Estimation of the effective elastic thickness of the lithosphere: progress and prospects
The lithospheric strength is a key factor in controlling the lithosphere dynamics and deformations. The effective elastic thickness (Te) of the lithosphere can always be used to address the lithospheric strength. Hence, it is a powerful tool for studying the large-scale lithospheric structure. Estim...
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| Format: | Article |
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Editorial Office of Reviews of Geophysics and Planetary Physics
2022-05-01
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| Series: | 地球与行星物理论评 |
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| Online Access: | https://www.sjdz.org.cn/en/article/doi/10.19975/j.dqyxx.2021-062 |
| _version_ | 1797858686394171392 |
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| author | Wen Shi Shi Chen Jiancheng Han Lulu Jia |
| author_facet | Wen Shi Shi Chen Jiancheng Han Lulu Jia |
| author_sort | Wen Shi |
| collection | DOAJ |
| description | The lithospheric strength is a key factor in controlling the lithosphere dynamics and deformations. The effective elastic thickness (Te) of the lithosphere can always be used to address the lithospheric strength. Hence, it is a powerful tool for studying the large-scale lithospheric structure. Estimates of Te over both continent and ocean are important for understanding the lithospheric strength with its lateral variations, crustal gravity isostatic state, lithospheric thermal state and rheological structure, and the coupling at the lithosphere-asthenosphere boundary. This article summaries the background of Te estimation and reviews the domestic and overseas research progress on the estimation methods. The main methods for estimating Te include forward modeling of deformations, spectral techniques (i.e., admittance and coherence) based on the cross-spectral analysis of the gravity and topography data, and direct estimations of Te based on the yield strength envelope. The method of deformation forward modeling estimates Te from the optimal lithospheric deflection model, with which the calculated theoretical gravity anomalies best fit the observed ones. The spectral technique calculates Te through analyzing the relationship between observed gravity and topography data in the spatial wavenumber domain, including admittance and coherence methods. The admittance method operates the Te estimation basically based on the spectrum ratio of the gravity to topography signals, while the coherence method works by examining the variation characteristics of the relationship between those two signals in wavenumber domain. Under long-wavelength loading, the lithosphere tends to act as a regional isostatic equilibrium mode. In this model, the lithosphere deflected and the gravity anomaly could be completely related to the topography, i.e., the correlation between those two is close to 1. In contrast, under short-wavelength loading, the lithosphere usually does not deflect due to the lithospheric strength, hence the gravity-topography correlation is close to 0. The gravity-topography correlation decreases from 1 to 0 with the wavenumber. The wavelength around the change point of the correlation with the value of 0.5 representing the state transition of the lithosphere from isostatic equilibrium to disequilibrium, is determined by the lithospheric strength, hence could be used to address Te. The yield strength envelope method estimates Te based on the rock mechanics experiments which usually study how strength varies according to temperature and composition of the crust and mantle lithosphere. Recently, with the development of modern digital signal processing technology, spectral techniques have gradually become the most popular approaches for the Te estimation. Calculating the observed admittance and coherence needs the gravity and topography auto-spectra and the cross-spectrum to be computed first. Those two spectra can be obtained using periodogram, maximum entropy, multitapers and wavelet methods. Periodogram is a direct spectral estimation method used up until the late 1990s，although it is not a very accurate one due to the spectral leakage. While maximum entropy spectral estimation can minimize the spectral leakage to some extent and yield accurate spectra in small-window spectral estimation, multitaper method deals with spectral leakage well circumvent the problem of small window sizes. The wavelet method has also been widely developed for computing spectra during Te estimation, because the wavelet transform can separate closely spaced and high-wavenumber features, whilst the windowed Fourier transform likely to smear the information, either in space or wavenumber depending on the window size. The anisotropy of the lithosphere is an important parameter of the lithospheric mechanical property and can largely affect the calculated Te values. To obtain reliable Te, the anisotropy of Te should be considered during the Te estimation. Moreover, Te anisotropy can affect the crustal stress state, crustal rheological properties, and microfractures developments. Those subjects can provide important clues for the study of breeding environments, occurrence processes, and mechanisms of earthquakes. This review also discusses the principles, advantages, and disadvantages of the estimation methods. Finally, this article provides avenues for future research. |
| first_indexed | 2024-04-09T21:17:23Z |
| format | Article |
| id | doaj.art-65d8fb30586c4ff08c9676045dc40a5e |
| institution | Directory Open Access Journal |
| issn | 2097-1893 |
| language | zho |
| last_indexed | 2024-04-09T21:17:23Z |
| publishDate | 2022-05-01 |
| publisher | Editorial Office of Reviews of Geophysics and Planetary Physics |
| record_format | Article |
| series | 地球与行星物理论评 |
