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KAUST Workshop on Seismic Hazard Assessment

26th - 28th November 2018

Advancing Seismic Hazard Assessment: Integrating geological and seismological observations into physics-based rupture simulations

Earthquakes are the deadliest and costliest natural catastrophes, and even moderately large events (M<7) may have devastating consequences. We cannot predict earthquakes, but we can forecast their consequences, to be prepared when they do occur. This is the topic of Seismic Hazard Assessment (SHA), that quantifies earthquake perils in terms of probability of shakings, due to future earthquakes in a region over a given period of time.

Conceptually simple, SHA suffers from too sparse and incomplete information about the seismic cycle that can be hundreds to thousands of years long. Recent worldwide earthquakes further highlighted the need to account for complex fault ruptures too, by considering potential interactions between nearby faults.

This workshop aims to advance current SHA practice, by integrating modern geological and seismological data into seismic-cycle and physics-based rupture simulations, to provide more reliable earthquake safety criteria tailored on the growth of populations and infrastructures.


News

11/25/2018
Following is a link to the workshop's agenda (agenda)

11/15/2018 

The workshop schedule is now finalized. Please have a look and identify the time and length of your presentation.
Under the "Location" tab, please find an updated map, containing locations of housing and session venues.

10/16/2018 
The website was updated to contain the list of attendees as well as schedule for short talk presentations and posters.
  • MondayNovember 26
  • TuesdayNovember 27
  • WednesdayNovember 28
8:00 AM

Breakfast at session venue

8:30 AM

Welcoming Remarks

9:00 AM

KEYNOTE LECTURE: Fault Zone Maturity, Fault Segmentation and Fault Asperities along the Marmara section of the North Anatolian Fault in Turkey: Implications for Seismic Hazard and risk in the Istanbul Metropolitan Region

Constraining the maximum likely magnitude of future earthquakes along active continental transform faults and discriminating between a locking or creeping status of fault section being late in their seismic cycle is of fundamental relevance to quantify the seismic hazard and risk for collocated population centers. In the first part of this presentation the maximum observed earthquake magnitudes along different sections of the North Anatolian Fault Zone (NAFZ) are discussed in relation to the age of the fault activity, cumulative offset, slip rate and maximum length of coherent fault segments based on a 2300-yr historical earthquake catalogue. While the largest M7.8–8.0 earthquakes are exclusively observed along the older eastern part of the NAFZ that also has longer coherent fault segments, the largest observed events along the younger western part of the fault zone do not (yet) exceed M7.5. This allows to put an upper boundary in terms of hazard and risk for the densely populated Marmara–Istanbul region with its 15+ million inhabitants. In the second part the current status of the Marmara section of the NAFZ is studied based on a newly compiled 10-yr seismicity catalogue for the Marmara region. While the eastern portion of the Marmara seismic gap offshore Istanbul is identified to be locked, the observation of M2.8 repeaters further to the west indicates that the western Marmara section deforms aseismically to a substantial extent. This would reduce the probability for the western part of the Marmara seismic gap to host a nucleation point for the pending Marmara earthquake which is in contrast to the Princes Islands segment offshore Istanbul. This is of relevance, since a nucleation of the Marmara event in the west and subsequent eastward rupture propagation towards the Istanbul metropolitan region would result in a substantially higher seismic hazard and resulting risk than if the earthquake would nucleate in the east and thus propagate westward away from the population centre Istanbul. The results from both studies are discussed with regard to their potential in better quantifying earthquake scenario models for the region and subsequent estimation of hazard and risk for Istanbul.

9:45 AM

Involvement of aseismic slip during the 2018 Lombok, Indonesia earthquake sequence: a seismological constraint

