Rupture process of the 2007 Niigata-ken Chuetsu-oki earthquake by non-linear joint inversion of strong motion and GPS data

We image the rupture history of the 2007 Niigata-ken Chuestu-oki (Japan) earthquake by a nonlinear joint inversion of strong motion and GPS data, retrieving peak slip velocity, rupture time, rise time and slip direction. The inferred rupture model contains two asperities; a small patch near the nucleation and a larger one located 10÷15 km to the south-west. The maximum slip ranges between 2.0 and 2.5 m and the total seismic moment is 1.6×1019 Nm. The inferred rupture history is characterized by rupture acceleration and directivity effects, which are stable features of the inverted models. These features as well as the source-to-receiver geometry are discussed to interpret the high peak ground motions observed (PGA is 1200 gals) at the Kashiwazaki-Kariwa nuclear power plant (KKNPP), situated on the hanging-wall of the causative fault. Despite the evident source effects, predicted PGV underestimates the observed values at KKNPP by nearly a factor of 10

Using geophysical data inversion to constrain earthquake dynamics: a study on dynamically consistent source time functions.

Earthquake kinematic models are often used to retrieve the main parameters of the causative dynamic rupture process. These models are usually obtained through the inversion of seismograms and geodetic data and they can be used as boundary conditions in dynamic modeling to calculate the traction evolution on the fault. Once traction and slip time histories are inferred at each point on the fault plane, it is feasible to estimate the dynamic and breakdown stress drop, the strength excess and the slip weakening distance (Dc). However the measure of these quantities can be biased by the adopted parametrization of kinematic source models. In this work we focus our attention on the importance of adopting source time functions (STFs) compatible with earthquake dynamics to image the kinematic rupture history on a finite fault. First, we compute synthetic waveforms, through a forward modeling, to evaluate the effects of STFs on the ground motion and on the radiated energy. Therefore, adopting different STFs, we perform kinematic inversion of strong motion and GPS data, using a new non linear two-stages search algorithm (Piatanesi et al., 2007) . We have quantitatively verified that the chioce of STFs affects ground motion time histories within the frequency band commonly used in kinematic inversion and that the inferred peak slip velocity and rise time strongly change among the inverted models. These differences has a dramatic impact when kinematic models are used to infer dynamic traction evolution. The shape of the slip weakening curve, the ratio between Dc and the final slip and the dynamic stress drop distribution are remarkably affected by the assumed STFs. We recommend the adoption in kinematic inversions of source time functions that are compatible with earthquake dynamics

Variability of kinematic source parameters and its implication on the choice of the design scenario

Near-fault seismic recordings for recent earthquakes (Chi Chi earthquake, 1999, and Parkfield earthquake, 2004) show the high spatial heterogeneity of ground motion. This variability is controlled by fault geometry, rupture complexity, and also by wave propagation and site effects. Nowadays, the number of available records in the near-source region is still not enough to infer a robust parameterization of the ground motion and to retrieve multiparametric predictive equations valid at close distances from the fault. The use of a synthetic approach may help to overcome this limitation and to study the strong ground motion variability. In this article we focus on ground-motion dependence on different earthquakes breaking the same fault, as it has been rarely recorded by instruments. We model seismic scenarios from different rupture models of a fault similar to the 1980 Irpinia, Italy, earthquake source (Mw 6.9). A discrete wavenumber/finite element technique is used to compute fullwave displacement and velocity time series in the low-frequency band (up to 2 Hz). We investigate the variability of the ground motion as a function of different source parameters (rupture velocity, slip distribution, nucleation point, and source time function), whose values depend on the state of knowledge of the physical model driving the process. The probability density functions of the simulated ground-motion parameters, such as displacement response spectrum and peak ground velocity, are used to identify particular scenarios that match specific engineering requests

Variability of kinematic source parameters and its implication on the choice of the design scenario

Near-fault seismic recordings for recent earthquakes (Chi Chi earthquake, 1999; Parkfield earthquake, 2004) show the high spatial heterogeneity of ground motion. This variability is controlled by fault geometry, rupture complexity, and also by wave propagation and site effects. Nowadays, the number of available records in near-source region is still not enough to infer a robust parameterization of the ground motion and to retrieve multi-parametric predictive equations valid at close distances from the fault. The use of a synthetic approach may help to overcome this limitation and to study the strong ground motion variability. In this paper we focus on ground-motion dependence on different earthquakes breaking the same fault, as it has been rarely recorded by instruments. We model seismic scenarios from different rupture models of a fault similar to the 1980 Irpinia, Italy, earthquake source (Mw 6.9). A discrete wavenumber-finite element technique is used to compute full-wave displacement and velocity time series in the low-frequency band (up to 2 Hz). We investigate the variability of the ground motion as a function of different source parameters (rupture velocity, slip distribution, nucleation point, source time function), whose values depend on the state of knowledge of the physical model driving the process. The probability density functions of the simulated ground motion parameters, such as displacement response spectrum (SD) and peak ground velocity (PGV), have been used to identify particular scenarios that match specific engineering requests

