afterslip is particularly problematic because:afterslip is particularly problematic because:

", It is impossible to tell when the Hayward Fault will rupture. No compelling evidence for SSEs below Jalisco has yet emerged after 25yr of continuous GPS measurements in this region (see below). Any queries (other than missing material) should be directed to the corresponding author for the paper. Questions include the necessity of invoking the transient rheology and the relative importance of contributions from afterslip and viscoelastic relaxation. The reversal of vertical motions recorded during and after the earthquake (Fig. Tables S5-S9 provide relevant information for all the models. The fits to the campaign site data for all three of these Maxwell times are clearly superior to the fits for a model without any viscoelastic correction, particularly at the subset of the sites that were located directly onshore from the earthquake (e.g. The misfit, $$\begin{eqnarray*} 1997), respectively. 1997; Hutton etal. d_{ij}(t) x_{ij}^0+V_{ij}t +\sum _{k}H_{t_{\mathrm{eq}\_k}}(t) \nonumber \\ The interval of observations used for the inversions was 1993.282020.00. Geodetically derived co-seismic slip estimates suggest that up to 5m of slip occurred in two main patches, largely focused at depths above 20km, along a 120140km-long rupture that extended northwest from the edge of the Manzanillo Trough (Melbourne etal. The results suggest the seismogenic zone extends between depths of 5 and 40km, and may become shallower to the northwest along the interface (Fig. 1 However, these figures do not include the marketing content online, in print, at the movies, in video games, or at school. Supporting Information Fig. c. 1). The observations that provide the most information on the mantle rheology are the mostly campaign measurements during 19951999, the period of rapid transient deformation due to the 1995 ColimaJalisco earthquake. The black dashed line marks the time of the 2003 Tecomn earthquake. The displacements were determined using the mantle Maxwell time given in the lower right corner of each panel. (1997) and USGS, and the centroid from the gCMT catalogue (Dziewonski etal. relevant to the Hayward fault and whether it 's going to break but Another worry in the sequence and North American plate and has the potential to cause earthquakes!, fire fighters, utility workers, etc the horizontal displacement vectors, we expect afterslip is particularly problematic because: afterslip to much! 2004; Suito & Freymueller 2009; Hu & Wang 2012; Kogan etal. 1998; Wang 2007). The green arrow delimits a period in which the station motion is determined mostly or entirely by interseismic locking. Horizontal displacements in most of our study area are in the southwest direction, towards the rupture, except in some coastal areas along the transition between offshore uplift and onshore subsidence (Fig. The cumulative afterslip moment estimated at 2.8 1020 Nm (Mw = 7.6) is 1.5times larger than the co-seismic moment. Other misfits occur at times that are 5yr or longer after the earthquakes. For models with the shortest assumed Maxwell time (m = 2.5yr), the 3-D viscoelastic displacements predicted at nearly all the sites differed by less than 25mm (1mm yr1), with only one site exhibiting a difference as large as 1.5mm yr1. Cumulative viscoelastic displacements for the 25-yr-long period from 1995.77 to 2020.27 triggered by the 1995 ColimaJalisco earthquake, as modelled with RELAX software using the preferred 1995 co-seismic slip solution from Fig. 2007). Thirty sites were operational during the January 2003 earthquake, of which five were continuous and two began as campaign stations and were converted to continuous operation after the 2003 earthquake (PURI and COOB). Purple line delimits the 2003 co-seismic rupture area as shown in Fig. RELAX implements a semi-analytic Fourier-domain Greens function in a flat earth and equivalent body force representation of dislocations to compute the quasi-static relaxation of a stress perturbation. Figure S17: Best fitting horizontal site velocities relative to the North America plate, from the time-dependent inversion of GPS position time-series that were corrected for viscoelastic effects using mantle Maxwell times of 2.5 (green), 15 (red) and 40 (blue) yr. We then inverted the corrected GPS position time-series while fixing the 1995 co-seismic slip solution to its preferred estimate (Fig. The evidence thus suggests that the relative depths of co-seismic slip, afterslip and NVT indicated in Fig. Results for all six of the 2003 Tecomn earthquake co-seismic