The 2018 Lombok earthquake sequence includes six significant earthquakes with Mw > 5.5, i.e.: Mw 6.5 (28 July), Mw 6.9 (5 August), Mw 5.9 (9 August), Mw 6.3, Mw 6.9, Mw 5.7 (19 August). Updated on 30 August 00:00 UTC, BMKG (Indonesian Agency) reported 2,017 events include 204 M>=4.0 earthquakes during the sequence. Approximately more than 500 people have died and nearly 500,000 people have been displaced due to the damage. The seismicity following the Mw 6.4 event on 28 July (before the first Mw 6.9) shows the typical aftershock characteristic (Omori-Utsu p-value = 1.00±0.13), but with low Gutenberg-Richter b-value (0.69±0.02), which is similar to foreshock’s b-value found in many cases of large earthquakes. While these foreshock characteristics may reflect the accumulation of stress and/or the occurrence of slow slip within the seismogenic zone. During the time period between the two Mw 6.9 events (5 August to 19 August), the seismicity show lower p-value (0.52±0.04) but higher b-value (0.82±0.03). This shows extremely slow decay of aftershocks that may include triggered aseismic slip. Following the second Mw 6.9 (19 August), the seismicity shows slightly higher p-value (0.74±0.09) and slightly lower b-value (0.72±0.01). We perform finite fault inversions for the M=6+ earthquakes to provide detail rupture process during the sequence. Our preliminary results reveal that the ruptures was initiated from a shallow depth moving inversely with a right lateral component on a low dipping fault. These suggest the earthquakes were caused by deformation on the Flores back-arc thrust fault that trending E-O. The implication of our finite fault model is the possibility of some repeating slips during the rupture of the large earthquakes. We perform template matching detection and detect many missing earthquakes that have not been listed in the regular catalog. The detection decreases the magnitude of completeness (Mc) from about 2.6 to ~ 1.6. Hundreds of repeating earthquakes (with correlation coefficients > 0.90) are detected that show the involvement of aseismic slip during the sequence. We convert the seismic moment of compositive repeaters to aseismic slip according to the empirical relation. The results may support the hypothesis that periodically the Flores Back-Arc Thrust undergoes a large episode of fault creep. Updated results will be presented in the workshop. We will also present the current effort on the development of earthquake source parameters database for moderate to large earthquake in the regions of Indonesia.

10:00 AM

The characteristics of fault ruptures, stress transfer and poroelasticity in seismogenic zones

We present the active tectonics, fault characteristics and stress transfer related to major earthquakes along the Africa-Eurasia plate boundary in northern Algeria and Morocco. Two seismogenic regions in the Tell Atlas and Rif Mountains illustrate the physical properties of earthquake ruptures, and Coulomb Failure Function (CFF) with stress transfer on active faults (see references below). In Algeria, the ΔCFF modeling applied to the sequence of shallow large and moderate earthquakes (Mw 5.5 – 7.1 from 1891 to 2003) shows an increase in Coulomb stress from 0.1 bar to 0.8 bar at a depth of 7 km, over most of the receiver faults. The chosen effective coefficient of friction μ ' ≤ 0.4 suggests a pore pressure increase probably due to the poroelastic deformations. The modeling shows a clear distinction between the size of earthquakes and the triggering process. In Morocco, the shallow earthquake migration with the May 26, 1994 (Mw 6.0), February 24, 2004 (Mw 6.4) and January 25, 2016 (Mw 6.3) mainshocks offers the possibility to (i) model the change in Coulomb Failure Function (CFF with low μ including the pore pressure change) and understand the interaction between fault-ruptures, (ii) analyze the effect of pore fluid on the rupture mechanism, and (iii) infer the clock-time advance. The ΔCFF modeling and the seismicity analysis show that this seismic sequence is apparently controlled by the poroelastic properties of the seismogenic zone. Our work open ways on the role of fluids and poroelastic deformation on fault-rupture interaction and seismic nucleation processes. The stress transfer modeling and variation of the Coulomb failure function contribute to a better understanding and evaluation of the seismic hazard and the seismic risk in densely populated areas.

10:15 AM

Coffee Break

10:30 AM

KEYNOTE LECTURE: The Dead Sea fault as a strike-slip fault model

The southern Dead Sea fault, about 600km from Lebanon to the Gulf of Aqaba, has been extensively investigated during the last decade to better constrain the rate of deformation at different time scales and the way earthquake activity accommodates such deformation. Due to its rather simple geometry and isolation from other active tectonic systems, the southern Dead Sea fault system could be considered as an ideal strike-slip fault model to test different possibilities of fault behavior. Here, we will review the most recent progress in term of data acquisition along that part of the fault and present some results about earthquake activity over several earthquake cycles, relevant to SHA studies along the Dead Sea fault, but also along any other large strike-slip fault. We will show that current data all point towards significant slip deficit along that section of the fault, which might become a major issue with the growing number of large infrastructures in construction or planned in direct vicinity of the fault.

