# The 2016 Mw 7.8 Pedernales, Ecuador, Earthquake: Rapid Response Deployment

Anne Meltzer, Susan Beck, Mario Ruiz, Mariah Hoskins, Lillian Soto-cordero, Joshua Stachnik, Colton Lynner, Rob Porritt, Daniel Portner, Alexandra Alvarado Cevallos Alvarado, et al.

► To cite this version:

Anne Meltzer, Susan Beck, Mario Ruiz, Mariah Hoskins, Lillian Soto-cordero, et al. The 2016 Mw 7.8 Pedernales, Ecuador, Earthquake: Rapid Response Deployment. Seismological Research Letters, 2019, 90 (3), pp.1346-1354. 10.1785/0220180364. hal-02202003

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The 2016 Mw 7.8 Pedernales, Ecuador,
Earthquake: Rapid Response Deployment

<table><tr><td>Item Type</td><td>Article</td></tr><tr><td>Authors</td><td>Meltzer, Anne; Beck, Susan; Ruiz, Mario; Hoskins, Mariah; Soto Cordero, Lillian; Stachnik, Joshua C.; Lynner, Colton; Porritt, Rob; Portner, Daniel; Alvarado, Alexandra; Hernandez, Stephen; Yepes, Hugo; Charvis, Philippe; Font, Yvonne; Regnier, Marc; Agurto Detzel, Hans; Rietbrock, Andreas; Leon Rios, Sergio; Diego Mercerat, E.</td></tr><tr><td>Citation</td><td>Anne Meltzer, Susan Beck, Mario Ruiz, Mariah Hoskins, Lillian Soto Cordero, Joshua C. Stachnik, Colton Lynner, Rob Porritt, Daniel Portner, Alexandra Alvarado, Stephen Hernandez, Hugo Yepes, Philippe Charvis, Yvonne Font, Marc Regnier, Hans Agurto Detzel, Andreas Rietbrock, Sergio Leon Rios, E. Diego Mercerat; The 2016 Mw 7.8 Pedernales, Ecuador, Earthquake: Rapid Response Deployment. Seismological Research Letters; 90 (3): 1346-1354. doi: https://doi.org/10.1785/0220180364</td></tr><tr><td>DOI</td><td>10.1785/0220180364</td></tr><tr><td>Publisher</td><td>SEISMOLOGICAL SOC AMER</td></tr><tr><td>Journal</td><td>SEISMOLOGICAL RESEARCH LETTERS</td></tr><tr><td>Rights</td><td>© Seismological Society of America.</td></tr><tr><td>Download date</td><td>27/09/2025 06:34:03</td></tr><tr><td>Item License</td><td>http://rightsstatements.org/vocab/InC/1.0/</td></tr><tr><td>Version</td><td>Final accepted manuscript</td></tr></table>
1 The 2016 Mw 7.8 Pedernales Earthquake, Ecuador: RAPID Response

2 Deployment

3

4 Anne Meltzerª, Susan Beckᵇ, Mario Ruizᶜ, Mariah Hoskinsª, Lillian Soto-Corderoª,

5 Joshua C. Stachnikª, Colton Lynnerᵇ, Rob Porrittᵈ, Daniel Portnerᵇ, Alexandra

6 Alvaradoᶜ, Stephen Hernandezᶜ, Hugo Yepesᶜ, Philippe Charvisᵉ, Yvonne Fontᵉ, Marc

7 Regnierᵉ, Hans Agurto-Detzelᵉ, Andreas Rietbrockf, Sergio Leon-Riosf, E. Diego

8 Merceratg

9

10 aDepartment of Earth and Environmental Sciences Lehigh University, Bethlehem, PA

11 bDepartment of Geosciences University of Arizona, Tucson AZ

12 cInstituto Geofísico at the Escuela Politécnica Nacional, Quito EC

13 dDepartment of Geosciences University of Arizona, Tucson AZ

14 now at the Institute of Geophysics, University of Texas, Austin, TX

15 eUniversité Côte d'Azur IRD, Géoazur, IRD, Nice, FR

16 fDepartment of Earth, Ocean and Ecological Sciences University of Liverpool,

17 Liverpool, UK, now at Geophysical Institute (GPI), Karlsruhe Institute of Technology,

18 Karlsruhe, Germany

19 gCEREMA Méditerranée, project team MOUVGS, Sophia Antipolis, France

20

21 Corresponding Author Anne Meltzer: ameltzer@lehigh.edu. Department of Earth

22 and Environmental Sciences, 1 West Packer Avenue, Lehigh University, Bethlehem,

