← Back to Sessions

Pn Wave Attenuation Beneath the Caribbean Plate

Description: 

The Caribbean plate is trapped among the North and South American continental plates and the Atlantic and Pacific oceanic plates (Freeland and Dietz, 1971). It suffers from the north-south trend squeeze from continental lithospheres and the east-west trend subduction of the oceanic plates, respectively (e.g., Stein et al., 1988). Therefore, the deformed Caribbean lithosphere is composed of terrains of different types tectonically squeezed together. The dynamic processes caused the upwelling of deep mantle materials and dramatically changed the property of the crust and uppermost mantle in this region. We use Pn-wave attenuation to investigate the thermal distribution in the uppermost mantle and provide seismological constraints on the mechanism of dynamic processes. Based on 19,200 broadband vertical-component digital seismograms, we investigate both the Pn-wave geometric spreading and attenuation in the Caribbean region. We extract Pn signals using a 0.7 km/s group-velocity window around their first arrival times obtained based on the machine learning, followed by measuring Pn spectra within the 0.5 to 10.0 Hz band. A frequency-dependent Pn geometric spreading function is obtained by fitting the observed Pn spectra. Then, a preliminary Pn attenuation model can be obtained from the two-station Pn spectra data. A frequency-dependent Pn-wave Q tomography is conducted based on both two-station and single-station data to construct the uppermost mantle Q model beneath the Caribbean plate (Yang et al., 2022; Zhao et al., 2015). Strong Pn attenuation can be observed beneath the Venezuela Basin, the southern part of the Colombia Basin, and the northern South American plate. Strong Pn attenuation in the junction area among the Venezuela Basin, the Atlantic subduction plate, and the northern South American plate, combining with previous velocity and anisotropy studies, reveals that there seems to be uppermost mantle flow in this region (Braszus et al., 2021; Growdon et al., 2009). This work is supported by the National Natural Science Foundation of China (grants U2139206, 41974054, 41974061).

Session: General Seismology

Type: Poster

Date: 4/18/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Lian-Feng Zhao

Student Presenter: No

Invited Presentation: 

Authors