Unravelling the excitation mechanism of very long-period (VLP) tremors in the Gulf of Guinea: evidence for vibrations of thin surface crustal plates

Xia，Yingjie1,2,3; Feng，Xuping1,2; Chen，Xiaofei1,2

2024-05-01

10.1093/gji/ggae090

Geophysical Journal International   影响因子和分区

0956-540X

1365-246X

The Gulf of Guinea exhibits a continuous emission of narrow-band and long-period signals (16, 26 and 27 s) on teleseismic records, yet the underlying excitation mechanism remains unclear. This study establishes a connection between these tremors and the vibration of thin, decoupled crustal plates at unexplored volcanoes in the gulf. We first formulate the damped plate oscillation equation, by incorporating the vibration of the thin surface crustal plate and magma flow in the subsurface sill. The findings reveal that a fundamental-mode vibration with a period of several dozen seconds can be induced by a crustal plate that is less than 1.0 km thick but extends over tens of kilometres in both length and width, given a subsurface sill depth exceeding 10.0 cm. The thin plate hypothesis also allows for excitation of a few overtone modes, but such waves in higher frequencies diminish over long distances, leaving only the monotonous fundamental-mode vibration at teleseismic stations. The long duration of Guinea tremors at each recurrence is attributed to the presence of low viscosity basaltic magma, which influences the damping factor. Direct wave loads at the shallow gulf serve as the primary vibration source, accounting for seasonal variations and recurring patterns. Sporadic energy bursts may also occur due to large storms. Radiation patterns of Guinea tremors are linked to the geometric structure of the thin plate. Our theoretical estimates of tremor spectra closely align with observed data, confirming the model’s accuracy in capturing reported Guinea tremor characteristics. This study provides valuable insights into the origins of very long-period tremors at continental volcanoes.

Seismic noise Subaqueous volcanism Theoretical seismology Volcano seismology

SCI ; EI

英语

第一

GEOSCIENCES

2-s2.0-85189137073

Scopus

1.Guangdong Provincial Key Laboratory of Geophysical High-resolution Imaging Technology,Southern University of Science and Technology,Shenzhen,518055,China
2.Department of Earth and Space Sciences,Southern University of Science and Technology,Shenzhen,518055,China
3.Department of Astronautical Science and Mechanics,Harbin Institute of Technology,Harbin,150006,China

Xia，Yingjie,Feng，Xuping,Chen，Xiaofei. Unravelling the excitation mechanism of very long-period (VLP) tremors in the Gulf of Guinea: evidence for vibrations of thin surface crustal plates[J]. Geophysical Journal International,2024,237(2):1079-1092.

Xia，Yingjie,Feng，Xuping,&Chen，Xiaofei.(2024).Unravelling the excitation mechanism of very long-period (VLP) tremors in the Gulf of Guinea: evidence for vibrations of thin surface crustal plates.Geophysical Journal International,237(2),1079-1092.

Xia，Yingjie,et al."Unravelling the excitation mechanism of very long-period (VLP) tremors in the Gulf of Guinea: evidence for vibrations of thin surface crustal plates".Geophysical Journal International 237.2(2024):1079-1092.