Recent earthquakes occurring near the site of the old Texas Stadium reveal a subsurface fault line that extends from Irving into West Dallas according to a preliminary report released Friday.
Seismology teams from Southern Methodist University and the United States Geological Survey presented an interim report to the mayors of Dallas and Irving.
It was based on information from more than 20 portable earthquake monitors installed by SMU around the earthquake sites. The monitors helped researchers narrow in on the fault line.
Initial results from SMU’s seismology team reveal the quakes were relatively shallow and concentrated along a narrow two mile line which indicates a fault extending from Irving into West Dallas, running north-by-northeast from TX Highway 114 to Walnut Hill Road along the Trinity River.
"This is a first step, but an important one, in investigating the cause of the earthquakes," said SMU seismologist Brian Stump. "Now that we know the fault's location and depth, we can begin studying how this fault moves – both the amount and direction of motion."
The earthquakes have occurred in the granite "basement" below the layers of sedimentary rock that make up the large geological formation known as the Fort Worth Basin.
A Dallas man who lives nearby told NBC 5 they've had enough.
“It is causing damage. Foundation is shifting. There are cracks in the walls. Afraid about windows breaking. Nothing has fallen off the shelves yet, but it's unnerving. That is for sure,” said Shane Larson.
According to the report the depths of the quakes have been between 4.5 and 7 kilometers, relatively close to the surface, which explains why people as far away as Plano felt even small magnitude 2 earthquakes.
The report does acknowledge public concerns about shale gas production and notes there is one set of inactive shale gas production wells near the Irving earthquake epicenters and that the wells ceased production in 2012.
"Scientific questions about the nature of events in North Texas have heightened local and national concerns about the impact of activities related to shale gas production on geological infrastructure and subsurface infrastructure," the report reads. "SMU scientists continue to explore all possible natural and anthropogenic (due to human activity) causes for the Irving earthquakes and do not have a conclusion at this time.”
SMU scientists had just installed the first of its local monitors in Irving in January when the area recorded its two largest 3.5 and 3.6 magnitude earthquakes. There will be 11 temporary seismographs running as part of the Irving network moving forward.
Stump says the initial mapping of the fault provides important information to allow city officials to know which parts of their cities might experience the worst shaking if the fault remains active.
According to the report, while activity appears to have slowed over time, SMU scientists say there's no way to predict when the series will end or what the largest magnitude will be.
NBC 5's Julie Fine contributed to this report.