1pUW2. Estimation of fracture speed for Arctic ice-induced acoustic events.

Session: Monday Afternoon, December 2

Time: 2:16

Author: Catherine Stamoulis
Location: Dept. of Civil and Environ. Eng., MIT, Cambridge, MA 02139
Author: Ira Dyer
Location: MIT, Cambridge, MA 02139


The estimation of source parameters such as peak frequency, Doppler shift, and fracture speed is fundamental in the study of radiation from ice motion processes in the central Arctic. For this purpose, a population of acoustic events from the SIMI experiment data was analyzed, and fracture parameters estimated in the frequency range between 10 and 350 Hz. Both low- and midfrequency events, i.e., with peak frequencies below 100 Hz and between 100 and 350 Hz, respectively, were detected. For each event, the Doppler shift was first obtained through cross correlation of the event spectra at hydrophones of the receiving array. This was subsequently used to determine the fracture speed, assuming both horizontal and vertical motion. In the case of ice fracture, the latter is the rupture propagation speed, the upper bound of which is the Rayleigh wave speed. Previously (Chen, 1990), this value (approximately 1700 m s[sup -1] for sea ice) has been assumed as the fracture speed. The present analysis shows that for the detected events, the fracture speed is considerably lower, specifically, between approximately 100 and 800 m s[sup -1]. This result suggests that ice fracture details affect significantly the propagation speed. [Work supported by ONR, Seismo-Acoustic Remote Sensing of the Arctic Environment.]

ASA 132nd meeting - Hawaii, December 1996