Injection-induced earthquakes on complex fault zones of the Raton Basin
illuminated by machine-learning phase picker and dense nodal array
Seismicity in the Raton Basin over the past two decades suggests
reactivation of basement faults due to wastewater injection. In the
summer of 2018, 96 short-period three-component nodal instruments were
installed in a highly active region of the basin for a month. A
machine-learning based phase picker-(PhaseNet) was adopted and
identified millions of picks, which were associated with events using an
automated algorithm – REAL (Rapid Earthquake Association and Location).
After hypocenter relocation with hypoDD, the earthquake catalog contains
9259 M -2.2 – 3 earthquakes focused at depths of 4-6km. Magnitude of
completeness (Mc) varies from -1 at night to -0.5 in daytime, likely
reflecting noise variation modulated by wind. The clustered hypocenters
with variable depths and focal mechanisms suggest a complex network of
basement faults. Frequency-magnitude statistics and the spatiotemporal
evolution of seismicity are comparable to tectonic systems.