Taira, Taka'aki

In the originally published version of this article, the plots of 5 min Global Navigation Satellite Systems (GNSS) time series shown in Figure 11b were for station CCCC, rather than P595. The corrected Figure 11 showing position time series of P595 is as follows.

The 2019 Ridgecrest earthquake sequence culminated in the largest seismic event in California since the 1999 Mw 7.1 Hector Mine earthquake. Here, we combine geodetic and seismic data to study the rupture process of both the 4 July Mw 6.4 foreshock and the 6 July Mw 7.1 mainshock. The results show that the Mw 6.4 foreshock rupture started on a northwest‐striking right‐lateral fault, and then continued on a southwest‐striking fault with mainly left‐lateral slip. Although most moment release during the Mw 6.4 foreshock was along the southwest‐striking fault, slip on the northwest‐striking fault seems to have played a more important role in triggering the Mw 7.1 mainshock that happened ∼34hr later. Rupture of the Mw 7.1 mainshock was characterized by dominantly right‐lateral slip on a series of overall northwest‐striking fault strands, including the one that had already been activated during the nucleation of the Mw 6.4 foreshock. The maximum slip of the 2019 Ridgecrest earthquake was ∼5m⁠, located at a depth range of 3–8 km near the Mw 7.1 epicenter, corresponding to a shallow slip deficit of ∼20%–30%⁠. Both the foreshock and mainshock had a relatively low‐rupture velocity of ∼2km/s⁠, which is possibly related to the geometric complexity and immaturity of the eastern California shear zone faults. The 2019 Ridgecrest earthquake produced significant stress perturbations on nearby fault networks, especially along the Garlock fault segment immediately southwest of the 2019 Ridgecrest rupture, in which the coulomb stress increase was up to ∼0.5MPa⁠. Despite the good coverage of both geodetic and seismic observations, published coseismic slip models of the 2019 Ridgecrest earthquake sequence show large variations, which highlight the uncertainty of routinely performed earthquake rupture inversions and their interpretation for underlying rupture processes.

Human activity causes vibrations that propagate into the ground as high-frequency seismic waves. Measures to mitigate the coronavirus disease 2019 (COVID-19) pandemic caused widespread changes in human activity, leading to a months-long reduction in seismic noise of up to 50%. The 2020 seismic noise quiet period is the longest and most prominent global anthropogenic seismic noise reduction on record. Although the reduction is strongest at surface seismometers in populated areas, this seismic quiescence extends for many kilometers radially and hundreds of meters in depth. This quiet period provides an opportunity to detect subtle signals from subsurface seismic sources that would have been concealed in noisier times and to benchmark sources of anthropogenic noise. A strong correlation between seismic noise and independent measurements of human mobility suggests that seismology provides an absolute, real-time estimate of human activities.