| spelling | doaj.art-65d8fb30586c4ff08c9676045dc40a5e2023-03-28T07:02:47ZzhoEditorial Office of Reviews of Geophysics and Planetary Physics地球与行星物理论评2097-18932022-05-0153330131510.19975/j.dqyxx.2021-0622021-062Estimation of the effective elastic thickness of the lithosphere: progress and prospectsWen Shi0Shi Chen1Jiancheng Han2Lulu Jia3Institute of Geophysics, China Earthquake Administration, Beijing 100081, ChinaInstitute of Geophysics, China Earthquake Administration, Beijing 100081, ChinaInstitute of Geophysics, China Earthquake Administration, Beijing 100081, ChinaInstitute of Geophysics, China Earthquake Administration, Beijing 100081, ChinaThe lithospheric strength is a key factor in controlling the lithosphere dynamics and deformations. The effective elastic thickness (Te) of the lithosphere can always be used to address the lithospheric strength. Hence, it is a powerful tool for studying the large-scale lithospheric structure. Estimates of Te over both continent and ocean are important for understanding the lithospheric strength with its lateral variations, crustal gravity isostatic state, lithospheric thermal state and rheological structure, and the coupling at the lithosphere-asthenosphere boundary. This article summaries the background of Te estimation and reviews the domestic and overseas research progress on the estimation methods. The main methods for estimating Te include forward modeling of deformations, spectral techniques (i.e., admittance and coherence) based on the cross-spectral analysis of the gravity and topography data, and direct estimations of Te based on the yield strength envelope. The method of deformation forward modeling estimates Te from the optimal lithospheric deflection model, with which the calculated theoretical gravity anomalies best fit the observed ones. The spectral technique calculates Te through analyzing the relationship between observed gravity and topography data in the spatial wavenumber domain, including admittance and coherence methods. The admittance method operates the Te estimation basically based on the spectrum ratio of the gravity to topography signals, while the coherence method works by examining the variation characteristics of the relationship between those two signals in wavenumber domain. Under long-wavelength loading, the lithosphere tends to act as a regional isostatic equilibrium mode. In this model, the lithosphere deflected and the gravity anomaly could be completely related to the topography, i.e., the correlation between those two is close to 1. In contrast, under short-wavelength loading, the lithosphere usually does not deflect due to the lithospheric strength, hence the gravity-topography correlation is close to 0. The gravity-topography correlation decreases from 1 to 0 with the wavenumber. The wavelength around the change point of the correlation with the value of 0.5 representing the state transition of the lithosphere from isostatic equilibrium to disequilibrium, is determined by the lithospheric strength, hence could be used to address Te. The yield strength envelope method estimates Te based on the rock mechanics experiments which usually study how strength varies according to temperature and composition of the crust and mantle lithosphere. Recently, with the development of modern digital signal processing technology, spectral techniques have gradually become the most popular approaches for the Te estimation. Calculating the observed admittance and coherence needs the gravity and topography auto-spectra and the cross-spectrum to be computed first. Those two spectra can be obtained using periodogram, maximum entropy, multitapers and wavelet methods. Periodogram is a direct spectral estimation method used up until the late 1990s，although it is not a very accurate one due to the spectral leakage. While maximum entropy spectral estimation can minimize the spectral leakage to some extent and yield accurate spectra in small-window spectral estimation, multitaper method deals with spectral leakage well circumvent the problem of small window sizes. The wavelet method has also been widely developed for computing spectra during Te estimation, because the wavelet transform can separate closely spaced and high-wavenumber features, whilst the windowed Fourier transform likely to smear the information, either in space or wavenumber depending on the window size. The anisotropy of the lithosphere is an important parameter of the lithospheric mechanical property and can largely affect the calculated Te values. To obtain reliable Te, the anisotropy of Te should be considered during the Te estimation. Moreover, Te anisotropy can affect the crustal stress state, crustal rheological properties, and microfractures developments. Those subjects can provide important clues for the study of breeding environments, occurrence processes, and mechanisms of earthquakes. This review also discusses the principles, advantages, and disadvantages of the estimation methods. Finally, this article provides avenues for future research.https://www.sjdz.org.cn/en/article/doi/10.19975/j.dqyxx.2021-062lithosphereeffective elastic thicknessadmittancecoherencemechanical anisotropy |
| spellingShingle | Wen Shi Shi Chen Jiancheng Han Lulu Jia Estimation of the effective elastic thickness of the lithosphere: progress and prospects 地球与行星物理论评 lithosphere effective elastic thickness admittance coherence mechanical anisotropy |
| title | Estimation of the effective elastic thickness of the lithosphere: progress and prospects |
| title_full | Estimation of the effective elastic thickness of the lithosphere: progress and prospects |
| title_fullStr | Estimation of the effective elastic thickness of the lithosphere: progress and prospects |
| title_full_unstemmed | Estimation of the effective elastic thickness of the lithosphere: progress and prospects |
| title_short | Estimation of the effective elastic thickness of the lithosphere: progress and prospects |
| title_sort | estimation of the effective elastic thickness of the lithosphere progress and prospects |
| topic | lithosphere effective elastic thickness admittance coherence mechanical anisotropy |
| url | https://www.sjdz.org.cn/en/article/doi/10.19975/j.dqyxx.2021-062 |
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