Showing papers by "Francesco Grigoli published in 2016"

Automated microseismic event location using Master-Event Waveform Stacking

Abstract: Accurate and automated locations of microseismic events are desirable for many seismological and industrial applications. The analysis of microseismicity is particularly challenging because of weak seismic signals with low signal-to-noise ratio. Traditional location approaches rely on automated picking, based on individual seismograms, and make no use of the coherency information between signals at different stations. This strong limitation has been overcome by full-waveform location methods, which exploit the coherency of waveforms at different stations and improve the location robustness even in presence of noise. However, the performance of these methods strongly depend on the accuracy of the adopted velocity model, which is often quite rough; inaccurate models result in large location errors. We present an improved waveform stacking location method based on source-specific station corrections. Our method inherits the advantages of full-waveform location methods while strongly mitigating the dependency on the accuracy of the velocity model. With this approach the influence of an inaccurate velocity model on the results is restricted to the estimation of travel times solely within the seismogenic volume, but not for the entire source-receiver path. We finally successfully applied our new method to a realistic synthetic dataset as well as real data.

The Mw 8.1 2014 Iquique, Chile, seismic sequence: a tale of foreshocks and aftershocks

Abstract: EGU2009-11040. Schurr, B., Asch, G., Rosenau, M., Wang, R., Oncken, O., Barrientos, S., Salazar, P.&Villotte, J.-P., 2012. The 2007M7.7 TocopillaNorthernChile earthquake sequence: implications for along-strike and downdip rupture segmentation and megathrust frictional behaviour, J. geophys. Res., 117, B05305, doi:10.1029/2011JB009030. Schurr, B. et al., 2014. Gradual unlocking of the plate boundary controlled the initiation of the 2014 Iquique earthquake, Nature, 512(7514), 299–

Inequality and Growth: A Heterogeneous Approach

Abstract: The combination of stagnant growth and high levels of income inequality renewed the debate about whether a more even distribution of income can spur economic activity. This paper tests for cross-country convergence in income inequality and estimates its impact on economic growth with a heterogeneous panel structural vector autoregression model, which addresses some empirical challenges plaguing the literature. We find that income inequality is converging across countries, and that its impact on economic growth is heterogeneous. In particular, while the median response of real per capita GDP growth to shocks in income inequality is negative and significant, the dispersion around the estimates is large, with at least one fourth of the countries in the sample presenting a positive effect. The results suggest that the negative effect is mainly driven by the Middle East and Central Asia and the Western Hemisphere across regions, and emerging markets across income levels. Finally, we find evidence that improved institutional frameworks can reduce the negative effect of income inequality on growth.

Inequality and Growth : A Heterogeneous Approach

Abstract: The combination of stagnant growth and high levels of income inequality renewed the debate about whether a more even distribution of income can spur economic activity. This paper tests for cross-country convergence in income inequality and estimates its impact on economic growth with a heterogeneous panel structural vector autoregression model, which addresses some empirical challenges plaguing the literature. We find that income inequality is converging across countries, and that its impact on economic growth is heterogeneous. In particular, while the median response of real per capita GDP growth to shocks in income inequality is negative and significant, the dispersion around the estimates is large, with at least one fourth of the countries in the sample presenting a positive effect. The results suggest that the negative effect is mainly driven by the Middle East and Central Asia and the Western Hemisphere across regions, and emerging markets across income levels. Finally, we find evidence that improved institutional frameworks can reduce the negative effect of income inequality on growth.

Seismicity of a slow deforming environment: Alentejo, south Portugal

Abstract: Mainland Portugal lays on a stable continental region characterized by slow tectonic rates. However, the region has been the source of moderate to large magnitude earthquakes in historical times. Remarkable seismic activity has also been recorded in the instrumental period. A clearly asymmetric distribution of earthquakes between north and south is observed. The Alentejo region (south Portugal) presents belts of high epicenter density and delimits a transition between a nearly aseismic zone, to the northeast, and an area with significant seismic activity to the south. Earthquake clusters are located within an area where the relation between small earthquakes (ML<4), tectonics and lithospheric rheology is not obvious.