23 PA, 18015, USA. +1.610.758.3673.
24 Abstract

The April 2016, Pedernales Earthquake ruptured a 100 km by 40 km segment of the subduction zone along the coast of Ecuador in an M<sub>w</sub> 7.8 megathrust event east of the intersection of the Carnegie Ridge with the trench. This portion of the subduction zone has ruptured on decadal time scales in similar size and larger earthquakes, and exhibits a range of slip behaviors, variations in segmentation, and degree of plate coupling along strike. Immediately after the earthquake, an international rapid response effort coordinated by the Instituto Geofísico at the Escuela Politécnica Nacional in Quito deployed 55 seismometers and 10 OBS above the rupture zone and adjacent areas to record aftershocks. In this article we describe the details of the US portion of the rapid response and present an earthquake catalog from May 2016-May 2017 produced using data recorded by these stations. Aftershocks focus in distinct clusters within and around the rupture area and match spatial patterns observed in long term seismicity. For the first two and a half months, aftershocks exhibit a relatively sharp cutoff to the north of the mainshock rupture. In early July an earthquake swarm occurred ~100 km to the northeast of the mainshock in the epicentral region of a M<sub>w</sub> 7.8 earthquake in 1958.

In December, an increase in seismicity occurred ~70 km to the northeast of the mainshock in the epicentral region of the 1906 earthquake. Data from the Pedernales earthquake and aftershock sequence recorded by permanent seismic and geodetic networks in Ecuador and the dense aftershock deployment provide an opportunity to examine the persistence of asperities for large to great earthquakes over multiple seismic cycles, the role of asperities and slow slip in subduction zone
47 megathrust rupture, and the relationship between locked and creeping parts of the
48 subduction interface.

49

50

51 **Introduction**

52 Subduction zone megathrust faults generate the largest earthquakes and
53 devastating tsunami. A spectrum of slip behaviors including earthquakes, non-
54 volcanic tremor, slow slip events (SSE), low-frequency earthquakes (LFE) and very
55 low-frequency earthquakes (VLFE) is observed in many subduction zones
56 contributing to the seismic cycle that ultimately culminates in large subduction zone
57 earthquakes (Bilek & Lay, 2018; Brown et al., 2009, 2013; Dragert et al., 2001; Ide,
58 2012; Lowry et al., 2001; Obara et al., 2002; Peng & Gomberg, 2010; Peterson &
59 Christensen, 2009; Rogers & Dragert, 2003; Saffer & Wallace, 2015; Schwartz &
60 Rokosky, 2007; Shelly et al., 2007; Wallace & Eberhart-Phillips, 2013). Lateral
61 variations in structure or mechanical properties in the subduction zone, roughness
62 on the down going plate, seamounts, seafloor offsets, ridges, and sediments,
63 segment the subduction zone and can act as asperities or as barriers inhibiting
64 rupture (Bangs et al., 2006; Husen & Kissling, 2002; Kodaira, 2000; Wang & Bilek,
65 2011, 2014). Features within the overriding plate, batholiths, forearc basins, and
66 faults can also influence rupture behavior (Hicks et al., 2014), and there are regions
67 in the downgoing slab as well as earthquakes in the overriding plate that may be
68 triggered by megathrust events (Sherrod & Gomberg, 2014). Linking physical
69 processes to the spectrum of deformation and understanding the interactions
70 between the range of slip behaviors and their contributions to the seismic cycle can
71 lead to improved hazard assessment and mitigation strategies (Brodsky & Lay,
72 2014; Kanamori, 2014).

