Subsea Permafrost in Harrison Bay, Alaska: An Interpretation from Seismic Data

• Main Authors: Neave,K Gerard, Sellmann,Paul V
• Other Authors: COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
• Format: Text
• Language: English
• Published: 1982
• Subjects: Physical and Dynamic Oceanography; Seismology; Snow; Ice and Permafrost; *SEISMIC WAVES; *PERMAFROST; VELOCITY; ANOMALIES; SEISMIC DATA; ATTENUATION; REFRACTION; SUBSURFACE; OCEAN BOTTOM; GEOPHYSICAL PROSPECTING; BEAUFORT SEA; PETROLEUM GEOLOGY; Harrison Bay(Alaska); Beaufort Sea; Ice; permafrost; Alaska
• Online Access: http://www.dtic.mil/docs/citations/ADA121020; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA121020

Velocity data derived from petroleum industry seismic records from Harrison Bay show that high-velocity material ( or = 2 km/s) interpreted to be ice-bonded permafrost is common. In the eastern part of the bay, the depth to high velocity material increases and velocity decreases in an orderly manner with increasing distance from shore until the layer is no longer apparent. The western part of the bay is less orderly, possibly reflecting a different geological and thermal history. This western part may be an inundated section of the low coastal plain characterized by the region north of Teshekpuk Lake, and could have contained deep thaw lakes, creating low velocity zones. Along some seismic lines, the high-velocity material extends approximately 25 km offshore. Two anomalies have been found which could be associated with rapidly degrading permafrost. One is strong attenuation, which was interpreted as an indication of gas in the shallow deposits. The other is the presence of considerable seismic noise, including identifiable small seismic events. The origin of this noise has not been positively established, and it is proposed that it may indicate that some movement is occurring in the sediments due to thaw.