Investigation of Earthquake Sources and Fracture Origin of Crustal Seismic Coda Using Seismograms Recorded at Depth in the Cajon Pass Drillhole

本研究是继续记录和分析一个 三轴一组10赫兹地震检波器放置在2.5公里的深度， Cajon Pass深钻孔，靠近南部的San Andreas断层 加州。 到目前为止，仪器已经记录了几个 频率高达400赫兹的数百次地震。 大多数大型 用2Hz三轴表面同时记录事件 地震仪 结果表明，地面地震记录严重 高频波振幅和井下地震图耗尽 具有高拐角频率和高频率幂律振幅 腐烂 将安装更多的宽带地震传感器， 2.0和3.5公里的深度，以提供一个改进的措施， 天然地震活动性和记录微震体积标度 地震活跃的地壳。 这项研究是一个组成部分， 国家地震减灾计划。

This research is to continue the recording and analysis of a triaxial set of 10 Hz geophones placed at a depth of 2.5 km in the Cajon Pass deep drill hole near the San Andreas fault in southern California. To date, the instrumentation has recorded several hundred earthquakes at frequencies up to 400 Hz. Most larger events were recorded simultaneously by a 2 Hz triaxial surface seismometer. Results suggest that surface seismograms are severely depleted in high frequency wave amplitudes and downhole seismograms have high corner frequencies and high frequency power law amplitude decays. Additional wide-band seismic sensors will be installed at 2.0 and 3.5 km depths in order to give an improved measure of natural seismicity and record microearthquake scaling in a volume of seismically active crust. This research is a component of the National Earthquake Hazard Reduction Program.