The existence of coherent patterns relating to oil and gas reservoirs in the low frequency domain has been established in many parts of the world. The underlying physical mechanisms of these so-called Direct Hydrocarbon Indicators (DHI) is a key focus of our research. Two mechanisms that can generate DHI in the background spectrum are of special interest: resonant amplification and resonant scattering. Resonant amplification effects of ambient seismic waves are likely candidates for hydrocarbon

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... microscale tremor signals. Resonant amplification effects behave like a secondary source within the reservoir. They are supported by the following observations: An often narrow frequency range of the anomaly, The mean absolute power of hydrocarbon tremors depends on the level of environmental noise, Signal power is proportional to hydrocarbon-bearing layer thickness of the reservoir, Three component recordings show a trough instead of a peak in the H/V-ratio, Investigations of the wave-field propagation directions using directionally-sensitive sensor arrays show that the signals causing the anomaly originate from the reservoir direction, Time reverse modeling indicates that the origin of the tremor signals is located within the reservoir