**2. Maule earthquake**

Maule earthquake affected an area of more than 650 km length between 33 and 38.6°S. Two main asperities are identified, the northern one with main slip of 18 m between 34 and 35°S with depth between 20 and 40 km, and the southern one with main slip of 10 m between 37 and 37.6°S [3, 24–26]. Before Maule earthquake, a seismic gap between 34 37° S, named the Pichilemu-Concepcion seismic gap [1, 2] was identified. An earthquake of Mw = 8.5 was expected in this area, and the previous big earthquake located in such area occurred in 1835. This seismic gap is characterized by a lack of coastal seismicity in this area (Campos et al. [1]. About vertical changes, an interseismic subsidence is noted, mainly in littoral zones located close to the trench such as Arauco Peninsula and Santa María Island between 37 and 37.7°S [5, 21].

#### *Crustal Faults Reactivated during 2010 Mw = 8.8 Maule Earthquake in South Chile DOI: http://dx.doi.org/10.5772/intechopen.109564*

When finally, Maule earthquake filled this gap, several anomalies that are not expected occurred. The Mw = 8.8 magnitude was bigger than the Mw = 8.5 predicted [1, 2], overlapping rupture zones of recent earthquakes [3, 5]. In the north, the 1985 Central Chile Mw = 8 earthquake ruptured also the zone between 33 and 34°S. Uplift of 50 cm was observed in the littoral zone that contrasted with the subsidence in the same zone, which was observed in 2010 Maule earthquake. The southern rupture zone of Maule earthquake was affected also by the Concepcion Mw = 8.1 earthquake of May 21st 1960, the first earthquake of the great 1960 seismic sequence. The place of Lebu (37.6°S) was uplifted 1.2 m during 1960 earthquake, such uplift was recovered between 1960 and 2010 earthquakes and after Maule earthquake, was uplifted again 2 meters. Mocha island (38.3°S) was uplifted 1.5 m during 1960 earthquake, but unlike Arauco Peninsula and Santa María Island (37–37.7°S), the 1960 coseismic uplift remained [5].

The Maule earthquake and related tsunami provoked around 570 inhabitants killed and hundreds injured with extensive damage. Land changes included coastal uplift and subsidence, being decreasing uplift arcward (toward east). The hinge zone between uplift and subsidence was around 123 km in the area ruptured by the northern asperity and around 135 km in the southern asperity, indicating the shallower position of the northern asperity [5].
