periods” of these waves varied from 112 to 312 seconds, and the epicentral distances from 16.5° to 103.2°. The data indicate that the velocity of P waves at the earth's surface is approximately 8 km/sec. This suggests that these P waves do not see or are not affected by the earth's crust, although the crustal thickness is known to be approximately 35 km. P wave data from five other stations for the Alaska earthquake of July, 1958 support the conclusions obtained from the Florissant data.

Tides in the Earth's Crust

1915 ◽  
Vol 79 (2058supp) ◽  
pp. 382-383
Author(s):  
Alphonse Berget
Keyword(s):  
Earth’S Crust ◽  
Earth's Crust
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