Task 5 - Potenza - Deliverable D17: Bedrock shaking scenarios

The main goal of this report is the computation of the bedrock seismic scenarios in the Potenza city (Southern Italy) to be used for evaluating damage scenarios (described in PS3-Deliverables D18-D19-D24). This area represents one of the prediction case studies, planned in the framework of Project S3 which aim is the production of ground shaking scenarios for high and moderate magnitude earthquakes. The area around Potenza was affected by several destructive earthquakes in historical time (Table 2.1.1) and a number of individual sources representing the causative faults of single seismic events with magnitude up to 7 were identified. Deeper and smaller faults are present very close to the Potenza city, generating events with M up to 5.7 (1990 Potenza earthquake). Due to the involved source-to-site distances (about 25 km) and to the computation resolution of the simulation techniques, the site is represented by a single point. In total 9 faults were identified and the deterministic shaking scenarios are computed for each of them. The following strategy is adopted to provide ground motions. We compute shaking scenarios at level 1, using a simplified simulation technique (DSM, Pacor et al.; 2005) for all the faults. By these simulations we identify the three faults (F3, F7. and F8) producing the maximum expected shaking at the Potenza city, in terms of peak ground acceleration, peak ground velocity and Housner intensity. Based on these results, simulations at level 2, using the broad band technique HIC (Gallovic and Brokeshova, 2007) have been performed at Potenza for F3, F7 and F8 sources. For the Potenza city, we decided to predict the shaking scenarios at level 2, in order to provide suitable estimates of the low frequency ground motion (e.g. velocity time series) and engineering parameters (e.g. Arias intensity) strictly related to the duration of the signals. For each source, we generated hundreds of rupture models varying slip distribution, nucleation points and rupture velocity, and for each model we simulated the acceleration time series by HIC. Then we computed the probability density functions (PDF) of the ground motion parameters (PGA, PGV, PGD, Arias and Housner intensities) and estimated several statistical quantities in order to select families of accelerograms to be used for damage analysis: mean and associated standard deviation, median, 75% percentile, 84% percentile, mode, minimum and maximum. Finally we provided to the engineering Research Unit 6 of this project three sets of 7 accelerograms, having ground motion parameters equal to the statistical requirements computed by the synthetic distributions. The first set includes 7 accelerograms (three components), each of them having PGA equal to the mean, median, mode, 75-percentile, 84-percentile, minimum and maximum values of the PGA distribution. The second set and third sets include 7 accelerograms (horizontal components only), having PGA and Housener Intensity in the neighborhood of the median values of the corresponding distributions. A further comparison of adopted procedure for the predicted ground motion at Potenza was performed with respect to stochastic ground motions generated with EXSIM method (Motazedian and Atkinson; 2005). Even if the scenarios modelling was carried out varying different kinematic parameters, the statistical parameter were quite similar. Finally to provide shaking scenarios in term of macroseismic intensity, we applied a probabilistic empirical approach, developed in Progetto DPC-INGV S1.Progetto INGV-DPC S3 “Scenari di scuotimento in aree di interesse prioritario e/o strategico”Published4.2. TTC - Scenari e mappe di pericolosità sismicaope

10 Hz GPS seismology for moderate magnitude earthquakes: the case of the Mw 6.3 L’Aquila (Central Italy) event

The 2009 April 6th Mw 6.3 L'Aquila destructive earthquake was successfully recorded by closely spaced 10-Hz and 1-Hz recording GPS receivers and strong motion accelerometers located above or close to the 50° dipping activated fault. We retrieved both static and dynamic displacements from Very High-Rate GPS (VHRGPS) recordings by using Precise Point Positioning kinematic analysis. We compared the GPS positions time series with the closest displacement time series obtained by doubly-integrating strong motion data, first, to assess the GPS capability to detect the first seismic arrivals (P waves) and, secondly, to evaluate the accelerometers capability to detect co-seismic offsets up to ~45 s after the earthquake occurrence. By comparing seismic and VHRGPS frequency contents, we inferred that GPS sampling rates greater than 2.5 Hz (i.e. 5 or 10 Hz) are required in the near-field of moderate magnitude events to provide “alias-free” solutions of coseismic dynamic displacements. Finally, we assessed the consistency of the dynamic VHRGPS results as a constraint on the kinematic rupture history of the mainshock. These results suggested that the high-rate sampling GPS sites in the near field can be as useful as strong motion station for earthquake source studies

