2016 USEIT: Loss Analysis of Earthquake Sequences Sophia Belvoir1, Vianca Severino2, Jenepher Zamora1, Jadson Silva4, Luis Gomez5, Jozi Pearson6, Mark Benthien6, Thomas Jordan6 1Pasadena City College, 2University of Puerto Rico, Mayagüez, 4University of Brazilia, 5Chaffey College, 6University of Southern California ABSTRACT The 2016 Undergraduate Studies in Earthquake Information Technology (USE-IT) intern research program challenged the Hazard and Risk Visualization Team to illustrate threatening and probable multi-event earthquake scenarios in California using ShakeMaps and risk analysis maps. The interns are implementing FEMA’s Hazards United States (HAZUS) software to estimate and visualize the potential losses including physical damage of infrastructure, economic loss, and social impacts of these mul- ti-earthquake sequences. This is the first time multiple events will be analyzed with HAZUS. As a team based project, USEIT interns depend on collaboration with other working groups within the intern program to identify potential earthquake sequences. The Rate-State earthQuake Simulator (RSQSim) was run on a high performance computer (HPC) to generate catalogs of events. Rupture sequences were then selected to be visualized in SCEC-VDO. Earthquake sequences that were seen as most threatening had ShakeMap files created utilizing seismic hazard analysis (OpenSHA) software. Multiple events were combined as single ShakeMaps and imported into HAZUS for analysis. Ground motion values were combined and calculated in two differ- ent ways for multi-event ShakeMaps: 1) by using the greatest value and 2) sum of the squares, where the maps overlap. The greatest value method proves more appropriate for events that are further apart geographically. The sum of the squares method is ideal for events that are closer together. This year interns can illustrate the most threatening multi-event scenarios with hazard and risk maps providing colleagues and the public with alternate scenarios to help create and revise safety plans, guidelines, and economic strategies. In California, most of the population is expecting the "Big One", but we are also interested in scenarios that involve more than one large (M7+) event within the same year, same month, same week, and even the same day on the San Andreas Fault, as well as other threatening southern California faults. THE HAZUS CHALLENGE: PUENTE HILLS AND WHITTIER SCENARIO CALCULATING MULTI-EVENT LOSSES The Grand Challenge required visualization of economic losses and casualties in multi-event scenarios, which FEMA’s HAZUS does not sup- port. We could compute HAZUS losses for each event independently, but this would potentially double count losses in certain circumstances (e.g. knocking down the same building twice) and undercount losses in others (ignoring cumulative damages from multiple events). Instead, we im- plemented three methods which combined Combined: Value Greater ShakeMap data for multiple events overlapping in Puente Hills M7.1 Fault both geographical location and time: greater val- ue(GV), root sum of squares (RSS), and total sum (TS). We present results with RSS combined shakemaps as they represent a middle ground Combined: RSS between the two extremes. Whittier Fault M7.1 Combined: Total Sum Sum Total Combined: MULTIPLE EVENT SCENARIOS Sequence 1 Sequence 2a Sequence 2b Sequence 3 Big Bend SAF Mojave SAF Mojave Section and SAF Mojave section and South San Gregorio Fault Section, Central/East SAF Carrizo Plain West Garlock Fault and North Coast SAF Garlock Fault and Pana- Combined magnitude: 7.6 Combined magnitude: 7.7 (Bay Area) mint Valley Combined magnitude: 7.8 Combined magnitude: 7.7 .