Francesco Grigoli

Bio: Francesco Grigoli is an academic researcher from International Monetary Fund. The author has contributed to research in topics: Monetary policy & Inflation targeting. The author has an hindex of 18, co-authored 125 publications receiving 1609 citations. Previous affiliations of Francesco Grigoli include University of Potsdam & Stanford University.

The November 2017 Mw 5.5 Pohang earthquake: A possible case of induced seismicity in South Korea

Abstract: The moment magnitude (Mw) 5.5 earthquake that struck South Korea in November 2017 was one of the largest and most damaging events in that country over the past century. Its proximity to an enhanced geothermal system site, where high-pressure hydraulic injection had been performed during the previous 2 years, raises the possibility that this earthquake was anthropogenic. We have combined seismological and geodetic analyses to characterize the mainshock and its largest aftershocks, constrain the geometry of this seismic sequence, and shed light on its causal factors. According to our analysis, it seems plausible that the occurrence of this earthquake was influenced by the aforementioned industrial activities. Finally, we found that the earthquake transferred static stress to larger nearby faults, potentially increasing the seismic hazard in the area.

Current challenges in monitoring, discrimination, and management of induced seismicity related to underground industrial activities: A European perspective

Abstract: Due to the deep socioeconomic implications, induced seismicity is a timely and increasingly relevant topic of interest for the general public. Cases of induced seismicity have a global distribution and involve a large number of industrial operations, with many documented cases from as far back to the beginning of the twentieth century. However, the sparse and fragmented documentation available makes it difficult to have a clear picture on our understanding of the physical phenomenon and consequently in our ability to mitigate the risk associated with induced seismicity. This review presents a unified and concise summary of the still open questions related to monitoring, discrimination, and management of induced seismicity in the European context and, when possible, provides potential answers. We further discuss selected critical European cases of induced seismicity, which led to the suspension or reduction of the related industrial activities.

The 2013 September–October seismic sequence offshore Spain: a case of seismicity triggered by gas injection?

Abstract: A spatially localized seismic sequence originated few tens of kilometres offshore the Mediterranean coast of Spain, close to the Ebro river delta, starting on 2013 September 5, and asting at least until 2013 October. The sequence culminated in a maximal moment magnitude Mw 4.3 earthquake, on 2013 October 1. The most relevant seismogenic feature in the area is the Fosa de Amposta fault system, which includes different strands mapped at different distances to the coast, with a general NE–SW orientation, roughly parallel to the coastline. However, no significant known historical seismicity has involved this fault system in the past. The epicentral region is also located near the offshore platform of the Castor project, where gas is conducted through a pipeline from mainland and where it was recently injected in a depleted oil reservoir, at about 2 km depth. We analyse the temporal evolution of the seismic sequence and use full waveform techniques to derive absolute and relative locations, estimate depths and focal mechanisms for the largest events in the sequence (with magnitude mbLg larger than 3), and compare them to a previous event (2012 April 8, mbLg 3.3) taking place in the same region prior to the gas injection. Moment tensor inversion results show that the overall seismicity in this sequence is characterized by oblique mechanisms with a normal fault component, with a 30◦ low-dip angle plane oriented NNE–SSW and a subvertical plane oriented NW–SE. The combined analysis of hypocentral location and focal mechanisms could indicate that the seismic sequence corresponds to rupture processes along shallow low-dip surfaces, which could have been triggered by the gas injection in the reservoir, and excludes the activation of the Amposta fault, as its known orientation is inconsistent with focal mechanism results. An alternative scenario includes the iterated triggering of a system of steep faults oriented NW–SE, which were identified by prior marine seismics investigations.

Automated seismic event location by waveform coherence analysis

Abstract: SUMMARY Automated location of seismic events is a very important task in microseismic monitoring operations as well for local and regional seismic monitoring. Since microseismic records are generally characterized bylowsignal-to-noiseratio,automated locationmethods arerequested to be noise robust and sufficiently accurate. Most of the standard automated location routines arebasedontheautomatedpicking,identificationandassociationofthefirstarrivalsofPandS waves and on the minimization of the residuals between theoretical and observed arrival times of the considered seismic phases. Although current methods can accurately pick P onsets, the automatic picking of the S onset is still problematic, especially when the P coda overlaps the S wave onset. In this paper, we propose a picking free earthquake location method based on the use of the short-term-average/long-term-average (STA/LTA) traces at different stations as observed data. For the P phases, we use the STA/LTA traces of the vertical energy function, whereas for the S phases, we use the STA/LTA traces of a second characteristic function, which is obtained using the principal component analysis technique. In order to locate the seismic event, we scan the space of possible hypocentral locations and origin times, and stack the STA/LTA traces along the theoretical arrival time surface for both P and S phases. Iterating this procedure on a 3-D grid, we retrieve a multidimensional matrix whose absolute maximum corresponds to the spatial coordinates of the seismic event. A pilot application was performed in the Campania-Lucania region (southern Italy) using a seismic network (Irpinia Seismic Network) with an aperture of about 150km. We located 196 crustal earthquakes (depth < 20km) with magnitude range 1.1 < ML < 2.7. A subset of these locations were compared with accurate manual locations refined by using a double-difference technique. Our results indicate a good agreement with manual locations. Moreover, our method is noise robust and performs better than classical location methods based on the automatic picking of the P and S waves first arrivals.

