Precise measurement of seismic activity is fundamental to planetary seismology. However, existing planetary microelectromechanical system (MEMS) seismometers encounter a critical bottleneck in balancing compact chip footprint, a low noise floor, and a wide measurement range. This paper presents a miniaturized MEMS seismometer, which has a compact chip footprint of only 5.2 mm × 6.5 mm. The device utilizes corrugated-gap capacitive sensing comb fingers, which significantly reduce sensing nonlinearity while maintaining high displacement sensitivity, effectively extending the linear measurement range and elevating the pull-in acceleration threshold. Furthermore, the system's effective resonant frequency is reduced by exploiting the electrostatic negative stiffness mechanism, which aims to suppress the seismometer's noise floor. Experimental results validate the seismometer's comprehensive performance, demonstrating a noise floor of 5.5 ng/Hz (closely approaching the mechanical thermal noise limit), a measurement range of ±34 mg, and a bandwidth of 70 Hz. Under continuous operation, the instrument successfully captured natural seismic signals from a magnitude 7.0 earthquake 3682 km away and a magnitude 5.5 event 1240 km away, achieving a 99.1% waveform correlation coefficient when compared against a commercial reference seismometer. Ultimately, this work presents a novel chip-level MEMS seismometer for distributed seismic networks and planetary seismic observation.