Characterizing Near?Field Surface Deformation in the 1990 Rudbar Earthquake (Iran) Using Optical Image Correlation

The 1990 Rudbar earthquake (Mw 7.3) broke along three right-stepping segments of the left-lateral fault, in western Alborz mountains (Iran), producing ?80 km surface rupture. Previously reported horizontal (?60 cm) field offsets were surprisingly low, and vertical (?95 unexpected, given relatively large moment release, shallow source depth, fault geometry, rake. We characterize displacement from optical image correlation satellite aerial images. A maximum ?6.5 m is observed eastern part rupture consistent with both a sharp pulse release rate ?10 s after initiation, macroseismic isoseismal curves. find ?2.2 mean slip, larger than measurements, but empirical scaling laws based upon seismological release. Estimates zone width on 1 resolution photos (and corrected for smoothing bias) are <200 m; these values increase artificially lower imagery, which more affected by bias. mismatch between displacements suggests probably featured significant off-fault deformation, its low structural maturity. Finally, we document continuation Kabateh segment, east Sefid Rud river. Slip this segment (1–2 m), less neighboring Zard Geli (1.5–6 m). two faults converge at Rud, appears to represent major feature controlling segmentation region.