Analysis of coseismic response of fixed-point deformation observation in eastern Anhui

The eastern Anhui region is located in the central southern section of the Tan Lu fault zone, and a fixed-point deformation observation network covering body strain and ground tilt will be established in 2022. Each deformation observation instrument has a good response to large earthquakes, manifested as long-period oscillation attenuation type coseismic deformation waves; For near earthquakes and local earthquakes, the main manifestations during the earthquake are pulses, steps, or grid drops.Based on 12 seismic events that occurred in 2023, the cosismic response characteristics of different instruments were analyzed, along with their correlations with earthquake magnitude and epicentral distance. Spectral analysis was conducted using the Fourier transform, and the earthquake detection capabilities of the instruments were compared. The results indicate that borehole tiltmeters are superior to borehole volumetric strainmeters in capturing seismic signals, with the second-sampled CBT borehole tiltmeter exhibiting the best performance. The seismic response delay increases nonlinearly with increasing epicentral distance and tends to stabilize with increasing magnitude. The cosismic duration is positively correlated with both epicentral distance and magnitude. The frequency band width and main frequency of CBT borehole inclinometer are slightly inferior to broadband seismometers, and the response ability of the two components is equivalent. The spectral difference is the result of the synergistic effect of the physical structure, core performance, and geological environment of the instrument.