Problems of the Joint Inversion of Temporal Gravity Variations with the Data on Land and Seafloor Displacements: a Case Study of the Tohoku-Oki Earthquake of March 11, 2011

National Report for the IAG of the IUGG 2019–2022

“…Based on the joint inversion of GRACE satellite data, offsets at GPS sites and bottom transponders, as well as displacement fields from satellite radar interferometry data, a new model of the rupture surface of the Tohoku earthquake, Japan, March 11, 2011 was constructed [Mikhailov et al, 2019a, b]. Using data on temporal variations in the GRACE gravity field coseismic and postseismic processes in the region of large earthquakes were studied: in the Wharton basin in 2012 [Diament et al, 2020], the Maule earthquake in Chile on February 27, 2010 [Mikhailov et al, 2020]. Models of the rupture surface of the Khuvsgul earthquake in Mongolia on January 12, 2021 , the Near Aleutian earthquake on the Commander Islands on July 17, 2027 , and the Near Ozernovsky earthquakes in Kamchatka were constructed based on SAR interferometry and GPS data.…”

“…Various numerical models have been developed to interpret the obtained strain fields. For example, when studying the Tolbachik lava field, which was formed as a result of the 2012-2013 eruption, an area with an anomalously high rate of surface subsidence was identified using SAR data [Mikhailov et al, 2020;Volkova et al, 2022]. A new mathematical model of lava flow cooling was constructed, which made it possible to obtain estimates of various physical properties of lava (the content of pores, glasses), the rate of formation of the flow thickness, and also to explain the reasons for the appearance of an area with an abnormally rapid subsidence of the lava surface.…”

Enigma of the Olyutorskii Earthquake Resolved by SAR Interferometry

“…Assuming that the medium accommodating the ruptures is purely elastic or viscoelastic, this inverse problem is linear but illposed. It should be noted that a successful resolution (chessboard) test does not necessarily guarantee good quality of the solution if the model of the seismic rupture does not properly approximate the real one (Mikhailov et al, 2019). Therefore, to obtain a reliable solution, it is crucial to incorporate as much additional data as possible.…”

Refinement of parameters gravitational anomaly relative to the focal zone of the 2011 earthquake (Japan) based on satellite data

“…In March 2011, the EWH value relative to the epicenter was 1.75 cm. The authors of [6] supposed that formation of the positive anomaly was related to the rising of the bottom of the ocean during the geodynamic activity in the region.…”

“…The purpose of the present study was to refine parameters of gravitational anomalies that occurred at the epicenters of strong earthquakes of magnitudes Mw > 8 that happened in the Pacific Ocean subduction zone, using GRACE data. As a case study, we considered the area of the hypocenter of the catastrophic Japan earthquake of Mw = 9.1, which occurred at 05:46:23 UTC on March 11, 2011. 1 Integrative processing of geophysical data Note that the data of monitoring gravitational anomalies observed during the strongest seismic events in these regions were analyzed using the GRACE measurements [6][7][8]. Analysis of the spatial structure of the anomalies confirmed the theoretical assumptions about the redistribution of the internal mass of solid Earth during geodynamic activity.…”