Earthquake Report: Panamá

There was just now an earthquake beneath Panamá. The major plate boundary in the region is a subduction zone (convergent plate boundary) where the Cocos and Nazca plates dive northwards beneath the Caribbean plate forming the Middle America trench (MAT).
This magnitude M = 6.1 earthquake appears to be associated with the transform plate boundary (strike-slip fault) that is formed between the Cocos and Nazca plates. I initially interpreted the earthquake mechanism (e.g. moment tensor) shows this to be a strike-slip earthquake along the Panamá fracture zone (PFZ). However, the earthquake is not currently deep enough according to the USGS Slab 2.0 data (that shows the depth of the megathrust subduction zone, or the top of the downgoing oceanic crust/slab). This is still possible, but it is also possible that this is in the upper plate, the Caribbean plate.
If this is in the upper plate (seems more probable), then there are several reasons for the temblor. Perhaps the PFZ is causing differential stress in the overriding plate (causing strike-slip faults to form subparallel to the PFZ and sister faults). Perhaps there is oblique relative plate motion, that is causing strain and slip partitioning in upper plate crustal faults. Perhaps there is some other complicated faulting in the upper plate that exists for some other reason (e.g. pre-existing structures inherited from the tectonic history). OR, it may be due to a combination of any of these possibilities. The fact that this earthquake (and a Christmas temblor in 2003) are aligned with the PFZ suggests that these quakes may be related to the PFZ. As Mr. Spock (Star Trek) would say, “fascinating.”
I have some early reports for quakes along this fz, though the quality of my reports have improved over time. See the May 2014 and January 2015 reports.
The Panama fracture zone (PFZ) has a few sister fracture zones, subparallel dextral (right-lateral) strike-slip faults that have been studied by looking at seismicity and structures of the seafloor. There was a series of large earthquakes in the region south of the MAT in 1934 (Camacho, 1991) ewith the largest magnitude quake at M = 7.5. Earthquakes in the magnitude 6 range are quite common for this system, with temblors M ≥ 6 over once a year.
After tweeting this report, Dr. Kristen Morell (assistant professor at U.C. Santa Barbara) pointed out to me that they did lots of work on the tectonics in the region for their Ph.D. research. I have added some figures from her work below. Morell shows that there are upper plate crustal faults that are associated with the PFZ. Dr. Morell uses a variety of methods to come to this conclusion, including geomorphology (always a great tool), fault mapping (and cross sections of thrust faults and folds), relative plate motions and reconstructions, exhumation analysis, etc. These articles are fundamental to our understanding in this region and we are lucky to have them.

Below is my interpretive poster for this earthquake

I plot the seismicity from the past month, with color representing depth and diameter representing magnitude (see legend). I include earthquake epicenters from 1918-2018 with magnitudes M ≥ 3.0 in one version.
I plot the USGS fault plane solutions (moment tensors in blue and focal mechanisms in orange), possibly in addition to some relevant historic earthquakes.

  • I placed a moment tensor / focal mechanism legend on the poster. There is more material from the USGS web sites about moment tensors and focal mechanisms (the beach ball symbols). Both moment tensors and focal mechanisms are solutions to seismologic data that reveal two possible interpretations for fault orientation and sense of motion. One must use other information, like the regional tectonics, to interpret which of the two possibilities is more likely.
  • I also include the shaking intensity contours on the map. These use the Modified Mercalli Intensity Scale (MMI; see the legend on the map). This is based upon a computer model estimate of ground motions, different from the “Did You Feel It?” estimate of ground motions that is actually based on real observations. The MMI is a qualitative measure of shaking intensity. More on the MMI scale can be found here and here. This is based upon a computer model estimate of ground motions, different from the “Did You Feel It?” estimate of ground motions that is actually based on real observations.
  • I include the slab 2.0 contours plotted (Hayes, 2018), which are contours that represent the depth to the subduction zone fault. These are mostly based upon seismicity. The depths of the earthquakes have considerable error and do not all occur along the subduction zone faults, so these slab contours are simply the best estimate for the location of the fault. Note how the slab contours end at the longitude of the PFZ.

