We analyze source parameters such as seismic moments M0 and corner frequencies fc of several thousands of volcano-tectonic earthquakes occurred in the summit of the Piton de la Fournaise (PdF) volcano from January 2014 to August 2023. This swarm seismicity, preceding frequent PdF eruptions, corresponds to a ring-fault system, regularly forced by pressurizations of the shallow magma reservoir and stresses caused by the pre-eruptive dyke propagation. We use 3-component broadband stations located in the close vicinity of the volcano 3-5.5 km. Smoothed amplitude envelopes of the coda waves are computed from a set of narrowly band-passed signals and are inverted to simultaneously extract the frequency-dependent coda decay factors, site effects, and source terms. The latter are used to compute the source spectra ratios between pairs of events. This results in statistically estimated fc and relative M0, calibrated then using well-defined magnitudes. As a result, we find an average stress-drop of the order of 10 Mya for the majority of shallow PdF earthquakes and a general trend fc ~M0-1/3, that is usually observed for the ”regular” tectonic seismicity. Given that the coda shape remained unchanged over 10 years of eruptions and stress drops varied insignificantly in space and time confirm that this seismicity is associated mostly with a pre-existing fault system without formation of new cracks. For the smallest events corner frequencies were estimated beyond Nyquist frequency 50 Hz. For the fc ranging from 5 Hz to 100 Hz the source radii range from 200 m to 10 m assuming a circular source model.