Six‐Component Earthquake Synchronous Observations Across Taiwan Strait: Phase Velocity and Source Location.

With the development of rotational seismometers, especially the high‐sensitivity optical seismometers, rotational motions have shown increasing benefits for calculation of dispersion curves, estimation of back azimuth and many other applications. Here we present the six‐component observations of 2019 Hualien mww6.1 earthquake simultaneously on both sides of Taiwan Strait. Seismograms and time‐frequency spectrums show that the attenuations for rotations are more significant than translations. Calculations of the surface wave phase velocity are performed for both stations through single‐station records, indicating a distinct difference owning to the instrument installation conditions and site effect. Comparison of theoretical dispersion curves is consistently in trends with estimations, and reveals the influence of higher‐mode surface waves. For the first time, we locate the source of a earthquake through intersection of two stations' back azimuths estimated through rotational methods. Results of comparing to translational polarization verify that rotational observation can distinctly reduce the deviation of source location. Plain Language Summary: We recorded the 2019 Hualien mww6.1 earthquake by two stations on both sides of Taiwan Strait. Both stations consist of a broad‐band seismometer and a fiber‐optic rotational seismometer. We compare the amplitudes and Time‐frequency spectrums of two stations' records and validate the attenuations for translational and rotational motions. Due to the shorter epicentral distance, NA01 station in Taiwan observed stronger signals than QS01 station in Fujian. We then use the rotational methods to compute surface wave phase velocity and dispersion curves, and validate the results by theoretical calculation through crust model. Estimation of back azimuths of two stations are used to locate the earthquake, indicating that rotational motions can reduce the deviation of source location. Key Points: Co‐located observations of three translational motions and three rotational motionsEstimate the phase velocity dispersion curves and back azimuths by rotational methodsLocate the earthquake source by three methods and evaluate the deviations [ABSTRACT FROM AUTHOR]