    Magnetic Anomalies

  • In the map below, I include a transparent overlay of the magnetic anomaly data from EMAG2 (Meyer et al., 2017). As oceanic crust is formed, it inherits the magnetic field at the time. At different points through time, the magnetic polarity (north vs. south) flips, the North Pole becomes the South Pole. These changes in polarity can be seen when measuring the magnetic field above oceanic plates. This is one of the fundamental evidences for plate spreading at oceanic spreading ridges (like the Gorda rise).
  • Regions with magnetic fields aligned like today’s magnetic polarity are colored red in the EMAG2 data, while reversed polarity regions are colored blue. Regions of intermediate magnetic field are colored light purple.
  • We can see the roughly east-west trends of these red and blue stripes. These lines are parallel to the ocean spreading ridges from where they were formed, at the Galapagos Spreading Ridge.

    I include some inset figures. Some of the same figures are located in different places on the larger scale map below.

  • In the upper right corner is a map from Hoernle et al. (2002) that shows the general plate tectonic configuration in this region. We can see the subduction zones, the spreading ridge, and the transform faults (e.g. the PFZ).
  • In the lower left corner there is a figure that shows how the spreading ridges (extensional plate boundaries) have been offset by the fracture zones (transform plate boundaries). Note how some of the spreading ridges are inactive (Meschede and Barckhausen, 2000)
  • In the upper left corner is a large scale map showing the detailes of the magnetic anomalies as they relate to the faults in the region ((Marcaillou et al., 2006).
  • In the lower right corner is a map that shows the details of the different earthquakes during the 1934 sequence (Camacho, 1991).
  • Here is the map with a month’s seismicity plotted.


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  • Here is the map with a century’s seismicity plotted.


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  • Here is the map with the Global Earthquake Model (GEM) strain map as an overlay (Kreemer et al., 2014). Strain is a quantification of the amount of deformation of the Earth over time. Technically, it is the change in shape (length, volume) per unit time. Note how the strain is localized along the subduction zone, as well as along the PFZ.


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Other Report Pages

Some Relevant Discussion and Figures

  • Here is the tectonic overview figure from Hoernle et al. (2002).


    • Gala´pagos Islands and hotspot tracks (Cocos, Coiba, Malpelo, and Carnegie Ridges), igneous complexes in Central America with Gala´pagos geochemical affinities, and western portion of Caribbean plate. Is. is Island, S.C. is spreading
    center.

  • This is another good overview map that shows the spreading center that creates the Nazca and Cocos plates (Coates et al., 2004).


    • Map of southern Central America (dark shading) and the Panama microplate (pale shading). Darien is picked out in pale shading. Dashed lines with teeth mark zones of convergence; zippered line is Panama-Colombia suture. Very heavy dashed line marks location of Neogene volcanic arc; black circles mark Paleogene-Eocene volcanic arc. NPDB – North Panama deformed belt; SPDB – South Panama deformed belt; PFZ – Panama fracture zone. Principal Neogene sedimentary basins located by striped ovals.

  • Here is a map showing an early interpretation of the magnetic anomalies of the Panama Basin (Lonsdale and Klitgord, 1978). The following 2 figures show an example of how shipboard measurements of magnetic intensity are interpreted for the seafloor shown in this figure. The gray bands are parts of the oceanic crust that share a similar magnetic polarity and a similar range in ages. They also present their interpretations of the crustal structures in the region. Recall that this map was prepared long before we had the excellent detailed bathymetry data that we may view in Google Earth (prepared as an inversion of gravity data collected from satellites and the Space Shuttle). Many of the subsequent interpretations of the tectonics in the region is based on this initial analysis.


    • Crustal structure between Malpelo and Panama, showing 1965 to 1975 epicenters (defining present plate boundaries), magnetic anomalies, tracks of profiles shown in Figures 6 and 8, and locations of sampling sites.

  • Here is a map showing the magnetic intensity observations as recorded from research cruises (Lonsdale and Klitgord, 1978). The wiggles are shown along the ship tracklines. The next figure shows one example of these magnetic profiles and how they interpret these data into the magnetic anomaly map of the seafloor.


