I recently flew as a passenger on a A320 similar to the one in the image. I used a Slam Stick X Vibration Data Logger to measure the landing shock, with the sensor mounted on the cabin floor. The resulting acceleration time history is shown in the following two figures, longer and shorter views. The main wheels touch down at the zero second mark. The nose wheels contact the runway about 3.5 seconds later.
The higher frequency energy between zero and 0.5 seconds consists of components in the 10 to 15 Hz frequency domain, likely representing structural modes. The sample rate was 400 samples per second.
See also: Landing Shock
– Tom Irvine