OCR Text |
Show management in these areas shall also be determined in consultation with DWR. Class 6, managed to protect existing resource preservation uses. This classification covers existing WMAs. Lands will be available for oil and gas leasing with no surface occupancy. Class 3, managed as open for consideration of any use. The remainder of the lake is recommended to be placed in Class 3. Class 4, managed for resource inventory and analysis. This is a temporary classification used while resource information is gathered pending a different classification. There are no Class 4 lands in the lake. The mineral lease descriptions in the 1995 plan are revised by the 1996 MLP. The sovereign land mineral lease categories now in place are shown in Appendix G. ( See Maps 9 and 10.) Geologic Hazards State law requires DFFSL to disclose known geologic hazards affecting leased property. Information on known hazards is routinely provided to lessees but, in general, there is no follow- up activity. Tectonic Subsidence In the event of an earthquake within the Salt Lake Valley, the potential exists for the valley floor to drop relative to the adjacent Wasatch Range. Such movement would likely occur along the multi- segmented Wasatch fault zone. Keaton ( 1986) suggests that displacement could be approximately five feet at the fault line. The zero- subsidence line would be about 10- 12 miles west of the fault. A drop and tilt of the valley floor of this magnitude would cause ( 1) waters of GSL to move east, and ( 2) a rise in the water table in low areas near the fault. These effects could vary depending on the surface elevation of the lake at the time and the amount of displacement along the fault. Earthquakes could also cause movement along the numerous north- south faults within and adjacent to the lake. Such movement could cause damage to highways, railroads, dikes and other existing or proposed structures in and around the lake. Surface Faulting Surface faulting may accompany large earthquakes ( greater than magnitude 6.0- 6.5) on active faults in the bed of GSL. One fault trends northwest along the west side of the Promontory Mountains and Antelope Island. Other faults are present elsewhere beneath GSL, particularly in the north arm ( Hecker, 1993). Because faults in GSL do not trend onshore, surface faulting resulting from an earthquake on one of these faults would not directly affect structures along the shoreline. However, surface faulting beneath the lake may rupture dikes or in- lake structures that straddle the faults, and may generate seiches which could indirectly damage both in- lake and shoreline structures by flooding. Little is known of the earthquake history of the faults in GSL, but evidence indicates some have been active in Holocene time. 115 |