    • Magnetic anomalies between Malpelo and Carnegie Ridges, numbered according to time scales listed in caption of Figure 2. Note anomaly 5 to 5B sequence along long 81°W, mirrored around extinct Malpelo rift spreading center at lat 1°40’N. Magnetic anomalies on western (Costa Rica rift) segment are from Hey and others (1977). Tracks are labeled for Conrad 11.11 (CON 11) Yaloc 69 (Y 69), Iguana 3, Cocotow 2 (CCTW 2), Cocotow 3 (CCTW 3), F. Drake 3 (FD 3), and some lines of Oceanographer 70 (OC 70). Unlabeled profiles on Costa Rica rift are from Oceanographer 69; those on Malpelo rift are from Oceanographer 70.

  • Here is the profile from Malpelo Ridge to Carnegie Ridge (Lonsdale and Klitgord, 1978). They present the observations compared to their modeled results at the top and a bathymetric profile along with sediment thickness on the bottom.


    • Profile of Cocotow 3 traverse between Malpelo and Carnegie Ridges (see Fig. 4 for location). Synthetic magnetic profile was generated using reversal time scale discussed in Figure 2 caption, spreading rates indicated at top of this figure, magnetization of 4 A/m, and magnetized layer that is 500 m thick and has an upper surface that coincides with basement relief. Note that anomaly match is poor
    within 50 to 100 km of Carnegie and Malpelo Ridges. Fit could have been improved by postulating a somewhat faster spreading rate for this region, but even so, we could not achieve as good a match as for central part of profile.

  • This is the result of their analyses (Lonsdale and Klitgord, 1978). These authors prepared a tectonic reconstruction given their knowledge of crustal structures and magnetic anomaly data.


    • Tectonic reconstructions tracing inferred history of eastern Panama Basin. (A) Middle Oligocene: Farallon plate interacting with Caribbean and South American plates, just before splitting into Nazca and Cocos plates. (B) Middle Miocene: Malpelo and Carnegie Ridges are being formed by hot spot centered on Nazca plate near axis of Nazca-Cocos spreading and are being continuously separated by spreading at boundary. (C) Late Miocene: slowdown of spreading on Malpelo rift, rejuvenation of fracture zone at long 83°W, and cessation of subduction at Panama Trench. (D) Early Pliocene: continued northward migration of Cocos Ridge, stagnation of Malpelo Ridge, and uplift of Coiba Ridge near Nazca-Cocos-Caribbean triple junction. (E) Pleistocene: Cocos and Carnegie Ridges have just arrived at Middle America and Ecuador Trenches, and triple junction has jumped west from Coiba to Panama fracture zone.

  • Here is the map from Meschede and Barchkausem (2000) that shows the complexity of the spreading ridges and the fracture zones in the region.


    • Overview of the eastern Panama Basin (modified from Meschede et al., 1998). Numbers indicate the ages of oceanic crust. The distribution of extinct spreading systems is from Meschede et al. (1998). CNS = Cocos-Nazca spreading system. RSB = rough/smooth boundary.

  • Here is the figure from Camacho (1991) showing their analysis of the faults and earthquake mechanisms from teh 1934 series of earthquakes (and others too). I include their focal mechanism in the posters above.


    • Map depicting lhe southwestern Panama continental manin and lhe Panama-Coiba Fracture Zone wilh some of its characteristic focal mechanisms.

  • Here is the detailed map from Marcaillou et al. (2006) showing the ages of the seafloor for the Panama Basin (the oceanic crust near and east of the PFZ).


    • Interpretation of the pattern of crustal isochrons (Hardy 1991; Lonsdale 2005) and plate boundaries in the Panama Basin (modified from Lonsdale 2005). Earthquakes (black dots) and fault plane solution are from the Harvard University archive of centroid-moment tensor solutions. Plain lines are active spreading axis and transform faults: Costa Rica Rift (CRR) and Panama Fracture Zone (PFZ). Dashed and dotted lines are fossil spreading axis and transform faults: Buenaventura Rift (BR), Malpelo Rift (MR), Coiba Fracture Zone (CFZ) and Yaquina Graben. Possible spreading activity along Sandra Rift (SR) is still in discussion.

