Webinars - Detail

Presenter #1: Dr. Nori Nakata (University of Oklahoma) 
Title: Data mining of IRIS Wavefield experiment in Oklahoma for seismicity and structure imaging 

The IRIS Oklahoma wavefield experiment provided one of the first three-component geophone-array datasets in our community and the unique opportunity for structural imaging and seismicity studies at local scales. Here, I discuss and demonstrate applications of the geophone arrays using the data of the experiment. The array in this experiment has a variety of different aspects, including linear and 2D arrays, and broadband sensors. The 2D array is useful to characterize the background seismic noise and its wave type. Linear arrays, with local (and global) earthquake records, are used for receiver-function analyses. The shape of sensors is not ideal for ambient-noise tomography, but I can still extract reliable correlation functions to represent a part of Green's functions. Coherent signals are extracted, not only between receivers in this array but also with receivers in Oklahoma regional networks. With the density of the sensors, the locations of microearthquakes around the array are well estimated, and I also use this array as an "antenna" to detect remote seismicity that occurred in the Fairview, Pawnee, and Cushing areas.


Presenter #2: Dr. Charles Langston (Center for Earthquake Research and Information, University of Memphis) 
Title: Arrays and Gradiometers of the IRIS Wavefields Community Experiment

One design element of the IRIS Wavefields Community Experiment was the fielding of four different seismic arrays for analyzing the wavefield of local and regional earthquakes to understand wave propagation and to determine source parameters, such as source depth, from observed seismic phases.  Three arrays are composed of 5 Hz, three-component nodal seismometers that were deployed at the end of June 2016 for one month. The fourth is a broadband phased array using 18 three-component seismometers with an aperture of about 12 km that was deployed from the end of June to November 2016.  Two of the 5 Hz arrays were arrays of opportunity in that the crossing points of the linear profiles were filled in with more closely spaced stations while crews were in the field.  The other 5 Hz array is composed of 112 nodal seismometers arranged in 7 squares of 16 instruments each to form a self-similar gradiometer for analyzing seismic strains and rotations for seismic wavelengths of 60m to 6 km.  The webinar will present an overview of phased array and wave gradiometry processing and motivation for fielding particular array geometries.  In addition, an effective method of calibrating amplitude statics and sensor orientations from a dense deployment of array sensors will be described and results given for the Oklahoma deployment.