Frequency and fluid effects on elastic properties of basalt: Experimental investigations

In order to investigate the effects of fluid and frequency on the elastic properties, we performed hydrostatic experiments on an Icelandic basalt specimen under both dry and saturated conditions. This basalt is characterized by a bimodal porosity, i.e., cracks and equant pores. The elastic properties ‐bulk moduli in our case‐ were investigated under high pressure through two experimental methods: (1) a classical one using ultrasonic P‐ and S‐waves velocities (frequency 10 6 Hz), (2) and a new one, using oscillation tests (frequency 10 −2 Hz). In dry condition, experimental data show no significant difference between high (HF) and low (LF) frequency bulk moduli. However, in saturated conditions, two effects are highlighted: a physico‐chemical effect emphasized by a difference between drained and dry moduli, and a squirt‐flow effect evidenced by a difference between HF and LF undrained moduli.