Utilization of Ambient Noise H/V Spectral Ratio for Subsurface Structure and Hydrocarbon Reservoir Characterization

Microtremors, the low-amplitude ground vibrations generated by ambient seismic noise, provide valuable information about both near-surface and deeper geological structures. Among passive seismic techniques, the Horizontal-to-Vertical (H/V) spectral ratio method has proven to be a stable and effective tool for detecting modifications in the microtremor wavefield caused by soft soil layers, complex topography, or subsurface heterogeneities. Over the past two decades, H/V analysis has been widely applied to estimate shear-wave (S-wave) velocity distributions in shallow sediments and to investigate deeper geological structures. Characteristic peaks in the H/V spectrum are generally associated with impedance contrasts in the subsurface, such as lithological boundaries or fluid-bearing formations. Variations in peak frequency have been shown to correlate with changes at the sediment–bedrock interface, even at depths exceeding ۱۰۰۰ meters. The method offers a non-invasive and cost-effective approach, particularly in geologically complex regions characterized by heterogeneous lithologies, fault networks, and irregular subsurface structures, where conventional active seismic surveys often face limitations. H/V analysis can effectively identify subsurface heterogeneities, layer boundaries, and variations in shear-wave velocity, and it has been successfully applied in geotechnical investigations, site effect studies, and hydrocarbon exploration. Recent studies have further demonstrated that low-frequency (<۱۰ Hz) anomalies in microtremor signals may serve as direct indicators of hydrocarbon-bearing formations, emphasizing the method’s sensitivity to both shallow and deep structural variations. Overall, the H/V spectral ratio method provides a reliable, non-invasive, and efficient tool for subsurface characterization and hydrocarbon reservoir assessment, particularly in complex geological settings where traditional methods may be limited.

کلیدواژه ها:

microtremor ، h/v spectral ratio ، ambient noise ، passive seismic ، seismic velocity structures