3D Finite Element Modeling of the 2009 L'Aquila Earthquake Deformation Field

The L'Aquila earthquake (Mw 6.3) occurred on April 6th at 01:32 UTC in the Central Appennines at a depth of about 9 km and was felt all over Central Italy. The main shock was preceded by a long seismic sequence started several months before and was followed by thousands of aftershocks, some of them with Mw>4. We built up a high resolution three-dimensional model, incorporating surface topography, which was discretized using 20-nodes brick elements. The element horizontal size is biased from 500 m to 2 km using the paving meshing algorithm in combination with an appropriate adaptive sizing function. A realistic rheology was introduced from a vp/vpvs travel time tomographic model. We computed the co-seismic deformation induced by the earthquake by means of a recently developed finite elements simulation tool, FEMSA (Finite Element Modeling for Seismic Applications). We used different seismic source models obtained from fault inversion of GPS measurements, joint inversion of strong motion and GPS data and from inversion of DInSAR displacements. The synthetic deformation patterns were compared with the experimental results in order to evaluate which source model better reconciles the data and quantify the trade off introduced by 1D simulations

Three-dimensional FEM derived elastic Green's functions for the coseismic deformation of the 2005 M_w 8.7 Nias-Simeulue, Sumatra earthquake

Using finite element models (FEMs), we examine the sensitivity of surface displacements to the location of fault slip, topography, and three-dimensional variations in elastic moduli in the context of a 2-D infinite thrust fault. We then evaluate the impact of these factors and fault geometry on surface displacements and estimates of the distribution of coseismic slip associated with the 2005 M_w 8.7 Nias-Simeulue, Sumatra earthquake. Topographic effects can be significant near the trench, where bathymetric gradients are highest and the fault is closest to the free surface. Variations in Young's modulus can significantly alter predicted deformation. Surface displacements are relatively insensitive to perturbations in Poisson's ratio for shear sources, but may play a stronger role when the source has a dilatational component. If we generate synthetic displacements using a heterogeneous elastic model and then use an elastic half-space or layered earth model to estimate the slip distribution and fault geometry, we find systematic residuals of surface displacements and different slip patterns compared to the input fault slip model. The coseismic slip distributions of the 2005 earthquake derived from the same fault geometry and different material models show that the rupture areas are narrower in all tested heterogeneous elastic models compared to that obtained using half-space models. This difference can be understood by the tendency to infer additional sources in elastic half-space models to account for effects that are intrinsically due to the presence of rheological gradients. Although the fit to surface observations in our preferred 3-D FEM model is similar to that from a simple half-space model, the resulting slip distribution may be a more accurate reflection the true fault slip behavior

Rapid Estimation of Damage to Tall Buildings Using Near Real‐Time Earthquake and Archived Structural Simulations

This article outlines a new approach to rapidly estimate the damage to tall buildings immediately following a large earthquake. The preevent groundwork involves the creation of a database of structural responses to a suite of idealized ground‐motion waveforms. The postevent action involves (1) rapid generation of an earthquake source model, (2) near real‐time simulation of the earthquake using a regional spectral‐element model of the earth and computing synthetic seismograms at tall building sites, and (3) estimation of tall building response (and damage) by determining the best‐fitting idealized waveforms to the synthetically generated ground motion at the site and directly extracting structural response metrics from the database. Here, ground‐velocity waveforms are parameterized using sawtoothlike wave trains with a characteristic period (T), amplitude (peak ground velocity, PGV), and duration (number of cycles, N). The proof‐of‐concept is established using the case study of one tall building model. Nonlinear analyses are performed on the model subjected to the idealized wave trains, with T varying from 0.5 s to 6.0 s, PGV varying from 0.125  m/s, and N varying from 1 to 5. Databases of peak transient and residual interstory drift ratios (IDR), and permanent roof drift are created. We demonstrate the effectiveness of the rapid response approach by applying it to synthetic waveforms from a simulated 1857‐like magnitude 7.9 San Andreas earthquake. The peak IDR, a key measure of structural performance, is predicted well enough for emergency response decision making

DARE: A Reflective Platform Designed to Enable Agile Data-Driven Research on the Cloud

The DARE platform has been designed to help research developers deliver user-facing applications and solutions over diverse underlying e-infrastructures, data and computational contexts. The platform is Cloud-ready, and relies on the exposure of APIs, which are suitable for raising the abstraction level and hiding complexity. At its core, the platform implements the cataloguing and execution of fine-grained and Python-based dispel4py workflows as services. Reflection is achieved via a logical knowledge base, comprising multiple internal catalogues, registries and semantics, while it supports persistent and pervasive data provenance. This paper presents design and implementation aspects of the DARE platform, as well as it provides directions for future development.PublishedSan Diego (CA, USA)3IT. Calcolo scientific

Forward and adjoint simulations of seismic wave propagation on fully unstructured hexahedral meshes

We present forward and adjoint spectral-element simulations of coupled acoustic and (an)elastic seismic wave propagation on fully unstructured hexahedral meshes. Simulations benefit from recent advances in hexahedral meshing, load balancing and software optimization. Meshing may be accomplished using a mesh generation tool kit such as CUBIT, and load balancing is facilitated by graph partitioning based on the SCOTCH library. Coupling between fluid and solid regions is incorporated in a straightforward fashion using domain decomposition. Topography, bathymetry and Moho undulations may be readily included in the mesh, and physical dispersion and attenuation associated with anelasticity are accounted for using a series of standard linear solids. Finite-frequency Fréchet derivatives are calculated using adjoint methods in both fluid and solid domains. The software is benchmarked for a layercake model. We present various examples of fully unstructured meshes, snapshots of wavefields and finite-frequency kernels generated by Version 2.0 ‘Sesame' of our widely used open source spectral-element package SPECFEM3

dispel4py: An Open Source Python Framework for Encoding, Mapping and Reusing Seismic Continuous Data Streams: Intensive Analysis and Data Mining

