To be precise, this can trigger a quake, in areas under tectonic stress. The role of pressurized fluids triggering quakes was first documented at the Rocky Mountain Arsenal north of Denver, where they were disposing of nerve gasses by pumping them thousands of feet down into the bedrock. A series of moderate quakes (5-6) hit Denver in the Late 60's. A conection was established once the injections were plotted next to quakes in a time series. That, and when the disposal stopped, so did the quakes.

What happens is the pressurized fluid doesn't lubricate the existing faults (by reducing the cooefficient of friction), rather it lowers the effective mean stress required for inelastic failure. That is, it breaks at a lower stress level. This is now very well known in oil and natural gas fields, where pressurization of wells is common.

It was clear that the California Project had not gotten to the point of over-pressurizing (fraking) the rocks, and the Swiss project was still drilling. However, drilling a deep hole requires using presurized drilling mud (to keep the bore from collapsing), and that might be enough to trigger a quake.

There is the possibility, of course, that the quakes had nothing to do with the drilling, but people are always going to blame the rig down the road first.