Tomography of <i>Q</i><sub>Lg</sub> in Sichuan‐Yunnan Zone

Zhou, Lianqing; Zhao, Chen; Xiu, Ji‐Gang; Chen, Zhangli

doi:10.1002/cjg2.1312

Cited by 16 publications

(34 citation statements)

References 16 publications

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“…On both sides of the Longmenshan fault zone, the crustal thickness varies from 35 km in the east Sichuan Basin to 70 km in the west. A variety of geophysical factors demonstrated strong gradient changes on LFZ sides, such as electrical structure [4], gravity field [5], seismic wave attenuation [6], and P-wave velocity structure [7].…”

Section: Tectonic Backgroundmentioning

confidence: 99%

Source rupture process of Lushan M S7.0 earthquake, Sichuan, China and its tectonic implications

2013

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The source rupture process of the M S 7.0 Lushan earthquake was here evaluated using 40 long-period P waveforms with even azimuth coverage of stations. Results reveal that the rupture process of the Lushan M S 7.0 event to be simpler than that of the Wenchuan earthquake and also showed significant differences between the two rupture processes. The whole rupture process lasted 36 s and most of the moment was released within the first 13 s. The total released moment is 1.9×10 19 N m with M W =6.8. Rupture propagated upwards and bilaterally to both sides from the initial point, resulting in a large slip region of 40 km×30 km, with the maximum slip of 1.8 m, located above the initial point. No surface displacement was estimated around the epicenter, but displacement was observed about 20 km NE and SW directions of the epicenter. Both showed slips of less than 40 cm. The rupture suddenly stopped at 20 km NE of the initial point. This was consistent with the aftershock activity. This phenomenon indicates the existence of significant variation of the medium or tectonic structure, which may prevent the propagation of the rupture and aftershock activity. The earthquake risk of the left segment of Qianshan fault is worthy of attention. . The early rupturing stage showed reverse faulting and later changed to right-lateral strike slip faulting, leaving 2 large slip areas along the LFZ on the surface. Aftershock activity also showed a unilateral pattern along the northeastern direction, consistent with the direction of rupture propagation. These seismological results were in accordance with the results of the post-earthquake investigation and of observations made during the disaster [2,3]. Evaluation of the source-rupture process using the digital seismic waveform data can provide information about the rupture scale, the way the fault moves, and the slip distribution on the fault within several hours of a strong earthquake. These estimations not only provide information regarding the seriously damaged areas and the way of dislocation but also information suitable for estimation of the scale of destruction and planning of rescue work. It can also provide information regarding the activity of the causative fault, the

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Section: Tectonic Backgroundmentioning

confidence: 99%

Source rupture process of Lushan M S7.0 earthquake, Sichuan, China and its tectonic implications

2013

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“…On the two sides of Longmenshan fault zone, the Q Lg structure [7], P wave velocity structure [8], electrical property structure [9], and gravity field [10], etc. are obviously different.…”

Section: Tectonic Backgroundmentioning

confidence: 99%

Rupture process of the Wenchuan M8.0 earthquake of Sichuan China: the segmentation feature

et al. 2009

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Moment tensor solution, rupture process and rupture characteristics of the great Wenchuan M8.0 earthquake are studied by using 39 long-period P and SH waveforms with evenly azimuth coverage of stations. Our results reveal that the Wenchuan M8.0 event consisted of 5 sub-events of M w ≥7.3 occurring succesively in time and space. Rupture started with a M w 7.3 introductory strike-slip faulting in the first 12 s, then within 12−40 s, two sub-events with M w 7.6 and M w 7.4 occurred within 80 km northeast from the initial point with the dominant rupture type of thrust moving. From 40 to 62 s, a M w 7.5 and M w 7.4 right-lateral strike-slip type of sub-events occurred on the two sides of Beichuan, 120 km away northeast from the initial point. The whole rupture process lasted 105 s and unilaterally propagated from the initial point on the WS section of the Yingxiu-Beichuan fault to the NE direction, resulting in a 230-km-long surface rupture zone and the average surface dislocation is up to 4 m. Two asperities are identified and the whole rupture process is formed by WS and NE parts. In the WS part named Dujiangyang-Wenchuan, where the initial point is located, the rupture process showed reverse faulting with the maximum slip of 8.2 m. Around Mianzhu, rupture changed to right-lateral strike slip faulting and formed a Beichuan-Qingchuan large slip area. The rupture area on this part is about 10 km in depth, shallower than on the WS part. The maximum slip is 6.53 m. Consequently, there formed 2 segments with the surface dislocation larger than 6 m. One is the Dujiangyan-Wenchuan segment with the maximum surface displacement of 6.44 m, the other is the Beichuan-Qingchuan segment with the maximum surface displacement of 6.53 m. This segmentation may have its geological and tectonic background. Wenchuan earthquake, moment tensor solution, rupture process, fault segmentation characteristics Citation: Zhao C P, Chen Z L, Zhou L Q, et al. Rupture process of the Wenchuan M8.0 earthquake of Sichuan, China: the segmentation feature.At 14:28 on May 12, 2008, a great earthquake occurred in Wenchuan County of Sichuan Province, China. It caused the most severe damage and affected the largest area among other earthquakes since New China was founded, and resulted in tremendous injuries and deaths, as well as disaster. Study on its source rupture process using the digital seismic waveform data can provide information about the rupture scale, the way of fault moving, as well as slip distribution on the fault within several hours after a strong earthquake occurred. These estimations can not only rapidly provide the information on the seriously damaged area and the way of dislocation as well as important information for estimating the destructed scale and doing rescue work, but can also provide important information about the activity of the causative fault and the tendency of the earthquake sequence. After the Wenchuan M8.0 earthquake occurred, several research groups immediately carried out the source rupture process inversion. We also e...

