Source Parameters of the 2003–2004 Bange Earthquake Sequence, Central Tibet, China, Estimated from InSAR Data

Abstract

A sequence of Ms ě 5.0 earthquakes occurred in 2003 and 2004 in Bange County, Tibet, China, all with similar depths and focal mechanisms. However, the source parameters, kinematics and relationships between these earthquakes are poorly known because of their moderately-sized magnitude and the sparse distribution of seismic stations in the region. We utilize interferometric synthetic aperture radar (InSAR) data from the European Space Agency's Envisat satellite to determine the location, fault geometry and slip distribution of three large events of the sequence that occurred on 7

Fault Geometry and Mechanism of the Mw 5.7 Nakchu Earthquake in Tibet Inferred from InSAR Observations and Stress Measurements

“…More importantly, the Nakchu earthquake occurred in the tectonically complex central Tibet, where prevailed the V-shaped conjugate strike-slip fault systems [56] (Figure 8), in which the northern NEE striking fault expresses the sinistral strike-slip, while the southern SEE striking fault the dextral strike-slip. With this complex tectonic setting, the extensional tectonic and the normal faults develop between them [55,57], as reflected by the focal mechanism solutions of historical earthquakes [58,59], the Global Centroid Moment Tensor catalog (M ≥ 5.0), and the Nakchu earthquake in this study (Figure 8). Meanwhile, the direction of the maximum extensional principal strain rates calculated using the spherical wavelet-based multiscale approach [60], based on the 1991-2016 GPS velocity fields [12], is almost perpendicular to the strike of the seismogenic fault (Figure 8).…”

“…dextral strike-slip. With this complex tectonic setting, the extensional tectonic and the normal faults develop between them [55,57], as reflected by the focal mechanism solutions of historical earthquakes [58,59], the Global Centroid Moment Tensor catalog (M ≥ 5.0), and the Nakchu earthquake in this study (Figure 8). Meanwhile, the direction of the maximum extensional principal strain rates calculated using the spherical wavelet-based multiscale approach [60], based on the 1991-2016 GPS velocity fields [12], is almost perpendicular to the strike of the seismogenic fault (Figure 8).…”

Source Parameter Estimation of the 2009 Ms6.0 Yao’an Earthquake, Southern China, Using InSAR Observations

“…Therefore, we further established a more realistic model that discretized the fault into several sub-faults to describe the uneven slip at different depths and locations of fault planes. Here, we adopted the Steepest Decent Method (SDM) geodetic inversion code developed by the authors of Reference [38] to establish the distribution models, which has been successfully applied to many fault inversion analyses (e.g., [39][40][41][42][43]). In the process of the inversion, a smoothing constraint on the slip was applied between adjacent sub-faults to stabilize the inversion.…”

Earth Observations for Geohazards: Present and Future Challenges

“…Their joint Okada inversion with multiple Sentinel-1A interferograms suggests that most of the slip occurs northwest of the epicenter with a maximum located in the shallowest 20 km; their Finite Element Model indicates that (i) its estimated maximum slip is comparable to the Okada model; and (ii) the von Mises stress distribution agrees with the depth distribution of the aftershock hypocenters. InSAR observations are utilised to investigate the 2003-2004 Bange, China earthquake sequence, involving a series of normal faulting events with Mw > 5.0, indicating that InSAR can provide reliable source parameters of shallow, moderate-sized earthquakes in areas that lack dense seismic networks [13]. Li et al [14] use Sentinel-1A interferograms to model the 2016 Mw 5.9 Menyuan, China earthquake; they find that the 2016 event has a different focal mechanism from a previous Ms 6.5 earthquake although both are at the two ends of a secondary fault, which is believed to reflect the left-lateral strike-slip characteristics of the Lenglongling fault zone.…”