A large continental normal‐faulting earthquake occurred in the Yinchuan Graben in northern China on 3 January 1739. This event is of significant interest for two reasons. First, it has been suggested on the basis of historical records of shaking that this was a magnitude 8.0 event. If this is true, the 1739 earthquake would be one of the largest continental normal‐faulting earthquakes ever recorded, and this should prompt us to consider the factors contributing to its unusual size. Second, there has been some debate in the literature about the causative structure, with at least three different faults posited as the seismogenic source. We use five¹⁴C ages to date a series of scarps on the East Helanshan Fault, which lies to the west of the graben, and bracket the scarp formation to the last 350 years. We use high‐resolution, stereo imagery from the Pleiades satellites to build a 1 to 2 m resolution DEM of the fault and combine this with field observations to map the East Helanshan rupture in detail. We then construct a throw distribution, determine the slip vector azimuth, and reassess the earthquake magnitude using simple scaling relationships. We conclude that the 1739 earthquake occurred on the East Helanshan Fault, had a rupture length of approximately 87 km, a maximum throw of 5.1 m, and an average throw of 3.0 m, yielding a best estimate magnitude in the rangeM_w 7.1 toM_w 7.6. We suggest that the previous magnitude estimates are biased by enhanced shaking of the sediments within the Yinchuan Graben.

We have assembled a catalogue of well-constrained focal mechanisms for earthquakes that occurred on continental dip-slip faults that have experienced only small displacements during their current phase of activity. Nodal planes for both reverse- and normal-faulting events are seen to vary between ∼30° and ∼60°, and are concentrated towards the centre of this range. The observed distributions suggest the reactivation of structures with a low coefficient of friction (less than ∼0.3, and possibly as low as ≤0.1). We propose that this low coefficient of friction corresponds to the presence of weak materials in pre-existing fault zones.

We investigate the mechanical properties of the oceanic lithosphere using earthquake focal mechanisms from subduction zone outer rises. We study regions where faulting oblique to the pre-existing mid-ocean ridge fabric implies the formation of new faults. The nodal-plane dips of dip-slip earthquakes on these faults are dominantly in the range 30–60°, with a strong peak concentrated around 45°. This distribution is inconsistent with the pattern that would result from high coefficients of friction (e.g. 0.6, equivalent to normal faults forming at 60° and thrust faults at 30°). We instead suggest that the observed distribution of dips implies that faults in the oceanic lithosphere have a low coefficient of friction, due to either low-friction clay minerals formed by hydrothermal alteration at the ridge, or due to an intrinsic level of friction that is lower than that suggested by laboratory studies

Suffering in the ecological realm exhibits structural parallels with diagnoses of human trauma. Viewing ecological suffering as traumatic allows for recent work in trauma theology to be applied in an ecological context. This article focusses specifically on the breakdown of communication that characterises traumatic events. In the ecological case, this is often a human failure to attend to suffering in the rest of the ecosphere. What is required is a witness to this ecological trauma. Following Shelly Rambo, such witnessing is not about proclamation or imitation, but rather entails simply remaining with the suffering. For Christians, Christ can be one such witness. In his life and his death, he bears witness to the traumas of the earth—especially in his refusal to abandon our wounded world at the crucifixion. And this Christic witnessing provides a blueprint for our own, practical response: not imitating the self-sacrifice, but following the witness. One, tangible example of this is given by the Stations of the Forests resource. Here, the fourteen stations of the cross are recast as a witness to the traumas of contemporary deforestation. Resources like this illustrate how a model of Christic witnessing can constitute a practical response to ecological trauma.

"Introduction" published on 19 Oct 2022 by Brill.