Response of tilt and strain meters in Hubei province to the 2011 Mw9. 0 Japan earthquake

:Tilt and strain meters of the deformation-observation network in Hubei Province all responded to the Mw9. 0 Japan earthquake on March 11, 2011. By analyzing the co-seismic responses, we found that firstly there was essentially a linear correlation between response time and epicentral distance. Secondly, there was some correlation between maximum response amplitude and earthquake magnitude as well as between the duration and earthquake magnitude. Thirdly, the response amplitudes and decay rates were different for different types of instruments. Due to less data-sampling frequency, the deformation instruments, could not display the first motion of P and S waves, but responded mainly to far-field surface waves. Before the earthquake, the NS earth tide component recorded by the cave stainmeter at Yichang was distorted for nearly eight hours. While digital deformation observation did not show complete information about the earthquake source, it still reflected some key features of seismic-wave propagation.