Mapping the 3‐D Lithospheric Structure of the Greater Permian Basin in West Texas and Southeast New Mexico for Earthquake Monitoring. Issue 11 (7th November 2019)

• Record Type: Journal Article
• Authors: Huang, Guo‐chin Dino; Savvaidis, Alexandros; Walter, Jacob I.
• Is Part Of: Journal of geophysical research. Volume 124:Issue 11(2019)
• Page Start: 11466
• Page End: 11488
• Publication Date: 2019-11-07
• Subjects: induced seismicity -- seismic tomography -- Vp/Vs ratio; Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1029/2019JB018351
• Languages: English
• ISSNs: 2169-9313

Abstract

Abstract: The Greater Permian Basin is not only a complex tectonic regime, but it has also been and continues to be a productive oilfield where the seismicity rate in the basin has significantly increased since 2008. Since 2015, our understanding of the seismogenesis in the basin has increased owing to the establishment of a statewide seismic network known as TexNet for monitoring earthquake activities. A crucial component of improving the accuracy of the hypocentral location is an accurate velocity model that can better confirm the existing regional tectonic regime. We collected data from current TexNet operations and previously deployed seismic arrays and performed a joint local and teleseismic earthquake tomographic inversion, resulting in a three‐dimensional tomography model for earthquake monitoring. The preferred three‐dimensional tomography model includes a prominent feature at a depth range of 0–20 km, where distinct lower wave speed anomalies overlap with the surface trace of the Delaware Basin. These anomalies suggest a basin‐scale lithological difference from surrounding regions and corroborate basin characteristics. Findings also suggest that the Midland Basin may be more lithologically uniform than the Delaware Basin. A strong correlation exists between dense seismicity clusters and the obtained lower V p / V s ratios. Four significant clusters having V p / V s ratios ranging from 1.689 to 1.720 were identified. Using the V p / V s ratio as a proxy to evaluate the state of the pore‐fluid pressure, we think this spatial correlation suggests that the Greater Permian Basin currently comprises overpressurized fluid‐filled host rocks. Plain Language Summary: Since 2017, a new statewide earthquake monitoring network, known as TexNet, has detected several active seismic zones in Texas. Among them, the Greater Permian Basin has a strong earthquake occurrence rate. In order to provide a better velocity model for the area of study, we followed two steps. First, on the basis of TexNet data from early 2017, we developed a one‐dimensional velocity model to account for the local geology better than the average Earth model does. A localized one‐dimensional model was thus adapted from this work. In this model, a subsurface layer with slower P wave speed is suggested to corroborate the regional tectonic setting as a sedimentary basin. Second, in late 2018, on the basis of the previous work, we collected more data and expanded the study area to cover the whole Greater Permian Basin. The resulting three‐dimensional tomography model features lower V p / V s ratios, indicating that currently the pore‐fluid pressure is high in the basin. Key Points: A statewide, earthquake‐monitoring network has been established in Texas We developed a tomographic velocity model for much of West Texas and southeast New Mexico for the purpose of earthquake monitoring Distribution of the V p / V s ratio shows basin‐scale features that suggest high pore‐fluid pressure existing in the Greater Permian Basin