Determining Crustal Attenuation With Seismic T Waves in Southern Africa. Issue 15 (7th August 2021)

• Record Type: Journal Article
• Authors: Zhou, Yong; Chen, Xiaofei; Ni, Sidao; Qian, Yunyi; Zhang, Yayun; Yu, Chuanhai; Zhong, Qiu; Zheng, Tingting; Xu, Min
• Is Part Of: Geophysical research letters. Volume 48:Issue 15(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-08-07
• Subjects: Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL094410
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Crustal attenuation structures obtained at high frequencies (>1 Hz) are important for seismic risk assessment and geodynamics studies in stable continents. However, it is difficult to infer attenuation in low seismicity regions using body and surface waves. In this study, we explore the potential of using seismic T phases to constrain the crustal attenuation. We analyzed the characteristics of T waves recorded on the seismic array deployed in southern Africa. The converted station‐side T‐P and T‐S phases were identified by analyzing the waveform, travel time, polarization, and frequency‐wavenumber features. The distinct differences in polarization and slowness are used to quantify contributions from T‐P and T‐S conversions. The inverted frequency‐dependent Qp and Qs (attenuation factor of local P and S waves, respectively) in the southern Africa are found to be 204 f 1.48 and 685 f 0.53, respectively. Our method could be extended to infer crustal attenuation features near the coasts of other continents. Plain Language Summary: Crustal attenuation structures of stable continents are important for seismic risk assessment and geodynamics studies to identify and mitigate destructive earthquakes that occur occasionally. Conventional methods using seismic phases, such as local P, local S, Lg and surface wave, are usually applied in areas with high seismicity; however, the use of these phases is not effective in low seismicity regions. Our study demonstrates the potential of employing seismic T phases to constrain the crustal attenuation structure in stable continents (low seismicity regions) near the coast. Based on the seismic waveform data recorded on an array in southern Africa, we identified the station‐side T‐P and T‐S phases, which were converted from acoustic T waves traveling through the sound fixing and ranging (SOFAR) channel in the ocean to the local P and S waves in continental crust. Then, the attenuation structure at high frequency in southern Africa was revealed with the characteristics of converted T‐P and T‐S phases, which match well with the previous results. This method can also be used to infer crustal attenuation in other stable continents near the coast, even if the continents do not experience high seismicity. Key Points: We demonstrate the potential of employing T waves for inverting crustal attenuation structure in coastal regions of stable continents The converted T ‐ P / S_ local phases were identified by analyzing the seismic waveform, travel time, polarization, and array techniques The crustal attenuation of Qp ( 204 f 1.48 ) and Qs ( 685 f 0.53 ) obtained in southern Africa match well with the previous results