Geophysical techniques are often implemented as quick and inexpensive ways to locate and characterize fractures in the subsurface, which is important for a number of geoscience fields. Seismic velocities are the most widely used proxies for identification of fractures, but the correlation is not always well defined. Here we present material property data: unconfined compressive strength, bulk density (ρ), Young's modulus (E), Poisson's ratio (ν), P wave velocity (V_p), and S wave velocity (V_s), in conjunction with microfracture densities measured on samples of granite collected before and after underground chemical explosions. Results indicate the relationship between fractures and material properties is complex, even in this single‐lithology environment. We interpret that this complexity arises from varying fracture mechanisms (e.g., dilation‐inducing fractures vs. compression‐inducing fractures) in different parts of the core, due to differences in stress conditions. Additional complexity may result from chemical interactions between the fresh fractures and the fluids in the area. Water content appears to have a significant, if not dominant, role in the unconfined compressive strength of the samples. We suggest caution when using elastic property measurements as a proxy for fracturing in areas of explosion‐induced damage, or in other areas where a variety of mechanisms induce fracturing.

中文翻译：

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花岗岩地下爆炸的材料特性与微断裂密度之间的复杂联系

物探技术通常以快速，廉价的方式来实现，以定位和表征地下裂缝，这对许多地球科学领域都非常重要。地震速度是用于识别裂缝的最广泛使用的代理，但是并不总是很好地确定这种相关性。在这里，我们提供材料特性数据：无侧限抗压强度，堆积密度（ρ），杨氏模量（E），泊松比（ν），P波速度（V _p）和S波速度（V _s）），以及在地下化学爆炸之前和之后采集的花岗岩样品上测得的微裂缝密度。结果表明，即使在这种单一岩性环境下，裂缝与材料性能之间的关系也是复杂的。我们认为，这种复杂性是由于应力条件的不同而在岩心的不同部位产生了不同的断裂机制（例如，膨胀诱导的断裂与压缩诱导的断裂）。新裂缝和该区域内流体之间的化学相互作用可能导致额外的复杂性。水分似乎在样品的无侧限抗压强度中具有重要的作用，即使不是显性的。我们建议在使用弹性特性测量值作为爆炸引起的破坏区域的压裂的代名词时要谨慎，