SEG-Y format chirp seismic data from geophysical surveys of Bear Lake, Utah-Idaho, 2002

Bear Lake is a tectonic lake that has existed for at least several hundred thousand years. The lake basin is a relatively simple half graben, a spoon-shaped depression tilted toward the main fault on the east side of the lake. The U.S. Geological Survey, in cooperation with researchers from several universities, has been studying the sediments of Bear Lake since 1996. The general purpose of this effort is to reconstruct past limnological conditions and regional climate on a range of timescales, from hundreds of years to hundreds of thousands of years. This research relates to a variety of human concerns, including water usage in the Bear River basin. Past work has included several coring operations, a seismic-reflection survey, sediment-trap deployments, a barge-mounted drilling operation with the GLAD800 drill rig, and a variety of other studies. The objectives of the September, 2002 operations, preliminarily reported here, were (1) to compile a detailed bathymetric map of the lake using swath-mapping techniques, in order to provide baseline data for a variety of applications and studies, and (2) to complete a sidescan-sonar survey of the lake, providing a nearly complete acoustic image of the lake floor. Limited amounts of subbottom acoustic-reflection data (CHIRP) were also collected, along with samples of lake-floor sediments representative of different kinds of backscatter patterns. These surveys followed an earlier subbottom acoustic-reflection survey (1997), using boomer and 3.5 kHz systems (S. M. Colman, unpublished data).贝尔湖（Bear Lake）是一处至少存在了数十万年的构造湖（tectonic lake）。该湖盆属于结构相对简单的半地堑（half graben），是一个朝湖东侧主断层倾斜的勺状凹陷。美国地质调查局（U.S. Geological Survey）联合多所高校的研究人员，自1996年起便对贝尔湖的沉积物展开研究。此项工作的核心目标是重建数百年至数十万年时间尺度下的古湖沼学环境与区域气候状况，相关研究涉及诸多人类关切议题，其中包括贝尔河流域的水资源利用问题。过往研究已开展了多次钻探取芯作业、地震反射勘测、沉积物捕集器布设、搭载GLAD800钻机（GLAD800 drill rig）的驳船式钻探作业，以及其他多项相关研究。 本文初步报道的2002年9月科考作业目标有二：其一，采用条带测深技术（swath-mapping techniques）绘制贝尔湖高精度水深地形图（bathymetric map），为各类应用与研究提供基准数据；其二，完成全湖侧扫声呐（sidescan-sonar）勘测，以获取近乎完整的湖床声学影像。本次作业还同步采集了少量海底底质声学反射数据（CHIRP），以及对应不同反向散射模式（backscatter patterns）的湖床沉积物样本。此次勘测接续了1997年开展的、使用电火花震源与3.5kHz声波系统（boomer and 3.5 kHz systems）的海底底质声学反射勘测（S. M. Colman，未发表数据）。