Finding Faults: Identifying Earthquake Hazards Around the WorldJudith HUBBARDHarvard UniversityMany earthquakes occur on faults that have not ruptured for hundreds, oreven thousands, of years. As a result, earthquakes sometimes seem unexpected,causing massive devastation in areas that are not adequately prepared. How can weidentify active faults before they slip and evaluate their earthquake hazard, and whyis earthquake prediction so difficult? Judith Hubbard, from Harvard University, willdiscuss how earth scientists use cutting-edge techniques, such as 3-D visualization,geophysical modeling and remote sensing, to better understand and forecastearthquakes in areas ranging from the Los Angeles basin in California to the Sichuanbasin in China, where the M7.9 Wenchuan earthquake occurred last year.In the Los Angeles basin, residents are very aware of earthquake hazards.However, many faults are hidden, either because they never reached the surface orbecause they have been buried by sediment. As a result, identifying these faults anddetermining their hazard can be difficult. In many cases, however, the sedimentsabove the fault record evidence of previous earthquakes.Scientists can therefore establish an earthquake history using seismic data to imagethe structure of the earth below the ground surface.The Wenchuan earthquake was striking, because it ruptured multiple faultsalong a mountain front rather than a single fault. Because fault area is correlated toearthquake magnitude, this caused the earthquake to be very large. Understandinghow earthquakes can rupture multiple faults is very important if scientists are toestimate earthquake hazards. In addition, before the Wenchuan earthquake occurredlast May, many scientists believed that earthquakes in the area were likely to besmall and rare. Ms. Hubbard will discuss why this is the case and how the M7.9earthquake changed earth scientists’ understanding of the area.