L'Italo-Americano

THURSDAY, DECEMBER 12, 2019 www.italoamericano.org 32 L'Italo-Americano " I grew up surrounded by the Alps in Veneto, fas- cinated by the Dolomites. My passion for science and natural phenomena, such as earthquakes and how mountain belts form and evolve through time, fueled my inspiration to study geology and geophysics and pursue a career in academia." Luca Dal Zilio goes back in time, as he explains to me how his passion became a profession, while walking me around the beautiful and peaceful buildings of the California Institute of Technology. "I focused on earthquakes, in particular on solving problems related to plate tectonics and the breaking of supercontinents." From Quinto di Treviso, a small village near Venice, at only 29 years old Luca research- es and studies as a post-doctoral scholar at the Caltech Seismological Laboratory, where he takes me to the second floor to show me the meeting room. "Here we usually have our morning coffee break, when we meet and chat about scientific problems. We all sit here and I have the chance to talk with my colleagues and my professors. It's a unique opportunity for a young researcher to interact with some of the legends in the field." So it is not really a break if you talk about work? We are very passionate about work ! So every time it's an excuse for me to interact. What was the most interest- ing coffee break for you? It definitely was when the Ridgecrest earthquake hap- pened: there was a lot of actions and our coffee breaks were very intense for many weeks. We came here and analyzed new data, and it was impressive to see how the lab was able to put together scientific results in less than two months, thus providing a scientific paper for the com- munity to understand exactly what happened. What are you studying exactly? Earthquakes happen quickly, usually in 10, 20 sec- onds. But there is a preparatory phase before an earthquake that can take decades, centuries and sometimes thousands of years. There is a long preparatory phase where plate tectonics are moving and are accumulating stress. The biggest challenge for me is trying to link this temporal scales to one another. So trying to link the long-term accumula- tion of stress and the physical parameters creating the condi- tions that generate an earth- quake. How do you do that? This phase is extremely long. It takes into account many physi- cal and chemical processes. The unique way to merge long-term and short-term processes is to use numerical models. With these tools, I try to put together equations and simulate the long term accumulation over cen- turies, and the release of stress during an earthquake that hap- pens in a few seconds. How crucial is for you to study here, in California? Historically speaking, California has a very long tradi- tion in this field, it represents a reference point for the people working on this topic; what I appreciate is the "earthquake cul- ture" you find here, which makes people aware of the risks. In many regions of the world earth- quakes happen, yet they take us always by surprise: they are a natural process like a storm or any kind of a natural event. They happen and they are going to happen for centuries to come. And people can easily forget about them. But here it's diffe- rent because there is a conti- nuous training, a continuous rising of awareness about earth- quakes and how one can really be just around the corner. Einstein was a visiting pro- fessor at Caltech in the early 1930s. How do you feel about that? We had some people that rep- resent seismology, that literally created this scientific discipline. We had Gutenberg, Richter and we still have Hiroo Kanamori who's a legend for us and it's such a big honor for me to print my results on a paper and go to his office and discuss with him my findings. I feel that is an extremely unique opportunity for me. So what has been so far you biggest satisfaction at CalTech? Recently, I was able to match some of the observations from the Cascadia subduction zone, which is a plate boundary that starts at the northern end of the San Andreas Fault and continues up north. That region is seismi- cally active, the risk is extremely high. We know that a magnitude higher than 8.5 up to 9 can easily occur in the next years and, at the moment, I'm trying to ana- lyze and understand what we call "silent earthquakes:" earthquakes so mild they are only registered by seismometers and GPS sta- tions, but not by people. About the Big One: we all wonder about when it is going to happen. There isn't any way to know, is it? That's correct. At the moment we can't predict earthquakes. So it's impossible for us to make any estimation in terms of the location and the exact time of the next event. What we can do is use genetic data. So we have sta- tions are all over an active region; these stations record "deformation," that is, how the surface of the Earth moves through time. We can use this to estimate the accumulation of elastic deformation and in part understand where and how the most energy accumulated. From there, we can kind of assess the seismic hazard of that region and say how high is the risk of earth- quakes. What's the field's goal for the future? There are different goals, really. In general, my PhD research is based upon the phi- losophy that"all models are wrong, but some are useful." So we are currently trying to make more sophisticated models to "simulate" the way our planet. Are you more scared of earthquakes or more fascinat- ed by them? I am extremely fascinated. I just find to see how our planet is so active incredibly interesting. For me, taking the car with my colleagues, go to Ridgecrest and look at the surface rupture after an earthquake is just incredible. This narrow rupture continues for many kilometers, and for us it is just the real demonstration of what we study every day. How was your reaction dur- ing the last small quakes we experienced? The first one was a 6.4 and the second was a 7.1. I was here in Pasadena, having a barbecue with my friends and we all rushed to Caltech. Fortunately, there were only very little dam- ages, so I'm really happy about that. What's your first reaction when you feel that everything is moving: are you more of a regular person or more of a scientist? More of a scientist, which is not necessarily a good thing. Earthquakes are something incredible for me, so being pre- sent when it happens is just ama- zing. Luca Dal Zilio comes from the Veneto region of Italy, but today he works for the Caltech Seismological Laboratory SILVIA GIUDICI LOS ANGELES ITALIAN COMMUNITY Dal Zilio at work From the Dolomites to Caltech: a chat with Luca Dal Zilio

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