11:15 AM

Seismotectonic and Seismic Hazard in northern Algeria: State of knowledge

The Tell Atlas chain of Northern Algeria is a tectonic plate boundary area (100 km wide and 1200 km long) where the African and Eurasian tectonic plates are converging in NW-SE direction at a rate of 5-8 mm/yr. Therefore, seismic hazard is a permanent threat either for people and their properties or for other basic infrastructures. Earthquakes are often produced by 20-30 km long active reverse faults associated to folds, distributed in an echelon system and which may be blind or not located offshore and on land (Bouhadad, 2013). The El-Asnam October 1980 (Ms =7.3) and the Zemmouri 2003 (Mw 6.8) earthquakes, both produced by faulted- folds, allowed us to understand the geometry of such structures. Several seismic hazard studies (at local and/or national scales) have been performed since 1980. However, the main problems is that seismicity data didn't extend back enough to understand the long term behavior of geological structures (seismicity catalogues cover about 300yrs). Therefore, geological data are necessary for a reliable seismic hazard analysis. The main problem with geological data are (i) Paleoseismological data are rare only available for the El Asnam fault, consequently, slip rate data, which is a key parameter in seismic hazard analysis, is obtained indirectly from uplift rates of marine and alluvial terraces, (ii) Several active faults which are blind and/or located offshore are still unidentified, sometimes revealed by moderate-sized earthquakes (Bouhadad 2001; Belabbes et al.2009; Bouhadad 2013), (iii) Difficulties to find datable materials on identified paleoliquefaction features triggered by unknown prehistoric and historic earthquakes (Bouhadad et al.2009). Keywords: Tell Atlas chain- faulted folds- seismotectonic-seismic hazard- blind faults- earthquakes.

11:30 AM

Building a fault database for the central Apennines, Italy

The central Apennines Fault2SHA laboratory is creating a fault map for the central Apennines bringing together the work of three research groups research groups; this will provide certainties in both location and activity at the fault trace level. We are also creating a database comprising primary and detailed data at the trace level such as slip-rate, geometry, palaeoseismic data and associations between faults and historical earthquakes. Having primary, open-access, accountable and detailed data will allow modellers to compute uncertainties in their hazard modelling, end-users to know where the inputs for such models are coming from and allows comparisons between different modelling approaches at different stages of modelling because the outputs are based on the same inputs. Detailed fault data is needed because: (1) calculated earthquake rates are altered because calculated strain-rates and hence moment release rates are changed; and (2) calculated ground shaking intensities at specific sites are altered due to changes in the source-to-site distance for ground motion prediction equations (GMPEs). Therefore, annual rates of exceeding specified ground shaking intensities at a specified site are changed when calculated using detailed fault geometry and slip-rate profiles rather than planar faults and simplified slip-rate profiles. The central Italian Apennines fault system is a good case study field area for conducting fault-based seismic hazard assessment (SHA) due to the wealth of data available. The normal faults capable of producing large magnitude earthquakes are exposed at the surface allowing high precision mapping and the constraining of the geometry, kinematics and long-term slip-rates. There are also many palaeoseismic data the historical record is considered complete back to 1349 for events >Mw5.8. within Europe, this region has had the two deadliest seismic sequences of the last ten years: the 2009 L’Aquila sequence and the 2016 Amatrice-Norcia sequence.

11:45 AM

Stand alone or interacting faults in fault-based seismic hazard models?

Probabilistic fault-based and time-dependent seismic hazard studies are commonly used to forecast the time between consecutive earthquakes; however the slip rate variability over time is critical for obtaining accurate results. Recently, geological and paleoseismological observations confirm this variability but rarely seismic hazard models consider it. A possible explanation is the presence of networks of active faults, which interact in a complex manner. Coseismic Coulomb stress changes have been invoked by several authors to explain the concatenation of moderate-to-strong earthquakes, but few authors have considered also the time-dependent viscoelastic relaxation of the lower crust and upper mantle as a possible additional source of stress changes at a regional scale. Here we present the results of some studies we have done on this topic in central Italy, suggested by the 2016-17 seismic sequence. We present also some insights on the coefficient of variation of the recurrence time using a simple earthquake simulator, as suggestion on how geometrical and physical parameters in a fault network may control the seismicity behaviour. In addition to the development of realistic fault models (comprising detailed fault traces and geologic data to constrain surface and sub-surface fault geometry) and the collection of field observations (to constrain long-term slip rates), slip rate variability over time appears as another key parameter that needs to be considered in future fault-based seismic hazard models, given that both coseismic and postseismic processes are possible explanations of the observation

