Revisiting the Seismicity in the Eagle Ford Shale: The Overlooked Role of Wastewater Disposal

The seismicity in the Eagle Ford play has increased dramatically over the last decade. Past studies identified hydraulic fracturing (HF) as the only driving force in this area. We conclude that although HF is the dominant causal factor, wastewater disposal (SWD) was also a triggering mechanism in certain zones. Notably, in the center of the shale, there is a small area where both causal factors overlap. Furthermore, a cluster of earthquakes on the Mexican side of the national border is almost certainly triggered by SWD within Texas. To our knowledge, this is the first such documented case globally. Next, our analysis investigated the causal factors of the 2011 M$_w$ 4.8 Fashing earthquake and of two recent M$_w$ 3.9 events, while also confirming that HF was the key driving force behind the 2018 M$_w$ 4.0 rupture. We employed new earthquake catalogs, established physics-based principles, and a robust hypothesis testing framework.