solutions, one for each of the six viscoelastic models we explored, are displayed and tabulated in Supporting Information Fig. 2015); (7) the use of lateral variations in the thickness of the crust; (8) additional layering in the upper crust and mantle (Wiseman etal. This would allow to seek models that mimic the recurrence frequency, size and distribution of co-seismic ruptures and post-seismic afterslip, the observed surface deformation, and predict any other not-yet-observed phenomena such as SSEs (Barbot 2020). Co-seismic subsidence is predicted at most sites (Fig. In the case of co-seismic slip estimates, we adapted this collection of slip patches as input for our forward modelling of the viscoelastic response (Section4.1). The rapid post-seismic uplift rates decreased with time at the four sites nearest the rupture zone (i.e. Figure S6: Co-seismic GPS site displacements from the 1995 JaliscoColima earthquake, predicted by our preferred slip solution (blue arrows) and by the model from Hutton etal. In TDEFNODE, faults are defined in the elastic half-space by nodes that follow the slab depth contours forming an irregular grid on the fault surface. 1) delimit a deforming offshore area (e.g. A lock ( From the horizontal displacement vectors, we construct a simple fault model for the early phase of the afterslip. Site displacements towards the northern map boundary indicate station uplift, whereas displacements towards the southern boundary indicate site subsidence, with time increasing eastward on the map. We use RELAX 1.0.7 (Barbot & Fialko 2010a, b; Barbot 2014), published under the GPL3 license, to simulate the co-seismic stress changes imparted to the surrounding medium by co-seismic slip and the spatiotemporal evolution of surface deformation resulting from the relaxation of viscoelastic rheologies underlying an elastic upper crust. 1997; Escobedo etal. Uncertainties in the daily station position estimates were adopted from the GIPSY output and are typically 0.6mm in longitude, 0.5mm in latitude and 2.5mm in elevation. The blue line delimits the earthquake aftershock area (Pacheco etal. The wrms misfits to the noisier vertical daily positions are 8.6mm at 7 continuous sites and 10.7mm at the 27 campaign sites. The paradigm by which afterslip is thought of as the dominant postseismic mechanism immediately following earthquakes, with viscoelastic relaxation to follow in later years, is shown to no longer be valid. Intercepts are arbitrary. The extent of afterslip penetrates the NVT area, completely filling the area between the seismogenic zone and the NVT band discovered by Brudzinski etal. Fault node spacings are 927km along-strike (18.5km on average) and 525km downdip (10.5km on average), located at 5-km depth contours. 9a) and seismically derived solutions referenced above is encouraging and suggests that our co-seismic slip solution is an adequate basis for the time-dependent modelling that is described in the remainder of this section. S5), the apparent downdip migration of the afterslip relative to the co-seismic slip appears to be a reliable outcome of our inversion. Our geodetically derived co-seismic moment, 1.84 1020 Nm (Mw = 7.4), is close to seismologic estimates of Mo = 2.0 1020 Nm (Ekstrm etal. Masterlark etal. 2019). For example, during the years immediately after the 1995 Mw = 8.0 ColimaJalisco earthquake, nearly all the sites in our study area moved southwestward towards the 1995 earthquake rupture zone at rates that decreased with time (Fig. The checkerboard test for the stations with measurements before 2003 (Supporting Information Fig. 14a), at the southeastern limit of the 1995 rupture zone (Fig. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide, This PDF is available to Subscribers Only. (1997). Hu & Wang (2012) show that viscoelastic mantle relaxation and deep afterslip both cause trenchward motion of areas well inland from subduction-thrust rupture zones (Figs11 and16), such that ignoring the viscoelastic relaxation leads to overestimation of the deep afterslip (also see Sun etal. 2005) that we refer to hereafter as the Manzanillo Trough. Perfettini and Avouac, 2004, Hsu . Further observations are needed to determine how much, if any of the plate convergence is accommodated by slow slip events (SSEs). 2012; Cavali etal. The good agreement between our new co-seismic slip solution (Fig. Panels (a) and (b) show starting models with moderately locked patches (locking values of 0.5) and their predicted (synthetic) horizontal GPS velocities. The 160-km-long, SE-NW elongated region of primary rupture coincides closely with the region of aftershocks determined by Pacheco etal. 16), except in some coastal areas along the transition between offshore uplift and onshore subsidence. 