  • UPDATE: Here are some key figures from Dr. Morell’s research.
  • The interaction of the Cocos Ridge with the MAT appears to be a key part of the tectonics associated with the PFZ. Here is the plate tectonic map from Morell et al. (2012).
  • My original maps included left-lateral strike-slip arrows on the subduction zone east of the PFZ because I had interpreted this as likely given the obliquity of relative plate motion there, but I was unsure if this was reasonable (I had not seen any maps showing this). Given the analysis by Dr. Morell, I have replaced these arrows in the interpretive posters. Sometimes it is good to go with one’s interpretations of their observations, regardless if they find these interpretations elsewhere. Good lesson.


    • (a) Digital elevation model of the plate tectonic setting surrounding the Cordillera de Talamanca (CT), southern Costa Rica and Cordillera Central (CC), western Panama. Tectonic plates shown are the Cocos plate (CO), Nazca plate (NZ), Caribbean plate (CA), Panama microplate (PM), with plate velocities relative to a fixed CA plate [Bird, 2003; DeMets et al., 1990; DeMets, 2001; Jin and Zhu, 2004; Kellogg and Vega, 1995]. MAT, Middle America Trench; EPR, East Pacific Rise; CNS-2, Cocos-Nazca-Spreading; PTJ, Panama Triple Junction; PFZ, Panama Fracture Zone; BFZ, Balboa Fracture Zone; CFZ, Coiba Fracture Zone; NP, Nicoya Peninsula; AG, Aguacate Range; OP, Osa Peninsula; BP, Burica Peninsula; FCTB, Fila Costeña Thrust Belt; NPDB, North Panama Deformed Belt; TV, Tisingal Volcano; IV, Irazú volcano; BV, Barú volcano; YV, La Yeguada volcano; EV, El Valle volcano. Bathymetric data supplied by ETOPO1 combined from Amante and Eakins [2009], Smith and Sandwell [1997], and Ranero et al. [2003]. Topography supplied by CGIR-CSI based on NASA’s SRTM4 data set. White triangles indicate active volcanoes. Yellow dashed lines indicate on-land projection of Cocos Ridge boundaries. (b) Inset showing location of Figure 1a based on ETOPO1 data. SA refers to the South American plate. (c) Velocity triangle for Panama Triple Junction. CR represents the axis of the Cocos Ridge. Red lines denote the PM-CO and PM-NZ vectors, respectively. Numbers shown are in mm/yr.

  • This figure shows how Dr. Morell interprets how the PFZ projects beneath the upper plate (Morell et al. (2013). Note how the faults in the Fila Costeña Thrust Belt terminate where this tear is projected.


    • Map of southern Central America, showing plate tectonic setting surrounding the Panama triple junction (PTJ) and Barú Volcano based on a stable Caribbean plate (DeMets et al., 1990; Kellogg and Vega, 1995; DeMets, 2001; Bird, 2003). MAT—Middle America Trench; CO—Cocos plate; NZ—Nazca plate; CA— Caribbean plate; PM—Panama micro plate; PTJ—Panama triple junction; PFZ—Panama fracture zone; BFZ—Balboa fracture zone; CFZ—Coiba fracture zone; TV—Tisingal Volcano; OP—Osa Peninsula; BP—Burica Peninsula; VG— Valle General. Elevations are based on National Aeronautics and Space Administration’s (NASA) SRTM v4 imagery. Bathymetry is combined from ETOPO1 and Ranero et al. (2003). Thrusts and shortening estimates outlined for Fila Costeña thrust belt are combined from Sitchler et al. (2007), Fisher et al. (2004), and Morell et al. (2008). Fault traces on Burica Peninsula are from Morell et al. (2011a) and back arc is from Brandes et al. (2007). Contour interval for bathymetry is 250 m.