12:00 PM

Dependency of near field ground motions on the structural maturity of the North Anatolian Fault Zone

Until now, many studies have been carried out in considering the influence of site-specific parameters on recorded ground motions but just a few in source-parameters like the long-term fault properties (Radiguet et al., 2009). In this study we empiricaly examine the regional variations of strong ground-motions in Turkey and the potential influence from the structural maturity of ruptured parts of the North Anatolian Fault Zone. According to Manighetti et al. (2007) we classified the entire fault zone based on the age, slip rate, cumulativ slip and length of the fault into three different parts (immature, intermediate and mature). We used 249 strong ground motion recordings of 41 shallow crustal earthquakes (Mw 4.0 – Mw 7.6) and various style of faulting to analyze the influence of the fault structural maturity with respect to other source and site properties. All events have a maximum distance of 20km to the main fault. We compare the recorded ground motions to empirical Ground Motion Prediction Equations of Chiou & Youngs (2010), Akkar & Bommer (2010), Akkar et al. (2014) and Bindi et al. (2014). The results show clearly, that earthquakes generated on the immature part of the fault zone produce larger ground motions than those on the mature part. Further residual analysis shows a large mistfit between the chosen GMPE’s and the ground motion recordings of the mature part. We have changed different dependent variables to see which parameter might have the biggest influence on these recorded ground motions. In all cases, the fault maturity has the largest influence on recorded ground motion amplitudes; hence we conclude that future GMPEs should include this important source parameter.

12:15 PM

Seismicity and earthquake focal mechanisms along the Gulfs of Suez and Aqaba

The northeastern part of Egypt is the most seismically active zone in Egypt due to its closeness to the seismic sources of Red sea and its northern two branches; Gulf of Suez and Gulf of Aqaba. The Red Sea rifting, the Gulf of Aqaba transform, and the triple junction of Arabian plate, African plate and Sinai sub-plate are the main causes of earthquake activity in this region. Moreover the area is affected by the active tectonic structures of Cairo-Suez district which induce intraplate seismicity. Prime examples of the destructive earthquakes that had been recorded in the northeastern part of Egypt are the 31March 1969 earthquake which occurred in the southern Gulf of Suez with a magnitude (ML 6.7), the 22 November 1995 Gulf of Aqaba earthquake (Mw7.3) which represent the largest instrumental earthquake in Egypt, and the 1 June 2013 earthquake (ML 5.1) which recorded in the central Gulf of Suez. In this study we analyze the waveform data of 42 earthquake with magnitude (ML≥3.0) recorded in the study region during the period 2010-2016. Analysis of the P-wave first onset polarity together with the moment tensor inversion techniques are here used in determination of earthquake focal mechanisms and source parameters. Based on the obtained results, we classified the study region into four seismic source zones (i.e. Gulf of Aqaba, northern Gulf of Suez, southern Gulf of Suez-northern Red Sea, and Cairo-Suez district). Strike slip faulting mechanism with minor normal component trending nearly E-W and N-S are reported for the events of Gulf of Aqaba, however some events show normal fault with strike slip component and their nodal planes trend NNW-SSE and ESE-WNW parallel to gulf's trend. Earthquakes in the Gulf of Suez show normal faulting mechanism with small strike-slip component and their nodal planes trend NNW-SSE parallel to the gulf's trend. Earthquakes in the Red Sea demonstrate normal source mechanisms trending parallel to the Red Sea rift. Normal faulting with subordinate shear component is the main focal mechanism indicated by the fault-plane solutions of the events of Cairo-Suez district. These results were compared with the fault plane solutions collected from previous studies (1997-2009) for each zone and showed a clear agreement. The results of this work may be contribute in seismic hazard studies and to improve the configuration of recording seismic stations in Egypt

12:30 PM

Lunch Break

2:30 PM

Breakout session: Promises and challenges of earthquake geology field observations for Seismic Hazard Assessment (SHA)

Breakout sessions will encompass moderated discussions as well as sufficient time for poster presentation

7:00 PM

Dinner at Saudi seafood restaurant

we will meet in front of KAUST Inn 2 at 6pm; visitors: please bring your passport (required because we leave KAUST); ladies: please remember to bring Abayas

