气候变化领域集成服务门户(CCPortal): Postglacial faulting near Crater Lake, Oregon, and its possible association with the Mazama caldera-forming eruption

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DOI	10.1130/B35013.1
	Postglacial faulting near Crater Lake, Oregon, and its possible association with the Mazama caldera-forming eruption
	Bacon C.R.; Robinson J.E.
发表日期	2019
ISSN	167606
起始页码	1440
结束页码	1458
卷号	131 期号:2021-09-10
英文摘要	Volcanoes of subduction-related magmatic arcs occur in a variety of crustal tectonic regimes, including where active faults indicate arc-normal extension. The Cascades arc volcano Mount Mazama overlaps on its west an ~10-km-wide zone of ~north-south-trending normal faults. A lidar (light detection and ranging) survey of Crater Lake National Park, reveals several previously unrecognized faults west of the caldera. Postglacial vertical separations measured from profiles across scarps range from ~2 m to as much as 12 m. Scarp profiles commonly suggest two or more postglacial surface-rupturing events. Ignimbrite of the ca. 7.6 ka climactic eruption of Mount Mazama, during which Crater Lake caldera formed, appears to bury fault strands where they project into thick, valley-filling ignimbrite. Lack of lateral offset of linear features suggests principally normal displacement, although predominant left stepping of scarp strands implies a component of dextral slip. West-northwest- east-southeast and north-northwest-southsoutheast linear topographic elements, such as low scarps or ridges, shallow troughs, and straight reaches of streams, suggest that erosion was influenced by distributed shear, consistent with GPS vectors and clockwise rotation of the Oregon forearc block. Surface rupture lengths (SRL) of faults suggest earthquakes of (moment magnitude) Mw≤6.5 from empirical scaling relationships. If several faults slipped in one event, a combined SRL of 44 km suggests an earthquake of Mw7.0. Postglacial scarps as high as 12 m imply maximum vertical slip rates of 1.5 mm/yr for the zone west of Crater Lake, considerably higher than the ~0.3 mm/yr long-term rate for the nearby West Klamath Lake fault zone. An unanswered question is the timing of surface-rupturing earthquakes relative to the Mazama climactic eruption. The eruption may have been preceded by a large earthquake. Alternatively, large surface-rupturing earthquakes may have occurred during the eruption, a result of decrease in east-west compressive stress during ejection of ~50 km3 of magma and concurrent caldera collapse. © 2019 Geological Society of America.
语种	英语
来源期刊	Bulletin of the Geological Society of America
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/184896
作者单位	U.S. Geological Survey, Volcano Science Center, 345 Middlefield Road, MS 910, Menlo Park, CA 94025-3561, United States
推荐引用方式 GB/T 7714	Bacon C.R.,Robinson J.E.. Postglacial faulting near Crater Lake, Oregon, and its possible association with the Mazama caldera-forming eruption[J],2019,131(2021-09-10).
APA	Bacon C.R.,&Robinson J.E..(2019).Postglacial faulting near Crater Lake, Oregon, and its possible association with the Mazama caldera-forming eruption.Bulletin of the Geological Society of America,131(2021-09-10).
MLA	Bacon C.R.,et al."Postglacial faulting near Crater Lake, Oregon, and its possible association with the Mazama caldera-forming eruption".Bulletin of the Geological Society of America 131.2021-09-10(2019).