Variable Fault Geometry Suggests Detailed Fault‐Slip‐Rate Profiles and Geometries Are Needed for Fault‐Based Probabilistic Seismic Hazard Assessment (PSHA)

It has been suggested that a better knowledge of fault locations and slip rates improves seismic hazard assessments. However, the importance of detailed along‐fault‐slip‐rate profiles and variable fault geometry has not yet been explored. We quantify the importance for modeled seismicity rates of using multiple throw‐rate measurements to construct along‐fault throw‐rate profiles rather than basing throw‐rate profiles on a single measurement across a fault. We use data from 14 normal faults within the central Italian Apennines where we have multiple measurements along the faults. For each fault, we compared strain rates across the faults using our detailed throw‐rate profiles and degraded data and simplified profiles. We show the implied variation in average recurrence intervals for a variety of magnitudes that result. Furthermore, we demonstrate how fault geometry (variable strike and dip) can alter calculated ground‐shaking intensities at specific sites by changing the source‐to‐site distance for ground‐motion prediction equations (GMPEs). Our findings show that improved fault‐based seismic hazard calculations require detailed along‐fault throw‐rate profiles based on well‐constrained local 3D fault geometry for calculating recurrence rates and shaking intensities.

[1]  Pablo G. Silva,et al.  Geomorphology of active faulting and seismic hazard assessment : New tools and future challenges , 2015 .

[2]  M. Everaerts,et al.  Relevance of active faulting and seismicity studies to assessments of long-term earthquake activity and maximum magnitude in intraplate northwest Europe, between the Lower Rhine Embayment and the North Sea , 2007 .

[3]  A. Nicol,et al.  Importance of pre-existing fault size for the evolution of an inverted fault system , 2016, Special Publications.

[4]  A. Blumetti,et al.  Quaternary earthquakes: Geology and palaeoseismology for seismic hazard assessment , 2017 .

[5]  Craig Glennie,et al.  Review of Earth science research using terrestrial laser scanning , 2017 .

[6]  Tiziana Rossetto,et al.  FRACAS: A capacity spectrum approach for seismic fragility assessment including record-to-record variability , 2016 .

[7]  C. Mansfield,et al.  Lateral displacement variation and lateral tip geometry of normal faults in the Canyonlands National Park, Utah , 1998 .

[8]  Pilar Villamor,et al.  Fault displacement accumulation and slip rate variability within the Taupo Rift (New Zealand) based on trench and 3‐D ground‐penetrating radar data , 2009 .

[9]  J. Lomax,et al.  Implications from palaeoseismological investigations at the Markgrafneusiedl Fault (Vienna Basin, Austria) for seismic hazard assessment , 2017 .

[10]  Visualisation of active normal fault scarps in the Apennines, Italy: A key to assessment of tectonic strain release and earthquake rupture , 2008 .

[11]  F. Stuart,et al.  Holocene slip rate variability along the Pernicana fault system (Mt. Etna, Italy): Evidence from offset lava flows. , 2017 .

[12]  G. Roberts,et al.  Geometry, kinematics and deformation rates along the active normal fault system in the southern Apennines: Implications for fault growth , 2007 .

[13]  N. Abrahamson,et al.  On the Use of Logic Trees for Ground-Motion Prediction Equations in Seismic-Hazard Analysis , 2005 .

[14]  H. Crowley,et al.  Seismic Hazard Assessment (2003–2009) for the Italian Building Code , 2011 .

[15]  D. Bindi,et al.  Ground motion prediction equations derived from the Italian strong motion database , 2011 .

[16]  P. Sammonds,et al.  Horizontal strain-rates and throw-rates across breached relay zones, central Italy: implications for the preservation of throw deficits at points of normal fault linkage , 2009 .

[17]  G. Roberts,et al.  Fault specific GIS based seismic hazard maps for the Attica region, Greece , 2015 .