8:00 AM

Breakfast at session venue

8:30 AM

KEYNOTE LECTURE: Probabilistic approaches in earthquake rupture simulations

A main driver for studying earthquakes is to understand the physics of the underlying rupture process in order to make reliable estimates of future earthquake rupture characteristics. Physics-based earthquake rupture simulations provide a mean to test our current understanding of the rupture process via comparison with observations from earthquake geology and seismology. These simulations constrain earthquake rupture initiation, propagation, and termination for a given set of initial and boundary conditions such as the complexity of fault geometry, fault roughness, fault strength, fault locking, and tectonic stressing rates. Depending on the physical representation of the rupture process and the adopted combination of initial and boundary conditions (i.e., rupture scenario), these simulations determine for instance the distribution of ground shaking, along-fault slip, as well as probability of earthquake size and occurrence. In many cases, earthquake rupture simulations consider only a very small number of rupture scenarios –primarily because of high computational cost. For natural faults however, many parameters that affect earthquake rupture are only poorly constrained and may vary in space and time. This condition substantially decreases the transferability of individual earthquake rupture simulations to natural faults. How much can we learn about the rupture process of natural earthquakes and its inherent variability from recreating them in numerical rupture simulations when the underlying initial and boundary conditions are so poorly constrained and/or considered constant and uniform?

9:15 AM

Microphysically-based modelling of earthquake cycles incorporating seismic and aseismic slip

Earthquake hazard studies benefit from an advanced capability to simulate earthquake cycles based on models that are consistent with laboratory observations. Such modelling provides a basis to integrate geodetic and seismological observations of fault slip into a quantitative mapping of fault properties, ultimately leading to an improved predictability of fault behaviour. Currently, rate-and-state friction (RSF) is most commonly used for the characterisation of laboratory friction experiments. However, the RSF framework provides little physical basis for the extrapolation of these results to the scales and conditions of natural faults, leaving questions regarding the applicability of the RSF parameters for predicting seismic cycle transients. As an alternative to RSF, microphysically-based models offer means for interpreting laboratory and field observations, but are generally over-simplified with respect to heterogeneous natural systems. In order to bridge the temporal and spatial gap between the laboratory and nature, we have implemented existing microphysical model formulations into an earthquake cycle simulator. This enables the study of natural seismic cycles by explicitly taking into account the interaction between e.g. fault gouge composition, temperature, and stress. We demonstrate the utility of this model by considering a compositionally heterogeneous fault zone, under conditions that facilitate earthquake nucleation. These simulations reveal the existence of two distinct types of earthquakes. The first class of earthquakes comprises relatively small seismic events that occur quasi-randomly in time and space. By contrast, the second class of earthquakes comprises fault-spanning events that may be analogous to real-world Mw > 8 events. Notably, these anomalously large events are time-predictable on the basis of fault stress. Thus, the microphysically-based approach offers new opportunities for investigating the long-term seismic cycle behaviour of natural faults, and to improve seismic hazard assessments.

9:30 AM

Frictional parameters of the 2015 Nepal earthquake, constrained by dynamic rupture models

Dynamic rupture model can provide much detailed insights into rupture physics that is capable of assessing future seismic risk. Many studies have attempted to constrain the slip-weakening distance, an important parameter controlling friction behavior of rock, for several earthquakes based on dynamic models, kinematic models, and direct estimations from near-field ground motion. However, large uncertainties of the values of the slip-weakening distance still remain, mostly because of the intrinsic trade-offs between the slip-weakening distance and fault strength. Here we use a spontaneously dynamic rupture model to constrain the frictional parameters of the 25 April 2015 Mw7.8 Nepal earthquake, by combining with multiple seismic observations such as high-rate cGPS data, strong motion data, and kinematic source models. With numerous tests we find the trade-off patterns of final slip, rupture speed, static GPS ground displacements, and dynamic ground waveforms are quite different. Combining all the seismic constraints we can conclude a robust solution without a substantial trade-off of average slip-weakening distance, ~0.6 m, in contrast to previous kinematical estimation of ~5 m. To our best knowledge, this is the first time to robustly determine the slip-weakening distance on seismogenic fault from seismic observations. The well-constrained frictional parameters may be used for future dynamic models to assess seismic hazard, such as estimating the peak ground acceleration (PGA) etc. Similar approach could also be conducted for other great earthquakes, enabling broad estimations of the dynamic parameters in global perspectives that can better reveal the intrinsic physics of earthquakes.

