Analysis of coseismic slip distributions and stress variations of the 2019 Mw 6.4 and 7.1 earthquakes in Ridgecrest, California

Duan, Hongbo; Chu, ZiMing; Zhang, Shuangcheng; Yang, Chengsheng; Chen, Jiaying; Lei, Junzhen

doi:10.1016/j.tecto.2022.229343

Cited by 7 publications

(4 citation statements)

References 47 publications

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“…This assumption is supported by (a) a focal mechanism inversion analysis by Duan et al. (2022) that found no appreciable change in the orientation with depth and (b) the agreement of the pre‐earthquake background stress state estimated from other studies using seismicity at depth with our own stress estimate (illustrated in Figures 3d–3f). Differences in the pre‐ and post‐stress states show a temporal rotation of SH max after the M w 7.1 event, which we estimate as −5.2 ±

1.8{}^{\circ}

, 1.3 ±

1.2{}^{\circ}

and 7.0 ±

1.2{}^{\circ}

(at the 1

\sigma

level, with clockwise as positive with respect to the primary ruptured faults) for the northern, central, and southern zones respectively (see Figure 5, Section S1 in Supporting Information S1 for details and Table 1).…”

Section: Resultssupporting

confidence: 87%

Fault Friction Derived From Fault Bend Influence on Coseismic Slip During the 2019 Ridgecrest M_w 7.1 Mainshock

2022

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Earthquakes are frictional slip instabilities which initiate when the applied shear stress exceeds the yield strength of the fault. During sliding the friction can increase (dynamic strengthening) or decrease (dynamic weakening), where the former inhibits rupture, and the latter can sustain a runaway failure which relieves a fraction of the accumulated stress along the fault surface. During the interseismic period the elastic stresses re-accumulate along the locked fault surface until the fault strength is reached again and another earthquake occurs. This basic description of the seismic cycle underlines the importance of fault strength in our understanding of when and how earthquakes occur. However, outstanding questions remain regarding the strength of faults including, is the frictional strength substantially lower during rupture than the static strength expected for a standard value of the static coefficient of friction (the ratio of the shear to normal stress which is generally around 0.6 for most rocks) (Byerlee, 1978)? If so, what is the extent of dynamic weakening? Are faults inherently weak or are intracrustal faults stronger than their more mature plate boundary counterparts? In this study we attempt to place empirical constraints on these important fault mechanical properties using observations of a surface rupturing event provided by satellite imaging data.The 2019 Ridgecrest earthquake sequence initiated on 4 July by a series of foreshocks which later ruptured a series of orthogonal faults near the city of Ridgecrest located north of the Mojave Desert

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1.8{}^{\circ}

, 1.3 ±

1.2{}^{\circ}

and 7.0 ±

1.2{}^{\circ}

(at the 1

\sigma

Section: Resultssupporting

confidence: 87%

Fault Friction Derived From Fault Bend Influence on Coseismic Slip During the 2019 Ridgecrest M_w 7.1 Mainshock

2022

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“…This assumes that the stress orientation does not vary significantly as a function of depth. This assumption is supported by i) a focal mechanism inversion analysis by Duan et al, (2022) that found no appreciable change in the orientation with depth, and ii) the agreement of the pre-earthquake background stress state estimated from other studies using seismicity at depth with our own stress estimate (illustrated in Fig. 3 d-f).…”

Section: Absolute Stress Magnitudessupporting

confidence: 85%

Fault Friction Derived from Fault Bend Influence on Coseismic Slip During the 2019 Ridgecrest Mw 7.1 Mainshock

