The characterization and recurrence of prehistoric earthquakes is a prime target of this project. The analysis of the distribution of individual paleoearthquakes in space and on time periods of 10³ to 10⁶ years is an indispensable supplement to the instrumental and historical records to assess the probability and severity of future earthquakes. Many devastating earthquakes in the past decade occurred on faults, which have not recorded any historic events (2003 Iran, 2005 Pakistan, 2008 Sezchuan, China, 2011 Christchurch, NZ).

Using geomorphological markers of surface rupturing earthquakes can provide useful information about the characteristics of seismogenic rupture especially with the growing availability of high-resolution topographic datasets. In this initiative we use a high-resolution topographic and visual data set acquired with the Modular Airborne Camera System (MACS), developed by the DLR (German Aerospace Center). The photogrammetrically derived DEM and True Ortho Images with 12 cm ground resolution permits the identification of small-scale geomorphic features and enables us to perform a fault zone and earthquake rupture characterization at unprecedented detail.

The Atacama Fault Zone, a trench-parallel fault zone located in the forearc of the N-Chilean convergent plate boundary, is a prime target to study a seismogenic fault over different time scales. It is located in the hyperarid Atacama desert where morphological markers are preserved in every single detail and traces of surface ruptures can be mapped along various segments along strike this 1000 km long fault system. For this detailed study we have chosen the 70 km long Salar del Carmen Fault Segment of the AFZ, which is characterized by abundant surface ruptures and at least 3 paleoearthquakes are documented in paleoseimolgical trenches. Along a 4.5 km long segment we acquired two additional datasets (5 cm and 40 cm) to explore resolution capabilities.

Investigating the dataset we focus on the following questions:

• What tools can we use/develop to exploit the dataset quantitatively?
• How large may earthquakes along the AFS become?
• How much slip do they produce in each event?
• Are endpoints to ruptures stable in time or is the segmentation of upper crustal faults arbitrary from event to event?
• Can we extrapolate the number of rupture events and recurrence intervals derived from paleoseismological trenches along strike, using geomorphic markers?

This dataset contributes geomorphic datasets to the Integrated Plate Boundary Observatory Chile (IPOC). It complements data acquired with the IPOC Creepmeter Array directly monitoring fault displacement on the Salar del Carmen fault segment. The integrated dataset of both methods will eventually cover seconds to 10⁶ years of displacement accumulation.

People involved

GFZ (both sec. 4.1): Pia Victor (PI), Oktawian Ewiak (PhD)

External: Olaf Zielke (KAUST, Saudi Arabia), Angela Landgraf (Uni Potsdam), Tilman Bucher (DLR, Adlershof)

Recent abstracts

• Ewiak, O., P. Victor, and O. Oncken (2015), Investigating multiple fault rupture at the Salar del Carmen segment of the Atacama Fault System (northern Chile): Fault scarp morphology and knickpoint analysis, Tectonics, 34(2), 187-212.
• Ewiak, O., Victor, P., Ziegenhagen, T. and O. Oncken (2012): Investigating the strain accumulation of upper plate faults at the N-Chilean convergent plate boundary at different spatial and temporal scales. Fall Meeting, AGU, San Francisco, USA.
• Bucher, T., Zielke O., Victor P., Lehmann F., Oncken O., (2012): Very High Resolution Photogrammetric DSMs and True-Orthoimages: Quantifying Surface Rupturing Earthquakes in Northern Chile.  GeoHannover 2012.
• Zielke, O., Victor, P., Oncken, O., Bucher, T., Lehmann, M. (2011): ~5cm ground resolution DEMs and Ortho-Imagery for the Atacama Fault System (AFS) in northern Chile, acquired with the Modular Airborne Camera System (MACS), Fall Meeting, AGU, San Francisco, USA.