Fracture Advancing Step Tectonics Observed in the Yuha Desert and Ocotillo, CA, Following the 2010 Mw7.2 El Mayor‐Cucapah Earthquake. Issue 9 (7th September 2018)

• Record Type: Journal Article
• Authors: Donnellan, Andrea; Parker, Jay; Heflin, Michael; Lyzenga, Gregory; Moore, Angelyn; Ludwig, Lisa Grant; Rundle, John; Wang, Jun; Pierce, Marlon
• Is Part Of: Earth and space science. Volume 5:Issue 9(2018)
• Page Start: 456
• Page End: 472
• Publication Date: 2018-09-07
• Subjects: UAVSAR -- geodetic imaging -- GPS -- stepover -- earthquake -- fault; Space sciences -- Periodicals; Geophysics -- Periodicals; 500.5
• DOI: 10.1029/2017EA000351
• Languages: English
• ISSNs: 2333-5084

Abstract

Abstract: Uninhabited aerial vehicle synthetic aperture radar (UAVSAR) observations 2009–2017 of the Yuha Desert area and Global Positioning System (GPS) time series encompassing the region reveal a northward migrating pattern of deformation following the 4 April 2010 Mw 7.2 El Mayor‐Cucapah (EMC) earthquake. The north end of the EMC rupture exhibits an asymmetric pattern of deformation that is substantial and smooth northeast of the rupture and limited but with surface fracturing slip northwest. The earthquake triggered ~1 cm of surface coseismic slip at the Yuha fault, which continued to slip postseismically. 2.5 cm of Yuha fault slip occurred by the time of the 15 June 2010 Mw 5.7 Ocotillo aftershock and 5 cm of slip occurred by 2017 following a logarithmic afterslip decay 16‐day timescale. The Ocotillo aftershock triggered 1.4 cm of slip on a northwest trend extending to the Elsinore fault and by 7 years after the EMC earthquake 2.4 cm of slip had accumulated with a distribution following an afterslip function with a 16‐day timescale consistent with other earthquakes and a rate strengthening upper crustal sedimentary layer. GPS data show broad coseismic uplift of the Salton Trough and delayed postseismic motion that may be indicative of fluid migration there and subsidence west of the rupture extension, which continues following the earthquake. The data indicate that the Elsinore, Laguna Salada, and EMC ruptures are part of the same fault system. The results also suggest that north‐south shortening and east‐west extension across the region drove fracture advancing step tectonics north of the EMC earthquake rupture. Plain Language Summary: Airborne radar and Global Positioning System observations of the Yuha Desert and Salton Trough suggest that the 2010 M7.2 El Mayor ‐ Cucapah earthquake rupture, the Laguna Salada fault in Baja California, Mexico, and the Elsinore fault in California are part of the same fault system. The M5.7 Ocotillo aftershock links these faults and is a result of stress propagation from afterslip on the El Mayor ‐ Cucapah rupture. Further east in the Salton Trough fluid migration also contributes to the observed results. Key Points: The Mw 5.7 Ocotillo aftershock of the El Mayor‐Cucapah earthquake extended north from a mainshock surface fracture to the Elsinore fault Postseismic slip on the Yuha fault and Ocotillo section and uplift in the Salton Trough continued for several years following the event Salton Trough spreading causes left slip on the Yuha fault resulting in a left step that links the Laguna Salada and Elsinore faults