Look very closely at the finger positions. They are being used independently, not all together as in a simple slap.
Notice, as well, the dark object in the mniddle of each drum head. From the Wikipedia:
The head of each drum has a central area of "tuning paste" called the syahi (lit. "ink"; a.k.a. shāī or gāb). This is constructed using multiple layers of a paste made from starch (rice or wheat) mixed with a black powder of various origins. The precise construction and shaping of this area is responsible for modification of the drum's natural overtones, resulting in the clarity of pitch (see inharmonicity) and variety of tonal possibilities unique to this instrument which has a bell-like sound.