9:45 AM

Unraveling earthquake dynamics through large-scale multi-physics simulations

Using physics-based earthquake scenarios, modern numerical methods and hardware specific optimizations sheds light on the dynamics, and severity, of earthquake behaviour. Typical subduction zones are characterised by curved thrust fault geometries that merge with the bathymetry under very shallow angles of narrow subduction wedges. Additionally, complicated networks of fault branches at high angles to the megathrust in the overriding and oceanic plates potentially generate strong gaining effects of vertical sea-floor displacements, making tsunami generation more likely. I will present high-resolution physics-based numerical simulations of the 2004 Sumatra-Andaman earthquake, including non-linear frictional failure on a megathrust-splay fault system, off-fault plasticity, seismic wave propagation up to 2.2 Hz in 3D media and bathymetry. The interplay of complex fault geometry and simple pre-stress state yields good agreement of ground-deformations in the near field and very long-period teleseismic data. The achieved degree of realism and accuracy is enabled by the open-source software SeisSol (www.seissol.org) that features seismic wave propagation of high-order accuracy in space and time (minimal dispersion errors) and computational optimizations targeting strong scalability on many-core CPUs, as clustered local time stepping.

10:00 AM

Dynamic rupture simulation of the 1992 Landers earthquake

The 1992 Mw 7.3 Landers earthquake raised awareness of unexpectedly large magnitude earthquakes caused by rupture of fault networks that were previously considered unconnected. While the overall kinematics of the event are thought to be well understood, many observations regarding its complicated rupture dynamics are still unresolved. Here, we present 3D spontaneous dynamic rupture simulations that improve our understanding of the earthquake source and ground motions of the multi-segment Landers event. The model incorporates a new degree of realism by incorporating the interplay of complex fault geometry, topography, 3D rheology, off-fault plasticity, and viscoelastic attenuation. These model complexities are enabled by the software package SeisSol (www.seissol.org) specifically suited for handling complex geometries and for the efficient use on modern high-performance computing infrastructure. We find that fault geometry, as well as amplitude and orientation of initial fault stresses primary control sustained rupture along all fault segments. The resulting complex source dynamics include reverse slip, direct branching, and dynamic triggering over large distances. Fault slip terminates spontaneously on most of the principal fault segments due to the underlying fault geometry. The model reproduces a broad range of observations, including seismic moment-rate, off-fault deformation patterns, seismic waveform characteristics, and peak ground velocities. Despite the complex rupture evolution, we find that ground motion variability is close to what is commonly assumed in Ground Motion Prediction Equations. We further investigate the effects of variations in modeling parameterization, e.g. purely elastic setups or models neglecting viscoelastic attenuation with respect to rupture transfer and directivity effect.

10:15 AM

Coffee Break

10:30 AM

KEYNOTE LECTURE: Fault slip dynamics inspired by tectonics, rock physics, seismology and mechanics

Active faults release elastic strain energy via a whole continuum of modes of slip, ranging from devastating earthquakes to Slow Slip Events and persistent creep. Understanding the mechanisms controlling the occurrence of rapid, dynamic slip radiating seismic waves (i.e. earthquakes) or slow, silent slip (i.e. SSEs) is a fundamental point in the estimation of seismic hazard along subduction zones. On top of showing slower rupture propagation velocity than earthquakes, SSEs exhibit different scaling relationships, which could reflect either different physical mechanisms or an intriguing lack of observations. Like earthquakes, SSEs are bound to occur along unstable portions of active faults, raising the question of the physical control of the mode of slip (seismic or aseismic) along these sections. Here, we use the numerical implementation of a simple rate-weakening fault model to explain the spontaneous occurrence, the characteristics and the scaling relationship of SSEs and earthquakes. Our unified framework only accounts for the geometrical complexity of fault networks and associated stress perturbations, leading to the emergence of all modes of slip from earthquakes to SSEs without appealing to complex rheologies or mechanisms. Our model helps resolving many of the existing paradoxes between observations and physical models of earthquakes and SSEs and reproduces all episodes of fault slip in nature, including those unexplained yet.

11:15 AM

Poster session

1hr dedicated to poster presentations. The posters will remain on display until the end of the workshop. The poster should not larger than 160x100cm (landscape).

12:30 PM

Lunch break

2:30 PM

Breakout session: Dynamic and multi-cycle earthquqake rupture simulation -Hints for estimating complex-geometry rupture probabilities

Breakout sessions will encompass moderated discussions as well as sufficient time for poster presentation.