  • Here is a map that shows how geomorphology can be used to interpret the tectonics of a region (Morell et al., 2013). The color of the stream channel networks represents the steepness of those channels. We can interpret steeper channels to represent regions of higher (or more recent) tectonic uplift rates.
  • Note how the steeper channels are to the west of the projection of the PFZ tear, coincident with the eastern termination of the Fila Costeña Thrust Belt.


    • Map of normalized steepness (ksn) values calculated over a 0.5 km window for drainage basins >107 m2 and excluding valley bottoms for Cordillera de Talamanca and western Cordillera Central. Numbers in northeastern flank of Talamanca correspond to knickpoint numbers shown in Table 2. The locations of longitudinal profiles in Figure 7 are marked as A, B and C, respectively. Faults shown in the Fila Costeña are based on Fisher et al. [2004], Morell et al. [2008], and Sitchler et al. [2007]. Faults drawn in the Limón back arc are approximated from topographic lineaments. Location shown in Figure 1. Base map sourced from DEM draped over slope map derived from SRTM data set. Inset in upper right is simplified geologic map for Cordillera de Talamanca region based on Denyer and Alvarado [2007].

  • Here is a larger scale map showing the geological mapping or late Cretaceous, Tertiary, and Quaternary rock units, and the detailed fault mapping (Morell et al., 2009). The inset shows a shaded relief map showing some of the north-south faults in the upper plate, which are suggested to reflect the crustal response of the PFZ in the upper plate.


    • Simplified geologic map of the southeast Fila Costeña Thrust Belt in the inner forearc of Costa Rica and western Panama (see Fig. 1 for location). Combined data from Sitchler et al. (in press) and this study, revised after Kolarsky and Mann (1995) and Mora (1979). Although the thrust belt continues to the northwest, we focus on the southeast termination. Black boxes indicate location of Figs. 3 and 5. OPFZ = On-land projection of the Panama Fracture Zone. Geology is draped on 90-m DEM supplied by NASA’s SRTM-3 dataset. Stratigraphic column modified after Sitchler et al. (in press), Phillips (1983) and Fisher et al. (2004). Inset A shows shaded DEM of area in white dotted box denoting scarps visible for right-lateral faults A and B based on SRTM-3 dataset.

  • This is an even more large scale map showing strike and dip measurement of the thrust faults mapped in the above figure, as well as more details of the north-south strike-slip raults. Note how they offset some of the thrust faults with a right-lateral _dextral_sense of motion. This is the same sense of motion as the PFZ. This is probably not a coincidence!


    • Bedrock geologic map of the southeastern termination of the Fila Costeña Thrust Belt showing strike and dip measurements within thrust sheets that dip to the northeast. The southeastern termination of the thrust belt roughly coincides with the on-land projection of the Panama Fracture Zone (OPFZ, red dashed line), which is migrating to the southeast with the Panama Triple Junction. F1, F2, F3, F4, and F5 refer to thrust faults 1, 2, 3, 4 and 5, respectively. Cross-sections show locations of balanced cross-sections in Fig. 4. All fault traces and contacts are approximated. Inset index map shows figure location in red box relative to the on-land projection of the Panama Fracture Zone.

  • The following two figures show the Tertiary to recent tectonic reconstructions from Morell (2015). These reconstructions are based on relative plate motion rates as constrained by magnetic anomalies mapped in the oceanic crust, as well as GPS and plate circuit relative plate motions from other researchers (e.g. MOREVEL from DeMets et al., 2010 and others). Frist we see the Morell (2015) magnetic anomaly map, then the plate history maps.


    • Digital elevation model [Smith and Sandwell, 1997; Amante and Eakins, 2009] showing Panama Basin and seafloor magnetic anomaly data surrounding the southern Central America subduction zone [Lonsdale and Klitgord, 1978; Wilson and Hey, 1995; Barckhausen et al., 2001; Lonsdale, 2005] based on chron time scale of Cande and Kent [1995]. The 22000 m contour is shown for prominent bathymetric features in the region, including Malpelo Ridge (MaR) and Coiba Ridge (CoR). BFZ, Balboa Fracture Zone; CFZ, Coiba Fracture Zone; CNS, Cocos-Nazca spreading center; COL, Colombia; CR, Costa Rica; EC, Ecuador; GHS, Galapagos hot spot; MR, Malpelo Rift; MAT, Middle America Trench; MoR, Morgan Rift; NI, Nicaragua; PA, Panama; PFZ, Panama Fracture Zone; SR, Sandra Rift; YG, Yaquina Graben. Inset: Present day plate boundaries of Cocos (CO), Nazca (NZ), Caribbean (CA), and South American (SA) plates. East Pacific Rise (EPR) and Cocos-Nazca Spreading Center (CNS) are also shown.