73

74 On April 16, 2016 the M<sub>w</sub> 7.8 Pedernales earthquake ruptured an approximately 100
75 km long by 40 km wide section of the subduction zone offshore Ecuador (Figure 1)
76 (USGS NEIC, 2016; Nocquet et al., 2017; Ye et al., 2016). The epicentral region of the
77 mainshock lies east of the intersection of the Carnegie Ridge with the subduction
78 zone along a section of the margin where the orientation of the trench shifts from
79 ~N20°E to ~N32°E. In 1906 an M<sub>w</sub> 8.8 earthquake ruptured a 500 km section of the
80 subduction zone from the Carnegie Ridge to Colombia (Kanamori & McNally, 1982;
81 Kelleher, 1972; Mayorga & Sánchez, 2016; Yi et al., 2016) (Figure 1). Smaller
82 patches of the segment that ruptured in 1906 slipped from south to north in a series
83 of major earthquakes: M<sub>w</sub>7.8 (1942), M<sub>w</sub> 7.7 (1958), and M<sub>w</sub> 8.2 (1979) (Kanamori
84 and McNally, 1982; Mendoza and Dewey, 1984; Swenson and Beck, 1996). The
85 2016 Pedernales earthquake ruptured the same portion of the subduction zone that
86 slipped in 1942 (Ye et al., 2016; Nocquet et al., 2017). The death toll from this
87 earthquake reached over 650. Close to 30,000 people were reported injured. Over
88 85,000 people received humanitarian assistance in the recovery and reconstruction
89 phase (International Federation of Red Cross and Red Crescent Societies, 2016). The
90 coastal cities of Manta, Portoviejo and Pedernales sustained significant damage
91 (Franco et al., 2017; Goretti et al., 2017; Lanning et al., 2016; Palacios et al., 2018).
92 Economic loss and the cost of recovery and reconstruction was estimated at $3.3
93 billion, ~3% of Ecuadorian GDP (National Planning and Development Secretariat, 94 Ecuador).

95

96 The 2016 Pedernales earthquake was preceded by a M<sub>w</sub> 4.8 foreshock by 11 97 minutes. The mainshock rupture propagated from north to south parallel to the 98 subduction interface (USGS NEIC, 2016; Ye et al., 2016, Nocquet et al., 2017).

99 Coseismic slip ranged from 1-6 meters and occurred in two distinct patches 100 (Nocquet et al., 2017) at depths between 15 and 30 km (Figure 1). The rupture 101 corresponds to a zone of high interseismic coupling as measured by GPS attributed 102 to asperities in the down going plate (Chlieh et al., 2014; Nocquet et al., 2014).

103 Immediately after the mainshock rupture aseismic afterslip was observed and 104 evolved over a 25 day period (Rolandone et al., 2018). Two distinct patches of 105 afterslip, each approximately 50 x 50 km, extended updip northwest and southwest 106 of the mainshock rupture toward the trench. Cumulative afterslip and equivalent 107 magnitude for the northern patch was up to 0.7 m and M<sub>w</sub> = 7.1; for the southern 108 patch up to 1.0 m and M<sub>w</sub> = 7.0 (Rolandone et al., 2018). The earthquake also 109 triggered a slow-slip event ~100 km south of the rupture with slip up to 0.8 m and 110 equivalent moment magnitude of M<sub>w</sub> = 6.7-6.8 (Rolandone et al., 2018). These same 111 three regions have experienced slow slip earthquakes, earthquake swarms, and 112 repeating earthquakes in the past (Holtkamp et al., 2011; Segovia et al., 2018; Vaca 113 et al., 2018; Vallee et al., 2013). Within this initial 25 day period, an additional deep 114 patch of aseismic afterslip was observed downdip to the southeast of the mainshock 115 rupture at 60 km depth (Rolandone et al., 2018).
116

117 In the wake of the earthquake an international rapid response effort coordinated by

118 the Instituto Geofísico at the Escuela Politécnica Nacional (IG-EPN) in Quito

119 deployed accelerometers, seismometers, OBS, and GPS receivers to record

120 aftershocks and measure post-seismic deformation (Font et al., 2016). In this article

121 we focus on the US seismic portion of the rapid response effort using IRIS PASSCAL

122 instruments (Meltzer and Beck, 2016). These data are openly available from the IRIS

123 Data Management Center (DMC). We provide an overview of the data acquired,

124 station locations, site conditions, data quality and availability. We also discuss

125 earthquake locations determined from these data over the 12-month temporary

126 deployment and make available the earthquake catalog produced by automatic

127 processing tools using the BRTT Antelope software (http://www.brtt.com, last

128 accessed May 2017). Finally, we use this and past experience to make

129 recommendations to enhance rapid response deployments to better capture the

130 unique observations that are only possible in the wake of large to great earthquakes.

131

132

133 **The Pedernales Aftershock Deployment**

134 Within three days of the 2016 April 16 Pedernales earthquake a team from IG-EPN

135 went to the epicentral region and deployed 5 broadband and 5 dual short period –

136 strong motion sensors. Between May 9 and May 22 teams from the US (Lehigh

137 University and University of Arizona), France (Université Côte d'Azur IRD, Géoazur

138 and CEREMA), and the UK (University of Liverpool) deployed a mix of short and
139 intermediate period, and broadband sensors (Figure 1). Short period 3-component
140 OBS were deployed by IRD at the end of May. The stations in the temporary
141 aftershock deployment augment data recorded by the National Seismic Network
142 (RENSIG) (Alvarado et al., 2018).