5:00 PM

Sunset cruise with dinner

8:00 AM

Breakfast at session venue

8:30 AM

KEYNOTE LECTURE: Toward Fully Physics-Based PSHA: Coupling Earthquake Simulators with Deterministic Ground Motion Simulations

Probabilistic seismic hazard analysis (PSHA) is typically performed by combining an earthquake rupture forecast (ERF) with a set of empirical ground motion prediction equations (GMPEs). ERFs have typically relied on observed fault slip rates, scaling relationships, and regional magnitude-frequency distributions to estimate the rate of large earthquakes on pre-defined fault segments. GMPEs, which regress against recorded ground motions, often lack data at short site-rupture distances and for large, complex ruptures. The CyberShake platform (Graves et al., 2011) replaces GMPEs with deterministic three-dimensional ground motion simulations, characterizing the effects of basin response and other path effects which are parameterized or treated as aleatory variability in GMPEs. Thus far, CyberShake has used empirical ERFs and kinematic rupture generators as input. In this study, we replace traditional ERFs with a multi-cycle physics-based earthquake simulator, the Rate-State Earthquake Simulator (RSQSim), developed by Dieterich & Richards-Dinger (2010). RSQSim simulations on the Uniform California Earthquake Rupture Forecast, Version 3 (UCERF3) fault system produce seismicity catalogs that match long term rates on major faults and yield remarkable agreement with UCERF3 when carried through to GMPE-based PSHA calculations (Shaw, 2018). Unlike traditional ERFs, RSQSim produces full slip-time histories for all simulated ruptures which can be used directly as input to deterministic wave propagation simulations (as opposed to the kinematic rupture generation approach in previous CyberShake studies). We couple the RSQSim model with CyberShake to create the first fully physics-based PSHA model. Resultant ground motions match GMPE estimates of mean and variability of shaking well over magnitudes and distances for which GMPEs are well constrained. Aggregated over many sources and sites, variability is similar to ergodic GMPE predictions. Variability is reduced for individual pairs of sources and sites, which sample a single path. This is expected in a non-ergodic model, and reduces exceedance probabilities for extreme ground motions at many sites. We will present these comparisons and preliminary fully physics-based RSQSim/CyberShake hazard curves.

9:15 AM

KEYNOTE LECTURE: The Mandate for Best Available Science

10:00 AM

Coffee Break + Poster time

10:45 AM

KEYNOTE LECTURE: Seismic hazard modelling in New Zealand: addressing the complexities

The occurrence of major damaging earthquakes in New Zealand in recent years have required regionally-focused efforts to update seismic hazard models in order for infrastructural recovery to proceed. Lessons learned from these major earthquakes have resulted in enhancements to the models, such as: consideration of complex multi-fault earthquake sources, and consideration of time and space-dependent hazard. Parallel efforts, such as the development of methods to evaluate the upper limits of ground motions, are being applied to seismic hazard assessments of critical facilities. The methods developed for these regional studies are expected to be integrated into future national-scale updates of seismic hazard.

11:30 AM

Comparison of experimental and theoretical hazards curves during the 2016-2017 Central Italy earthquakes

I will present the comparison of experimental and theoretical hazard curves of an aftershock probabilistic seismic hazard assessment (APSHA) done in Central Italy, during the 2016-17 sequence started. The APSHA models a fault source with a realistic geometry, activity rates follow an Omori-Utsu decay curve, calibrated using the data of the days after the main earthquake, and the magnitude distribution of aftershocks is assumed to follow a Gutenberg-Richter distribution. The decay curve is updated after the two major events occurred on Oct 26th and Oct 30th. The hazard results can be computed for any exposure period (e.g. 1 month) but they are intrinsically time-dependent. The earthquake sequence has been recorded by both national and regional networks. Using the wealth of strong motion records available, we compare the observed ground motions at sites within our study area to the results of our hazard analysis.