[18]  P. Boncio,et al.  Do static stress changes of a moderate‐magnitude earthquake significantly modify the regional seismic hazard? Hints from the L'Aquila 2009 normal‐faulting earthquake (Mw 6.3, central Italy) , 2014 .

[19]  P. Sammonds,et al.  Relationship between topography, rates of extension and mantle dynamics in the actively-extending Italian Apennines , 2012 .

[20]  S. Stein,et al.  2000 years of migrating earthquakes in North China: How earthquakes in midcontinents differ from those at plate boundaries , 2011 .

[21]  Carmine Galasso,et al.  Earthquake Engineering Field Investigation Team (UK) – Data and Discussion on the 2016 Central Italy Mission , 2017 .

[22]  Massimiliano Stucchi,et al.  A seismic source zone model for the seismic hazard assessment of the Italian territory , 2008 .

[23]  Carlo Alberto Brunori,et al.  A database of the coseismic effects following the 30 October 2016 Norcia earthquake in Central Italy , 2018, Scientific Data.

[24]  Antonio Pepe,et al.  Geodetic model of the 2016 Central Italy earthquake sequence inferred from InSAR and GPS data , 2017 .

[25]  P. Tapponnier,et al.  Active oblique extension in the central Apennines (Italy): evidence from the Fucino region , 1999 .

[26]  R. Civico,et al.  Surface ruptures following the 30 October 2016 Mw 6.5 Norcia earthquake, central Italy , 2018 .

[27]  Remko Scharroo,et al.  Generic Mapping Tools: Improved Version Released , 2013 .

[28]  D. Wells,et al.  New empirical relationships among magnitude, rupture length, rupture width, rupture area, and surface displacement , 1994, Bulletin of the Seismological Society of America.

[29]  S. Stein,et al.  Mid-continental earthquakes: Spatiotemporal occurrences, causes, and hazards , 2016 .

[30]  Fault interaction processes and continental extension in the central Apennines, Italy , 2017 .

[31]  Bruno Pace,et al.  Layered Seismogenic Source Model and Probabilistic Seismic-Hazard Analyses in Central Italy , 2006 .

[32]  K. Assatourians,et al.  EqHaz: An Open‐Source Probabilistic Seismic‐Hazard Code Based on the Monte Carlo Simulation Approach , 2013 .

[33]  G. Roberts,et al.  Active normal faulting during the 1997 seismic sequence in Colfiorito, Umbria: Did slip propagate to the surface? , 2016 .

[34]  A. Michetti,et al.  Spatial and temporal variations in growth rates along active normal fault systems: an example from The Lazio–Abruzzo Apennines, central Italy , 2004 .

[35]  Z. Mildon,et al.  Coseismic Throw Variation Across Along‐Strike Bends on Active Normal Faults: Implications for Displacement Versus Length Scaling of Earthquake Ruptures , 2018, Journal of Geophysical Research: Solid Earth.

[36]  F. Visini,et al.  Insights on a Key Parameter of Earthquake Forecasting, the Coefficient of Variation of the Recurrence Time, Using a Simple Earthquake Simulator , 2014 .

[37]  Roberto Paolucci,et al.  Engineering ground motion record selection in the ITalian ACcelerometric Archive , 2011 .

[38]  F. Visini,et al.  Seismic hazard in central Italy and the 2016 Amatrice earthquake , 2016 .

[39]  Alessandro Maria Michetti,et al.  Fault scarps and deformation rates in Lazio–Abruzzo, Central Italy: Comparison between geological fault slip-rate and GPS data , 2005 .

[40]  Z. Mildon,et al.  Coulomb stress transfer and fault interaction over millennia on non-planar active normal faults: the Mw 6.5–5.0 seismic sequence of 2016–2017, central Italy , 2017 .

[41]  M. Frezzotti,et al.  Late Pleistocene Glacial Events in the Central Apennines, Italy , 1997, Quaternary Research.

[42]  A. F. Pacheco,et al.  Updating seismic hazard at Parkfield , 2004, physics/0411003.