143

144 In total, 55 temporary stations were deployed on land over a 300 km x 90 km region
145 (Figure 1). OBS deployed offshore near the trench extend lateral coverage to ~160
146 km and provide critical observations west of the mainshock and aftershock
147 sequence. Station coverage adjacent to the 2016 rupture, extends north to
148 Esmeraldas in the vicinity of the 1958 rupture, and south to Manta where slow slip
149 events and earthquake swarms are common. The temporary deployment
150 encompasses the aftershock zone of the previous 1942 (M<sub>w</sub>=7.9) earthquake and
151 the epicenter and part of the estimated rupture area of the 1906 M<sub>w</sub> 8.8 earthquake
152 in Ecuador (Figure 1).

153

154 On land, 35 broadband sensors, a mix of STS-2 (n=9), CMG-3 (n=10), and Trillium
155 Compact sensors (n=16) were deployed over the entire 300 x 90 km area covered
156 by the temporary network (Figure 1). Fourteen intermediate period (CMG-40T)
157 sensors were deployed in the central portion of the network adjacent to and south
158 of the southern end of the rupture spanning a portion of the margin where lateral
159 variation in plate coupling is observed (high to low, north to south; Chlieh et al.,
160 2014). Six short period (Lennartz LE 3D Lite) sensors were deployed in the
161 southern portion of the network adjacent to where slow slip events and earthquake
162

swarms are observed. Station spacing within the network varied from 10-20 km.

163

The distribution of sensors in part reflects coordination between the teams to limit the geographic area covered by each deployment team to speed up installation of the network (EC: north, US: north, FR: central, and UK: south). The 19 broadband stations from IRIS PASSCAL were installed May 11 through May 16 2016

164

165

166

167

predominantly in the northern part of the network with a few stations deployed in the central and southern part of the network to infill broadband coverage (Figures 1 and 2).

168

169

170

171

The majority of the stations in the temporary deployment remained in the field for 12 months. The OBS recorded data for five and a half months and were removed in mid November 2016. The 19 IRIS PASSCAL stations were demobilized in early May 2017 along with most of the on land temporary stations. Twelve of the stations deployed by IRD remained in the field into August 2017.

172

173

174

175

176

177

All stations were deployed at low elevation sites in the forearc (Figure 1). For the most part, the IRIS PASSCAL stations are far from bedrock with sensors placed in soil varying from sandy, to organic rich, to almost solid clay (Table S1 in the electronic supplement to this article). The one exception is EC19 where weathered ophiolite outcrops at the surface. By necessity, approximately a third of the stations are along the coast. Much of Esmeraldas and Manabí provinces are lightly populated, rural and agricultural with small to moderate size towns and resort areas interspersed. The majority of the stations are in rural settings (Figure S1 in the

178

179

180

181

182

183

184
electronic supplement to this article). For security, stations were located on the property of host families, generally (though not always) within proximity of houses (Table S1 in the electronic supplement to this article). The IRIS PASSCAL stations were recorded by Reftek RT130 data loggers at 100 samples per second. Each station was powered by a 12v 100 amp hour deep cycle battery and a 65-watt solar panel. Sensor vaults were simple and easy to install quickly. Sensors were placed on granite tiles, covered with an inverted plastic barrel, and buried approximately 0.5 to 1.0 meter below the surface (Figure S2 in the electronic supplement to this article).

## Data Quality and Availability

Data from the 19 IRIS PASSCAL stations were archived at the IRIS DMC and openly available after service runs in September (2016) and March (2017) and after demobilization in May (2017). The average percent data recovery for the deployment was 92.4% with individual stations ranging from 50% to 100% (Table S1 and Figure S3 in the electronic supplement to this article). The only known sensor issue at the time of the initial deployment was at EC20 where the east component was bad.

Over the course of the 12 month deployment 4 additional sensors (EC01, EC04, EC06, EC17/21) developed issues (Table S1 in the electronic supplement to this article), two stations (EC11 and EC12) developed issues with the Reftek data loggers issues, and one station EC07 had data logger and sensor cable issues. Over the
208 course of the deployment, 8 of 19 stations (42%) had issues severe enough to
209 impact data acquisition. The failure rate is in part due to environmental factors, high
210 humidity in an equatorial environment (condensation) and significant rainfall
211 during the rainy season, December through March (flooding of some vaults and
212 station boxes), but it also reflects an aging broadband pool.

