SAN FERNANDO CITY, La Union: The Philippine Volcanology and Seismology (Phivolcs) on Thursday said it is monitoring the cracks in the floors of houses in the village of Nagyubuyuban and the collapsed landscape in its vicinity. Research specialist Edna Patricia Mendoza said the cracks and collapse indicated a possible fault line that may be vulnerable to a major movement in case an earthquake may occur. She said landslide sensors will be installed in the area to monitor the movement of the fault line. She said the cracks shows an enormous soil movement probably caused by an active earthquake fault line which is slowly collapsing, mostly during heavy rains. The installation of sensors begun in 2008 in several areas to observe its extent of dangers it may result during earthquakes and landslides.