ZI (2016-2017): Investigation of crustal structure of the Matador Arch, testing of short period vs long period receiver function

• Texas Tech University, United States of America

There are two goals in this project: 1) To investigate crustal structure of the Matador Arch (MA). This is generally thought of a small feature of only local importance. But recent work shows geophysical anomalies into the upper mantle that may be associated with this feature. Once believed to be a minor uplift cause by compression in late Paleozoic during the assembly of Pangaea. Recent work has shown the MA to be a strike slip system with localized pull apart basins and uplifted blocks. The MA is also in line with volcanic trends, one to the east that is most likely due to mafic intrusions during the Proterozoic and a another intrusive dike (to the west) that was intruded during the past few million years. We believe that the alignment of these trends is not a coincidence and may imply the MA has been a zone of weakness in the crust that has been exploited at several different times over the past 1.1 GA. 2) To test the hypothesis that a small array of low cost short period geophones can out preform a single, more expensive, broadband seismometer. We believe that the signal generated noise, (scattering from 3-D structure that is beyond the resolution of our method. Our procedure will be to deploy a large number of short period seismometers intermixed with portable broadband instruments across a region crossing the Matador Arch near a permanent broadband seismic station. The southern end of our deployment will overlap with the SEIDCAR Broadband deployment. We will use none broadband seismometers owner by TTU, 6 of which will be deployed using PASSCAL RT130 data loggers. We are requesting 10 L28 4.5 Hz three component seismometers to deploy with these broad band instruments. The seismometers will be relocated once every month or two to provide data for 3-D imaging of the crust. The short period instruments will be deployed in clusters of 3 instruments around the broadband instruments. If possible, we would like to End the project by deploying 20 to 40 Fairfield 3-C seismometers for one month. The goal will be to image 3-D structure of the entire crust. We plan to determine if there are changes in the Moho structure across the Matador Arch. But we will also try to image 3-D of the mid to upper crust using receiver functions and tomography. There are large salty lakes near the Matador Arch that appear to be the result of subsidence along faults (possibly due to karsting). But these lakes follow a trend that may be related to the Matador arch. We believe these basins may coincide with pull-apart basing along the strike-slip faults of the Marador Arch. These features are generally considered to be beyond the resolution of passive body wave methods. But we believe the availability of a large number of low cost short period instruments may enable us to improve our resolution sufficiently to image these features. We have produced reliable receiver functions in this area in the past using PASSCAL 4.8 Hz 3-component seismometers with only 1 month of data. We believe we can produce a 3-D image from similar equipment deployed for only a few months.

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