Three-dimensional P velocity structure in Beijing area

Abstract

A detail three-dimensional P wave velocity structure of Beijing, Tianjin and Tangshan area (BTT area) was determined by inverting local earthquake data. In total 16 048 P wave first arrival times from 16048 shallow and mid-depth crustal earthquakes, which occurred in and around the BTT area from 1992 to 1999 were used. The first arrival times are recorded by Northern China United Telemetry Seismic Network and Yanqing-Huailai Digital Seismic Network. Hypocentral parameters of 1 132 earthquakes with magnitude ML=1.7-6.2 and the three-dimensional P wave velocity structure were obtained simultaneously. The inversion result reveals the complicated lateral heterogeneity of P wave velocity structure around BTT area. The tomographic images obtained are also found to explain other seismological observations well.

Seismic Imaging and Seismicity Analysis in Beijing-Tianjin-Tangshan Region

“…The tomoDD method uses the differential arrival times which are free from origin-time errors, and thus it removes some fuzziness from the velocity model. Our starting 1D model is inferred from a minimum 1D velocity model [2] for the crust (0∼25 km depth) and from deep seismic soundings [25,26] for the deeper crust and upper mantle (25∼40 km depth) (Figure 4). A 3D regular grid is used in this study [27].…”

“…A lot of studies have been performed in the past three decades to invert for the three-dimensional (3D) seismic velocity structure of the crust and upper mantle beneath this region using arrival times from local and/or teleseismic events [2,[9][10][11][12][13][14][15] as well as the seismicity in this region [16][17][18][19][20][21][22][23][24]. However, the spatial resolution and the accuracy of event T a n g s h a n -H e j i a n -C i x i a n z o n e S a n h e -L i n s h o u z o n e H u a i l a i -W e i x i a n z o n e (1) T a i h a n g s h a n U p l i f t 5∼5.9 6∼6.9 7∼7.9 ≥ 8…”

“…To improve the resolution of regional tomography, some seismic tomographic techniques have been developed, such as double-difference tomography (tomoDD) [6], which uses both absolute and relative arrival time data to determine a 3D velocity structure jointly with the absolute and relative event location. Furthermore, most of the previous efforts have focused on the crustal and mantle structure [2,[9][10][11][12][13][14][15] whereas little effort has been devoted to the study of relationship between seismicity of small earthquakes and velocity anomaly. Where is the location of top boundary of low velocity beneath Tangshan area?…”

Shear-wave velocity structure of the crust and uppermost mantle in the Shanxi rift zone

“…This phenomenon is in agreement with the previous studies. For example, studies of traveltime tomography in North China (Wang 2005;Zhu et al 1990;Yu et al 2003) show that distribution of the strongest earthquakes also has similar pattern. During the process of tectonic movement, a large amount of strain energy can be accumulated in the relatively weak zones (near anomalies gradient areas), thereby potentially causing earthquakes (He et al 2009).…”

Caucasus Seismic Information Network: Data and Analysis Final Report

“…The (Yu et al, 2003;Kissling et al, 1994). We inverted the arrival-time data in our selected dataset for a 1-D velocity model representing the whole study area by minimizing the root mean square (rms) error of the travel-times.…”