<p>Eastern Tehran, because of the presence of major faults such as the Mosha Fault and significant historical earthquakes, was selected to study the precursory seismic behavior prior to the ML 5.1 earthquake on May 7, 2020. In this study, seismic parameters (<i>a</i>-value, <i>b</i>-value, and <i>z</i>-value) were analyzed using ZMAP tool. Seismic data were extracted from the catalog of the International Institute of Earthquake Engineering and Seismology (IIEES) for the period 2010–2023. The catalog was first declustered using the Reasenberg method with standard parameters. Subsequently, the magnitude of completeness (<i>M</i>_<i>c</i>) was estimated, and events smaller than this threshold were removed. The <i>b</i>-value near the epicenter of the ML 5.1 Mosha earthquake was estimated to be about 0.68 for the entire catalog. Considering the spatial variations of <i>M</i>_<i>c</i> in the region (ranging from 1.9 to 3.5) and its effect on the <i>b</i>-value, changes in this parameter were analyzed for the two periods 2016–2018 and 2018–2020. The results indicated that prior to the Mosha earthquake, the <i>b</i>-value decreased from approximately 0.85 to 0.6. The analysis of the <i>z</i>-value during 2010–2016 showed seismic quiescence around the epicenter; however, from 2016 onwards, the region gradually experienced increased seismic activity. These changes reflect the gradual release of accumulated stress in the area, accompanied by heightened seismic activity, which may have contributed to of the ML 5.1 earthquake. This study emphasizes the necessity of expanding the seismic station network and reducing the spacing between them to enable the detection of microearthquakes across the entire region. Such improvements would ensure more complete recording of microseismic events, increase the reliability of the results, and provide a more realistic assessment of seismicity parameters and seismic hazard.</p>