Scientific workflows are needed by many scientific communities, such as seismology, as they enable easy composition and execution of applications, enabling scientists to focus on their research without being distracted by arranging computation and data management. However, there are challenges to be addressed. In many systems users have to adapt their codes and data movement as they change from one HPC-architecture to another. They still need to be aware of the computing architectures available for achieving the best application performance. We present dispel4py, an open-source framework presented as a Python library for encoding and automating data-intensive scientific methods as a graph of operations coupled together by data-streams. It enables scientists to develop and experiment with their own data-intensive applications using their familiar work environment. These are then automatically mapped to a variety of HPC-architectures, i.e., MPI, multiprocessing, Storm and Spark frameworks, increasing the chances to reuse their applications in different computing resources. dispel4py comes with data provenance, as shown in the screenshot, and with an information registry that can be accessed transparently from within workflows. dispel4py has been enhanced with a new run-time adaptive compression strategy to reduce the data stream volume and a diagnostic tool which monitors workflow performance and computes the most efficient parallelisation to use. dispel4py has been used by seismologists in the project VERCE for seismic ambient noise cross-correlation applications and for orchestrated HPC wave simulation and data misfit analysis workflows; two data-intensive problems that are common in today's research practice. Both have been tested in several local computing resources and later submitted to a variety of European PRACE HPC-architectures (e.g. SuperMUC & CINECA) for longer runs without change. Results show that dispel4py is an easy tool for developing, sharing and reusing data-intensive scientific methods

Three-dimensional numerical modeling of bottom-diffracted surface-reflected arrivals in the North Pacific [poster]

Poster presented AGU Fall Meeting, San Francisco, Californai USA, December 14-18, 2015Bottom-diffracted surface-reflected (BDSR) arrivals were first identified in the 2004 Long-range Ocean Acoustic Propagation Experiment (Stephen et al, 2013, JASA, v.134, p.3307-3317). The BDSR mechanism provides a means for acoustic signals and noise from distant sources to appear with significant strength on the deep seafloor. At depths deeper than the conjugate depth ambient noise and PE- predicted arrivals are sufficiently quiet that BDSR paths, scattered from small seamounts, can be the largest amplitude arrivals observed. The Ocean Bottom Seismometer Augmentation in the North Pacific (OBSANP) Experiment in June-July 2013 was designed to further define the characteristics of the BDSRs and to understand the conditions under which BDSRs are excited and propagate. The reciprocal of the BDSR mechanism also plays a role in T-phase excitation. To further understand the BDSR mechanism, the SPECFEM3D code was extended to handle high-frequency, deep water bottom scattering problems with actual bathymetry and a typical sound speed profile in the water column. The model size is 38km x 27km x 6.5km. The source is centered at 10Hz with a 5Hz bandwidth. Work supported by NSF and ONR.The data acquisition was funded by the Office of Naval Research and the computer modeling using SPECFEM3D was supported by the National Science Foundation

DARE: A Reflective Platform Designed to Enable Agile Data-Driven Research on the Cloud

The DARE platform has been designed to help research developers deliver user-facing applications and solutions over diverse underlying e-infrastructures, data and computational contexts. The platform is Cloud-ready, and relies on the exposure of APIs, which are suitable for raising the abstraction level and hiding complexity. At its core, the platform implements the cataloguing and execution of fine-grained and Python-based dispel4py workflows as services. Reflection is achieved via a logical knowledge base, comprising multiple internal catalogues, registries and semantics, while it supports persistent and pervasive data provenance. This paper presents design and implementation aspects of the DARE platform, as well as it provides directions for future development.PublishedSan Diego (CA, USA)3IT. Calcolo scientific

Turning the rumor of the May 11, 2011, earthquake prediction in Rome, Italy, into an information day on earthquake hazard

A devastating earthquake was predicted to hit Rome on May 11, 2011. This prediction was never officially released, but it grew on the internet and was amplified by the media. It was erroneously ascribed to Raffaele Bendandi, an Italian self-taught natural scientist who studied planetary motions and related them to earthquakes. Indeed, around May 11, 2011, there was a planetary alignment, and this fed the credibility of the earthquake prediction. During the months preceding May 2011, the Istituto Nazionale di Geofisica e Vulcanologia (INGV) was overwhelmed with requests for information about this prediction, by the inhabitants of Rome and by tourists. Given the echo of this earthquake prediction, on May 11, 2011, the INGV decided to organize an Open Day at its headquarters in Rome, to inform the public about Italian seismicity and earthquake physics. The Open Day was preceded by a press conference two days before, to talk with journalists about this prediction, and to present the Open Day. During this 'Day', 13 new videos were also posted on our YouTube/INGVterremoti channel to explain earthquake processes and hazards, and to provide periodic updates on seismicity in Italy from the seismicity monitoring room. On May 11, 2011, the INGV headquarters was peacefully invaded by over 3,000 visitors, from 10:00 am to 9:00 pm: families, students with and without teachers, civil protection groups, and many journalists. This initiative that was built up in a few weeks has had very large feedback, and was a great opportunity to talk with journalists and people about earthquake prediction, and more in general about the seismic risk in Italy