213
214 Representative frequency dependent noise levels for stations in the temporary
215 deployment are included in Figure S3 in the electronic supplement to this article.

216 For the most part stations have intermediate noise levels in three period bands: 0.1-
217 1 second, 1-10 seconds, and 10-100 seconds on the vertical component. Noise levels
218 at long periods are higher on the horizontal components. Higher noise levels
219 between 1 and 10 Hz reflect high earthquake activity associated with the aftershock
220 sequence. There are no consistent differences in noise characteristics between
221 coastal vs. inland sites, soil vs. bedrock sites, or between stations located tens vs.
222 hundreds of meters from local houses or buildings.

223
224 All data from the US portion of the Pedernales earthquake aftershock deployment
225 are archived and openly available at the IRIS DMC, network code 8G (2016-2017)
226 (http://www.iris.edu/dms/nodes/dmc/). Data from France and the UK will be
227 available through Réseau Sismologique & Géodésique Français (RESIF) summer
228 2019..

229

230
231 Automatic Earthquake Catalog

232 Earthquake locations were determined for events recorded by the PASSCAL stations
233 through automatic processing using tools from the BRTT Antelope software
234 (http://www.brtt.com, last accessed May 2017). Automatic detections were picked
235 using short term average (STA) versus long term average (LTA) ratios on vertical
236 and horizontal components for P and S waves respectively (P waves: 1-10 Hz,
237 STA/LTA>4.0; S waves: 1-5 Hz, STA/LTA>4.0). Detections are associated into
238 potential earthquake arrivals using a precomputed travel time grid built with the
239 iasp91 velocity model. Hypocenter locations are determined via an iterative least
240 squares inversion of travel time residuals (Pavlis et al., 2004). Traditional Richter
241 (local) magnitude (Ml) is calculated automatically for events with a minimum of
242 three stations with a signal to noise ratio greater than 3.

243

244 The automatic catalog contains 3246 events (Figure 2). The magnitude of
245 completeness, Mc = 2.3, is estimated using the maximum curvature method
246 (Wiemer and Wyss, 2000; Wiemer and Katsumata, 1999). Using Mc = 2.3 and the
247 maximum likelihood method for calculating b-values (Aki, 1965) and magnitude
248 binning width of 0.1, results in b=0.88. Manual inspection of the automatic catalog
249 indicates that events with at least eight phases and locations errors less than 10 km
250 (using 68% confidence ellipses) are reliably earthquakes. Earthquakes were
251 detected and associated with less than 8 phases, but the number of false detections
252 or spurious signals is higher. Location errors and comparisons between the full
253 catalog and events with at least 8 phases are provided in Figures S4 and S5 in the
254 electronic supplement to this article. These formal uncertainties do not reflect any
255 bias introduced by using a 1D global velocity model in a region with 3D velocity
256 heterogeneity. The full catalog, including magnitudes and uncertainties, is included
257 in QuakeML format in the electronic supplement to this article.

258

259

260 **Initial Observations**

261 Aftershocks of the Pedernales earthquake show a clear pattern of clustering within,
262 around, and to the north and south of the rupture (Figure 2). From south to north
263 earthquake clusters are observed under the coastline north of Manta (A Figure 2),
264 updip and extending to the trench at the southern end of the rupture (B Figure 2),
265 within the rupture zone between the two patches of higher slip (C Figure 2), updip
266 at the trench and down dip of the mainshock extending beneath the coast at the
267 northern end of the rupture (D Figure 2), offshore Punta Galera 20 km north of the
268 end of the rupture and on land east of the offshore Galera cluster (E Figure 2), ~70
269 km northeast of the mainshock in the vicinity of Atacamas (F Figure 2), and ~100
270 km northeast of the mainshock at Esmeraldas (G Figure 2). The eastern down dip
271 limit of seismicity is quite sharp (Figure 2). The up dip limit is more diffuse but this
272 could change, as data from the OBS are included.

