Extracting borehole strain precursors associated with the Lushan earthquake through principal component analysis

Zhu, Kaiguang; Chi, Chengquan; Yu, Zhenglei; Zhang, Weichen; Fan, Mengxuan; Li, Kaiyan; Zhang, Qiong

doi:10.4401/ag-7633

Cited by 9 publications

(10 citation statements)

References 23 publications

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“…For ground-based stations, PCA (principal component analysis) has been applied to ULF magnetic field data from three stations to separate signals generated by different sources and extract the main anomalous features of an earthquake [36]. PCA has also been applied to 3-component borehole strain data to extract the anomalies in the eigenvalues and eigenvectors [37].…”

Section: Introductionmentioning

confidence: 99%

Precursor Analysis Associated With the Ecuador Earthquake Using Swarm A and C Satellite Magnetic Data Based on PCA

Zhu

Fan

et al. 2019

IEEE Access

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In this paper, we revisit this earthquake by simultaneously analyzing the magnetic field data of Swarm satellite A and satellite C based on principal component analysis (PCA), and the eigenvalues and principal components are calculated throughout 2016. We find that the first principal component mainly contains the signal originating from solar-terrestrial effects such as geomagnetic activity since the first eigenvalue and the geomagnetic index are highly correlated. Therefore, the second principal component is used to extract the anomalies associated with the Ecuador earthquake in terms of skewness and kurtosis. The anomalous tracks of the S-K (Skewness-Kurtosis) coefficient are accumulated from 90 days before the event to 30 days after. The cumulative number follows an accelerating power-law behavior before the earthquake and decelerating recovery behavior after the earthquake; moreover, the inflection point of the sigmoidal fitting curve is close to the time of the earthquake. The cumulative number of anomalous tracks in the random regions shows a linear increase, further verifying the correlation between anomalies extracted and the Ecuador earthquake. This phenomenon could be related to the preparation phase and the aftershock phase of the Ecuador earthquake.

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Section: Introductionmentioning

confidence: 99%

Precursor Analysis Associated With the Ecuador Earthquake Using Swarm A and C Satellite Magnetic Data Based on PCA

Zhu

Fan

et al. 2019

IEEE Access

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“…According to their results, anomalies occurred for six to four months and four days before the Lushan earthquake from the nearest GZ station to the epicentre. Later, Yi et al [26] and Zhu et al [27] respectively used wavelet analysis and principal component analysis to confirm that the anomalies at the GZ station were preceded by the Lushan earthquake; However, environmental disturbances were not excluded from the borehole strain data in their studies.…”

Section: Introductionmentioning

confidence: 99%

Borehole Strain Observations Based on a State-Space Model and ApNe Analysis Associated With the 2013 Lushan Earthquake

Zhu

Hattori

et al. 2021

IEEE Access

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YRY-4 borehole strainmeters have been installed in Sichuan Province, China, since 2008, aimed at monitoring the crustal activities associated with earthquakes. In this study, data from six YRY-4 strainmeters at the southwestern endpoint of the Longmenshan fault zone were analysed, to study the relationship of tectonic strain changes with the 2013 Lushan earthquake. We developed a state-space model to remove the strain response due to air pressure, solid tides and the changes in the water level to preferentially isolate non-tectonic disturbances. Strain responses to each influencing factor were estimated using the environmental coefficients computed in the state-space model by an adaptive Kalman filter with measurement noise. The results were consistent with the expected response of the strainmeter systems. The corrected strain considered to originate from underground tectonics provides new insights into the changes in the pre-earthquake strain. Approximate negentropy (ApNe) and b value were introduced to quantify the probability distribution of the corrected borehole strain and compared with the local seismic activities. The nearest station and two further stations, almost simultaneously recorded short-term ApNe anomalies six to four months before the earthquake. The anomalous region also had a correspondingly low b value. Moreover, the anomaly acceleration rates of each station were dependent on the epicentral distances. Further comparison with the strain of random periods illustrated the significance of the extracted anomalies. Our results indicate that the corrected strain may contain seismogenic information and reflect the accelerated strain accumulation of focal areas before the earthquake.INDEX TERMS State-space model, Kalman filter, ApNe, b values, short-term strain anomalies, Lushan earthquake.

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“…Before the Wenchuan earthquake, studies on the Longmenshan fault mainly focused on the fault slip rates [2]. After the Wenchuan earthquake, studies on the Longmenshan fault mainly concentrated on the seismogenic process [3,4], stress state [5,6], coseismic surface rupture [7], kinematic characteristics [8][9][10][11], and deep tectonic environment [12][13][14][15] of the fault area. Liu et al [16] and Yin et al [17] analysed the spatiotemporal distribution of the early aftershocks following the Wenchuan earthquake.…”

Section: Introductionmentioning

confidence: 99%

Spatiotemporal Evolution of Earthquakes in Longmenshan Fault and Adjacent Area, before and after the 2008 Wenchuan Earthquake

Fan

Wang

et al. 2021

Shock and Vibration

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Seismicity sequence following a main earthquake usually contains much meaningful information for unveiling the focal mechanism and predicting the reoccurrence interval of large earthquakes. The spatiotemporal evolution of earthquakes before and after the 2008 Wenchuan earthquake (Ms 8.0) is analysed comprehensively in this study. The frequency-magnitude relation of the 3493 earthquake events retrieved from the database of the International Seismological Centre indicates that the adopted catalogue is complete for magnitudes ≥Ms 3.4. The seismicity during the 10 years before the Wenchuan earthquake remained stable, including the magnitudes and focal depths. However, seismicity attenuated sharply in the year following the Wenchuan earthquake, and the magnitude of earthquakes before the Wenchuan earthquake decreased gradually. The area of the seismogenic zone of the 2008 Wenchuan earthquake was smaller than the earthquake stricken area. The earthquakes that occurred in the Longmenshan fault area and adjacent area in the study period were mainly shallow earthquakes. The focal depths of earthquakes in the study area became stable gradually after the Wenchuan earthquake, mainly within the range from 10 to 16 km. The earthquakes in the study area were mainly distributed with an along-dip distance of 0–20 km, and the seismicity was distributed uniformly along the fault strike.

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Extracting borehole strain precursors associated with the Lushan earthquake through principal component analysis

Cited by 9 publications

References 23 publications

Precursor Analysis Associated With the Ecuador Earthquake Using Swarm A and C Satellite Magnetic Data Based on PCA

Precursor Analysis Associated With the Ecuador Earthquake Using Swarm A and C Satellite Magnetic Data Based on PCA

Borehole Strain Observations Based on a State-Space Model and ApNe Analysis Associated With the 2013 Lushan Earthquake

Spatiotemporal Evolution of Earthquakes in Longmenshan Fault and Adjacent Area, before and after the 2008 Wenchuan Earthquake

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