During and after the destruction of underground structures, the elastic properties of subsurface rocks may undergo significant changes. Monitoring and detecting these subtle changes in elastic properties require techniques with high precision and high spatiotemporal resolution, which are challenging to achieve with conventional geophysical methods. Although nonlinear elastic characteristics have been used in seismic monitoring of faults and volcanoes, monitoring on fine spatiotemporal scales remains difficult. In this study, we developed a new technique to simultaneously monitor the nonlinear elastic properties of near-surface structures from both temporal and spatial perspectives by recording continuous seismic noise. We conducted a four-day continuous environmental noise monitoring campaign along a dense seismic array in Singapore. During the monitoring period, rock mass damage occurred along the measurement line. Using an approach analogous to “pump-probe” techniques, we analyzed the changes in nonlinear elastic properties during the local damage process at high spatiotemporal resolution. The results indicate that local damage can influence the nonlinear elastic behavior across the entire array. However, there are significant differences between the undamaged and damaged areas, as well as across different stages of damage. These observations and insights can provide timely warnings of minor changes in urban underground spaces, helping to prevent more significant damage and allowing for the implementation of effective, targeted measures. Moreover, this technique can accurately detect existing underground collapses and anomalous geological structures, which has important engineering implications for the detection of urban subsidence and the exploration of underground cavities in mining areas. It can play a crucial role in monitoring urban underground structural changes and providing early warnings of natural disasters areas.

中文翻译：

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浅层地下非线性弹性时空特征分析


在地下结构破坏期间和之后，地下岩石的弹性特性可能会发生重大变化。监测和检测弹性特性的这些细微变化需要高精度和高时空分辨率的技术，而传统地球物理方法很难实现这些技术。尽管非线性弹性特性已被用于断层和火山的地震监测，但在精细的时空尺度上进行监测仍然很困难。在这项研究中，我们开发了一种新技术，通过记录连续的地震噪声，从时间和空间角度同时监测近地表结构的非线性弹性特性。我们在新加坡的密集地震阵列沿线进行了为期四天的连续环境噪声监测活动。监测期间，沿测量线发生岩体损伤。使用类似于 “pump-probe” 技术的方法，我们在高时空分辨率下分析了局部损伤过程中非线性弹性特性的变化。结果表明，局部损伤会影响整个阵列的非线性弹性行为。但是，未损坏区域和损坏区域之间以及损坏的不同阶段之间存在显着差异。这些观察和见解可以及时警告城市地下空间的微小变化，有助于防止更严重的破坏，并允许实施有效、有针对性的措施。 此外，该技术可以准确检测现有的地下坍塌和异常地质结构，这对城市沉降的检测和矿区地下空洞的勘探具有重要的工程意义。它可以在监测城市地下结构变化和提供自然灾害区域的早期预警方面发挥关键作用。