273

274 The cumulative number of events, number of events per day, and event magnitude
275 per day indicate a high rate of seismicity that gradually decays with time (Figure 3
276 and animation in the electronic supplement to this article). Superimposed on this
gradual decay are small bursts of activity, spatially focused higher rates of seismicity, lasting from several days up to a week. Higher magnitude events ($5 \le M \le 7$) are interspersed throughout the post-seismic sequence up to 9 months after the mainshock. By the end of January 2017 both the magnitude and frequency of events decay to background levels through the end of the temporary deployment. Two significant upticks in seismicity correlate with an earthquake swarm in July 2016 at Esmeraldas and a series of moderate earthquakes ($M_{I}4-5$) in December 2016 at Atacames. For the most part, both moderate to large and small magnitude events occur within the clusters (Figure 2). Notable exceptions are the cluster of events within the rupture zone between the two patches of larger slip (C Figure 2), and a cluster of events between the mainshock and the series of magnitude 6 earthquakes to the east (east end of D, Figure 2). These two areas contain only smaller magnitude events (Figure 2).

For the first two and a half months after the mainshock, earthquakes are generally restricted to Punta Galera and south (Figure 2 and animation in the electronic supplement to this article). On June 18th, a month after the mainshock, two large aftershocks, $M_{w} 6.8$ and $M_{w} 6.9$ (USGS NEIC, 2017), occurred within 8 hours of each other, beneath the coast at the northern end of the rupture in an area where interseismic plate coupling is high (Nocquet et al., 2017; Rolandone et al., 2018). In July an earthquake swarm occurred in the upper plate ~100 km northeast of the rupture beneath the town of Esmeraldas (Hoskins et al., 2018). The swarm occurred close to the southern edge of the 1958 $M_{w} 7.7$ earthquake (Figures 1 and 2). The
swarm contains events with local magnitudes up to 5 within the sequence, but is not preceded by a large magnitude event. During the July swarm at Esmeraldas, two large earthquakes (M<sub>w</sub>5.9 and M<sub>w</sub>6.3, NEIC, 2017) occurred in the earthquake cluster beneath the coast at the northern end of the rupture (Figure 2). In contrast, the uptick in seismicity in December at Atacames begins with a M<sub>w</sub> 5.2 event and contains multiple events of similar magnitude (M<sub>w</sub> 5.4, M<sub>w</sub> 4.8, M<sub>w</sub> 4.8; USGS NEIC, 2017) over the next 7-9 days. Ground shaking associated with the June 18 events and the Esmeraldas and Atacames sequences caused additional damage to buildings weakened in the main shock.

309

The general pattern of earthquake clustering from Punta Galera south was established within the first week of the mainshock (IG-EPN catalog; Rolandone et al., 2018). This clustering is also observed in the long-term catalog (from south to north the Manta, Jama, and Galera clusters; Font et al., 2013; Segovia et al., 2018; Vaca et al., 2018). These clusters outline regions of aseismic slip that evolved over a 25 day period after the mainshock (Rolandone et al., 2018), ending just as the temporary deployment was being installed. These regions continued to be the site of focused seismic activity for months and contain the majority of the magnitude 4 and larger events (Figure 2). The Galera cluster lies between the northern end of the patch of aseismic slip and a region of high interseismic plate coupling associated with Punta Galera. The Jama cluster is associated with a region of high interseismic coupling (Collot et al., 2017; Nocquet et al., 2017; Rolandone et al., 2018).

322
323 North and northeast of the rupture, toward the epicentral regions of the 1906 and
324 1958 great earthquakes, the earthquake clusters with epicenters on land trending
325 north toward Atacames align with the eastern boundary of Miocene Borbon Basin
326 (Reyes and Michaud, 2012) and a break in topography associated with uplifted
327 Miocene sediments. A series of crustal faults (e.g. Galera fault, Mache lineament, and
328 others) are mapped in this area and farther east toward Esmeraldas (Eguez et al.,
329 2003). The relationship between observed seismicity and crustal faults is being
330 explored using high precision earthquake relocation methods.

331

332 Earthquake catalogs combining data from the complete rapid response deployment
333 (EC, US, FR, and UK temporary stations) and permanent network stations have been
334 completed (Soto-Cordero et al, 2017 and in prep; Agurto et al, 2017 and in review).

335 These catalogs support the observations presented here, but reveal additional detail
336 on the temporal and spatial evolution of the sequence of events following the
337 Pedernales earthquake especially in the central and southern portions of the
338 temporary deployment. The number of events detected using stations from the
339 complete temporary array increased three fold and the magnitude of completeness
340 improved by 0.5 to M<sub>c</sub> 1.8. Preliminary joint inversion for earthquake location and
341 3D velocity structure shifts event locations within individual earthquake clusters
342 but does not shift the spatial distribution of the clusters themselves.

