Abstract
We obtain estimates of the seismic velocity and attenuation for White Island volcano by use of high-impact sand-bag drops from helicopter. Three drops were attempted, two at either end of a 6-station linear array within the crater floor, and the third in the volcano's crater lake. The bags were dropped from ∼310–380 m height and contained ∼700 kg of sand. The impact velocity was estimated at ∼60–70 m/s yielding a kinetic energy of about 106 Nm, giving P-wave onsets to a distance of ∼1 km. We obtained a seismic velocity estimate ofVp = 1.2 km/s for the unconsolidated crater floor and Vp = 2.2 km/s for rays traversing through consolidated rock outside the crater. Attenuation was very strong (Q< 10)="" for="" both="" consolidated="" and="" unconsolidated="" parts="" of="" the="" volcano.="" this="" trial="" shows="" that="" low="" cost="" helicopter="" mass="" drops="" can="" be="" successfully="" applied="" to="" safely="" determine="" sub-surface="" properties="" at="" hazardous="">