Milliner¹,

Aati²,

Avouac³

2022

Preprint

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The variation of stress on faults is important for our understanding of fault friction and the dynamics of earthquake ruptures. However, we still have little observational constraints on their absolute magnitude, or their variations in space and in time over the seismic cycle. Here we use a new geodetic imaging technique to measure the 3D coseismic slip vectors along the 2019 Ridgecrest surface ruptures and invert them for the coseismic stress state. We find that the coseismic stresses show an eastward rotation that becomes increasingly transtensional from south-to-north along the rupture, that matches the known background stress state. We find that the main fault near the Mw 7.1 mainshock hypocenter was critically stressed. Coseismic slip was maximum there and decreased gradually along strike as the fault became less optimally oriented due its curved geometry. The variations of slip and stress along the curved faults are used to infer the static and dynamic fault friction assuming Mohr-Coulomb failure. We find shear stresses of 4-9 MPa in the shallow crust (~1.3 km depth) and that fault friction drops from a static, Byerlee-type, value of 0.61 ± 0.14 to a dynamic value of 0.29 ± 0.04 during seismic slip. These values explain quantitatively the slip variations along a transpressional fault bend.

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“…For example, using the shear-wave splitting method, a study by Meltzer et al (2007) found that the crustal anisotropy in southeastern Tibet is related to the ongoing collision between the Indian Plate and the Eurasian Plate. Similarly, a study by Duan et al (2022) found that the 2019 Ridgecrest earthquakes in manuscript submitted to Journal of Geophysical Research California were related to preexisting faults in the Earth's crust that were reactivated by the ongoing tectonic stresses associated with the collision between the Pacific Plate and the North American Plate. Therefore, continental collisions result in concentrated and perturbed tectonic stresses in the crust, and how these stresses evolved has important implications for understanding the Earth's tectonic processes and the effects on intraplate earthquakes.…”

Section: Introductionmentioning

confidence: 96%

Crustal Structures and Anisotropy in Southeastern China: Continental Collision and Intraplate Earthquakes

Huang

Jiang

et al. 2023

Preprint

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This study investigates the role of crustal structures and anisotropy in the context of intraplate earthquakes resulting from concentrated and perturbed tectonic stresses in southeastern China. Using the teleseismic receiver function method, we reveal the crustal structures and anisotropy in two earthquake-prone regions. The crust is stratified into two anisotropic layers, with the upper-middle crust having an orogen-perpendicular slow axis and the lower crust with a fast axis aligned with the orogen. The structures highlight the differential movement between the continental blocks, with an increase in the intensity of intraplate earthquakes across this boundary and supporting a link between decoupled crustal deformation and seismicity. Mesozoic collision generated the orogen-parallel fabrics in the upper-middle crust, ductile shearing yielded orogen-perpendicular fast directions at the lower crust, and mismatch evolution between continental blocks reactivated by present collision provides stress conditions conducive to the occurrence of earthquakes in southeastern China.

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Analysis of coseismic slip distributions and stress variations of the 2019 Mw 6.4 and 7.1 earthquakes in Ridgecrest, California

Cited by 7 publications

References 47 publications

Fault Friction Derived From Fault Bend Influence on Coseismic Slip During the 2019 Ridgecrest M_w 7.1 Mainshock

Fault Friction Derived From Fault Bend Influence on Coseismic Slip During the 2019 Ridgecrest M_w 7.1 Mainshock

Fault Friction Derived from Fault Bend Influence on Coseismic Slip During the 2019 Ridgecrest Mw 7.1 Mainshock

Crustal Structures and Anisotropy in Southeastern China: Continental Collision and Intraplate Earthquakes

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Analysis of coseismic slip distributions and stress variations of the 2019 Mw 6.4 and 7.1 earthquakes in Ridgecrest, California

Cited by 7 publications

References 47 publications

Fault Friction Derived From Fault Bend Influence on Coseismic Slip During the 2019 Ridgecrest Mw 7.1 Mainshock

Fault Friction Derived From Fault Bend Influence on Coseismic Slip During the 2019 Ridgecrest Mw 7.1 Mainshock

Fault Friction Derived from Fault Bend Influence on Coseismic Slip During the 2019 Ridgecrest Mw 7.1 Mainshock

Crustal Structures and Anisotropy in Southeastern China: Continental Collision and Intraplate Earthquakes

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Fault Friction Derived From Fault Bend Influence on Coseismic Slip During the 2019 Ridgecrest M_w 7.1 Mainshock

Fault Friction Derived From Fault Bend Influence on Coseismic Slip During the 2019 Ridgecrest M_w 7.1 Mainshock