**3. Results**

As can be seen from Figure 1a and as noted by Cathles and Prinzhofer [4], the changes in H2 concentration are closely aligned with the maximum rate of decrease in daily atmospheric pressure (the atmospheric tide). Unlike the atmospheric tide, which has one dominant cycle per day, the solid earth tidal strain has two cycles per day (Figure 1b). Although one of the cycles could assist the H2 venting, no changes in H2 concentration are associated with the second which is equally strong.
