## 1 Introduction  
The Republic of Serbia is situated in the central-western Balkans and is surrounded by the Rhodopes and Balkan Mountains to the south-east, the Carpathian Mountains to the north-east, the Dinaric Alps to the south-west, and the Pannonian Basin to the north-west (see Figure 1--top right). The depth of the Moho is around 25 km below the Pannonian Basin and around 45 km below the Dinarides. The epicenters of the 1900-2024 regional earthquakes with \(M_{W}\geq 3.5\), which were compiled by USGS [1], are displayed in Figure 1, bottom right. It can be seen that the entire territory of Serbia is seismically active. However, southern parts of Serbia are next to the Mediterranean-Trans-Asian belt, which is characterized by a comparatively high frequency of stronger seismic events, while in north Serbia, which is part of the Pannonian Basin, larger earthquakes are extremely infrequent. In addition to local seismic activity, Serbia is impacted by the Vrancea earthquakes, the epicenter of which is depicted in Figure 1--top right. Figure 1--bottom right, also shows epicenters of the two most catastrophic earthquakes to ever strike former Yugoslavia: the 26 July 1963, M6.0 Skopje earthquake and the 15 April 1979, M6.9 Montenegro earthquake, as well as the three most populous cities in Serbia (Belgrade, Novi Sad, and Nis). Figure 1, on the left, shows central Serbia and the epicenters of earthquakes with \(M_{W}\geq 5.0\), which were compiled by the Seismological Survey of Serbia for the period between 1456 and 2010 [2]. Epicenters of the most destructive earthquakes in central Serbia in the past 100 years are also shown. Neither USGS [1] nor Seismological Survey of Serbia [2] mention a single event with magnitude \(M_{W}\) larger than 6 in Serbia. This study focuses on the two strongest earthquakes on the territory of the Republic of Serbia in the past three hundred years that occurred in its central part in the valleys of the Morava and Resava rivers, the first on 4 February 1739, and the second on 8 April 1893 (24 January 1739, and 27 March 1893, respectively, according to Julian calendar, which was in use in Serbia till 1919). According to the earthquake catalogs of the Seismological Survey of Serbia prior to 2013, the magnitudes of these two earthquakes, evaluated based on macroseismic intensities, were 6.0 and 6.5, respectively [3,4]. Approximately the same values were given in the catalog of [PERSON] et al. [5], in which the two magnitudes (once again assessed on the basis of macroseismic data) were 6.1 and 6.6, respectively, while in the SHEEC catalog [6], the same value of 6.42 was given for both earthquakes. However, in the latest (2013) catalog of the Seismological Survey of Serbia [2], the magnitude values for the two earthquakes were reduced from 6.0 to \(M_{\rm W}=5.7\) and from 6.5 to \(M_{\rm W}=5.8\), respectively, without any references or explanation as to how they obtained these values. Figure 1: Earthquakes in Serbia and the region: (**bottom right**)—epicenters of the regional earthquakes with \(M_{\rm W}\geq 3.5\), compiled by USGS for the period between 1900 and 2024 [1], including the epicenters of the two most devastating earthquakes in former Yugoslavia, (**top right**)—a geographic map of the Balkan region and Serbia (shown within the frame), also showing the location of the Vrancea, Romania seismic source zone, (**left**)—epicenters of the earthquakes in central Serbia with \(M_{\rm W}\geq 5.0\), compiled by the Seismological Survey of Serbia for the period between 1456 and 2010 [2]. The objective of this paper is to assess the relevance of the recent magnitude values provided by the Seismological Survey of Serbia. Moreover, studying historical earthquakes sheds light on real seismic potential in the valleys of the Morava and Resava rivers. We first analyze in detail the data of the earthquake of 8 April 1893. For this event, in addition to the existing 318 data, we managed to obtain, in the past ten years, another 220 data in the form of written reports on the earthquake effects.