The July 2019 Ridgecrest, California, earthquake sequence produced cross‐fault ruptures from a Mw6.4 left‐lateral foreshock and a Mw7.1 right‐lateral mainshock. We use interferometric synthetic aperture radar and satellite optical imagery to characterize the surface displacements and subsurface fault slip characteristics of the sequence. We document ~46 km of surface rupture and peak slip values of ~5 m associated with the Mw7.1 and evidence that the two ruptures crossed each other. We additionally document evidence of triggered creep along 20–25 km of the central Garlock fault. Static stress change analysis shows that the foreshock sequence systematically promoted slip at the Mw7.1 hypocenter. Moreover, we find static stress changes promoted slip on the Garlock fault only in locations where we document surface creep, strongly indicating that the Garlock fault is sensitive to static stress changes. A potential rupture of the Garlock fault where slip was promoted could produce a Mw6.7–7.0 earthquake.
[1] At late Quaternary timescales, offset fluvial terrace risers are among the most common landforms used to determine rates of strike-slip faulting. Although diachroneity in the age of riser segments on opposite sides of the fault has been noted previously, an unexplored source of uncertainty associated with deriving slip rates from these markers centers on quantifying the size of the displacement uncertainty such diachroneity introduces. To evaluate the impact of riser diachroneity, we investigated the Tuzidun site (37.73°N, 86.72°E) along the Cherchen He reach of the active central Altyn Tagh Fault. The east bank of the channel is flanked by a left-laterally offset terrace riser. While the measured offset is 54 ± 3 m, geochronologic measurements and analysis of riser topography indicate that the downstream riser segment formed between 6.0 ± 0.8 ka and 5.7 ± 0.4 ka, while the upstream riser segment may have been laterally refreshed as recently as 0.5 ± 0.2 ka. A valley wall on the west bank of the channel places a maximum limit of 38 ± 6 m on the amount of possible lateral erosion of the upstream riser. This bound, in turn, limits the total offset since formation of the downstream riser to range from 54 ± 3 to 89 ± 7 m. Together, these observations bracket the millennial Altyn Tagh Fault slip rate to range from 9.0 ± 1.3 to 15.5 ± 1.7 mm a À1 . More generally, this investigation shows that the observed riser displacement does not necessarily correlate with the age of either riser segment (downstream or upstream of the fault) in cases where one segment is displaced while the other is subjected to lateral erosion. If this diachroneity goes undetected, erroneous slip rate measurements are likely to result.
This supplement describes the data collection and processing techniques for each 6 individual component of our multi-disciplinary analysis of the rupture process of 7 the 12 January 2010 Haiti earthquake (hereafter termed the 2010 Leogane 8 earthquake). First we describe details of the finite fault modeling technique, and 9 results for single-plane fault models using teleseismic data. Next we discuss InSAR 10 data sources and detailed processing, before presenting details of the geological 11 field deployment and data collection. Finally we present alternate joint inversions to 12 our preferred kinematic rupture model (figure 3), comparing these models to the 13 preferred solution, and discussing the relative merits of each. We present two 14 alternate rupture models; a three-plane model (figure S5) to show the effects of 15 north vs. south dip for fault B, the Leogane fault; and a three-plane model exploring 16 the effects of initiating rupture on fault B rather than fault A, the EPGF-like structure 17 ( figures S6 7). 18 19
Teleseismic Bodywave Finite fault modeling 20We invert for the rupture process of the earthquake using broadband teleseismic P-21 and SH-body waveforms recorded at GSN stations worldwide. Data were selected 22 based upon quality (high signal-to-noise ratios) and azimuthal distribution. 23Waveforms are first converted to displacement by removing the instrument 24 response and then used to constrain the slip history based on the finite fault 25 inversion algorithm of Ji et al. 1 . To improve our resolution of rupture onset, 26
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