## 1 Introduction
In addition, the spatial scale of the ionosphere is large so the position fluctuation of the IPP can basically be ignored, and the satellite is regarded as stationary relative to the earth. Given the stationary nature of the GEO satellite in relation to Earth, the ground-based receiving stations are able to continuously acquire TEC data for the fixed IPPs in the ionosphere. This ability is equivalent to setting up multiple fixed-position, time-continuous monitoring devices on the ground, which effectively enhances the spatiotemporal resolution of ionospheric monitoring. The disturbances of ionospheric TEC have been studied extensively using BeiDou satellite data. However, the existing research mainly focuses on the effects of space weather, such as solar and geomagnetic activity [25; 26]. [PERSON] et al. [27] investigated the variation characteristics of ionospheric TEC based on specified piercing points using GEO observation data. They compared the TEC obtained through GEO-measured data with other data sources and demonstrated that it has a higher level of confidence. [PERSON] et al. [28] undertook a statistical investigation to explore the temporal and spatial variation characteristics of ionospheric TEC during the period of the August 2018 geomagnetic storm. [PERSON] et al. [29] observed a significant increase in ionospheric TEC before and after the occurrence of a magnetic storm, verifying the feasibility of monitoring ionospheric spatiotemporal changes using the BeiDou GEO satellite. Despite advancements in TEC research, the understanding of seismic disturbances inferred from GEO satellite TEC data is limited. [PERSON] et al. [30] used TEC data inverted by GEO satellites at IPPs from ground-based receiving stations in mainland China to explore the pathways in which earthquakes may affect TEC and discussed the coupling relationship between the lithosphere and the ionosphere. [PERSON] et al. [31] scrutinized the TEC disturbances during the Menyuan M86.9 earthquake, utilizing the data obtained from the BDS GEO. Their analysis revealed a resonance coupling effect existing within the lithosphere and ionosphere. The Crustal Movement Observation Network of China (CMONOC), also known as the Land State Network, has made continuous advancements in the utilization of BDS data since 2015. Currently, approximately 170 stations are capable of receiving GEO satellite data in China. Several studies have demonstrated a significant correlation between seismoionospheric anomalies and the magnitude of earthquakes [10]. Consequently, investigating earthquakes of higher magnitudes can offer more favorable prospects for the examination of ionospheric anomalies and the elucidation of the mechanisms underlying seismic ionospheric disturbances. On 8 August 2017, a strong earthquake with a magnitude of Ms7.0 occurred in Jiuzhaigou County, Sichuan Province. Researchers had identified anomalous disturbance in the ionospheric parameters, specifically in terms of TEC, prior to this earthquake [32; 33; 34; 35; 36]. However, existing analyses primarily rely on GPS single-station data or global ionospheric mapping (GIM); research employing TEC data inverted by the BeiDou GEO satellite is currently lacking for this particular seismic event. In light of this, our study aims to investigate the ionospheric disturbance across spatial and temporal dimensions prior to the Jiuzhaigou Ms7.0 earthquake utilizing the TEC data of BDS GEO acquired from CMONOC. From this study, we aim to further understand the characteristics of ionospheric perturbations triggered by earthquakes and explore the mechanism underlying seismoionospheric coupling.