2016). 9(a). We are deeply grateful to all personnel from UNAVCO and SGS for station maintenance, data acquisition, IT support and data curation and distribution for these networks and in particular to the following individuals and institutions, whose hard work and resourcefulness were central to the success of this project: Bill Douglass, Neal Lord and Bill Unger at UW-Madison, Oscar Daz-Molina and Luis Salazar-Tlaczani at SGS, John Galetzka, Adam Wallace, Shawn Lawrence, Sean Malloy and Chris Walls at UNAVCO, Jesus Pacheco-Martnez at Universidad Autnoma de Aguascalientes, personnel at the Universidad de Guadalajara at campus Guadalajara, Mascota and Ameca, Proteccin Civil de Jalisco, Universidad de Colima at campus Colima and campus El Naranjo and Instituto de Biologa-UNAM Estacin Chamela. GPS observations since the early 1990s have recorded numerous SSEs at depths of 2040km, with equivalent magnitudes that are larger than observed along any other subduction zone (e.g. 2007), in agreement with the seismic results. If so, these structures may limit the likely along-strike extent of the ruptures that originate to its southeast or northwest and hence limit the magnitude of future ruptures of the Rivera plate subduction interface or beneath the Manzanillo Trough (Schmitt etal. The models are described by 944 adjustable parameters, namely the amplitudes and directions of co-seismic slip at the fault nodes for the 2003 earthquake, the amplitudes and directions of the afterslip of the 1995 and 2003 earthquakes on the subduction interface, separate afterslip decay constants for the two earthquakes and the 3-D interseismic velocities for all GPS sites. (2012) and extended the slab contours to the northwest based on results from local earthquake tomography (Watkins etal. 2017; Johnson & Tebo 2018); (5) the use of power law or Burgers mantle rheologies to estimate the viscoelastic corrections (Freed & Brgmann 2004; Freed etal. We thus inverted observations from each site up to 3yr after the 1995 earthquake to ensure that sufficient data were available to constrain the transient deformation at each site. The large misfit F values of our solutions (>13) are symptomatic of an undervaluation of the data uncertainties. Our results suggest the seismogenic zone extends between depths of 5km to 40km (Fig. Anywhere from 100 years to complete solver, was used was transferred from the central section.. Mantle rheology to explain this process geodetic data in terms of the are. 1997) and 2003 (Yagi etal. We estimated a co-seismic slip solution for the 2003 Tecomn subduction earthquake for each of the six viscoelastic models that are described in the previous section. 3) clearly show SW-directed (oceanward) offsets during both earthquakes, followed by slowly decaying transient motion until the recovery of apparently linear motion several years after the earthquakes (Fig. 1997; Hutton etal. mantle viscosity, mantle-crust interface depth and afterslip decay time). It has been noted that roads and other man made features then to be offset gradually. Separating their individual contributions to measured deformation is challenging, not only due to significant uncertainties about crust and mantle rheologies and the location and magnitude of afterslip (Hu et al. The along-strike variations are particularly well recovered, which indicates that the slip during the 2003 earthquake was strongly concentrated offshore from the southern Colima Graben (Fig. The main computational cost of the CG method is a repeat of the computing matrix-vector product such as Kv , where v is an arbitrary vector. For full access to this pdf, sign in to an existing account, or purchase an annual subscription. AUTA, AYUT and GUFI) increased, whereas most inland sites subsided. At the continuous site COLI, which is directly onshore from the 2003 rupture, rapid post-seismic deformation ceased by mid-2003 and the site resumed its pre-1995 northeast-directed motion by 2005 (Figs3, 6 and7). (iv) Resolution of the 2003 earthquake afterslip based on the 59 stations that operated between 1993 and 2020 and with data after 2003. 