DI024-0010
S-coda wave analysis of InSight seismic data to determine the scattering and intrinsic attenuation in the crust of Mars
Tuesday, 15 December 2020
Poster
Foivos Georgios Karakostas1, Nicholas C Schmerr1, Ross Maguire2, Doyeon Kim3, Quancheng Huang4, Taichi Kawamura5, Keisuke Onodera6, Philippe Henri Lognonné7, Domenico Giardini8 and William Bruce Banerdt9, (1)University of Maryland College Park, College Park, MD, United States, (2)University of New Mexico Main Campus, Albuquerque, NM, United States, (3)Cornell University, Ithaca, NY, United States, (4)University of Maryland, Department of Geology, College Park, MD, United States, (5)Université de Paris, Institut de physique du globe de Paris, Paris, France, (6)Université de Paris, Institut de Physique du Globe de Paris, Paris, France, (7)Université de Paris, Institut de physique du globe de Paris, CNRS, Paris, France, (8)Swiss Federal Institute of Technology (ETH), Zurich, Switzerland, (9)JPL/NASA/Caltech, Pasadena, CA, United States
Abstract:
The attenuation of seismic waves is caused by both scattering and loss to friction, and informs on the grain size, temperature, volatile abundance, and nature of heterogeneity within the interior of a planet. Attenuation of seismic waves from scattering originates where there are significant changes in seismic velocity or density, and is common in regions with highly fractured rocks, high porosities, or complex geological structures. Intrinsic attenuation, or loss of seismic energy to internal friction, is governed by deformation along grain boundaries and results in the dissipation of seismic energy to heat. The estimation of these two types of attenuation by studying the decay of seismic waves can provide useful information about the subsurface and, depending on the magnitude and epicentral distance of the seismic events, the structure in greater depths of the planetary interior.
In this study, we perform an attenuation analysis on a dataset of martian seismic events, recorded by the NASA InSight mission seismometer (SEIS), and catalogued by the Marsquake Service (MQS). We focus on S-wave codas, as their decay and duration depend on the parameters that control both the aforementioned types of attenuation, and are readily apparent in InSight seismograms. As the events are recorded by only one seismometer, our analysis provides a one-dimensional attenuation model of the Martian crust and shallow mantle. Our approach fits envelopes of the coda, allowing variation in thickness and diffusivity of layer in the shallow crust, that sits over a more elastic layer of the Martian crust. From the model results, we infer the bulk intrinsic and scattering attenuation (Qi and Qs respectively) for individual events in the dataset. Our initial results show a frequency dependent intrinsic attenuation, whereas both types of attenuation are decreasing with the epicentral distance and the seismic velocity, indicating the presence of a strongly scattered non-elastic shallow layer.
