Analysis of Long-Term Gravitational and Seismic Measurements in the Pamir - Tien-Shan Region

Sverdlik, Leonid; Lazareva, Ekaterina N.

doi:10.1051/e3sconf/202022303014

E3S Web Conf.

2020

DOI: 10.1051/e3sconf/202022303014

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Analysis of Long-Term Gravitational and Seismic Measurements in the Pamir - Tien-Shan Region

Leonid Sverdlik

Ekaterina N. Lazareva

Abstract: Long-term variations (2003–2015) of the Equivalent Water Height (EWH) above the geoid's contour obtained from GRACE satellite measurements are analyzed to establish the relationship between changes in the gravitational field with the stress-strain state of the geological environment and the seismic process in Central Asia (Pamir and Tien-Shan regions). The earthquakes gravitational effects study, based on the use of various GRACE models allows us to distinguish the component of the gravity field, which may be … Show more

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Cited by 2 publications

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Filling the gap between GRACE and GRACE follow-on observations based on principal component analysis

Gu,

Huang,

Huang

et al. 2023

Geophysical Journal International

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Summary The Gravity Recovery and Climate Experiment (GRACE) and its successor, GRACE Follow-On (GRACE-FO), have revolutionized the approach to monitoring global mass variations. However, the presence of several gaps, notably the continuous 11-month gap between the two missions, has generated a disruption in observations and hindered the analysis and application of the data. To address this problem, we have proposed a spectral domain gap-filling approach based on principal component analysis (PCA). Our simulation experiments demonstrate that the PCA gap-filling technique has significant potential to successfully reconstruct global mass variation and accurately capture real signals for most basins with an accuracy of less than 2 cm. When applied to actual missing data, our methodology delivers highly consistent results with previously published filling approaches, such as singular spectrum analysis and improved multichannel singular spectrum analysis method, for most of the global basins. Noteworthy, in the case of the Nelson basin, our PCA gap-filling method outperforms other methods in capturing seasonal signals and the return to a normal level of the terrestrial water storage changes in 2018. A comparison in the spectral domain indicates that the accuracy of the PCA-filling output is comparable to the original GRACE(-FO) data. Moreover, our method exhibits high generality, allowing for direct application to continuous GRACE(-FO) data without other additional data processing and without differentiating the types of missing data. Therefore, the proposed PCA gap-filling method offers exciting opportunities to guarantee the continuity of global mass change observations and benefit subsequent applications that require continuous data records.

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Filling the gap between GRACE and GRACE follow-on observations based on principal component analysis

Gu,

Huang,

Huang

et al. 2023

Geophysical Journal International

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The relationship between GRACE gravity and the seismic b-value: a case study of the Northern Chile Triple Junction (25° S–40° S)

Sun,

Li,

Guo

et al. 2024

Geophysical Journal International

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Summary The northern Chile Triple Junction (CTJ) is characterized by the ongoing subduction of the Nazca plate beneath the South American plate. The geological structures within the subduction zone undergo complex changes, resulting in significant tectonic activities and intense seismicity along the western margin of South America. Based on the Gravity Recovery and Climate Experiment (GRACE) data and earthquake catalogues, this study selects the northern CTJ area (25°S-40°S, 75°W-65°W) as the research object, adopts the mathematical methods of Independent Component Analysis (ICA) and Principal Component Analysis (PCA) to separate the earthquake-related signals within the GRACE data, and fits the changes of seismic b-values through the frequency-magnitude relationship. The characteristics of gravity changes before and after seismic events, the seismic activity parameter b-values, and the relationship between the gravity signals and b-values are discussed. The results show that mathematical methods can effectively extract seismic-related gravity components from the GRACE data. ICA, compared to PCA, provides better results in capturing the temporal variations associated with b-value time series, which exhibit good consistency in long-term trend changes. The average change of b-values in the study area is 0.66 ± 0.003, fluctuating over time. Generally, prior to larger seismic events, b-values tend to decrease. Along the western margin of South America, b-values are low; this aligns with the active tectonic activities between subducting plates. Additionally, a certain correlation between b-values and gravity changes is observed, but due to the influence of tectonic activities, the correspondence between b-values and gravity anomalies may not be consistent across different areas. The b-value is highly consistent with the strain rate model. Low b-values correspond to high strain rates along the western edge of South America, which is in line with the tectonic characteristics of frequent seismic activity in this area. A gradual concentration of gravity anomalies before major earthquakes is observed, accompanied by the gradual accumulation of smaller seismic events. Meanwhile, several months before the two major earthquakes, the spatial distribution of gravity appears to be similar to the co-seismic signals, but the nature of its generation remains to be explored. These methods and results not only add to the applications of GRACE in seismic studies but also raise questions for further exploration.

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Analysis of Long-Term Gravitational and Seismic Measurements in the Pamir - Tien-Shan Region

Cited by 2 publications

References 6 publications

Filling the gap between GRACE and GRACE follow-on observations based on principal component analysis

Filling the gap between GRACE and GRACE follow-on observations based on principal component analysis

The relationship between GRACE gravity and the seismic b-value: a case study of the Northern Chile Triple Junction (25° S–40° S)

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