Fault2SHA IGCP project funded!

International Geoscience Programme Council Project 2020-23

Project Title : OLLIN Identification (and characterization) of seismogenic faults in populated areas of Latin America and its incorporation into seismic hazard assessment

PI : María Ortuño Candela – Universitat de Barcelona

OLLIN is a project aiming to set up a new collaborative framework between specialists and young researchers from both sides of the Atlantic to improve geological knowledge and seismic hazard assessment (SHA) of two populated regions of Latin America. These are the Transmexican Volcanic belt (TMVB) and the Northern Southamerica Plate Boundary (NSAPB), which extends from Ecuador to Colombia and Venezuela. To do so, three fundamental steps are undertaken; Firstly, data on the seismogenic potential of faults in these areas is gathered, discussed and selected. The most likely fault rupturing mechanisms are discussed, which will lead us to focus the fieldwork on areas which are relevant to SHA but lack information on key seismic parameters (slip rates, segmentation, complex versus simple ruptures, maximum expected earthquakes, etc.). Secondly, the incorporation of that knowledge on seismogenic fault models into the SHA is conducted using existing Fault2SHA tools. This step includes the adaptation of those tools to these specific Latin American settings and the generation of new ones. Finally, results dissemination to society is ensured by the participation of stakeholders from civil protection, geological surveys and other end-users through special meetings, training courses and on-line access that allow to keep track of progress and results.

New Project Funded

ANR EQTIME 2020-2024 

Project Title : Quantifying the temporal and spatial slip variability in the earthquake cycle spanning months to million years timescales.

PI : Lucilla Benedetti CEREGE

Partners:  IRSN – Gesociences Montpellier – ISTERRE – OGS – Univ Chieti

Understanding how successive earthquakes accrue on faults to produce tectonic landforms is still poorly understood. The way deformation is accommodated throughout the crust, in response to the far-field plate tectonics force imposes at plate boundaries, strongly affects the seismic cycle and may control earthquake triggering and the spatial pattern of fault ruptures. The Apennines range, host of the 2016 seismic sequence (5 shocks Mw5-6.5 over 9 months), is a unique area where the accumulation and release of slip over multiple seismic cycles, over time scales of 1yr-1 Myr and spatial scales of 1m-100km, can be determined. We will combine frontier methodologies in geochronology, remote sensing, geodesy, geophysics, high-resolution topographical data acquisition, seismic hazard modelling, all developed and/or mastered by our teams, to quantitatively constrain how portions of the seismic cycle scale up over multiple cycles to produce the cumulative escarpments we see in the landscape. 

Mw 5.7 close to the Wasatch Fault Zone.

On March 18, 2018 at 7:09 AM local time a normal faulting Mw5.7 earthquake occurred near the town of Magna, Utah, about 18 km west from the active Wasatch Fault Zone (WFZ), at a depth of 11.7 km. The WFZ is located at the boundary between the extensional Basin and Range province to the west and the more stable Colorado Plateau to the east. It extends north-south for about 350 km, from southern Idaho to central Utah. Based on geomorphic, structural, and paleoseismological studies, the WFZ has been divided in 10 segments, 6 of which (Brigham City, Weber, Salt Lake City, Provo, Nephi, Levan) define the central WFZ (Figure). This Mw 5.7 event occurred at the same latitude of the Salt Lake City segment in a region characterized by distributed faulting and several synthetic and antithetic faults (e.g., West Valley Fault Zone, Great Salt Lake Fault Zone). With the current available information, it is difficult to identify the fault responsible for this event.

In the last months two papers concerning earthquake interactions and probabilistic seismic hazard of the WFZ were published by members of the FAULT2SHA Working Group (Verdecchia et al., 2019, GJI; Valentini et al., 2020, BSSA).

Verdecchia and coauthors used an approach based on physical (coseismic + postseismic Coulomb stress changes) and statistical (probability calculations) to determine if the stress changes due to the youngest paleoevents have significantly modified the present-day probability of occurrence of large earthquakes on each of the segments of the central WFZ. The authors show that regardless of any uncertainties in this approach, Coulomb stress changes strongly affect the time-dependent probability of a large earthquake on the Brigham City, Salt Lake City, and Provo segments. These results indicate that the seismic hazard connected with single-segment ruptures on the central WFZ might be underestimated, if the effects of stress changes are not considered.

Valentini and coauthors assess the impact that the Wasatch fault segmentation model has on seismic hazard by evaluating the time-independent long-term rate of ruptures on the fault that satisfy fault-slip rates and paleoseismic event rates, adapting standard inverse theory used in the Uniform California Earthquake Rupture Forecast (Vers. 3) and implementing a segmentation constraint in which ruptures across primary structural complexities are penalized. 

LOGO CONTEST WINNER!

We have the new Fault2SHA LOGO. After a long and hard contest we have our logo. We hope you like it!

Thanks to averyone send us a proposal and congratulations to the winner Brice Lebrun.