2017/09/26 by Qimin Wu, Martin Chapman, M. C. Chapman · 1 citation
Earth and Planetary Sciences · Computer Science · #earthquake and tectonic studies #Seismology and Earthquake Studies #Earthquake Detection and Analysis
paper · doi:10.1785/0120170098
Research Article| September 26, 2017 Stress‐Drop Estimates and Source Scaling of the 2011 Mineral, Virginia, Mainshock and Aftershocks Qimin Wu; Qimin Wu aDepartment of Geosciences, Virginia Tech, 4044 Derring Hall, Blacksburg, Virginia 24061, [email protected], [email protected] Search for other works by this author on: GSW Google Scholar Martin Chapman Martin Chapman aDepartment of Geosciences, Virginia Tech, 4044 Derring Hall, Blacksburg, Virginia 24061, [email protected], [email protected] Search for other works by this author on: GSW Google Scholar Bulletin of the Seismological Society of America (2017) 107 (6): 2703–2720. https://doi.org/10.1785/0120170098 Article history first online: 27 Sep 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Qimin Wu, Martin Chapman; Stress‐Drop Estimates and Source Scaling of the 2011 Mineral, Virginia, Mainshock and Aftershocks. Bulletin of the Seismological Society of America 2017;; 107 (6): 2703–2720. doi: https://doi.org/10.1785/0120170098 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyBulletin of the Seismological Society of America Search Advanced Search Abstract We estimate corner frequencies and stress drops for the 2011 Mw 5.65 Mineral, Virginia, earthquake and aftershocks using a multiwindow coda spectral ratio method. We apply a Bayesian approach using a Markov chain Monte Carlo algorithm to fit the observed spectral ratios of selected event pairs with the Brune omega‐square source spectral model to obtain reliable measurements of corner frequency as well as the associated uncertainties. We show that the use of S‐wave coda provides more stable source spectral ratios than using direct S waves, and select event pairs by examining the common decay characteristics of narrowband coda envelopes. We determined an unusually high stress drop of ∼67 MPa for the mainshock, assuming a simple Brune‐type source model. The results of our modeling of the mainshock spectrum at the nearest recording station suggest similar values of stress drop for the two main subevents responsible for most of the moment release. The estimated stress drops for 46 aftershocks (Mw 0.71–4.13) range from ∼0.02 to 50 MPa with a median value of 3 MPa. The aftershocks with Mw≥2.5 have high stress drops within a small range of ∼3–50 MPa, with a median value of 16 MPa. We observe an apparent decrease of stress drop with decreasing magnitude below Mw∼2.5. Rather than suggesting a possible breakdown of self‐similar source scaling, we attribute this apparent magnitude dependence to limited signal‐to‐noise ratios for small shocks, limited frequency bandwidth, and particularly, to a group of small magnitude earthquakes that occurred in a loose cluster several kilometers to the northeast of the mainshock. Those events have unusually low stress drops, compared with aftershocks in the main aftershock cluster, and may possibly indicate triggering of seismicity on a set of relatively weak fault or joint planes. We found no temporal pattern or depth dependence in the estimated stress drops. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.