Task 1 - Scenari di scuotimento - Deliverable D1: Linee guida per il calcolo degli scenari di scuotimento

L'analisi dinamica del livello di sicurezza ingegneristico, in particolare per strutture strategiche in una zona ad elevato potenziale sismogenetico, tiene conto dei parametri di picco e di diverse caratteristiche del moto del suolo, come ad esempio la durata, la “non-stazionarietà” e i “critical-pulse” (McGuire, 1995). Di conseguenza, è richiesta una modellazione dettagliata sia della struttura sia dell’input sismico necessario a verificarne la risposta sismica. I codici per la progettazione in zona sismica richiedono che l’input sismico per le analisi dinamiche sia composto da un set di “time-histories” a cui la struttura deve resistere durante la sua esistenza, e da un livello di pericolosità caratteristico della zona sismogenetica in cui la struttura di interesse è ubicata. A tale scopo l’input sismico e la pericolosità di un’area sono stimati con approcci di tipo deterministico o probabilistico. La scelta dell'approccio da adottare per le valutazioni di pericolosità non è immediata, poiché i due metodi sono molto diversi e presentano entrambi vantaggi e svantaggi. In generale l’approccio deterministico valuta l’entità del moto sismico causato da uno specifico evento di cui si considera nota la localizzazione e la magnitudo; l’approccio probabilistico definisce invece la probabilità che un determinato parametro dello scuotimento sia superato in un particolare intervallo temporale (ad esempio 10% di probabilità di superamento in 50 anni) a partire dallo studio sulla sismicità dell’area. La differenza fondamentale tra l’approccio deterministico e quello probabilistico è che nel primo vengono simulate le serie temporali, ma non si associa alcuna probabilità al parametro di scuotimento valutato, viceversa nel secondo sono descritti solo alcuni parametri del moto e la probabilità è inclusa direttamente nell’analisi

Task 1 - Scenari di scuotimento - Deliverable D0: Tecniche di simulazione

Progetto INGV-DPC S3 “Scenari di scuotimento in aree di interesse prioritario e/o strategico”Published4.1. Metodologie sismologiche per l'ingegneria sismicaope

Soluble CD137 as a dynamic biomarker to monitor agonist CD137 immunotherapies

Background On the basis of efficacy in mouse tumor models, multiple CD137 (4-1BB) agonist agents are being preclinically and clinically developed. The costimulatory molecule CD137 is inducibly expressed as a transmembrane or as a soluble protein (sCD137). Moreover, the CD137 cytoplasmic signaling domain is a key part in approved chimeric antigen receptors (CARs). Reliable pharmacodynamic biomarkers for CD137 ligation and costimulation of T cells will facilitate clinical development of CD137 agonists in the clinic. Methods We used human and mouse CD8 T cells undergoing activation to measure CD137 transcription and protein expression levels determining both the membrane-bound and soluble forms. In tumor-bearing mice plasma sCD137 concentrations were monitored on treatment with agonist anti-CD137 monoclonal antibodies (mAbs). Human CD137 knock-in mice were treated with clinical-grade agonist anti-human CD137 mAb (Urelumab). Sequential plasma samples were collected from the first patients intratumorally treated with Urelumab in the INTRUST clinical trial. Anti-mesothelin CD137-encompassing CAR-transduced T cells were stimulated with mesothelin coated microbeads. sCD137 was measured by sandwich ELISA and Luminex. Flow cytometry was used to monitor CD137 surface expression. Results CD137 costimulation upregulates transcription and protein expression of CD137 itself including sCD137 in human and mouse CD8 T cells. Immunotherapy with anti-CD137 agonist mAb resulted in increased plasma sCD137 in mice bearing syngeneic tumors. sCD137 induction is also observed in human CD137 knock-in mice treated with Urelumab and in mice transiently humanized with T cells undergoing CD137 costimulation inside subcutaneously implanted Matrigel plugs. The CD137 signaling domain-containing CAR T cells readily released sCD137 and acquired CD137 surface expression on antigen recognition. Patients treated intratumorally with low dose Urelumab showed increased plasma concentrations of sCD137. Conclusion sCD137 in plasma and CD137 surface expression can be used as quantitative parameters dynamically reflecting therapeutic costimulatory activity elicited by agonist CD137-targeted agents