Frequency dependent Lg attenuation in Northeast China and Korean Peninsula

Abstract:

Lg spectra are collected from 452 crustal events spanning from 1995 to 2014 in Northeast (NE) China and surrounding areas using 202 seismic stations from Northeast China extended seismic Array (NECESSArray), GSN stations in NE Asia, China national seismic network, IRIS PASSCAL experiments in NE China, Korean and Japanese permanent seismic networks to study Lg attenuation in NE Asia. Using reverse two-station and two-station methods we obtained frequency dependent Lg attenuation models for a frequency range between 0.5 Hz to 5 Hz with a resolution of about 2^°. We solved for the geometric spreading term by fitting the amplitude to the two-station distance ratios and the absolute distances. The best fit yields a spreading coefficient of 0.36 instead of the traditional cylindrical spreading term of 0.50. Lg Q values in NE China and the Korean Peninsula vary from 50 to 1600. Q values increase rapidly in the Songliao Basin (SNB) for higher frequencies (≥ 2Hz), while they stay relatively constant in the Great Xing’an Range (GXR). Low attenuation regions are found in the Great Xing’an, Lesser Xing’an (LXR) and Songen-Zhangguangcai Ranges (SZR). Overall, attenuation is high in the Songliao, Sanjiang (SNB), Bohai (BHB), Erlian (EB) and Hailar (HB) basins. The highest attenuation is found in the vicinity of Wudalicanchi (WVF), Changbaishan (CBV), and Quaternary volcanic regions, the southern Songliao Basin, west of Erlian Basin, Bohai Basin and the Sanjiang Basin. In general regions with low attenuation (Q > 800) have a low heat flow value (<70 mW/m²) and very thin (< 1 km) or no sediments.