    Plate reconstruction models for the Cocos (CO) and Nazca (NZ) plates relative to the Caribbean plate from 4 Ma to recent. BFZ, Balboa Fracture Zone; CaR, Carnegie Ridge; CFZ, Coiba Fracture Zone; CNS, crust derived from the Cocos-Nazca spreading center; CocR, Cocos Ridge; CoR, Coiba Ridge; CR, Costa Rica; EPR, crust derived from the East Pacific Rise; GH, Galapagos hot spot; MaR, Malpelo Ridge; MoR, Morgan Rift; MR, Malpelo Rift; PA, Panama; PFZ, Panama Fracture Zone; PTJ, Panama Triple Junction; RSB, rough-smooth boundary; SMD, seamount domain; SR, Sandra Ridge; YG, Yaquina Graben.


    Plate reconstruction models for the Cocos and Nazca plates relative to the Caribbean plate from 6 to 10 Ma. CaR, Carnegie Ridge; CFZ, Coiba Fracture Zone; CNS, crust derived from the Cocos-Nazca spreading center; CocR, Cocos Ridge; CR, Costa Rica; EPR, crust derived from the East Pacific Rise; GH, Galapagos hot spot; MaR, Malpelo Ridge; MR, Malpelo Rift; PA, Panama; PFZ, Panama Fracture Zone; PTJ, Panama Triple Junction; SMD, seamount domain, SR, Sandra Ridge; YG, Yaquina Graben.

Geologic Fundamentals

  • For more on the graphical representation of moment tensors and focal mechanisms, check this IRIS video out:

  • Here is a fantastic infographic from Frisch et al. (2011). This figure shows some examples of earthquakes in different plate tectonic settings, and what their fault plane solutions are. There is a cross section showing these focal mechanisms for a thrust or reverse earthquake. The upper right corner includes my favorite figure of all time. This shows the first motion (up or down) for each of the four quadrants. This figure also shows how the amplitude of the seismic waves are greatest (generally) in the middle of the quadrant and decrease to zero at the nodal planes (the boundary of each quadrant).


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  • Here is another way to look at these beach balls.

  • There are three types of earthquakes, strike-slip, compressional (reverse or thrust, depending upon the dip of the fault), and extensional (normal). Here is are some animations of these three types of earthquake faults. The following three animations are from IRIS.

    • Strike Slip:

    Compressional:

    Extensional:

  • This is an image from the USGS that shows how, when an oceanic plate moves over a hotspot, the volcanoes formed over the hotspot form a series of volcanoes that increase in age in the direction of plate motion. The presumption is that the hotspot is stable and stays in one location. Torsvik et al. (2017) use various methods to evaluate why this is a false presumption for the Hawaii Hotspot.


    • A cutaway view along the Hawaiian island chain showing the inferred mantle plume that has fed the Hawaiian hot spot on the overriding Pacific Plate. The geologic ages of the oldest volcano on each island (Ma = millions of years ago) are progressively older to the northwest, consistent with the hot spot model for the origin of the Hawaiian Ridge-Emperor Seamount Chain. (Modified from image of Joel E. Robinson, USGS, in “This Dynamic Planet” map of Simkin and others, 2006.)

  • Here is a map from Torsvik et al. (2017) that shows the age of volcanic rocks at different locations along the Hawaii-Emperor Seamount Chain.


    • Hawaiian-Emperor Chain. White dots are the locations of radiometrically dated seamounts, atolls and islands, based on compilations of Doubrovine et al. and O’Connor et al. Features encircled with larger white circles are discussed in the text and Fig. 2. Marine gravity anomaly map is from Sandwell and Smith.

