Three‐Dimensional Q Value Tomography for Xiuyan Meteorite Impact Crater

Abstract

Until 2009, 176 meteorite impact craters have been found in the world. Since the 80's of 20th century, Chinese scholars have confirmed, from the geological, geochemical and drilling data, that a circular structure was formed by meteorite impacting in Xiuyan County, Liaoning Province. But the deep structures and the overall characteristics of the crater need still to be confirmed by using the geophysical methods. In this paper, threedimensional Q structure has been obtained for the first time by using seismic refraction data in order to have a total understanding of the crater. Q value structure is of great significance for understanding the non-elastic and nonuniform nature of the crust. Using three-dimensional Q tomography method based on absorption characteristic time t * , the amplitude spectra have been obtained and by fitting the amplitude spectrum, t * values have been obtained, which reflect seismic wave attenuation. The three-dimensional Q value structure has been obtained by using t * values through three-dimensional Q tomography method. The results showed that the Q-value layer from the surface to the depth of 100 m within the crater corresponds to the upper 107 m thick lake sediments, the Q-value layer from the depth of 100 m to 300 m corresponds to the lower 188 m thick breccia accumulation lens. The Q-value layer from the depth of 300 m to 700 m corresponds to the broken Lower Proterozoic metamorphic rock layer with less impacting. The wave impedance interface about 250 m deep corresponds to the meteorite impact interface confirmed by geological drilling at the 260 m depth.

High‐Resolution Seismic Exploration of Xiuyan Impact Crater Structures

“…The stratum of meteorite crater, as metamorphite of Liaohe lithogroup of lower Proterozoic, is composed of leptite, amphibolite, griotte, gneiss and metabasalt [18] . The surface of the whole crater body is covered by vegetation like subshrubs and farm corps, and the top of crater lip and slopes of both sides is generally covered by weathered soil, sedentary product and slope wash of a few meters thick, with scattered bedrock outcrops (mainly leptite) in some parts.…”

“…which are difficult to resolve by geomorphology, surface geology and geochemistry. But, as a ring structure and a special geophysical field formed in the target rock under the meteorite impact, the rock density and velocity structure are different from wall rock, therefore, seismic sounding method is adopted to obtain the configuration and structure features of meteorite craters by studying the differences of seismic wave velocity, density of different rocks and the characteristics of seismic reflected wave and refractive wave from different lithologic or fault interfaces [17,18] . In this project, combined exploration of high-resolution seismic reflection and refraction is adopted to investigate the configuration and structure features of Luoquanli meteorite crater so as to provide reliable basic data for further study on its origin.…”