DOI: 10.5061/dryad.573n5tbj8
title: Attenuation and velocity tomography of the northern East African Rift

description: This dataset corresponds to compressional (P) and shear-wave (S) velocity
 (V) and attenuation (q) teleseismic tomography of the MER, from rift to
 flank. This is the most comprehensive body wave travel time and
 attenuation dataset collected in the MER and Afar to date, where
 attenuation (quantified as t*) is collected using a new methodology for
 measurement and quality control of differential t* for teleseisms,
 avoiding extrinsic focusing. The resultant imaging includes the only 3-D
 attenuation tomography model of a continental rift. Together, the
 well-resolved co-located models (VP, VS, qS) help constrain the physical
 conditions within the rift through Bayesian analysis that makes explicit
 parameter trade-offs.  The northern East African Rift, including
 the Main Ethiopian Rift (MER) and Afar, have been the focus of decades of
 seismological investigations and dense broadband coverage. Sometimes
 invoked as an archetype for a narrow continental rift, the confined
 surficial extension here stands in contrast to geophysical indicators of
 an asymmetric, broad swath of perturbed mantle. Thermodynamic conditions
 in this region are challenging to pin down, with melt, temperatures, and
 perhaps volatiles playing a part in both dynamics and controlling seismic
 observables. I find that the rift is highly asymmetric, with a sharp
 eastern boundary but extensive low velocities, high attenuation, and
 implied melt organization throughout much of the western Ethiopian
 Plateau, including coincident with volcanism around Lake Tana. A
 deep-seated plume is connected to shallow rifting. Attenuation and
 velocity both imply a concentration of extensional strain along the
 western edge of the Afar triangle.
description: All details are provided in the associated manuscript.
description: # Attenuation and velocity tomography of the northern East African Rift
 [https://doi.org/10.5061/dryad.573n5tbj8](https://doi.org/10.5061/dryad.573n5tbj8) ## Description of the data and file structure ### Files and variables #### File: evinfo.mat **Description:** MATLAB file with information about the earthquake events used in the study. Not all earthquakes provided usable data.  ###### Variables * evinfo is a structure with [`norids`x1] arrays corresponding to the number of earthquakes (`norids` = "number of origin IDs"). It contains the following fields: orids (Origin IDs, simply a numerical label of the earthquake), `elats` (latitudes), `elons` (longitudes), `eldeps` (depths, in km), `evmags` (moment magnitudes), `evtimes` (origin times, in serial time format), `evtimes_IRISstrs` (origin times, in 'yyyy-mm-dd HH:MM:SS:sss' format), `datestamp` (origin time in 'yyyymmddHHMM' format). #### File: stainfo.mat **Description:** MATLAB file with information about the stations used in the study. Not all stations provided usable data.  ###### Variables * `sta` (station names), `nwk` (network codes) * slats: [553×1 double] * slons: [553×1 double] * selevs: [553×1 double] * ondate: [553×1 double] * offdate: [553×1 double] * ondate_str: {553×1 cell} * offdate_str: {553×1 cell} * nstas: 553 * nchans: [553×1 double] * chans: {553×10 cell} * chandips: [553×10 double] * chanazs: [553×10 double] * chanresps: {553×10 cell} * staunqid #### File: tomodata_dT_Pall.dat **Description:** Data text file with measured differential travel times ("dT") for P waves. This comprises all differential measurements at all stations measured for each event (organized by event) ###### Columns * % fields: rayp gcarc seaz sta nwk orid elat elon edep dT sd c_freq * ray parameter (s/deg) * great circle distance from event to station (deg) * station-event azimuth (or "back-azimuth") in deg clockwise from N * station code * network code * event identifier (integer) * event latitude (deg) * event longitude (deg) * event depth (km) * dT value (s) **this is the measured datum for this station-event combination** standard deviation (s) [*note this is estimated, and subject to some error*] centre frequency (Hz) for the filter window used in the measurement. Can vary between events, but will be the same for all measurements on a given event. #### File: tomodata_dT_Sall.dat **Description:** As for `tomodata_dT_Pall.dat` but for S-waves. #### File: tomodata_dR_Pall.dat **Description:**  As for `tomodata_dT_Pall.dat` but for differential t* measurements. The 10th column is a t* estimate (corrected to 1 Hz), also in units of seconds. #### File: tomodata_dR_Sall.dat **Description:**  As for `tomodata_dR_Pall.dat` but for S-waves. #### File: regional_bayes_inv.zip **Description:** This zip file contains `.mat` files that describe the bayesian inversion for average thermodynamic properties within regions. #### File: tomo_models.zip **Description:** Zip file containing the tomographic models of the East African Rift and its environs. There are four models: `dVmod_P`, `dVmod_S`, `dqmod_P`, `dqmod_S`, where "V" refers to velocity models (parameterised as fractional perturbations in slowness) and "q" refers to attenuation models (parameterised as fractional perturbations in 1/Q value). "P" and "S" refer to the wave type. These models and inversion information are each described by three main MATLAB structures: `model_Pall_....mat` and `par_Pall....mat`, and `data_Pall...mat`.  The first of these, `model`, contains the final model values `mval` which is an Mx1 array of perturbations, where M is the number of nodes in the model space (this value, and the locations of the nodes, are described in `par`). The `model` structure also contains the station and event static terms: `estatic` and `sstatic`, of which there are Nsta and Nevt, respectively (described in `data`). Finally, `model` contains information about the percentage variance reduction. #### File: VBR_LUT.zip **Description:** This zip file contains files associated with the the "look up table" (LUT) that links values of Vs and Qs to state variables. \ Inside this zip file, there is a MATLAB file `make_LUT_VBRc.m` that contains the code used to make these LUTs. To run this script, you will need to obtain the Very Broadband Rheology calculator package (to deal with anelasticity), and also the Abers and Hacker 2016 codes for computing stable mineral assemblages and anharmonic velocities. See "Code/software" below. Required subfunctions for this `make_LUT_VBRc.m` are in the `functions` directory within this zip file. The other directory, named `data` contains the LUT arrays as `.mat` files with the naming format `VBR_Box_XXXkm_melt.mat`, where "XXX" stands in for the three-character depth, in km. The available depths are 55, 80, 110, 140, 175, 210, 250, and 290 km. Each of these `.mat` files contains MATLAB structures that are the inputs (`in`) and outputs (`out`) of the VBRc calculation (as well as unimportant output fields `status`, `version_used` and `error_message`). The `in` structure contains state variable inputs and relevant parameters for the anelastic calculations. The `out` structure contains the computed values of anharmonic and anelastic moduli, Q, and diffusion creep shear viscosity values for the LUT. ## Code/software MATLAB [Very Broadband Rheology calculator (optional, to re-calculate LUT)](https://github.com/vbr-calc/vbr) [Abers & Hacker 2016 MATLAB toolbox](https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2015GC006171) ## Access information Other publicly accessible locations of the data: All data used for this study is openly available via the EarthScope DMC under the network codes 2H (DOI: 10.7914/SN/2H_2009), AF (DOI: 10.7914/SN/AF), XI (DOI: 10.7914/SN/XI_2000), XW (DOI: 10.7914/SN/XW_2009), Y6 (DOI: 10.7914/SN/Y6_2016), YQ (DOI: 10.7914/SN/YQ_2017), YR (DOI: 10.15778/RESIF.YR1999), YY (DOI: 10.7914/SN/YY_2013), ZF (no DOI available), G (DOI:10.18715/GEOSCOPE.G), IU (DOI:10.7914/SN/IU), GE (DOI: 10.14470/TR560404) and XJ, XM, YJ, for which no DOI is available but which are all associated with the EAGLE experiment(Bastow et al., 2011).