High-Resolution Seismic Profile and Sidescan-Sonar Data Collected During June 1980 Offshore New Jersey, Whitefoot Cruise 80-1

1983 ◽  
Author(s):  
Charles E. McClennen
2000 ◽  
Author(s):  
William C. Schwab ◽  
J.F. Denny ◽  
Bradford Butman ◽  
W.W. Danforth ◽  
D.S. Foster ◽  
...  

1992 ◽  
Author(s):  
William C. Schwab ◽  
R.M. Webb ◽  
W.W. Danforth ◽  
T.F. O'Brien ◽  
B.J. Irwin

2019 ◽  
Author(s):  
Maria Makarova ◽  
◽  
Kenneth G. Miller ◽  
Luca G. Podrecca ◽  
Richard A. Mortlock ◽  
...  

Geophysics ◽  
1998 ◽  
Vol 63 (2) ◽  
pp. 479-489 ◽  
Author(s):  
Thomas L. Pratt ◽  
James F. Dolan ◽  
Jackson K. Odum ◽  
William J. Stephenson ◽  
Robert A. Williams ◽  
...  

High‐resolution seismic reflection profiles at two different scales were acquired across the transpressional Santa Monica Fault of north Los Angeles as part of an integrated hazard assessment of the fault. The seismic data confirm the location of the fault and related shallow faulting seen in a trench to deeper structures known from regional studies. The trench shows a series of near‐vertical strike‐slip faults beneath a topographic scarp inferred to be caused by thrusting on the Santa Monica fault. Analysis of the disruption of soil horizons in the trench indicates multiple earthquakes have occurred on these strike‐slip faults within the past 50 000 years, with the latest being 1000 to 3000 years ago. A 3.8-km-long, high‐resolution seismic reflection profile shows reflector truncations that constrain the shallow portion of the Santa Monica Fault (upper 300 m) to dip northward between 30° and 55°, most likely 30° to 35°, in contrast to the 60° to 70° dip interpreted for the deeper portion of the fault. Prominent, nearly continuous reflectors on the profile are interpreted to be the erosional unconformity between the 1.2 Ma and older Pico Formation and the base of alluvial fan deposits. The unconformity lies at depths of 30–60 m north of the fault and 110–130 m south of the fault, with about 100 m of vertical displacement (180 m of dip‐slip motion on a 30°–35° dipping fault) across the fault since deposition of the upper Pico Formation. The continuity of the uncomformity on the seismic profile constrains the fault to lie in a relatively narrow (50 m) zone, and to project to the surface beneath Ohio Avenue immediately south of the trench. A very high‐resolution seismic profile adjacent to the trench images reflectors in the 15 to 60 m depth range that are arched slightly by folding just north of the fault. A disrupted zone on the profile beneath the south end of the trench is interpreted as being caused by the deeper portions of the trenched strike‐slip faults where they merge with the thrust fault.


Geophysics ◽  
1994 ◽  
Vol 59 (8) ◽  
pp. 1278-1289 ◽  
Author(s):  
William J. Lutter ◽  
Rufus D. Catchings ◽  
Craig M. Jarchow

We use a method of traveltime inversion of high‐resolution seismic data to provide the first reliable images of internal details of the Columbia River Basalt Group (CRBG), the subsurface basalt/sediment interface, and the deeper sediment/basement interface. Velocity structure within the basalts, delineated on the order of 1 km horizontally and 0.2 km vertically, is constrained to within ±0.1 km/s for most of the seismic profile. Over 5000 observed traveltimes fit our model with an rms error of 0.018 s. The maximum depth of penetration of the basalt diving waves (truncated by underlying low‐velocity sediments) provides a reliable estimate of the depth to the base of the basalt, which agrees with well‐log measurements to within 0.05 km (165 ft). We use image blurring, calculated from the resolution matrix, to estimate the aspect ratio of imaged velocity anomaly widths to true widths for velocity features within the basalt. From our calculations of image blurring, we interpret low velocity zones (LVZ) within the basalts at Boylston Mountain and the Whiskey Dick anticline to have widths of 4.5 and 3 km, respectively, within the upper 1.5 km of the model. At greater depth, the widths of these imaged LVZs thin to approximately 2 km or less. We interpret these linear, subparallel, low‐velocity zones imaged adjacent to anticlines of the Yakima Fold Belt to be brecciated fault zones. These fault zones dip to the south at angles between 15 to 45 degrees.


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