Journal cover Journal topic
Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 2.281 IF 2.281
  • IF 5-year value: 2.693 IF 5-year 2.693
  • CiteScore value: 2.43 CiteScore 2.43
  • SNIP value: 1.193 SNIP 1.193
  • SJR value: 0.965 SJR 0.965
  • IPP value: 2.31 IPP 2.31
  • h5-index value: 40 h5-index 40
  • Scimago H index value: 73 Scimago H index 73
Volume 16, issue 12 | Copyright
Nat. Hazards Earth Syst. Sci., 16, 2511-2528, 2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 30 Nov 2016

Research article | 30 Nov 2016

Seismic hazard in low slip rate crustal faults, estimating the characteristic event and the most hazardous zone: study case San Ramón Fault, in southern Andes

Nicolás P. Estay1,2,3, Gonzalo Yáñez1,2,3, Sebastien Carretier4,5,6,7, Elias Lira1, and José Maringue1,2 Nicolás P. Estay et al.
  • 1Pontificia Universidad Católica de Chile, Santiago, Vicuña Mackenna 4686, Chile
  • 2CIGIDEN, Santiago, Vicuña Mackenna 4686, Chile
  • 3CEGA, Universidad de Chile, Beauchef 850, Santiago, Chile
  • 4IRD, UR 234, GET, 14 avenue E. Belin, 31400, Toulouse, France
  • 5Université de Toulouse, UPS, GET, 14 avenue E. Belin, 314000, Toulouse, France
  • 6CNRS, GET, 14 avenue E. Belin, 314000, Toulouse, France
  • 7Departamento de Geología, FCFM, Universidad de Chile, Beauchef 850, Santiago, Chile

Abstract. Crustal faults located close to cities may induce catastrophic damages. When recurrence times are in the range of 1000–10000 or higher, actions to mitigate the effects of the associated earthquake are hampered by the lack of a full seismic record, and in many cases, also of geological evidences. In order to characterize the fault behavior and its effects, we propose three different already-developed time-integration methodologies to define the most likely scenarios of rupture, and then to quantify the hazard with an empirical equation of peak ground acceleration (PGA). We consider the following methodologies: (1) stream gradient and (2) sinuosity indexes to estimate fault-related topographic effects, and (3) gravity profiles across the fault to identify the fault scarp in the basement. We chose the San Ramón Fault on which to apply these methodologies. It is a  ∼30km N–S trending fault with a low slip rate (0.1–0.5mmyr−1) and an approximated recurrence of 9000 years. It is located in the foothills of the Andes near the large city of Santiago, the capital of Chile (>6000000 inhabitants). Along the fault trace we define four segments, with a mean length of  ∼ 10km, which probably become active independently. We tested the present-day seismic activity by deploying a local seismological network for 1 year, finding five events that are spatially related to the fault. In addition, fault geometry along the most evident scarp was imaged in terms of its electrical resistivity response by a high resolution TEM (transient electromagnetic) profile. Seismic event distribution and TEM imaging allowed the constraint of the fault dip angle (∼65°) and its capacity to break into the surface. Using the empirical equation of Chiou and Youngs (2014) for crustal faults and considering the characteristic seismic event (thrust high-angle fault,  ∼ 10km, Mw = 6.2–6.7), we estimate the acceleration distribution in Santiago and the hazardous zones. City domains that are under high risk include the hanging wall zone covered by sediments and narrow zones where the fault could break the surface. Over these domains horizontal PGA can be greater than 0.5g and eventually produce building collapse.

Publications Copernicus
Short summary
This paper develops a seismic hazard methodology for crustal faults without direct evidence of present activity. The knowledge of this fault type is important when faults are located closer than 10 km from a highly populated area. The San Ramón Fault, close to Santiago, the capital of Chile, was chosen to test this methodology. The main result is the identification of some areas (close to the fault) where damage would be severe if the expected earthquake occurs.
This paper develops a seismic hazard methodology for crustal faults without direct evidence of...