Seismologist Says San Diego Fault Line Is Hundreds of Years Away From an Earthquake

The Rose Canyon fault line starts near Mission Valley and heads north toward La Jolla where it joins other faults

After two major earthquakes rocked Southern California over the holiday weekend, many looked to one of San Diego’s own fault lines as a potential threat -- but one seismologist says that’s hundreds of years away.

Drake Singleton is a Ph.D. candidate at San Diego State University whose thesis focuses on the Rose Canyon Fault, which runs through some of San Diego’s most populated areas.

Singleton’s work is helping to determine how fast the Rose Canyon is moving at depth -- an important parameter to accurately characterize the seismic hazard for San Diego.

Several years ago, Singleton was part of a team that created a so-called “paleoseismic trench” in Old Town’s Presidio Park. He estimated earthquakes occur on the fault line every 700 years, on average -- and that the last earthquake struck in the mid-1700s.

“The Rose Canyon fault line, based on the data that we have, looks like it’s right in the middle of its cycle and not toward the later. I would say the seismic hazard is lower than other faults in California, but still there,” Singleton told NBC 7.

He said there is a lower seismic hazard compared to the San Andreas and San Jacinto fault lines. But he also added the Rose Canyon Fault could potentially have a maximum magnitude in the high 6s -- or possibly a 7.

“A lot of major freeways cross the fault zone, so there would be disruption to travel as well as damaged water pipes, that sort of thing,” said Singleton.

The San Diego County Office of Emergency Services, using a FEMA disaster evaluation model, put together estimated damage figures based on a 6.9 magnitude earthquake along the Rose Canyon fault line.

Costs would include $1,094,267,000 in structural damage, $5,317,666,000 in non-structural damage, and $1,972,043,000 in contents damage.

  • Non-Structural Damage: mechanical and electrical equipment, piping and elevators, partitions and exterior walls, ornamentation and glass
  • Contents Damage: furniture, computers, lighting, fixtures, etc.

Additionally, the county estimated that 122 to 292 people would be hospitalized, 1,307 to 1,720 would need basic first aid care, and somewhere between 12 and 57 people would die.

In 2001 the City of San Diego identified 858 buildings to be unreinforced masonry (URM) buildings, subject to the City of San Diego’s Retrofit Ordinance.

The buildings were constructed before 1939 and had at least one-load bearing wall constructed of brick or with hollow clay tile. Over the past several years, the San Diego Development Services Department gained voluntary compliance for the majority of the identified URM buildings.

  • 62% (530 buildings) have been partially or completely retrofitted
  • 20% (173 buildings) were demolished
  • 16% (137 buildings) were subsequently re-evaluated and determined not to be URM buildings
  • 2% (18 buildings) still need to be retrofitted and are being prepared for further enforcement

The county also determined there were 23 commercial URMs in the unincorporated parts of San Diego.

“We all live in earthquake country in California, so you should be prepared for an earthquake, but compared to other faults in California, San Diego has a lower seismic hazard,” said Singleton.

To view potential earthquake, wildfire, flooding, or tsunami hazards near you, visit Ready San Diego’s website.

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