Issues

Front: On 16 December 2018, an M_L 5.7 earthquake struck Xingwen County, Sichuan Province, China, and on 3 January 2019, an M_L 5.3 earthquake occurred 8 km to the west, resulting in extensive damage to nearby structures. Lei et al. (this issue) reports that these earthquakes are the largest and most damaging in the Changning shale gas block, where 11 M_L ≥ 4.0 events (including three M_L ≥ 5.0) have been observed since hydraulic fracturing (HF) began in 2014. A 3D view (top) shows a simplified geological section overlapping with relocated hypocenters for observed earthquakes. The shaded image shows the landscape and well pads in which hydraulic fracturing was performed or is ongoing. The map view (bottom) shows active HF pads and three days of pre- and aftershocks of the 16 December 2018 M_L 5.7 earthquake. The shaded area shows the change of Coulomb failure stress (ΔCFS) from the M_L 5.7 earthquake to receiver faults of (strike, dip, rake) = (170, 83, 12) and depth of 2 km. ZJ indicates the location of Zhoujia village, which suffered the most extensive damage.

Back: By coincidence (and scaling) the acceleration response spectrum of the 2011 Goch (Germany) earthquake recorded at the 130 m level of the north tower of Cologne Cathedral follows the shape of this World Heritage Monument. Hinzen (this issue) describes the ground motion parameters of two similarly sized local earthquakes (M_L 4.3) measured by a 40-station network with several stations with identical epicentral distances, including the five stations in the cathedral.