Friday Informal Seminar Hour - G. NInto Occhipinti (IPGP)
No Magnitude, No Glory - The recent history of Ionospheric Seismology from Sumatra 2004 to Chile 2015 through the revolutionary observations of Tohoku-Oki 2011
Detection of ionospheric anomalies following the Sumatra and Tohoku earthquakes (e.g., Occhipinti et al. 2006, 2010, 2011, 2013) demonstrated that ionosphere is sensitive to earthquake and tsunami propagation: ground and oceanic vertical displacement induces acoustic-gravity waves propagating within the neutral atmosphere and detectable in the ionosphere. Observations supported by modelling proved that ionospheric anomalies related to tsunamis and Rayleigh waves are deterministic and reproducible by numerical modeling via the ocean/neutral-atmosphere/ionosphere coupling mechanism (Occhipinti et al., 2008, 2010). Ionospheric observations, compared with classic seismometers, consistent with the propagation of Rayleigh waves related to 38 events, with a magnitude larger than 6.2, is showed here to prove that “ionospheric seismometers” are useful seismological data to estimated magnitude and better cover the Earth. Concerning tsunamis, to prove that the their signature in the ionosphere is routinely detected we show here perturbations of total electron content (TEC) measured by GPS and following tsunamigenic earthquakes from 2004 to 2011 (Rolland, Occhipinti et al. 2010, Occhipinti et al., 2013), nominally, Sumatra (26 December, 2004 and 12 September, 2007), Chile (14 November, 2007), Samoa (29 September, 2009) and the recent Tohoku-Oki (11 Mars, 2011). Based on the observations close to the epicenter, mainly performed by GPS networks located in Sumatra, Chile and Japan, we highlight the TEC perturbation observed within the first hour after the seismic rupture. This perturbation contains information about the ground displacement, as well as the consequent sea surface displacement resulting in the tsunami. In addition to GPS-TEC observations close to the epicenter and measured by GEONET network, new exciting measurements in the far-field were performed by Airglow measurement in Hawaii: those measurements show the propagation of the IGWs induced by the Tohoku tsunami in the Pacific Ocean (Occhipinti et al., 2011). This revolutionary imaging technique is today supported by two new observations of moderate tsunamis: Queen Charlotte (M: 7.7, 27 October, 2013) and Chile (M: 8.2, 16 September 2015). The potential idea to put an Airglow camera on a satellite opens new exciting perspectives for tsunami detection.
In this talk we present all this new earthquake and tsunami observations in the ionosphere and we discuss, under the light of modelling, the potential role of ionospheric sounding in magnitude estimation, oceanic monitoring and future tsunami warning system.
About the Speaker
Thanks to technological advances over the past fifteen years the ionosphere has today become the new sensitive medium to seismc events. Surface waves (Rayleigh and tsunami) emitted after large earthquakes are known to induce, by dynamic coupling, atmospheric infrasonic and gravity waves propagating upward through the atmosphere. These waves growing up to the top of the atmosphere are strongly amplificated by the effect of exponential decreasing of density with altitude. Ionospheric Seismology may thus turn out to be a useful new tool in investigating mantle tomography, seismic activity in others planets and improving tsunami detection & ocean monitoring.
About this Series
The Friday Informal Seminar Hour [FISH, Earth Resources Laboratory] is a postdoc-run weekly seminar series within the ERL. Topics include research relating to geophysics, and in particular seismology, with applications in Earth resources exploration such as e.g. seismics exploration, microseismicity, earthquake physics, and Earth imaging techniques. The seminars usually take place on Fridays at 12 noon in 54-209 (term-time only). 2016/2017 co-ordinators: William Frank (firstname.lastname@example.org), Chen Gu (email@example.com), Joshua Kastorf (firstname.lastname@example.org)