Multiscale variations of the crustal stress field throughout North America.

The Earth's crustal stress field controls active deformation and reflects the processes driving plate tectonics. Here we present the first quantitative synthesis of relative principal stress magnitudes throughout North America together with hundreds of new horizontal stress orientations, revealing coherent stress fields at various scales. A continent-scale transition from compression (strike-slip and/or reverse faulting) in eastern North America to strike-slip faulting in the mid-continent to predominantly extension in western intraplate North America is likely due (at least in part) to drag at the base of the lithosphere.

Physics-based forecasting of man-made earthquake hazards in Oklahoma and Kansas.

Reinjection of saltwater, co-produced with oil, triggered thousands of widely felt and several damaging earthquakes in Oklahoma and Kansas. The future seismic hazard remains uncertain. Here, we present a new methodology to forecast the probability of damaging induced earthquakes in space and time.

Response to Comment on "How will induced seismicity in Oklahoma respond to decreased saltwater injection rates?".

Goebel . question our forecasted response of induced seismicity to reduction of saltwater injection rates in north-central Oklahoma and raise the concern that "the probability of future damaging earthquakes may be underestimated." We compare our prediction to earthquake data recorded in the 8 months after publication.

How will induced seismicity in Oklahoma respond to decreased saltwater injection rates?

In response to the marked number of injection-induced earthquakes in north-central Oklahoma, regulators recently called for a 40% reduction in the volume of saltwater being injected in the seismically active areas. We present a calibrated statistical model that predicts that widely felt ≥ 3 earthquakes in the affected areas, as well as the probability of potentially damaging larger events, should significantly decrease by the end of 2016 and approach historic levels within a few years. Aftershock sequences associated with relatively large magnitude earthquakes that occurred in the Fairview, Cherokee, and Pawnee areas in north-central Oklahoma in late 2015 and 2016 will delay the rate of seismicity decrease in those areas.

Effects of rock mineralogy and pore structure on stress-dependent permeability of shale samples.

We conducted pulse-decay permeability experiments on Utica and Permian shale samples to investigate the effect of rock mineralogy and pore structure on the transport mechanisms using a non-adsorbing gas (argon). The mineralogy of the shale samples varied from clay rich to calcite rich (i.e.

Oklahoma's recent earthquakes and saltwater disposal.

Over the past 5 years, parts of Oklahoma have experienced marked increases in the number of small- to moderate-sized earthquakes. In three study areas that encompass the vast majority of the recent seismicity, we show that the increases in seismicity follow 5- to 10-fold increases in the rates of saltwater disposal. Adjacent areas where there has been relatively little saltwater disposal have had comparatively few recent earthquakes.

Earthquake triggering and large-scale geologic storage of carbon dioxide.

Despite its enormous cost, large-scale carbon capture and storage (CCS) is considered a viable strategy for significantly reducing CO(2) emissions associated with coal-based electrical power generation and other industrial sources of CO(2) [Intergovernmental Panel on Climate Change (2005) IPCC Special Report on Carbon Dioxide Capture and Storage. Prepared by Working Group III of the Intergovernmental Panel on Climate Change, eds Metz B, et al. (Cambridge Univ Press, Cambridge, UK); Szulczewski ML, et al.

Did earthquakes keep the early crust habitable?

The shallow habitable region of cratonal crust deforms with a strain rate on the order of approximately 10(19) s(1). This is rapid enough that small seismic events are expected on one-kilometer spatial scales and one-million-year timescales. Rock faulting has the potential to release batches of biological substrate, such as dissolved H(2), permitting transient blooms.