*Article* **Acoustic Pressure, Particle Motion, and Induced Ground Motion Signals from a Commercial Seismic Survey Array and Potential Implications for Environmental Monitoring**

**Robert D. McCauley 1, Mark G. Meekan <sup>2</sup> and Miles J. G. Parsons 2,\***


**Abstract:** An experimental marine seismic source survey off the northwest Australian coast operated a 2600 cubic inch (41.6 l) airgun array, every 5.88 s, along six lines at a northern site and eight lines at a southern site. The airgun array was discharged 27,770 times with 128,313 pressure signals, 38,907 three-axis particle motion signals, and 17,832 ground motion signals recorded. Pressure and ground motion were accurately measured at horizontal ranges from 12 m. Particle motion signals saturated out to 1500 m horizontal range (50% of signals saturated at 230 and 590 m at the northern and southern sites, respectively). For unsaturated signals, sound exposure levels (SEL) correlated with measures of sound pressure level and water particle acceleration (*r*<sup>2</sup> *=* 0.88 to 0.95 at northern site and 0.97 at southern) and ground acceleration (*r*<sup>2</sup> *=* 0.60 and 0.87, northern and southern sites, respectively). The effective array source level was modelled at 247 dB re 1μPa m peak-to-peak, 231 dB re 1 <sup>μ</sup>Pa2 m mean-square, and 228 dB re 1 <sup>μ</sup>Pa2·m2 s SEL at 15◦ below the horizontal. Propagation loss ranged from −29 to −30log10 (*range*) at the northern site and −29 to −38log10(*range*) at the southern site, for pressure measures. These high propagation losses are due to near-surface limestone in the seabed of the North West Shelf.

**Keywords:** seismic airgun source; particle motion; ground motion; propagation loss
