The occurrence of a large number of earthquakes in the inter and intraplate settings of the Japan Trench leads to ruptures with varying frequencies. To capture the temporal distribution of energy and their ranges of frequencies, we have used the Intrinsic Mode Functions (IMFs) derived from the vertical components of the strong-motion records. Here we present an “energy release function”, which is yet another way of representing frequency-dependent energy release. Without the assumptions of the area of slip and elastic moduli, this provides a new representation of the energy released at the source. Choice of the appropriate IMF and thus the range of frequencies representing the source was based on the best fitting teleseismic model for the same earthquake. We analysed the strong-motion records for three earthquakes (all in the magnitude range of 7.1 to 7.3), representing interplate, intraplate, and intraslab settings and used borehole data from the KiK-net. These were the Miyagi 2005 (Interplate), Tohoku 2011 (Intraslab), and Honshu 2012 (intraplate). We used the Hilbert-Huang Transform, a combination of Empirical Mode Decomposition (EMD) and Hilbert Transform (HT) to develop the spectra for vertical components of each of these earthquakes. A combination of the IMFs within the frequency band (0.1 to 3 Hz) that mostly represent the frequency range used for teleseismic source inversion (0.01 to 2 Hz) was used to develop the spectra in each case. The shape of the spectra generally mimics that of the moment rate function. Where the moment-rate function follows a single pulse, the spectrum is able to generate its shape, and the sub-events are represented through independent pulses of energy. We believe that the representation of an earthquake source based on its frequency content and temporal pattern has important applications in predicting the shaking effects of an earthquake.