[43]  Z. K. Mildon,et al.  Surface faulting during the August 24, 2016, central Italy earthquake (Mw 6.0): Preliminary results , 2016 .

[44]  P. Galli,et al.  Paleoseismology of silent faults in the Central Apennines (Italy): the Mt. Vettore and Laga Mts. faults , 2003 .

[45]  Walter H. F. Smith,et al.  New, improved version of generic mapping tools released , 1998 .

[46]  P. Sammonds,et al.  A 667 year record of coseismic and interseismic Coulomb stress changes in central Italy reveals the role of fault interaction in controlling irregular earthquake recurrence intervals , 2017 .

[47]  A. Valentini,et al.  Integrating faults and past earthquakes into a probabilistic seismic hazard model for peninsular Italy , 2017 .

[48]  R. Finkel,et al.  Slip history of the Magnola fault (Apennines, Central Italy) from 36Cl surface exposure dating: Evidence for strong earthquakes over the Holocene , 2004 .

[49]  A. Switzer,et al.  Can the risk of coastal hazards be better communicated? , 2018 .

[50]  Z. Mildon,et al.  Evaluating models of Coulomb stress transfer: Is variable fault geometry important? , 2016 .

[51]  D. Pantosti,et al.  Twenty years of paleoseismology in Italy , 2008 .

[52]  P. Sammonds,et al.  Comparison of earthquake strains over 102 and 104 year timescales: Insights into variability in the seismic cycle in the central Apennines, Italy , 2010 .

[53]  Francesca Romana Cinti,et al.  Coseismic ruptures of the 24 August 2016, Mw 6.0 Amatrice earthquake (central Italy) , 2017 .

[54]  Richard J. Phillips,et al.  Slip distributions on active normal faults measured from LiDAR and field mapping of geomorphic offsets: an example from L'Aquila, Italy, and implications for modelling seismic moment release , 2015 .

[55]  Robert J. Geller,et al.  Why earthquake hazard maps often fail and what to do about it , 2012 .

[56]  Y. Kagan,et al.  Plate-Tectonic Analysis of Shallow Seismicity: Apparent Boundary Width, Beta, Corner Magnitude, Coupled Lithosphere Thickness, and Coupling in Seven Tectonic Settings , 2004 .

[57]  D. P. Schwartz,et al.  A Record of Large Earthquakes on the Southern Hayward Fault for the Past 500 Years , 2002 .

[58]  Bruno Pace,et al.  FiSH: MATLAB Tools to Turn Fault Data into Seismic‐Hazard Models , 2016 .

[59]  G. Roberts.  Fault orientation variations along the strike of active normal fault systems in Italy and Greece: Implications for predicting the orientations of subseismic-resolution faults in hydrocarbon reservoirs , 2007 .

[60]  C. Scholz,et al.  Growth of a normal fault system: observations from the Lake Malawi basin of the east African rift , 2000 .

[61]  G. Roberts,et al.  Viscous roots of active seismogenic faults revealed by geologic slip rate variations , 2013 .

[62]  A. Michetti,et al.  Orogen-scale uplift in the central Italian Apennines drives episodic behaviour of earthquake faults , 2017, Scientific Reports.

[63]  Y. Kagan.  Seismic moment distribution revisited: I. Statistical results , 2002 .

[64]  Julian J. Bommer,et al.  Consistent Source-to-Site Distance Metrics in Ground-Motion Prediction Equations and Seismic Source Models for PSHA , 2012 .

[65]  J. P. Faure Walker,et al.  Long-term strain rates as a tool for understanding the mechanics of continental extension and the importance of local 3D fault geometry for local throw-rates across faults , 2015 .

[66]  B. E. Shaw,et al.  Uniform California Earthquake Rupture Forecast, Version 3 (UCERF3)—The Time‐Independent Model , 2014 .

[67]  Yan Y. Kagan,et al.  Earthquakes: Lessons for the Future , 2022 .

[68]  Jörg Keller,et al.  Rapid environmental changes in southern Europe during the last glacial period , 1999, Nature.