Identification of earthquakes and anthropogenic events around the southern Great Lakes

Abstract:

The relationship between large water volume and seismic activity gathers more attention due to the potential hazard in populated regions. Within the Great Lakes, a steady increase in the water level has been observed since 2013, and it causes wide concerns of flood and extreme weather conditions around the Lakes. The long-term water level observation shows a 2.2 feet above average in 2019. Meanwhile, a ML 4.0 earthquake struck Lake Erie on June 10th 2019 when the Lake had high water levels. It was the largest earthquake in this region for the past 20 years. This raises up a question of whether the increasing water level alters the stress state of local faults and promotes earthquake activity.

To better understand the impact of the increasing water level on local seismicity, we monitored the long-term seismic behavior and measured the stress changes from water loading. We identified uncatalogued events by applying a single-station matched filter technique to the continuous recording of station M52 since 2013 when it was first deployed. We used clustering analysis to categorize repetitive events sharing waveform similarity, resulting in at least 4 main clusters of signals with varying dominant frequencies. ~400 more earthquakes were detected besides 36 catalogued events. We also found events with dominating lower frequencies (1-5Hz) and long durations which are surface quarry blasts in Ohio. Another active cluster spanning similar frequency range with local earthquakes is likely associated with nearby mining sites. Moreover, our analysis unveiled an intriguing cluster with mainly short S waves at a narrow frequency band (6-10Hz). We further constrained the source information of a broad spectrum of signals using polarity analysis and event location. We resolved the seasonal variation of stress changes on fault planes induced by water load using the finite element method Pylith and compared the results to the new event catalog. Our findings revealed complex coupling between water level change, stress change, and seismicity in the southern Great Lakes region.