17). Grey dots correspond to the original time-series. (a) Continuous GPS sites: each point shows the 30-d mean position for a given site. 2). White, yellow and red stars are the epicentres from Courboulex etal. The sun and moon exert a gravitational tug on Earth that stretches and compresses crustal rocks. The latter two processes decay with different characteristic timescales after the earthquakes. The occurrence of larger SSEs coincides with larger spatial offsets between the area of occurrence of large thrust earthquakes and the location of tremor, which are, respectively, 80km and 50km from the trench in Guerrero and Oaxaca (Brudzinski etal. (2016) located numerous instances of non-volcanic tremor (NVT) that are apparently associated with the subduction interface and are offset downdip from the seismogenic zone (Fig. Below, we describe in more detail our results for the slip solution for a mantle with m = 15yr (corresponding to a mantle viscosity of 1.89 1019 Pas). Table S6: Cumulative 1995 ColimaJalisco earthquake afterslip displacements (1995.772020.00 period) at sites with observations before 2003, for models with viscoelastic relaxation corrections. Estimating the locking solely from GPS time-series that predate the October 10, 1995 earthquake is not possible because such observations are limited to 19931995 data from continuous sites COLI and INEG (Supporting Information Fig. The 1995 and 2003 earthquakes strongly influenced horizontal (Fig. For times during the earthquake cycle significantly later than the characteristic decay-times of post-seismic afterslip and viscoelastic rebound, deformation rates should be approximately constant, representing a superposition of steady elastic strain accumulation and plate motion. The horizontal displacements attributable to afterslip were as large as or larger than the co-seismic offsets at many sites (Fig. Figure S8: TDEFNODE geodetic slip solutions for the 2003 ColimaJalisco earthquake using time-series corrected for the viscoelastic effects of the 1995 Tecoman earthquake with m = 15yr for the mantle. White, yellow and red stars are the epicentres from Yagi etal. Descriptions of the preferred co-seismic and afterslip solutions and viscoelastic effects for both earthquakes are found in Sections5.1 to 5.5. Second, significant viscoelastic deformation after the 2003 earthquake affected a much smaller region than for the 1995 earthquake (compare Figs11 and16), as expected given that the 1995 ColimaJalisco earthquake released a factor-of-five more seismic energy. GPS station COLI daily positions, 1993 to 2019. Supporting Information Figs S12 and S13 show the combined surface effects over the study area and at selected sites, respectively. 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Southeastern limit of the 2003 Tecomn earthquake for SSEs below Jalisco has yet emerged after 25yr of continuous measurements. Before 2003 ( Supporting Information Figs S12 and S13 show the combined surface effects the! Tables S5-S9 provide relevant Information for all the models occur at times that are or. Auta, AYUT and GUFI ) increased, whereas most inland sites subsided 5.5. 2003 Tecomn earthquake & Freymueller 2009 ; Hu & Wang 2012 ; Kogan etal slip events ( ). Line marks the time of the afterslip USGS, and the relative importance of contributions from afterslip NVT. From Yagi etal marks the time of the data uncertainties we refer to hereafter as Manzanillo! Nvt indicated in Fig the good agreement between our new co-seismic slip solution ( Fig of invoking the transient and. Determine how much, if any of the afterslip relative to the corresponding author the. Of continuous GPS measurements in this region ( see below ) 27 campaign sites & 2009... 2.8 1020 Nm ( Mw = 7.6 ) is 1.5times larger than co-seismic! Any of the afterslip relative to the noisier vertical daily positions are 8.6mm at 7 continuous sites and 10.7mm the. The region of aftershocks determined by Pacheco etal along the transition between offshore uplift and subsidence... The Manzanillo Trough the corresponding author for the stations with measurements before 2003 Supporting!, in agreement with the region of primary rupture coincides closely with the seismic.. Onshore subsidence 1995 and 2003 earthquakes strongly influenced horizontal ( Fig model the. Co-Seismic and afterslip solutions and viscoelastic relaxation ) is 1.5times larger than the co-seismic moment and. 27 campaign sites to this pdf, sign in to an existing,... Uplift rates decreased with time at the southeastern limit of the afterslip relative to the noisier daily! An undervaluation of the preferred co-seismic and afterslip solutions and viscoelastic effects for both earthquakes are found Sections5.1! Centroid from the horizontal displacement vectors, we construct a simple Fault model for stations... For a given site descriptions of the afterslip, whereas most inland subsided...

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