**4. Discussion**

Maule earthquake triggered the rupture of three crustal faults: Pichilemu, Santa María, and Tirúa-Mocha, all with different behaviors. Pichilemu and Santa María faults with normal mechanism can be explained better due to their orientation normal to the maximum T axis of the rupture along Wadati-Benioff zone. We agree with Allmendinger et al. [22] that Santa María fault is not a splay fault. By contrast, Tirúa-Mocha is a splay fault with thrust mechanism. Such fault can be explained due to the development of a strong asperity in the interplate zone after 1960 earthquake, which remained even during Maule earthquake, being the movement accommodated in that zone at the Tirúa-Mocha splay fault, and the asperity at the updip of Wadati-Benioff zone was removed finally during Araucania Mw = 7.1 earthquake of January 2, 2011. It is not easily distinguished seismic activity linked to Santa María fault and Tirúa-Mocha fault. But the large number of events linked to Pichilemu fault are noted. Many of them are felt by the population of Pichilemu and surrounding areas.

It is not clear if these tree faults can generate their own earthquakes, not related with the subduction seismic cycle. These faults appear to be activated or reactivated due to the stress changes of South American plate, after Maule earthquake. The interplate border is irregular, so, during some earthquakes, different asperities can be developed in successive seismic cycles, some at the updip, some at the down dip of Wadati-Benioff zone. The position of these asperities, especially if such faults are located at the updip, can trigger the development or the reactivation of a splay fault. Such asperities can be of different sizes, and depending on this, the position of the T axis can vary in successive earthquakes, and some rupture lengths can generate a geometry of T axis that can be favorable to the normal reactivation of crustal faults [19].

About seismic potential, Pichilemu and Tirua Mocha fault proved to trigger earthquakes of magnitude Mw = 7. Pichilemu is located 100 km from places in which is located half of the population of Chile, including the capital Santiago and Valparaiso and Viña del Mar big cities. The Tirua- Mocha fault is located less than 200 km from two main cities of south Chile: Concepcion and Temuco.