11:45 AM

A New Seismic Hazard Model for Ecuador

We present a comprehensive probabilistic seismic hazard study for Ecuador, a country exposed to a high seismic hazard from megathrust subduction earthquakes and moderate-to-large shallow crustal earthquakes. Building on knowledge gained during the last decade about historical and contemporary seismicity, active tectonics, geodynamics, and geodesy, several alternative earthquake recurrence models have been developed. We propose an areal seismic zonation for the seismogenic crustal, inslab, and interface sources, modified from Yepes et al. (2016), to account for the information gained after the 2016 Mw 7.8 Pedernales megathrust earthquake. Three different earthquake catalogs are used to account for uncertainties in magnitude–frequency distribution modeling. This first approach results in low hazard estimates for some areas near active crustal fault systems with low instrumental seismicity, but where geology and/or geodesy document rapid slip rates and high seismic potential. Consequently, we develop an alternative fault and background model that includes faults with earthquake recurrence models inferred from geologic and/or geodetic slip-rate estimates. The geodetic slip rates for a set of simplified faults are estimated from a Global Positioning System (GPS) horizontal velocity field from Nocquet et al. (2014). Various scenarios are derived by varying the percentage of motion that takes place aseismically. Combining these alternative earthquake recurrence models in a logic tree, and using a set of selected ground-motion models adapted to Ecuador’s different tectonic settings, mean hazard maps are obtained with their associated uncertainties. At the sites where uncertainties on hazard estimates are highest (difference between 84th and 16th percentiles > 0,4g), the overall uncertainty is controlled by the epistemic uncertainty on the source model.

12:00 PM

FRESH: an approach for computing earthquake ruptures and rates of occurrences in fault systems

Use of faults in seismic hazard models allows capturing the recurrence of large-magnitude events and therefore improve the reliability of probabilistic seismic hazard assessment (PSHA). In the past decades, fault segmentation provided an important framework for quantifying fault-based PSHA. However, in the last years, complex coseismic ruptures (e.g. 2010 M 7.1 Canterbury, 2012 Mw 8.6 Sumatra, 2016 Mw 7.8 Kaikōura, 2016 Mw 6.5 central Italy) imposed to pay particular attention to the treatment of all possible combinations of rupture scenarios for PSHA. Here we present a new methodology to model rate of ruptures along fault systems, based on a floating rupture approach called FRESH: Floating-Rupture for Seismic Hazard. It represents an alternative to SHERIFS, an approach recently proposed to go one step beyond the strictly-segmented one commonly used in Europe. Differences in the approaches are related to the way slip rate, rupture geometries and MFD are modelled. We demonstrate that FRESH, as well as SHERIFS, is able to solve for the long-term rate of ruptures with resulting PSHA that reflect the fault system geometry and slip rates, without any assumption on segment boundaries. Now that multi-fault rupture approaches are available, simplistic, uniform slip rate approaches along complex fault systems should be avoided to the benefit of local data collection, which should be strongly encouraged.

12:15 PM

Need for inclusion of physics-based fault models into seismic hazard assessment: The example of the Dead Sea Fault

The well constrained historical and palesoseismological seismic history along the Dead Sea fault (DSF), attesting to several strong surface-rupturing earthquakes during the last 4000 year, indicates rates of M> 6 events that are much higher than what a linear extrapolation based on instrumentally recorded events (M<5) would suggest. The origin of such a mismatch, probably linked to the clustered nature of seismicity in this region , is still not well understood. Clearly instrumental seismicity along the DSF system is not a good indicator for the estimate of hazard for M>6 events. Lefevre et al (2018) used slip-balancing arguments to infer at least 2 m of seismic-slip budget deficit, suggesting that an earthquake cluster of M>6.0 events “ might happen over the entire region in the near future”. However, how to compute the probability of this cluster remains an open question. The first step to tackle this question is to build a long-term tectonic deformation model. Based on published rupture scenario, slip rates and seismogenic depth estimates, we parametrized a fault model using the SHERIFS (Seismic Hazard and Earthquake Rate In Fault Systems) approach. Similarly to UCERF3, but based on an iterative approach, SHERIFS (Chartier et al., 2017) considers the possibility of earthquake ruptures involving several fault sections. Comparisons of modelling results with observations calls for (i) significant deviations of the DSF system Magnitude Frequency distribution (MFD) from Gutenberg-Richter behavior and (2) additional large, very low-probability rupture scenarios in order to minimize the error in the SHERIFS modelling approach. To move forward, it will be crucial to include physics-based simulations to test the physical possibility of such major events in multi-fault rupture models, the potential link between the apparent non-Gutenberg-Richter MFD and earthquake clustering, and to derive earthquake probability models suitable clustered seismicity.

12:30 PM

Lunch break

2:30 PM

Breakout session: How Physics-Based Earthquake Simulators Might Help Improve Earthquake Forecasts

This breakout sessions will encompass moderated discussions as well as sufficient time for poster presentation.

6:30 PM

Dinner at Pure restaurant


List of Speakers

Keynote lectures

Short talk presentation