Backscatter A [CSUMB]--Offshore of Carpinteria, California

This part of SIM 3261 presents data for part of the acoustic-backscatter map (see sheet 3, SIM 3261) of the Offshore of Carpinteria map area, California. The raster data file is included in "BackscatterA_CSUMB_OffshoreCarpinteria.zip," which is accessible from http://pubs.usgs.gov/ds/781/OffshoreCarpinteria/data_catalog_OffshoreCarpinteria.html.
The acoustic-backscatter map of the Offshore of Carpinteria map area, California, was generated from backscatter data collected by California State University, Monterey Bay, Seafloor Mapping Lab (CSUMB) and by the U.S. Geological Survey (USGS). These metadata describe the acoustic-backscatter data collected by CSUMB and reprocessed by the USGS. See "BackscatterB_USGS_OffshoreCarpinteria_metadata.txt" metadata for a description of the acoustic-backscatter data collected by the USGS. The southeastern nearshore and shelf areas, as well as the western midshelf area, were mapped by CSUMB in the summer of 2007, using a 244-kHz Reson 8101 multibeam echosounder. Within the acoustic-backscatter imagery, brighter tones indicate higher backscatter intensity, and darker tones indicate lower backscatter intensity. The intensity represents a complex interaction between the acoustic pulse and the seafloor, as well as characteristics within the shallow subsurface, providing a general indication of seafloor texture and sediment type. Backscatter intensity depends on the acoustic source level; the frequency used to image the seafloor; the grazing angle; the composition and character of the seafloor, including grain size, water content, bulk density, and seafloor roughness; and some biological cover. Harder and rougher bottom types such as rocky outcrops or coarse sediment typically return stronger intensities (high backscatter, lighter tones), whereas softer bottom types such as fine sediment return weaker intensities (low backscatter, darker tones).

本SIM 3261数据集的本章节提供加利福尼亚州卡平特里亚近海制图区部分声背散射（acoustic-backscatter）地图的相关数据，详见SIM 3261第3幅图。该栅格数据文件打包于"BackscatterA_CSUMB_OffshoreCarpinteria.zip"压缩包中，可通过链接http://pubs.usgs.gov/ds/781/OffshoreCarpinteria/data_catalog_OffshoreCarpinteria.html获取。
加利福尼亚州卡平特里亚近海制图区的声背散射地图，由蒙特雷湾加利福尼亚州立大学海底测绘实验室（CSUMB）与美国地质调查局（USGS）采集的背散射数据生成。本元数据用于说明由CSUMB采集、USGS重新处理的声背散射数据。如需了解USGS采集的声背散射数据详情，请参阅"BackscatterB_USGS_OffshoreCarpinteria_metadata.txt"元数据文件。
2007年夏季，CSUMB使用244kHz Reson 8101多波束测深仪，对该区域的东南近岸与陆架区域以及西部陆架中部区域完成了测绘。在声背散射影像中，色调越亮代表背散射强度越高，色调越暗则代表背散射强度越低。
背散射强度反映了声脉冲与海底之间以及浅表层地下特征间的复杂相互作用，可用于大致推断海底质地与沉积物类型。
背散射强度受多种因素影响：声源级、海底成像所用频率、掠射角、海底组成与特征（包括粒径、含水率、体积密度及海底粗糙度），以及部分生物覆盖物。
质地坚硬且表面粗糙的海底类型（如岩层出露区或粗粒沉积物）通常会产生更强的背散射强度（高背散射，对应亮色调）；而质地柔软的海底类型（如细粒沉积物）则会产生较弱的背散射强度（低背散射，对应暗色调）。