Agustín Udías is Emeritus Professor at the Universidad Complutense de Madrid (UCM). He is the author of many papers about seismicity, seismotectonics of the Azores-Gibraltar, and the physics of seismic sources, and has also written several textbooks including Principles of Seismology (Cambridge University Press, 1999). Professor Udías has served as Editor-in-Chief of Física de la Tierra and the Journal of Seismology, and earlier as the Vice-President of the European Seismological Commission. He is a member of the Accademia Europeae, the Seismological Society of America, the American Geophysical Union, amongst other societies, and is a Fellow of the Royal Astronomical Society. Raúl Madariaga is Emeritus Professor of Geophysics at the École Normale Supérieure (ENS) in Paris. During his career he has served as Director of the Seismological Laboratory of the Institut de Physique du Globe (IPG), and Director of the Geology Laboratory of ENS. Professor Madariaga is a Fellow of the American Geophysical Union and has been awarded the Stefan Muller medal of the European Geophysical Society and also the H. F. Reid Medal, the highest award of the Seismological Society of America. He has been an editor of several journals a well as a member of the Board of Science, and he is the author of 140 papers in leading scientific journals as well as several articles in Earth Science encyclopaedias. Elisa Buforn is a Professor of Geophysics at the Universidad Complutense, Madrid, teaching courses on geophysics, seismology, physics and numerical methods. She has published papers on topics ranging from source fracture processes and seismicity to the seismotectonics of the Ibero-Maghrebian region and Azores-Gibraltar, and is the author of various textbooks including Solved Problems in Geophysics (Cambridge University Press, 2012). Professor Buforn currently serves as Editor-in-Chief of Física de la Tierra, and is on the editorial board of the Journal of Seismology. She has participated on many international scientific committees and is a member of the Seismological Society of America, American Geophysical Union, Royal Astronomical Society, and other distinguished societies.