Sunday, August 26, 2012

Salton Sea Quake Activity Spikes With Large Swarm

A large earthquake swarm is occurring in the Salton Sea area just NW of Brawley, CA. The largest event so far has been a mag 5.4 tremblor which I personally felt at my home in San Diego. I am currently watching the action happen on the USGS site, and my real time Google Earth plugin. USGS reports the quakes at shallow depths of 13km (at the deepest) to <1km at the shallowest. The swarm has generated over 25 quakes at this time and is ongoing, with quakes actually getting more powerful at this time. Within one hour there were one 4.9, two 4.5 quakes, a 4.3, two quakes of 5.3 mag, plus many mag 1.0-3.9 quakes. Many smaller tremors are occurring.

*****UPDATE***** another 5.5 quake struck the same area.

The center of the activity is quite concentrated on the fault line that runs through Brawley and the Salton Sea (Salton Buttes) area. This area does have active geothermal prospecting, as well as a history of volcanic eruptions, although it has not occurred during historical time.

As these quakes are currently happening there is no data to suggest whether or not the quakes are purely tectonic, or possibly volcanic in nature. The area sees a large number of earthquakes each year, however this swarm is particularly intense for the region.

The region was shaken in 2010 by a large 7.4 magnitude earthquake centered near the Cerro Prieto volcano in Northern Mexico. The area has seen a rise in the number of very small quakes since then.

I will update this story as more info becomes available through USGS and other news media.

Below is a screen cap of the current state of the swarm, with the largest quake highlighted.

Here are some links form local news about the quakes, I will add these links as they become available.


In a statement form USGS, they stated:

“[The Brawley Seismic Zone] is a broad zone with lots of little faults,” explained Abbott.“This area has clearly activated. We will likely experience swarms of 3, 4 and 5-magnitude [earthquakes] but they are not likely to increase in intensity. Of course, there are no guarantees on this, but history says they likely won’t get bigger – that we will experience more of the same or smaller quakes,” he added.

Source: SoCal Rattled by Quake Swarms | NBC 7 San Diego 

Here is the current list of quakes in the swarm (from USGS)

