Crustal Lg attenuation within the North China Craton and its surrounding regions.

We report on a broad-band high-resolution attenuation model for the North China Craton and surrounding regions based on regional Lg-wave data. Vertical broad-band waveforms recorded at 39 stations from 176 crustal earthquakes are collected to extract the Lg-wave amplitude spectra between 0.05 and 10.0 Hz. We use the dual-station method to generate a preliminary QLg model and use it as the initial model. Then, we combine the dual- and single-station data together to jointly invert the QLg distribution and Lg source excitation functions. These inversions are conducted independently at individual frequencies without using any a priori assumption about the frequency dependences in QLg and source terms. The maximum spatial resolution is approximately 1° × 1° in well-covered areas for frequencies between 0.05 and 2.0 Hz. The QLg image is then used to determine the relationship between the attenuation and different geological structures. Results show an average Q0 (1 Hz QLg) of 374 for the entire North China Craton with an increasing trend from east to west. Average Q0 values are 337, 361 and 421 for the east, central and west blocks, respectively. For the surrounding regions, the Eastern Tibetan plateau has a very low Q0 of 188, while the Northeast China Plate and the Tianshan–Xingmeng fold belts are characterized by high Q0 values of 506 and 424, respectively. We also investigate regional variations of the Lg attenuation in low-frequency band between 0.2 and 1.0 Hz. [ABSTRACT FROM AUTHOR]