Mapping the Alaskan Lithosphere Based Upon Joint Full-Waveform Inversion of Ambient Noise and Local Earthquake Data
Description:
Alaska is one of the most tectonically active regions in North America, with unique and complex geologic structures shaped by multiple episodes of tectonic processes in the geologic history. We aim to construct a high-resolution shear-velocity model of the entire Alaskan lithosphere to better understand the tectonic evolution of this region.
We use high-quality broadband seismic data, bolstered by the USArray deployment in Alaska, to image the shear velocity of the crust and uppermost mantle. To resolve both shallow and deep structures in the lithosphere, we jointly use ambient noise data and local earthquake data to perform full-waveform seismic inversion. For ambient noise data, continuous seismic records are collected and processed to extract the three-component empirical Green’s functions (EGFs) between station pairs, and frequency-dependent travel-time shifts are measured between the EGFs and the simulated Green’s functions. For local earthquake data, instead of directly using the absolute travel-time shifts, we measure the difference of the frequency-dependent travel-time shifts between station pairs, known as double difference (Yuan et al. 2016), to enhance receiver-side resolution and mitigate the effect of inaccurate event centroid times. The waveforms are filtered at a period band of 12-50s for ambient noise data, and 25-120s for local earthquake data, for measurements, which are then inverted using the adjoint tomography method to obtain the structural model. The forward and adjoint simulations are carried out using the SPECFEM3D_Cartesian package on a mesh customized to the dimension of the study region. The dynamic mini-batch technique (van Herwaarden et al. 2020) is used to accelerate the inversion process.
We present our model from the surface down to 150km depth, revealing the variation of crustal thickness in this region, magmatic activities and a segmented subducted slab in Southern Alaska. At broad scale, the tomographic image shows that the Alaskan lithosphere can be divided into three blocks, each with a distinct tectonic feature.
Session: Structure and Behavior of the Alaska-Aleutian Subduction Zone [Poster Session]
Type: Poster
Date: 5/3/2024
Presentation Time: 08:00 AM (local time)
Presenting Author: Qinya
Student Presenter: No
Invited Presentation:
Authors
Tianshi Liu Corresponding Author tianshi.liu@mail.utoronto.ca University of Toronto |
Kai Wang wangk@ustc.edu.cn University of Science and Technology of China |
Carl Tape ctape@alaska.edu University of Alaska Fairbanks |
Bin He binhebj@gmail.com University of Texas at Dallas |
Yingjie Yang yangyj@sustech.edu.cn Southern University of Science and Technology |
Ping Tong tongping@ntu.edu.sg Nanyang Technological University |
Qinya Liu Presenting Author qinya.liu@utoronto.ca University of Toronto |
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Mapping the Alaskan Lithosphere Based Upon Joint Full-Waveform Inversion of Ambient Noise and Local Earthquake Data
Category
Structure and Behavior of the Alaska-Aleutian Subduction Zone