2.75km N of Brawley, California33.027°N115.532°W11.8
2.54km NW of Brawley, California33.005°N115.565°W12.4
3.86km N of Brawley, California33.038°N115.527°W12.4
3.64km SE of Westmorland, California33.005°N115.591°W14.3
3.66km W of Brawley, California32.973°N115.599°W8.5
2.92km NW of Brawley, California32.998°N115.549°W0.3
2.95km W of Brawley, California32.970°N115.588°W12.9
2.84km N of Brawley, California33.022°N115.536°W10.0
2.52km W of Brawley, California32.974°N115.561°W1.4
2.73km N of Brawley, California33.013°N115.536°W0.0
3.95km SSE of Westmorland, California32.986°N115.603°W11.8
4.37km NE of Brawley, California33.033°N115.479°W12.1
2.85km N of Brawley, California33.026°N115.524°W11.9
2.95km WSW of Brawley, California32.959°N115.585°W0.0
3.65km WNW of Brawley, California32.997°N115.587°W11.4
3.14km WSW of Brawley, California32.966°N115.577°W13.7
3.22km N of Brawley, California33.005°N115.534°W9.2
3.57km ENE of Brawley, California33.001°N115.457°W5.1
3.44km N of Brawley, California33.020°N115.523°W9.4
5.55km NNW of Brawley, California33.024°N115.549°W9.0
2.65km NNW of Brawley, California33.030°N115.545°W12.2
2.53km N of Brawley, California33.008°N115.529°W0.8
3.15km NNW of Brawley, California33.024°N115.543°W4.7
3.017km NNW of Seeley, California32.938°N115.775°W12.2
2.83km N of Brawley, California33.009°N115.528°W9.6
2.53km NW of Brawley, California33.004°N115.553°W12.0
2.53km NW of Brawley, California33.007°N115.553°W12.0
3.45km NNW of Brawley, California33.026°N115.543°W11.9
3.54km NW of Brawley, California33.012°N115.564°W12.7
2.55km N of Brawley, California33.029°N115.535°W10.0
3.05km WNW of Brawley, California32.996°N115.582°W12.5
2.63km NW of Brawley, California33.000°N115.561°W11.1
2.57km SW of Brawley, California32.928°N115.577°W7.9
2.98km SE of Brawley, California32.934°N115.457°W3.5
2.54km NW of Brawley, California33.008°N115.559°W9.6
3.65km N of Brawley, California33.025°N115.541°W13.6
2.83km NNW of Brawley, California33.010°N115.541°W9.8
3.44km SE of Westmorland, California33.007°N115.586°W12.8
2.85km NNW of Brawley, California33.021°N115.558°W24.8
2.54km WNW of Brawley, California32.989°N115.572°W12.4
3.24km WNW of Brawley, California32.993°N115.575°W0.2
3.34km N of Brawley, California33.018°N115.530°W9.1
4.35km SSE of Westmorland, California32.990°N115.598°W13.8
2.64km WNW of Brawley, California32.998°N115.572°W7.7
3.44km ENE of Brawley, California32.995°N115.485°W7.9
4.93km NW of Brawley, California32.998°N115.559°W3.1
5.34km NNW of Brawley, California33.019°N115.546°W12.3
2.66km N of Brawley, California33.035°N115.536°W10.2
3.45km NNW of Brawley, California33.023°N115.561°W13.7
3.45km NNW of Brawley, California33.021°N115.564°W12.5
3.53km NNW of Brawley, California33.003°N115.546°W11.0
4.64km NNW of Brawley, California33.019°N115.545°W13.1
4.05km NNW of Brawley, California33.026°N115.547°W13.8
2.55km NNW of Brawley, California33.024°N115.541°W13.4
2.55km NNW of Brawley, California33.027°N115.542°W13.3
3.05km N of Brawley, California33.027°N115.538°W14.5
3.15km NNW of Brawley, California33.024°N115.546°W13.5
2.64km NW of Brawley, California33.008°N115.560°W12.2
2.74km NW of Brawley, California33.014°N115.560°W12.7
2.64km NNW of Brawley, California33.011°N115.551°W12.0
2.64km NW of Brawley, California33.010°N115.556°W12.2
2.54km NNW of Brawley, California33.017°N115.556°W12.2
3.35km NNW of Brawley, California33.023°N115.549°W13.4
2.94km NNW of Brawley, California33.017°N115.555°W12.7
2.62km NW of Brawley, California32.996°N115.548°W6.0
3.85km NW of Brawley, California33.019°N115.563°W13.2
2.54km NNW of Brawley, California33.018°N115.555°W12.4
2.53km NW of Brawley, California32.998°N115.559°W11.4
2.53km NNW of Brawley, California33.010°N115.548°W12.0
2.54km NNW of Brawley, California33.015°N115.552°W12.5

*****UPDATE 8/27/12 *****

The Earthquake swarm has subsided. The majority of the quakes occurred yesterday, and slowed down to normal regional levels by late night/afternoon. Although some geologists were saying that the fault line had 'activated' and that there will probably be thousands of similar events in the coming weeks/months, I would suspect that the main events are over and we will see maybe 10-12 smaller quakes a day until even that activity subsides.

The quakes were activated by an intersection of fault lines at the base of the San Andreas fault. The area is rife with many relatively small fault lines. The last time the area was this active was in the 1970's, and before that in the 1930's. It's starting to make a pretty neat pattern of 40-year periods of quiescence, which is probably not significant in the grand scheme of things, but something worth noting nonetheless.

As it stands, the swarm had nearly 1,000 quakes, and over 400 of them were magnitude 2.5 or greater.

As I can say from firsthand experience, the shaking in San Diego was very light, almost not noticeable. The folks out there in Brawley had some minor damage to trailers, some structures, and some things were shaken off of shelves. By and large all damage was minimal, but many reports point to scared children who did not wish to go back in their houses for the night, and I am sure many residents were a bit spooked by the frequency of the quakes. one resident said they felt like they were popping off nearly every few minutes.

So far this morning, things appear to have calmed down quite considerably. The below picture shows all the quakes from yesterday's swarm.