343

344

345 **Lessons Learned.**
346 While the seismic rapid response deployment after the Pedernales earthquake was relatively smooth and efficient, improvements in instrumentation and protocols 347 established in advance of destructive events are needed to facilitate rapid 348 deployments and field studies after large subduction zone earthquakes. Rapid 349 response deployments have the potential to uniquely capture a range of subduction 350 zone processes complementing the observations from permanent networks to shed 351 new light on rupture of megathrust earthquakes and transient processes associated 352 with these events. Real-time data from rapid response deployments can be used to 353 monitor the post seismic evolution of aftershock sequences and triggered seismicity 354 to improve aftershock forecasting and seismic hazard assessment immediately after 355 large magnitude events. Systemic changes are needed in rapid response 356 deployments in to order maximize what we can learn about earthquake rupture and 357 post-seismic response, and to reduce risk in the wake of large magnitude 358 earthquakes. 359

360

361 After a large earthquake, time is of the essence to capture the immediate post- 362 seismic response. The first stations from the international rapid response effort 363 were installed three weeks after the main shock. This reflects the time required to 364 marshal resources (financial, technical, and human), ship instruments, arrange 365 customs clearance, acquire materials and supplies, and arrange transportation to 366 the field. This time needs to be shortened to no more than 48 to 72 hours. Advance 367 planning and regional instrument pools can ensure that protocols are in place and 368 resources accessible to speed the time between event and response. Appropriate
369 robust instrumentation is needed, that can be deployed easily and quickly, and
370 operate reliably in a range of environments and site conditions. Integrated systems
371 are needed that take advantage of new options for power supply, allow for multiple
372 collocated sensors to record the full spectrum of ground motions (strong to weak),
373 include options for real time communications, and directly capture and log
374 metadata. Rapid response efforts need to adopt a system approach from instrument
375 deployment to data capture and integration, time series analysis, and data products
376 including robust earthquake locations, magnitudes, and source characterization.
377 Coordination, collaboration, and near-real time open data should be the standard for
378 all rapid response efforts.

379

380

381 **Data & Resources**

382 All data from the US portion of the Pedernales earthquake aftershock deployment
383 can be obtained from the IRIS Data Management Center,

384 http://www.iris.edu/dms/nodes/dmc/ network code 8G (2016-2017)

385 doi: 10.7914/SN/8G_2016. The full automatic catalog is included in the electronic

386 supplement to this article in QuakeML format. Maps and figures were made using

387 the Generic Mapping Tools version 5.2.1 http://gmt.soest.hawaii.edu (Wessel et al.,
388 2013).

389

390

391 **Acknowledgments**
392 The US Seismic Rapid Response deployment was supported by the NSF RAPID
393 Program Award EAR-1642498 and by the PASSCAL facility of the Incorporated
394 Research Institutions for Seismology (IRIS) through the PASSCAL Instrument Center
395 at New Mexico Tech with support from the National Science Foundation under
396 Cooperative Agreement EAR-1261681 and by the Department of Energy National
397 Nuclear Security Administration. Financial support for the international rapid
398 response effort was provided by: the Instituto Geofísico at the Escuela Politécnica
399 Nacional (IG-EPN) in Quito Ecuador; L'Institut de recherche pour le développement
400 (IRD) Géoazur at Université de la Côte d'Azur, and CEREMA France; and the Natural
401 Environment Research Council (NERC) in the United Kingdom. We thank the US
402 Embassy in Quito for expediting customs clearance for the IRIS PASSCAL instrument
403 shipment. We are grateful to Emilio Acosta, Carlos Ayol, Christian Cisueros, Marcos
404 Cordova, Pablo Cruz, Carlos Macias, Marcelo Ortiz, Daniel Pacheco, Xavier Parra,
405 Gabriela Ponce, Mónica Segovia, Daniel Sierra, Juan Carlos Singaucho, Ivan Tapa,
406 Roberto Toapanda, and Mayra Vaca from IG-EPN for their assistance with logistics
407 and fieldwork. We are also grateful to the many people of Esmeraldas and Manabí
408 provinces who allowed us to install stations on their property and made sure the
409 stations were secure during the deployment. We thank the anonymous reviewers
410 for helpful comments to improve the manuscript.

