Triggered slip on multifaults after the 2018 Mw 6.4 Hualien earthquake by continuous GPS and InSAR measurements

Abstract

On 6 February 2018 at 23:50 local time, a M w 6.4 earthquake struck eastern Taiwan. We characterize the instantaneous surface ground motion and the permanent displacement induced by this event from continuous GPS data and SAR images within a short time after the mainshock. We use high-rate GPS positioning techniques to obtain epoch-by-epoch positions peak ground displacement to assess potential seismic damage. The maximum coseismic GPS horizontal displacement of about 450 mm trending to the northeast is observed at the station HUAL located on the hanging wall of the Milun fault. The PEPU located on the footwall of the Milun fault shows a coseismic horizontal displacement of 280 mm trending to the southwest and a coseismic uplift of about 70 mm. Moreover, ascending and descending tracks of ALOS-2 and Sentinel-1 SAR images are processed to estimate coseismic surface deformation along the line-of-sight (LOS) toward the satellite. Then, wide coverage from east-west and uplift components of surface deformation is fulfilled by combining the LOS displacement from ascending and descending interferograms. The main deformation area revealed by both GPS results and D-InSAR interferograms is concentrated around the Milun and Lingding faults. Significant uplift on the footwall of the northern Lingding Fault implies that the Milun fault and an unknown westdipping fault close to the Lingding fault were triggered. Both the two nodal planes of the M w 6.4 Hualien event could be different with the kinematic behavior of the Milun fault and Lingding fault. Thus we suggest that slip on multiple faults was triggered during the 0206 event.

Probing the Variation in Aseismic Slip Behavior Around an Active Suture Zone: Observations of Repeating Earthquakes in Eastern Taiwan

“…The CRF that is responsible for the 1‐ to 2‐cm/year uplift rate of the mountain (Ching et al, 2011; Ching, Rau, & Zeng, 2007; Ching, Rau, Lee, & Hu, 2007; Rau et al, 2008; Yu et al, 1997) was the site of the 2013 M L 6.4 Ruisui and the 2014 M L 5.9 Fenglin earthquakes and has been inferred to be a west‐dipping blind fault (Biq, 1965; Canitano et al, 2015; Chuang et al, 2014; Lee et al, 2014; Shyu et al, 2006; Wen et al, 2016; Wu et al, 2006). The western digging fault was also inferred to correspond to the 2018 Hualien events (Tung et al, 2019; Yen et al, 2019). Based on the findings of past geological and seismological investigations, the CRF can be subdivided into five segments from north to south: Hoping, Fenglin, Yuli, Chulu, and Binlang segments (Chen et al, 2018), as indicated by the blue lines in Figure 1.…”

Introduction to the special issue on the 2018 Hualien, Taiwan, earthquake

“…To begin with Tung et al (2019) determined the coseismic deformation of the 2018 Hualien event using the continuous GPS measurements and InSAR analyses and they found that the main deformation is concentrated on the Milun and the Lingding faults. Moreover, they suggested that an unknown west-dipping fault close to the Lingding fault was triggered during the earthquake sequence.…”

“…Moreover, they suggested that an unknown west-dipping fault close to the Lingding fault was triggered during the earthquake sequence. Tung et al (2019) also obtained 1-Hz GPS positions peak ground displacement to evaluate the earthquake damages of the Hualien area. Wu et al (2019), on the other hand, investigated and re-measured more than 100 benchmarks set up by various agencies by using network RTK.…”

Temporal Variations of Earthquake Magnitude‐Frequency Relation in the Source Area of M ≥ 6.0 Earthquakes: A Systematic Survey in Taiwan

“…A M L 5.8 earthquake and its aftershocks within 2 days before the 2018 M L 6.3 Hualien earthquake are essentially foreshocks (the yellow star and circles in Figure 9a) and in space distinguishable from the high coseismic slip area. Some studies suggested that the high coseismic slip distribution on the Milun fault may be a triggered fault slip by the 2018 M L 6.3 Hualien earthquake (Lee et al., 2018; Tung et al., 2019). To verify the correlation, we resurveyed the temporal b ‐value in the high coseismic slip area based on an epicenter released by the Real‐Time Moment Tensor Monitoring System (RMT; https://rmt.earth.sinica.edu.tw/) (the red star in Figure 9a).…”