Macro-Financial Linkages and Heterogeneous Non-Performing Loans Projections: An Application to Ecuador

Abstract: We propose a stress testing framework of credit risk, which analyzes macro-financial linkages, generates consistent forecasts of macro-financial variables, and projects NPL on the basis of such forecasts. Economic contractions are generally associated with increases in non-performing loans (NPL). However, despite the common assumption used in the empirical literature of homogenous impact across banks, the strength of this relationship is often bank-specific, and imposing homogeneity may lead to over or underestimating the resilience of the financial system to macroeconomic woes. Our approach accounts for banks’ heterogeneous reaction to macro-financial shocks in a dynamic context and potential cross-sectional dependence across banks caused by common shocks. An application to Ecuador suggests that substantial heterogeneity is present and that this should be taken into account when trying to anticipate inflections in the quality of portfolio.

Misalignment Angle Correction of Borehole Seismic Sensors: The Case Study of the Collalto Seismic Network

Abstract: One of the most critical problems affecting seismological data acquisition is related to possible misorientation of three‐component seismic sensors. This generally happens when their orientation cannot be measured directly, as in the case of sensors deployed in boreholes. We describe here the sensor reorientation procedure of the Collalto Seismic Network, a microseismic monitoring network located in northeastern Italy that consists of 10 broadband three‐component stations deployed in boreholes. We apply a procedure based on the misfit minimization of a complex trace recorded by a given station with respect to a reference station for which orientation is known. The main advantage of this methodology is that the reorientation of seismic sensors can be viewed as a linear inverse problem in the complex domain, which ensures that the preferred solution corresponds to the global minimum of a misfit function. Furthermore, it is also possible to simultaneously use more than one seismic event to better constrain the solution of the inverse problem. In this article, we further compare the orientation results obtained for a seismometer–seismometer sensor pair with those obtained using an accelerometer–seismometer sensor pair. We finally show the reorientation results for all the stations of the network, obtained using eight teleseismic events that occurred between January 2012 and May 2014.

Macro-Financial Linkages and Heterogeneous Non-Performing Loans Projections: An Application to Ecuador

Abstract: We propose a stress testing framework of credit risk, which analyzes macro-financial linkages, generates consistent forecasts of macro-financial variables, and projects non-performing loans (NPL) on the basis of such forecasts. Economic contractions are generally associated with increases in NPL. However, despite the common assumption used in the empirical literature of homogeneous impact across banks, the strength of this relationship is often bank-specific, and imposing homogeneity may lead to over or underestimating the resilience of the financial system to macroeconomic woes. Our approach accounts for banks’ heterogeneous reaction to macro-financial shocks in a dynamic context and potential cross-sectional dependence across banks caused by common shocks. An application to Ecuador suggests that substantial heterogeneity is present and that this should be taken into account when trying to anticipate inflections in the quality of portfolio.

Power It Up : Strengthening the Electricity Sector to Improve Efficiency and Support Economic Activity

Abstract: Poor performance of the electricity sector remains a drag to economic efficiency and a bottleneck to economic activity in many low-income countries. This paper proposes a number of models that account for different equilibria (some better, some worse) of the electricity sector. They show how policy choices (affecting insolvency prospects or related to rules for electricity dispatching or tariff setting), stochastic generation costs, and initial conditions, affect investment in generation and electricity supply. They also show how credible (non-credible) promises of stronger enforcement to reduce theft result in larger (smaller) electricity supply, lower (higher) government subsidies, and lower (higher) tariffs and distribution losses, which in turn affect economic activity. To illustrate these findings, the paper reviews the experience of Haiti, a country stuck in a bad equilibrium of insufficient supply, high prices, and electricity theft; and that of Nicaragua, which is gradually transitioning to a better equilibrium of the electricity sector.

Macro-Financial Linkages and Heterogeneous Non-Performing Loans Projections; An Application to Ecuador

Abstract: We propose a stress testing framework of credit risk, which analyzes macro-financial linkages, generates consistent forecasts of macro-financial variables, and projects non-performing loans (NPL) on the basis of such forecasts. Economic contractions are generally associated with increases in NPL. However, despite the common assumption used in the empirical literature of homogeneous impact across banks, the strength of this relationship is often bank-specific, and imposing homogeneity may lead to over or underestimating the resilience of the financial system to macroeconomic woes. Our approach accounts for banks’ heterogeneous reaction to macro-financial shocks in a dynamic context and potential cross-sectional dependence across banks caused by common shocks. An application to Ecuador suggests that substantial heterogeneity is present and that this should be taken into account when trying to anticipate inflections in the quality of portfolio.