基于大当量人工爆破的短周期地震背景噪声相关函数准确性验证研究

Noise Correlation Function (NCF) has been developed to image the structure of the earth interior and obtains abundant results. It is also applied to monitor the temporal changes of earth’s velocities and the high-precision locations of earthquakes, which shows wide application prospects. One of the core problems of Ambient Noise Tomography (ANT) is whether the NCF can truly see as the interstation Green’s Function or not. The availabilities of NCFs by using the methods of laboratory experimentations and theoretical derivations have been studied by some researchers, and the accuracy from period 10-30 second has been validated from a Ground Truth earthquake. However, the accuracy of short-period (about 1 second) NCF is not validated until now. Short-period NCF is much important to image shallow structure, to study medium velocity changes, to simulate strong ground motion and to monitor volcano activities. Therefore, this project plans to deploy a seismograph on the source of a 1-ton artificial blasting, and conduct cross-correlation with permanent stations to obtain NCF and to extract surface wave information, then compare with the surface waveform and dispersion from artificial explosion to validate the accuracy of short-period NCF, which is influenced by different observation intervals, seasons or years. This study can provide empirical foundation of earth’s shallow structure imaging and media velocity changes.

利用背景噪声相关函数（NCF）进行地下结构成像的研究取得了丰富的成果，并已经拓展到地下介质波速变化监测、高精度震中定位等领域，表现出广阔的应用前景。地震背景噪声成像研究的核心问题之一是NCF能否准确反映台站间的格林函数。虽然地震学工作者已经从室内实验、理论推导研究了NCF的有效性，并通过位置准确测定的地震验证了10-30秒周期的NCF作为格林函数的准确程度，但是对周期约1秒的短周期NCF的准确性尚未进行验证。而短周期NCF在地球浅部成像和介质变化的研究中起着关键作用，对于强地面运动模拟、火山监测具有重要意义。为此，本项目拟在吨级人工爆破的源区架设流动台、与固定台之间作NCF计算以提取面波信息，并与人工爆破激发的面波信息进行对比，以验证短周期NCF的准确性。分析不同观测时间长度、不同季节、不同年度等因素对NCF精度的影响，为基于背景噪声的地球浅部结构成像及介质变化监测研究提供实证基础。