***** UPDATE 8/28/2012 *****

After the quake swarm, scientists are weighing in on the causes. Most scientists say this is likely just a tectonic swarm, but Julie Dutton with USGS says "In volcanically active areas, earthquake swarms often indicate imminent eruptions, Dutton said. The only potential candidates for volcanic eruptions near Brawley are the Salton Buttes, five small lava domes that flank the Salton Sea and haven't erupted in close to 10,000 years." (From

While, yes, the area has not erupted in 10,000 years, it still remains geothermally active, and the area is used for geothermal energy. Chaiten volcano in Chile blew after over 10,000 years of silence, with no warning, so the possibility does always exist, however unlikely it might be. A real indicator of an imminent eruption however would be if the swarm is sustained, and the quakes grew shallower and shallower (indicating rising magma) which did not occur in this particular case.

The quakes ranged from some 13km below the surface to nearly at the surface, in a highly randomized fashion that does not seem to point to magma intrusion in the area, but like most rift-zone volcanoes, the process is highly unpredictable. More than likely the area will not see any volcanic activity for many decades to come.


  1. Wow, this crap is crazy. Another M5+ quake. Those people in Brawley must be on pins and needles right now. I wonder too if this is caused by tectonic or volcanic forces. I'm interested to hear what the folks at the USGS are thinking about that right now. It looks like there's a good chance of a M6+ quake today or over the next few days. Stay safe out there.

  2. So far these quakes don't feel anywhere near as powerful as the 7.4 Easter quake. San Diegans are used to quakes of this size, most people don't notice them. The alarming thing is how many there are and the size of them in the swarm. The larger ones were preceded by smaller ones, which is usually the reverse of what occurs.

  3. I would really like to hear your thoughts on the Sulfuric smell today across the inland empire and fish kill that occurred a few days ago. Do you think they could be an indication of activity.

  4. To answer your question, here are the possibilities. One possibility is that the recent earthquake swarm at Brawley was related to magma dike intrusion, however to my knowledge there is no USGS source verifying this, however at least one USGS geologist stated that quake swarms like this are typically related to such an event. The other possibility is that this was purely tectonic in nature, and did not involve volcanic activity.

    If you are in the area and smelling a sulfur type smell, there are actually a lot of possibilities. One of course is that gases are escaping from volcanic activity beneath the surface. Another possibility could be a sewage spill, algae bloom within the Salton Sea, or discharge from the various geothermal power plants in the area.

    Since the Salton Buttes have not had any eruptive activity for over 10,000 years, it is unlikely, though possible, that volcanism in the area may be returning, although I personally find it to be a bit unlikely.

    90% of magmatic dike intrusions do not result in an eruption.

    If you look at this blog's archives, you can see such an event that occurred recently in Sierraville, CA, where harmonic tremor indicated deep dike intrusion, but with no surface results.

    The Brawley and Salton Sea area which is experiencing heightened seismicity is also an agricultural area, with runoff from the various farms producing many pungent odors, so it would not surprise me to learn that some chemistry is taking place...

    However, given that the region is/was prone to volcanic activity, the possibility cannot be ignored.

    The USGS California Volcano Observatory (CALVO) monitors the area, and I am sure that if either harmonic tremor or gas emission was detected, they would be the first to know. They are typically pretty good at advanced analysis of seismic signals and gaseous anomalies.

    The short answer? Probably not volcanic in nature. The 7.4 Easter quake produced some liquefaction in the Mexicali area, which spouted sulfur smelling water from tiny fissures that opened up, which is similar to what you are describing. It could simply be that mineralized and sulfuric water was ejected from the ground during the large quake swarm at Brawley, or what you are experiencing is the occasional 'Stink wave' that comes from the heavily polluted Salton Sea...

    I would keep an eye out for any USGS follow ups on this matter.

  5. This is the most recent update from USGS:

  6. I thought I would provide you the link. The Salton Sea was confirmed the source.

  7. Rotten smell wreaks havoc across Southern California! After doing some research, The Times reported this smell to be like rotten eggs. The scientists are saying it was because of a fish die-off in the Salton Sea. In the story below they say they are not sure if the swarms of quakes are tectonic or volcanic. In many cases before volcanic activity, a rotten egg smell is observed. So, With the geothermal plant in place in the Salton Sea with thermal readings from the drill sites hitting 671 Degrees Fahrenheit, could we predict that we may have some volcanic instability in the area? This area is also on two major fault lines! Are we getting the real story?

  8. Here are some VERY interesting links:


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