Large [moment magnitude (M(w)) ≥ 7] continental earthquakes often generate complex, multifault ruptures linked by enigmatic zones of distributed deformation. Here, we report the collection and results of a high-resolution (≥nine returns per square meter) airborne light detection and ranging (LIDAR) topographic survey of the 2010 M(w) 7.2 El Mayor-Cucapah earthquake that produced a 120-kilometer-long multifault rupture through northernmost Baja California, Mexico. This differential LIDAR survey completely captures an earthquake surface rupture in a sparsely vegetated region with pre-earthquake lower-resolution (5-meter-pixel) LIDAR data. The postevent survey reveals numerous surface ruptures, including previously undocumented blind faults within thick sediments of the Colorado River delta. Differential elevation changes show distributed, kilometer-scale bending strains as large as ~10(3) microstrains in response to slip along discontinuous faults cutting crystalline bedrock of the Sierra Cucapah.

The 4 April 2010 moment magnitude (M w) 7.2 El Mayor-Cucapah earthquake revealed the existence of a previously unidentifi ed fault system in Mexico that extends ~120 km from the northern tip of the Gulf of California to the U.S.-Mexico border. The system strikes northwest and is composed of at least seven major faults linked by numerous smaller faults, making this one of the most complex surface ruptures ever documented along the Pacifi c-North America plate boundary. Rupture propagated bilaterally through three distinct kinematic and geomorphic domains. Southeast of the epicenter, a broad region of distributed fracturing, liquefaction, and discontinuous fault rupture was controlled by a buried, southwest-dipping, dextral-normal fault system that extends ~53 km across the southern Colorado River delta. Northwest of the epicenter, the sense of vertical slip reverses as rupture propagated through multiple strands of an imbricate stack of eastdipping dextral-normal faults that extend ~55 km through the Sierra Cucapah. However, some coseismic slip (10-30 cm) was partitioned onto the west-dipping Laguna Salada fault, which extends parallel to the main rupture and defi nes the western margin of the Sierra Cucapah. In the northernmost domain, rupture terminates on a series of several north-northeast-striking cross-faults with minor offset (<8 cm) that cut uplifted and folded sediments of the northern Colorado River delta in the Yuha Desert. In the Sierra Cucapah, primary rupture occurred on four major faults separated by one fault branch and two accommodation zones. The accommodation zones are distributed in a left-stepping en echelon geometry, such that rupture passed systematically to structurally lower faults. The structurally lowest fault that ruptured in this event is inclined as shallowly as ~20°. Net surface offsets in the Sierra Cucapah average ~200 cm, with some reaching 300-400 cm, and rupture kinematics vary greatly along strike. Nonetheless, instantaneous extension directions are consistently oriented ~085° and the dominant slip direction is ~310°, which is slightly (~10°) more westerly than the expected azimuth of relative plate motion, but considerably more oblique to other nearby historical ruptures such as the 1992 Landers earthquake. Complex multifault ruptures are common in the central portion of the Pacifi c North American plate margin, which is affected by restraining bend tectonics, gravitational potential energy gradients, and the inherently three-dimensional strain of the transtensional and transpressional shear regimes that operate in this region.

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Northwest directed slip from the southern San Andreas Fault is transferred to the Mission Creek, Banning, and Garnet Hill fault strands in the northwestern Coachella Valley. How slip is partitioned between these three faults is critical to southern California seismic hazard estimates but is poorly understood. In this paper, we report the first slip rate measured for the Banning fault strand. We constrain the depositional age of an alluvial fan offset 25 ± 5 m from its source by the Banning strand to between 5.1 ± 0.4 ka (95% confidence interval (CI)) and 6.4 + 3.7/−2.1 ka (95% CI) using U‐series dating of pedogenic carbonate clast coatings and 10Be cosmogenic nuclide exposure dating of surface clasts. We calculate a Holocene geologic slip rate for the Banning strand of 3.9 + 2.3/−1.6 mm/yr (median, 95% CI) to 4.9 + 1.0/−0.9 mm/yr (median, 95% CI). This rate represents only 25–35% of the total slip accommodated by this section of the southern San Andreas Fault, suggesting a model in which slip is less concentrated on the Banning strand than previously thought. In rejecting the possibility that the Banning strand is the dominant structure, our results highlight an even greater need for slip rate and paleoseismic measurements along faults in the northwestern Coachella Valley in order to test the validity of current earthquake hazard models. In addition, our comparison of ages measured with U‐series and 10Be exposure dating demonstrates the importance of using multiple geochronometers when estimating the depositional age of alluvial landforms.

The fermentation of undigested foods in the large bowel, by its resident bacteria, results in the production of several chemicals including volatile gases. Perturbance in gut bacteria is known to influence colonic and metabolic health, but to determine this requires prolonged culture (often unsuccessful) or expensive genomic sequencing. Clearly this is not practical for daily clinical practice. Previously, we have reported our insights into fermentonomics through the detection of volatile organic compounds (VOCs) in patients with gastrointestinal and metabolic diseases, using the electronic nose. In this paper we report on the changes in the fermentone produced by patients undergoing complete versus partial bowel cleansing. Using urine samples, preliminary results from 23 individuals receiving bowel cleansing indicate the ability of the electronic nose to distinguish between the partial and complete procedures. Moreover in a subset of individuals, we have been able to track evolving bacterial recolonization over time using the e-nose and field asymmetric ion mobility spectrometry (FAIMS). Such an approach has practical application in tracking bacterial dysbiosis following perturbation.