Some liquid explosives have two different detonation behaviors: high velocity detonation (HVD) or low velocity detonation (LVD). The detonation behavior depends on the level of the initiating shock pressure. The detailed structure of LVD in liquid explosives has not yet been clarified. A physical model was proposed that LVD is not a self-reactive detonation, but rather a supported-reactive detonation from the cavitation field generated by precursor shock waves. In this study, high-speed photography was used to investigate the detonation behavior of nitromethane (NM) with the various initiating shock pressures. Stable LVD was not observed, only transient LVD was observed. A very complicated structure of LVD was observed: the interaction of multiple precursor shock waves, multiple oblique shock waves, and a cavitation field. Multiple shock waves propagating in non-detonating NM were observed for shock pressures below the range required for LVD, while above the LVD range HVD was observed.