Quakes are not uncommon in the state, so there are monitoring stations in Peñamiller, Extoraz, Peña Blanca and 10 in the Sierra Gorda, including Jalpan de Serra, Landa de Matamoros, Arroyo Seco, Pinal de Amoles and San Joaquín. More are planned for Tolimán and Cadereyta. In January 2011, about 70 small quakes caused some damage in the Peñamiller area, in the north, causing a certain amount of panic in the area, because the tremblers continued, with an average strength of 3.5 on the Richter magnitude scale. This is not normal for this area. The quakes are believed related to mining in the area, but the government denies this.