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Getting real about earthquakes in Arizona: AZGS at work for Arizona

On the evening of 1 Nov. 2015, residents of the Phoenix Metro area were rudely awakened when a magnitude 4.1 earthquake shook the valley. According to the Arizona Republic, and numerous other Phoenix-based media outlets, people across the Valley of the Sun felt a sharp jolt followed by several seconds of ground shaking. There were no reports of injuries or damage. That modest earthquake generated the sort of media attention that might normally accompany a punishing magnitude 5 or 6 earthquake. But as with real estate sales, it’s all about location.

The mainshock was situated 11miles NNE of Black Canyon City at a depth of 6.8 miles; approximately 30 miles north of downtown Phoenix. The earthquake was felt at Camp Verde to the north, and Casa Grande to the south.

Arizona experiences about 100 earthquakes annually, most go unfelt. Since April 2010, Arizona communities reporting felt earthquakes, include: Yuma, Duncan, Grand Canyon Village, Prescott, Sedona, Tucson, and Phoenix, to name just a few communities.

The largest earthquake to shake Arizona occurred in May 1887. The epicenter of the magnitude (M) 7.5 earthquake was south of Douglas in Sonora, Mexico. The ground surface was ruptured for 62 and nearly 60 people were killed by collapsing buildings. Ground shaking in Tucson knocked people off their feet (Dubois & Smith, 1980). Dislodged boulders rolled down the slopes of the Santa Catalina Mountains and other mountains ranges in southern and southeastern Arizona. And reports of moderate to severe shaking ranged from Yuma in the west, east to Albuquerque, and south to Mexico City.

Though infrequent, large magnitude earthquakes of M6.0 to M7.0+ occur in Arizona. The impact or socio-economic intensity of future events rests largely on the state of Arizona preparedness. It is likely that a well-prepared and resilient community will roll (pun intended) with the punch.

Role for AZGS in seismic monitoring and outreach.  As the State’s geological survey, we take earthquakes and earthquake hazards seriously. Since 2009, we have increasingly engaged in a statewide seismic monitoring program and earthquake outreach regarding the nature and geologic hazards of damaging earthquakes in Arizona.

This past week the Federal Emergency Management Agency (FEMA) awarded AZGS with a grant of ~ $31,000 for earthquake programming. As required by the National Earthquake Hazard Reduction Program (NEHRP), AZGS will match that grant dollar-for-dollar, thereby providing $62,000 to power our earthquake research and outreach in 2018.

AZGS NEHRP Grant Objectives

Using NEHRP and matching funds, we have identified two areas of research and outreach to improve existing hazard models and outreach efforts.

Research: We’ll revisit and enhance existing earthquake impact simulation models for Yuma and Prescott. These models stem from a natural hazard analysis tool, Hazus, provided by FEMA to ‘estimate damage and loss of buildings, lifelines and essential facilities from scenario and probabilistic earthquakes.’

  • Results from this work will be shared with civil authorities and emergency management services in Yuma, Prescott and surrounding communities.   
  • AZGS research scientist Jeri Young will run two statewide HAZUS simulations implementing improved statewide datasets and make the results public via the Natural Hazards in Arizona Viewer.
  • Run Flagstaff HAZUS loss-estimate maps and tables, and provide the Flagstaff-area emergency managers, city and county planners, and civil authorities.

Outreach:  We will improve and aggressively promote AZGS’ earthquake outreach program and associated web resources for all of our Arizona stakeholders – county, tribal, and municipal authorities, the emergency management community, the education community, health and geriatric providers, businesses, industry, and the Arizona public.

  • Organize, stage, and host the Great Arizona Shakeout 2017 and 2018 in collaboration with: Arizona Dept. of Emergency Management and Military Affairs (DEMA); Arizona County & Tribal emergency managers; municipal emergency managers; Arizona Red Cross; Arizona K-12 school districts; business and industry. 
  • Work with print, TV and social media throughout Arizona to promote Great Arizona Shakeout 2017 & 2018.
  • Improve the earthquake and fault themes at the Natural Hazards in Arizona viewer by incorporating a temporal search component to the earthquake epicenter theme. 
  • Throughout the year, deploy posts at AZGS social media sites promoting earthquake awareness.
Contributed by M. Conway and J. Young.