Ecuador, Peru, and Colombia faults hint where large earthquakes could strike

By David Jacobson, Temblor

See the new faults

south-america-fault-map-peru-ecuador-colombia
Temblor fault map of Ecuador, Peru, and Colombia showing the last 30 days of earthquakes.

 

On Monday, we posted a blog about how we just added faults for approximately 50 countries. Now, that number has grown even more, with the addition of several countries in northwest South America, including Colombia, Ecuador, Peru, and many more. The source, known as the Active Tectonics of the Andes (ATA) database, comes from a group of researchers at the University of Kansas, and the Instituto del Petroleo in Colombia. Fault locations are from literature, field mapping, digital elevation models, earthquakes, and the regional velocity field that was obtained from GPS studies.

Because we just added these countries, we thought we’d take a look at some of the data and how it stacks up to earthquakes in the region. In the map below, M=4.5+ earthquakes with a depth less than 70 km are shown. First, it can be seen that the region has multiple sources of seismicity, including the offshore subduction zone, and complex networks of shallow crustal faults.

South-America-Fault-Map
This map shows the faults from the ATA Database and the last year of M=4.5+ earthquakes with a depth less than 70 km. This map shows that most of the inland earthquakes occurred on faults which are now visible on Temblor.

 

Several things can be seen from this map. First, the inland earthquakes tend fall on or close to faults in the our new database on on Temblor. Secondly, in Ecuador, nearly all of the larger magnitude earthquakes in the last year occurred in the northwest corner of the country, away from the main network of inland faults. Many of these earthquakes were along the offshore subduction zone. The main exception to this is a single M=4.7 earthquake near the capital city of Quito on September 5, 2016. While this earthquake is not as large as many of those felt in the region, light to moderate shaking was felt in the capital, in which over 1.5 million people live. In the figure below, you can see a Temblor map of Ecuador with the faults shown. Additionally, the Global Earthquake Activity Rate (GEAR) model is turned on, which shows the likely earthquake magnitude in your lifetime anywhere on earth.

Ecuador-Fault-Map
Temblor map of the western part of Ecuador. This map shows faults and the last 30 days of earthquakes. Additionally, the Global Earthquake Activity Rate (GEAR) model shows the earthquake magnitude likely in your lifetime anywhere on earth.

 

Being able to see where faults are is extremely important to earthquake-prone regions like this for the simple reason that earthquakes occur on faults, and large earthquakes occur on large faults. So, being able to identify the faults around you allows you to understand where earthquakes could occur.

Colombia-Fault-Map
Temblor map of the western part of Colombia. This map shows faults and the last 30 days of earthquakes. Additionally, the Global Earthquake Activity Rate (GEAR) model shows the earthquake magnitude likely in your lifetime anywhere on earth.

 

While we have just posted this database, if any local organizations have more updated maps, we would gladly amend our website to better reflect the active tectonics of the region.

 

Sources
Veloza et al., 2012 GSA Today (ATA Database)
USGS

  • RasInNm

    It is taken as almost a tautology that earthquakes occur on faults and faults are delineated by seismicity, but curiously enough, seismicity catalogues are not often linked to fault maps, and vice versa. They may be plotted on the same map, but one is hard pressed to find a data base that assigns events to faults or expedites finding all events for a given fault. When I was on staff at USC just prior to the formation of SC/EC, I pushed hard for support to build such a database for eq’s in Southern California and the LA Basin in particular. So, I am very happy to see your fault maps and your seismicity plots and wonder if you have any interest or intention of linking the two. I am now retired from Los Alamos National Lab where I worked in scientific visualization and uncertainty quanitification, but still I retain my primary focus (unavoidable pun) on making better sense of seismicity than we have. As to my credentials, I got my PhD in geophysics at Princeton in 1977 under Tony Dahlen and Tom Jordan. I look forward to your response.

    • Ross Stein

      It’s very difficult to assign all but large quakes to mapped faults. High resolution ‘double-difference’ earthquake relocations often reveal that seismicity very close to major faults is instead occurring on minor or secondary faults. So, we have a long way to go.

      • RasInNm

        Ross,
        Thank you so much for your prompt and thoughtful response. If we substitute fault systems for fault and think of faults as a hierarchical system, the issue of secondary faults is moot. We only see faults as they are expressed on the surface or along scarps, thus suggesting that faults are actually narrow physical regions. How narrow is one of the concepts I would hope to quantify. I would propose that the whole process be an iterative one, starting with guessing a fault plane based on a combination of fault mechanisms and plane fitting, followed by a relocation using a constrained optimization that penalizes locations outside the plane or gauge region. I am very familiar with constrained optimization having applied it to moment tensor inversion that forced the solution to be a double couple (strelitz, 1977). In a later paper in GJRAS I showed that the non double couple components could be used to look at rheological changes in the very near source region.

        What is the structure of your catalog of faults? Is it amenable to a deep learning approach to labeling events? Is there a computer ready source of arrival times (I remember using the blue ISC summaries of events and arrivals as a first cut in my study of deep focus eqs and then carefully editing it to remove horrible picks).

        Perhaps I should reveal my self and my sympathies. No doubt you’ve identified me as Richard Strelitz, PhD, Princeton 1977. I’ve done a lot of interesting science since then, working for everyone from NASA, EPA, and FDA, until I finally wound up at LANL where I pursued by interest in uncertainty quantification and the limits of inference. I retired last year due in no little part to the health issues that arise from the thin air of Northern New Mexico after decades in the corrosive atmosphere of NYC and Pasadena. At present, I call Little Rock, AR home and am affiliated with McData, Inc, a big data/deep learning consultancy based in China. My lifelong interest lies in trying to answer the fundamental question of epistemology “How do we know what we know”, especially as applied to earthquakes and as such, I am attracted to the stance of skepticism about so-called characteristic earthquakes and any attempt to apply essentially empirical patterns to earthquake prediction.
        Once again, thank you for your time and response. I hope that this overly long note piques your interest and begins a possible collaboration.