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“…At present, studies on the large-scale tomography of the subsurface attenuation structure are mainly based on Lg waves and surface waves. Studies of Lg wave attenuation tomography have been carried out in many parts of the Chinese mainland (e.g., Bao et al, 2011;Hearn et al, 2008;Pei et al, 2006;Taylor et al, 2003;Xie et al, 2004;Zhao et al, 2010Zhao et al, , 2013Zhou et al, 2008Zhou et al, , 2011. Since the amplitudes of Lg waves were measured over a wide frequency range and the amplitudes of Lg waves vary with frequency, the tomographic results will include the average attenuation values in the corresponding periods; these average values will introduce some ambiguity to the interpretation of structural features with regard to the scale of those features.…”

Section: 1029/2020gc008971mentioning

confidence: 99%

Rayleigh Wave Attenuation Tomography in the Crust of the Chinese Mainland

Zhou

Song

Yang

et al. 2020

Geochem Geophys Geosyst

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In this study, we report a first major effort to measure surface wave amplitudes and to map attenuation structures of the Chinese mainland with dense modern broadband seismic networks in the country. We developed a method of phase‐matched filtering to automatically extract fundamental‐mode Rayleigh waves and to measure the spectral amplitudes. The results are compatible with those from the previous manual method with great improvement in efficiency. Using the automatic method, we extracted a large quantity of the amplitudes of Rayleigh waves at periods of 10 and 20 s recorded by 141 broadband stations from the China Digital Seismograph Network and 656 broadband stations from the China Regional Seismic Network. We performed tomographic inversions using the method of two‐station amplitude ratios and obtained images of the surface wave attenuation maps at periods of 10 and 20 s for the Chinese mainland. The tomographic model resolution reaches 1–2° in central and eastern China, 3–5° in western China, and 5° in the southeastern margin of the Tibetan Plateau and northeastern China. The tomographic results demonstrate good correspondence with geological structures. The distribution of strong historical earthquakes indicates that in the Chinese mainland, these earthquakes occurred mainly in high‐attenuation areas or the junctions between high‐ and low‐attenuation areas.

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Tomography of Q_Lg in Sichuan‐Yunnan Zone

Cited by 16 publications

References 16 publications

Source rupture process of Lushan M S7.0 earthquake, Sichuan, China and its tectonic implications

Source rupture process of Lushan M S7.0 earthquake, Sichuan, China and its tectonic implications

Rupture process of the Wenchuan M8.0 earthquake of Sichuan China: the segmentation feature

Rayleigh Wave Attenuation Tomography in the Crust of the Chinese Mainland

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Tomography of QLg in Sichuan‐Yunnan Zone

Cited by 16 publications

References 16 publications

Source rupture process of Lushan M S7.0 earthquake, Sichuan, China and its tectonic implications

Source rupture process of Lushan M S7.0 earthquake, Sichuan, China and its tectonic implications

Rupture process of the Wenchuan M8.0 earthquake of Sichuan China: the segmentation feature

Rayleigh Wave Attenuation Tomography in the Crust of the Chinese Mainland

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Tomography of Q_Lg in Sichuan‐Yunnan Zone