**1. Introduction**

Chile is a seismic country due to its tectonic framework, dominated by the subduction of Nazca Plate beneath South American Plate at approximately 7 cm/yr at N77°E trend. The Wadati Benioff zone has N10°E strike and 20°E dip. Geological hazard consequences of this are earthquakes, tsunami, and volcanic activity. Subduction earthquakes of thrust focal mechanism included the biggest ever recorder, the Mw = 9.5 Valdivia earthquake that occurred on May 22, 1960 and the sixth, the February 27, 2010 Mw = 8.8 Maule earthquake. In a same segment of the subduction zone, Mw = 8 earthquakes occurred every 100 years and an Mw = 9 earthquake every 300 years or more [1–9]. **Figure 1** shows some of the main subduction earthquakes and rupture lengths that occurred in central and south Chile, divided in Central Chile, Concepción, and Valdivia segments. The epicenters of the subduction seismicity are located from 10 km east to the trench to 160 km eastward in the littoral zones and hypocenters between 10 and 55 km being deeper eastward [1, 9]. Other Nazca intraplate earthquakes are due to slab pull with normal mechanism [10–13]. Epicenters of these earthquakes are located 160–270 km from the trench eastward and hypocenters between 100 and 200 km. The Chillán Mw = 8 earthquake of January 25, 1939 [10]

#### **Figure 1.**

*Significant earthquakes in central and south Chile divided in three segments: Central Chile, Concepcion, and Valdivia. Right: years and extension of the ruptures of the earthquakes. Blue years: Central Chile earthquakes; green years: Concepcion earthquakes; and red years: Valdivia earthquakes.*

was the deadliest earthquake that occurred in Chile with more than 25,000 persons killed. Other significant slab pull earthquakes are the Punitaqui 1997 Mw = 7.1 [12] and Tarapaca 2005 Mw = 7.8 [14]. Other Intraplate earthquakes are located at South American Plate with strike slip mechanism. These events are concentrated in crustal faults along the axis of Andes Cordillera of N-S strike and vertical dip, right lateral movement [15–18]. Significant earthquakes of such kind are 2001 Mw = 6.3 Aroma earthquake, 2004 Mw = 6.4 Curicó earthquake, and 2007 Mw = 6.2 Aysén earthquake. Due to the shallow hypocentral depths (≤10 km), in mountain areas, these earthquakes generate significant damages due to the landslides triggered.

However, crustal faults can also generate significant earthquakes or being activated or reactivated during significant subduction earthquakes. The 2010 Maule earthquake activated two crustal faults: the Pichilemu fault of normal mechanism [19–21], the normal Santa Maria fault [22, 23], and the Tirúa-Mocha fault of thrust mechanism [5]. In this paper, we assess the seismic potential of such faults.
