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Lateral Variations of Crustal Lg-Wave Attenuation in the Scandinavia Peninsula and Its Vicinity

Description: 

The Scandinavian Peninsula region includes the Baltic shield and a series of passive continental margins, which are featured by abrupt changes in crustal thickness (Ziegler, 1986). A potential point of subduction initiation is likely located in the passive continental margins existed weak zone. Seismic Lg wave is sensitive to the sudden change of the waveguide structure, thermal anomaly, and weak zone in the crust (Bouchon, 1982). The Lg attenuation structure can provide constraints on the location of potential subduction initiation. Then, we construct a broadband Lg attenuation model between 0.05 and 20.0 Hz by conducting the Lg wave Q tomography (Zhao et al., 2010) in and around the Scandinavian Peninsula, with resolutions of reaching 1° or higher in the regions with dense ray path coverage. A total of 37,735 vertical-component broadband digital seismograms was used to create a dataset which is larger and more updated than those previously used in this region (Demuth et al., 2019). The dataset is composed of seismograms from 449 earthquakes recorded by 863 stations, mostly from the IRIS and GEOFON Seismic Network between 1992 and 2021. Prominent lateral variations of Q_Lg values at various frequencies and the consistent between Q_Lg distributions and the regional geological blocks were observed. The Baltic Shield, a large stable crust, is characterized by weak attenuation. The relatively low Q values in the North Sea Basin presented strong attenuation, presumably because the covered sediments and the developed graben structure hindered the propagation of the Lg wave. And strong Lg attenuation was observed in the passive continental margins, where the crust is weakening caused by underground high-temperature anomalies, changes in crust thickness, and overlying thick sediments. Therefore, it is speculated that the potential subduction initiation zone in the future may be located near the Lofoten-Vesterålen Margin with the strongest attenuation. This research was supported by the National Natural Science Foundation of China (41974061, 41974054, 41630210, and U2139206).

Session: Earth’s Structure From the Crust to the Core [Poster]

Type: Poster

Date: 4/18/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Zhen Liu

Student Presenter: Yes

Invited Presentation: 

Authors