Effect of sea-bottom elasticity on the propagation of acoustic–gravity waves from impacting objects

Abstract

Recent analysis of data, recorded on March 8th 2014 at the Comprehensive Nuclear-Test-Ban Treaty Organisation’s hydroacoustic stations off Cape Leeuwin Western Australia, and at Diego Garcia, has led to the development of an inverse model for locating impacting objects on the sea surface. The model employs the phase velocity of acoustic–gravity waves that radiate during the impact, and only considers their propagation in the water layer. Here, we address a significant characteristic of acoustic–gravity waves: the ability to penetrate through the sea-bottom, which modifies the propagation speed and thus the arrival time of signals at the hydrophone station. Therefore, we revisit some signals that are associated with the missing Malaysian Aeroplane MH370, and illustrate the role of sea-bottom elasticity on determining impact locations.

Acoustic–gravity waves from multi-fault rupture

“…The first lies in the assumption of constant depth, and thus effective techniques that take into account changes due to topography without computing the whole 3-D domain need to be developed. The second reason is the neglect of sea-floor elasticity, which turns out to be important for both tsunami and acoustic-gravity wave arrival times (Kadri 2019). For the tsunami, neglecting elasticity results in overestimation of the phase speed (Watada 2013;Watada, Kusumoto & Satake 2014;Abdolali et al 2015bAbdolali et al , 2018.…”

“…Hence, acoustic-gravity waves can not only act as excellent precursors, but they could also provide vital information on the geometry and dynamics of the effective uplift, which eventually shapes the main characteristics of the tsunami. Note that sea-bottom elasticity can significantly affect the phase speed of acoustic-gravity waves but only in shallow water (Eyov et al 2013;Kadri 2019). On the other hand, water compressibility and sea-bottom elasticity affect the phase speed of surface gravity waves and should be considered when accurate transoceanic tsunami modelling is sought Abdolali, Kadri & Kirby 2019).…”

“…Note that sea-bottom elasticity can significantly affect the phase speed of acoustic–gravity waves but only in shallow water (Eyov et al. 2013; Kadri 2019). On the other hand, water compressibility and sea-bottom elasticity affect the phase speed of surface gravity waves and should be considered when accurate transoceanic tsunami modelling is sought (Abdolali & Kirby 2017; Abdolali, Kadri & Kirby 2019).…”

WITHDRAWN: MH370 Controlled Eastward Veering and Descent After the 6th Arc

“…In early 2021, the fuel starvation theory which guided previous searches was challenged by the "Penang Longitude" (PL) theory [6] which not only reconciled the drift model analyses but also reconciled the pilot's home simulator tracks, satellite anomalies and hydroacoustic sounds heard at listening stations at Perth Canyon [7], Cape Leeuwin and Diego Garcia [8]; which were all abandoned previously as they could not be reconciled with a crash site along the 7 th arc. The theory was predicated on the notion that there is one precise location for MH370, namely where the 33 o S latitude intersects the longitude of Penang, where all evidence appears to plausibly intersect at an ultra-deep hole.…”

On the propagation of acoustic–gravity waves due to a slender rupture in an elastic seabed

“…Moreover, the slender-fault model was applied to more complex, multi-fault scenarios, such as the 2016 Kaikoura earthquake (Hamling et al 2016), via linear superposition -but still with a rigid seabed. However, the elastic properties of the solid medium should not always be ignored (Abdolali, Kadri & Kirby 2019;Kadri 2019) since the water compressibility and seabed elasticity affect the phase speed of surface waves, and thus the arrival times of transoceanic tsunamis (Abdolali et al 2019). A complementary work by Eyov et al (2013) investigated the consequences of imposing an elastic seabed as support for a liquid layer residing in a gravitational field upon the form of the dispersion relation.…”