Four earthquakes, the strongest registering 6.9 magnitude, struck the Gulf of California off Mexico's west coast Monday, according to multiple monitoring services, with no reports of damage.

The tremors caused no casualties and no major damage said Carlos Valdez, head of Mexico's National Seismological Center (SSN), which has ruled out the risk of tsunamis.

The series of quakes began with a 5.8-magnitude tremor at 10:55 am local time (1755 GMT), followed by one registering a magnitude of 6.9 five minutes later.

Two more tremors, measuring 5.0 and 5.9 magnitude, followed within an hour, according to reports by the US Geological Survey (USGS), SSN and the US Tsunami Warning Center.

USGS said the epicenter of the strongest quake was 89 kilometers (56 miles) north-northeast of Santa Isabel in Baja California, Mexico, and had a depth of 10 kilometers (6.2 miles), with a variation of plus or minus 7.1 kilometers (4.4 miles).

The Gulf of California is a small strip of ocean in between the Baja California peninsula and Sonora state. No damage was reported in either area.

Much of Baja California, Mexico's northernmost and westernmost state, is sparsely populated, filled instead with deserts and mountains. But its coast, dotted with small fishing ports, is very popular with tourists attracted to its diverse marine life.

The quakes were not felt on the other side of the gulf in Sonora state's capital Hermosillo, an AFP journalist reported, although local media reported the tremors were felt across the border in San Diego, California, where they prompted the evacuation of a downtown office building.

The Baja California cities of Tijuana and Ensenada, close to the biggest quake's epicenter, also had no reported damage, Valdez told AFP.

There appeared to be no imminent threat of tidal waves from the quakes, USGS said, although individual governments were advised to make their own decisions on whether to issue a tsunami warning.

"Earthquakes of this size sometimes generate local tsunamis that can be destructive along coasts located within a few hundred kilometers of the earthquake epicenter," it added.

"Authorities in the region of the epicenter should be aware of this possibility and take appropriate action."

But Valdez said "these events are not uncommon in this region." The tremor, he explained, is caused by tectonic plates being displaced laterally, which does not cause tsunamis.

These types of quakes therefore only produce minor damage, unlike those caused by tectonic plates pressing against one another in a more vertical fashion.