411

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656

657

658 Full mailing address for each author

659

660 Anne Meltzerª, ameltzer@lehigh.edu

661 Mariah Hoskinsª, mac716@lehigh.edu

662 Lillian Soto-Corderoª, lis213@lehigh.edu

663 Joshua C. Stachnikª, jfstachnik@gmail.com

664 ªDepartment of Earth and Environmental Sciences Lehigh University, Bethlehem,

665 PA, 1 West Packer Avenue, Lehigh University, Bethlehem, PA, 18015, USA.

666

667 Susan Beckᵇ, slbeck@email.arizona.edu

668 Colton Lynnerᵇ, colton.lynner@gmail.com

669 Daniel Portnerᵇ, portner@email.arizona.edu

670 ᵇDepartment of Geosciences University of Arizona, Tucson AZ

671

672 Mario Ruizᶜ, mruiz@igepn.edu.ec

673 Alexandra Alvaradoᶜ, aalvarado@igepn.edu.ec

674 Stephen Hernandezᶜ, hernandez.stephen@gmail.com

675 Hugo Yepesᶜ, hyepes@igepn.edu.ec

676 ᶜInstituto Geofísico at the Escuela Politécnica Nacional, Quito EC

677

678 Rob Porrittᵈ, rporritt@ig.utexas.edu

679 ᵈDepartment of Geosciences University of Arizona, Tucson AZ

680 now at the Institute of Geophysics, University of Texas, Austin, TX

681

682 Philippe Charvisᵉ, philippe.charvis@geoazur.unice.fr

683 Yvonne Fontᵉ, font@geoazur.unice.fr

684 Marc Regnierᵉ, regnier@geoazur.unice.fr

685 Hans Agurto-Detzelᵉ, agurto@geoazur.unice.fr

686 ᵉUniversité Côte d'Azur IRD, Géoazur, IRD, Nice, FR

687

688 Andreas Rietbrockf, andreas.rietbrock@kit.edu

689 Sergio Leon-Riosf, sergio.leon-rios@kit.edu

690 ᶠDepartment of Earth, Ocean and Ecological Sciences University of Liverpool,

691 Liverpool, UK, now at Geophysical Institute (GPI), Karlsruhe Institute of Technology,

692 Karlsruhe, Germany

693
694 E. Diego Mercerat, diego.mercerat@cerema.fr

695 CEREMA Méditerranée, project team MOUVGS, Sophia Antipolis, France

696

697

698 **List of Figure captions.**

699 Figure 1. Station map Pedernales earthquake international seismic rapid response.

700 Inset South America, Ecuador outlined by red box. 2016 Pedernales earthquake
701 mainshock location (white star) and coseismic slip contours from Nocquet et al.

702 (2017), coseismic slip contour 1m, maximum slip 6 m. Coastal stations from the
703 permanent national network in black, other colors in key designate temporary

704 stations. RAMP: Rapid Array Mobilization Procedure. IG-EPN: Instituto Geofísico at
705 the Escuela Politécnica Nacional, IRD: Institut de Recherche pour le Développement,

706 BB: broadband sensors, IP: intermediate period sensors, SP: short-period sensors,

707 OBS: ocean bottom seismometer. Historic earthquakes, epicenters yellow stars,
708 estimated rupture areas red dashed ellipses after Swanson and Beck (1996), Beck

709 and Ruff (1984), and Bilek (2010).

710

711 Figure 2. Earthquake epicenters and temporal sequence of events from automatic
712 catalog produced from IRIS PASSCAL stations, May 2016-May 2017, minimum of

713 eight phases and errors less than 10 km, n=2499 events. IRIS PASSCAL stations blue
714 triangles. Mainshock location and coseismic slip contours from Nocquet et al.

715 (2017), coseismic slip contour 1m, maximum slip 6 m. Slab contours every 10 km

716 depth from Slab2 (Hayes et al., 2018). Temporal sequence of events plotted by

717 latitude (vertical axis=latitude, horizontal axis = Julian Day), circles scaled and color
718 coded by magnitude: yellow M1≥6, orange 6> M1≥5, brown 5> M1≥4, red M1<4.

719 Earthquake clusters designated by letters discussed in the text. See Figure 1 for
720 topography and bathymetry scaling.

721

722 Figure 3. (a) Cumulative number of events, (b) number of events per day, and (c)

723 event magnitude per day from automatic catalog produced from IRIS PASSCAL

724 stations, May 2016-May 2017 minimum of eight phases and errors less than 10 km,

725 horizontal axis is Julian Day.. Partial data gap around jd250 due to
726 disk storage problems. Uptick in seismicity associated with Esmeraldas and

727 Atacames swarms labeled in (b).