Crustal structure across the Bering Strait, Alaska: Onshore recordings of a marine seismic survey
No abstract available.
Bering Sea, Bering Strait region, Chukchi Sea↗
Geology topics
Lorraine W. Wolf
Publications and source records attributed to Lorraine W. Wolf.
The earthquake potential of the New Madrid seismic zone
The fault system responsible for New Madrid seismicity has generated temporally clustered very large earthquakes in A.D. 900 ± 100 years and A.D. 1450 ± 150 years as well as in 1811–1812. Given the uncertainties in dating liquefaction features, the time between the past three New Madrid events may be as short as 200 years and as long as 800 years, with an average of 500 years. This advance in understanding the Late Holocene history of the New Madrid seismic zone and thus, the contemporary tectonic behavior of the associated fault system was made through studies of hundreds of earthquake-induced liquefaction features at more than 250 sites across the New Madrid region. We have found evidence that prehistoric sand blows, like those that formed during the 1811–1812 earthquakes, are probably compound structures resulting from multiple earthquakes closely clustered in time or earthquake sequences. From the spatial distribution and size of sand blows and their sedimentary units, we infer the source zones and estimate the magnitudes of earthquakes within each sequence and thereby characterize the detailed behavior of the fault system. It appears that fault rupture was complex and that the central branch of the seismic zone produced very large earthquakes during the A.D. 900 and A.D. 1450 events as well as in 1811–1812. On the basis of a minimum recurrence rate of 200 years, we are now entering the period during which the next 1811–1812-type event could occur.
Arkansas, Kentucky, Missouri, Tennessee↗
Data report for onshore-offshore wide-angle seismic recordings in the Bering-Chukchi Sea, Western Alaska and eastern Siberia
This report presents fourteen deep-crustal wide-angle seismic reflection and refraction profiles recorded onland in western Alaska and eastern Siberia from marine air gun sources in the Bering-Chukchi Seas. During a 20-day period in August, 1994, the R/V Ewing acquired two long (a total of 3754 km) deep-crustal seismic-reflection profiles on the continental shelf of the Bering and Chukchi Seas, in a collaborative project between Stanford University and the United States Geological Survey (USGS). The Ewing's 137.7 liter (8355 cu. in.) air gun array was the source for both the multichannel reflection and the wide-angle seismic data. The Ewing, operated by the Lamont-Doherty Earth Observatory, steamed northward from Nunivak Island to Barrow, and returned, firing the air gun array at intervals of either 50 m or 75 m. About 37,700 air gun shots were fired along the northward directed Lines 1 and 2, and more than 40,000 air gun shots were fired along the southward directed Line 3. The USGS and the University of Alaska, Fairbanks (UAF), deployed an array of twelve 3-component REFTEK and PDAS recorders in western Alaska and eastern Siberia which continuously recorded the air gun signals fired during the northward bound Lines 1 and 2. Seven of these recorders also continuously recorded the southward bound Line 3. These wide-angle seismic data were acquired to: (1) image reflectors in the upper to lower crust, (2) determine crustal and upper mantle refraction velocities, and (3) provide important constraints on the geometry of the Moho along the seismic lines. In this report, we describe the land recording of wide-angle data conducted by the USGS and the UAF, describe in detail how the wide-angle REFTEK and PDAS data were reduced to common receiver gather seismic sections, and illustrate the wide-angle seismic data obtained by the REFTEKs and PDAS's. Air gun signals were observed to ranges in excess of 400 km, and crustal and upper /mantle refractions indicate substantial variation in the crustal thickness along the transect.
Alaska↗