Economic growth and income inequality

Abstract: We investigate whether income inequality affects subsequent growth in a cross-country sample for 1965-90, using the models of Barro (1997), Bleaney and Nishiyama (2002) and Sachs and Warner (1997), with negative results. We then investigate the evolution of income inequality over the same period and its correlation with growth. The dominating feature is inequality convergence across countries. This convergence has been significantly faster amongst developed countries. Growth does not appear to influence the evolution of inequality over time. Outline

Inequality and Growth: What Can the Data Say?

Abstract: This paper describes the correlations between inequality and the growth rates in cross-country data. Using non-parametric methods, we show that the growth rate is an inverted U-shaped function of net changes in inequality: Changes in inequality (in any direction) are associated with reduced growth in the next period. The estimated relationship is robust to variations in control variables and estimation methods. This inverted U-curve is consistent with a simple political economy model, although, as we point out, efforts to interpret this model causally run into difficult identification problems. We show that this non-linearity is sufficient to explain why previous estimates of the relationship between the level of inequality and growth are so different from one another.

The Price of Inequality: How Today's Divided Society Endangers Our Future

Abstract: The Price of Inequality: How Today's Divided Society Endangers Our Future. Joseph E. Stiglitz, 414 pages, New York: W. W. Norton & Company, 2012.I LOVE THESE GUYS''(Joseph Stiglitz) is an insanely great economist,'' so writes Paul R. Krugman, who should know. These two like to write books for the populace at large on the topic of macroeconomics. Krugman also likes to spout offon Sunday news shows like ''Meet the Press,'' and on all the cable news programs. You can see Krugman arguing with Bill O'Reilly on Meet the Press. From YouTube: ''Don't call me a liar, pal, that's what you do all the time,'' says O'Reilly; ''This is not your show, so you can't cut offmy mic,'' says Krugman. Judging by their expressions, I was glad Tim Russert (6- 3-) was there in the studio at the time to protect Krugman (5- 7-) (O'Reilly stands 6- 4-). Conservative pundits dislike both economists, but pretty much leave Stiglitz alone.Krugman makes it a point to stay out of government affairs. Stiglitz does just the opposite, and he sometimes gets burned. Stiglitz was part of Bill Clinton's Council of Economic Advisers and was Chief Economist for the World Bank. After much criticism of the way the International Monetary Fund (IMF) conducted lending to developing countries, he was pretty much fired from the World Bank. Comparing the two, you would have to say that Stiglitz is more the bleeding heart, while Krugman says that what he dislikes most is the dishonesty he sees in political-economic discourse. Both are champions of the common man.Since Stiglitz can make the very valid claim for being ''an insanely great economist,'' most everything he says in his books should be taken seriously. There are some real gems in this book. I especially like the perspective he lends to some of the more peculiar things that happened before, during, and after the financial crisis. People hear about these things in the news from some announcer who makes them sound like just more news-bites, but they are, after all, unprecedented (and largely absurd). Take ''robo-signing'' for instance (page 198).WHAT GOES FOR NEWSRobo-signing was part of what happened during the foreclosure process after the massive numbers of defaults of subprime mortgages. Big banks intentionally did not follow mandated law. Apart from ignoring debtors' rights, an ensuing mess followed. Robo-signing was nothing less than a blatant attempt at rewriting property law, and resulted in lying to the courts about the state of each property's title, literally hundreds of times. No bank officer was charged with a crime. By contrast, the savings and loan crisis of the 1980s led to 829 individual convictions and 650 prison sentences. Nowadays the big banks just pay fines as part of settlements where they admit no guilt, and it's just part of doing business.Take algorithmic or ''flash'' trading in the stock exchanges (page 164). These are buys and sales made in nanoseconds on the basis of extracting information from the patterns of prices and trades. Nothing like real information gathered through market research on an industry, or on a firm in a certain industry, backs up these trades. But traders swear that ''price discovery'' is happening this way, and that all this backs up the efficient markets model. So on May 6, 2010 stock prices plummeted to a point where the Dow Jones temporarily lost 10% of its value. There are reasons to believe that these trades ''make markets not just more volatile but also less 'informative' '' (page 166). Still, the talk on the street is all about efficient markets (echoing Alan Greenspan's failures at the Federal Reserve).Take failed privatizations. When electric power in California was liberalized and Enron manipulated prices and public power to its advantage, this was a story about the company's accounting practices, not about privatizing something that had no business being privatized. …