  • Here is a great tweet that discusses the different parts of a seismogram and how the internal structures of the Earth help control seismic waves as they propagate in the Earth.

    References:

  • Camacho, E., 1991. The Puerto Armuelles Earthquake (southwestern Panama) of July 18, 1934 in Rev. Geol. Amer. Central, v. 13, p. 1-13.
  • Coates, A.G., Collins, L.S., Aubry, M.-P., and Berggren, W.A., 2004. The Geology of the Darien, Panama, and the late Miocene-Pliocene collision of the Panama arc with northwestern South America in GSA Bulletin, v. 116, no. 11/12, p. 1327-1344, doi: 10.1130/B25275.1;
  • Frisch, W., Meschede, M., Blakey, R., 2011. Plate Tectonics, Springer-Verlag, London, 213 pp.
  • Hayes, G., 2018, Slab2 – A Comprehensive Subduction Zone Geometry Model: U.S. Geological Survey data release, https://doi.org/10.5066/F7PV6JNV.
  • Hoernle, K., van den Bogaard, P., Werner,R., Lissinna, B., Hauff, F., Alvarado, G., Garbe-Schönberg, D., 2002. Missing history (16–71 Ma) of the Gala´pagos hotspot: Implications
    for the tectonic and biological evolution of the Americas in Geology, v. 30, no. 9, p. 795-798
  • Kreemer, C., G. Blewitt, E.C. Klein, 2014. A geodetic plate motion and Global Strain Rate Model in Geochemistry, Geophysics, Geosystems, v. 15, p. 3849-3889, https://doi.org/10.1002/2014GC005407.
  • Lonsdale, P. and Klitgord, K.D., 1978. Structure and tectonic history of the eastern Panama Basin in GSA Bulletin, v. 89, p. 981-999
  • Morell, K. D., Fisher, D.M., Gardner, T.W., 2008. Inner forearc response to subduction of the Panama Fracture Zone, southern Central America in EPSL, v. 268, p. 82-85, http://doi.org/10.1016/j.epsl.2007.09.039
  • Morell, K. D., Kirby, E., Fisher, D. M., and van Soest, M. 2012. Geomorphic and exhumational response of the Central American Volcanic Arc to Cocos Ridge subduction in J. Geophys. Res., v. 117, B04409, https://doi.org/10.1029/2011JB008969.
  • Morell, K. D., Gardner, T.W., Fisher, D.M., Idleman, B.D., and Zellner, H.M., 2013. Active thrusting, landscape evolution, and late Pleistocene sector collapse of Barú Volcano above the Cocos-Nazca slab tear, southern Central America in GSA Bulletin, v. 125, no. 7/8, p. 1301-1318 https://doi.org/10.1130/B30771.1
  • Morell, K. D., 2015. Late Miocene to recent plate tectonic history of the southern Central America convergent margin in Geochem. Geophys. Geosyst., v. 16, p. 3362–3382, https://doi.org/10.1002/2015GC005971.
  • Meyer, B., Saltus, R., Chulliat, a., 2017. EMAG2: Earth Magnetic Anomaly Grid (2-arc-minute resolution) Version 3. National Centers for Environmental Information, NOAA. Model. https://doi.org/10.7289/V5H70CVX
  • Marcaillou, B., Charvis, P., and Collot, J.-V., 2006. Structure of the Malpelo Ridge (Colombia) from seismic and gravity modelling in Mar Geophys Res., DOI 10.1007/s11001-006-9009-y
  • Meschede, M., and Barckhausen, U., 2000. Plate tectonic evolution of the Cocos-Nazca spreading center in Silver, E.A., Kimura, G., and Shipley, T.H. (Eds.), Proc. ODP, Sci. Results, 170: College Station, TX (Ocean Drilling Program), p. 1–10
  • Müller, R.D., Sdrolias, M., Gaina, C. and Roest, W.R., 2008, Age spreading rates and spreading asymmetry of the world’s ocean crust in Geochemistry, Geophysics, Geosystems, 9, Q04006, https://doi.org/10.1029/2007GC001743

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