Setting up a Levelling Network for the Detection of Reliable Subsidences

In August 1989 on the north west coast of Peloponnesus earthquake tremors of average Ms = 4.8 of the Richter scale occurred and consequently damage was done to constructions in the area of Agia Triada in the city of Patras. Additionally in the above area a crack of 1500m length appeared on the ground with southwest-northeast direction (approx. azimuth 80°-Fig.1). The direction of the crack coincides with one of the main directions of the faults existing in the wider area. The position of the crack generally is the same with a fault which extends eastern up to Panachaikon mountain. (Kalteziotis et al, 1991). For the detection of vertical displacements a monitoring levelling network was established. Moreover pairs of special markers on both sides of the fault had been placed earlier for the observation of the behaviour of the ground through direct observations.