Papers by Jaime CAMPOS M.
12 13 Abstract: 14 The subduction in Chile is very active with in average a Mw 8 event every ten ... more 12 13 Abstract: 14 The subduction in Chile is very active with in average a Mw 8 event every ten years along the coast. 15 This activity is the result of the fast convergence (~ 7 cm/yr) of the Nazca plate subducting under the 16
Frontiers in Earth Science, 2020
Geophysical Research Letters, 2016
W phase moment tensor inversion has proven to be a reliable method for rapid characterization of ... more W phase moment tensor inversion has proven to be a reliable method for rapid characterization of large earthquakes. For global purposes it is used at the United States Geological Survey, Pacific Tsunami Warning Center, and Institut de Physique du Globe de Strasbourg. These implementations provide moment tensors within 30-60 min after the origin time of moderate and large worldwide earthquakes. Currently, the method relies on broadband seismometers, which clip in the near field. To ameliorate this, we extend the algorithm to regional records from high-rate GPS data and retrospectively apply it to six large earthquakes that occurred in the past 5 years in areas with relatively dense station coverage. These events show that the solutions could potentially be available 4-5 min from origin time. Continuously improving GPS station availability and real-time positioning solutions will provide significant enhancements to the algorithm.
Nonlinear Processes in Geophysics, 2015
We study the main parameters of earthquakes from the perspective of the first digit phenomenon: t... more We study the main parameters of earthquakes from the perspective of the first digit phenomenon: the nonuniform probability of the lower first digit different from 0 compared to the higher ones. We found that source parameters like coseismic slip distributions at the fault and coseismic inland displacements show first digit anomaly. We also found the tsunami runups measured after the earthquake to display the phenomenon. Other parameters found to obey first digit anomaly are related to the aftershocks: we show that seismic moment liberation and seismic waiting times also display an anomaly. We explain this finding by invoking a selforganized criticality framework. We demonstrate that critically organized automata show the first digit signature and we interpret this as a possible explanation of the behavior of the studied parameters of the Tohoku earthquake.
Journal of Geophysical Research: Solid Earth, 2015
Many efforts have been made to quickly estimate the maximum runup height of tsunamis associated w... more Many efforts have been made to quickly estimate the maximum runup height of tsunamis associated with large earthquakes. This is a difficult task because of the time it takes to construct an accurate tsunami model using real-time data from the source. It is possible to construct a database of potential seismic sources and their corresponding tsunami a priori. However, such models are generally based on uniform slip distributions and thus oversimplify the knowledge of the earthquake source. Here we show how to predict tsunami runup from any seismic source model using an analytic solution that is specifically designed for subduction zones with a well-defined geometry, i.e., Chile, Japan, Nicaragua, and Alaska. The main idea of this work is to provide a tool for emergency response, trading off accuracy for speed. The solutions we present for large earthquakes appear promising. Here runup models are computed for the following: the 1992
Nonlinear Processes in Geophysics Discussions, 2015
We study main parameters of earthquakes from the perspective of the first digit phenomenon: the n... more We study main parameters of earthquakes from the perspective of the first digit phenomenon: the nonuniform probability of the lower first digit different from zero compared to the higher ones. We found that source parameters like coseismic slip distributions at the fault and coseismic inland displacements show first digit anomaly. We also found the tsunami runups measured after the earthquake to display the phenomenon. Other parameters found to obey first digit anomaly are related to the aftershocks: we show that seismic moment liberation and seismic waiting times also display an anomaly. We explain this finding by invoking a self-organized criticality frame. We show that critically organized automata show the first digit signature and we interpret this as a possible explanation of the behavior of the studied parameters of the Tohoku earthquake.
Physics of the Earth and Planetary Interiors, 2002
We study the possible seismic gap in the Concepción-Constitución region of south-central Chile an... more We study the possible seismic gap in the Concepción-Constitución region of south-central Chile and the nature of the M = 7.8 earthquake of January 1939. From 1 March to 31 May 1996 a seismic network of 26 short period digital instruments was deployed in this area. We located 379 hypocenters with rms travel time residuals of less than 0.50 s using an approximate velocity distribution. Using the VELEST program, we improved the velocity model and located 240 high precision hypocenters with residuals less than 0.2 s. The large majority of earthquakes occurred along the Wadati-Benioff zone along the upper part of the downgoing slab under central Chile. A few shallow events were recorded near the chain of active volcanos on the Andes; these events are similar to those of Las Melozas near Santiago. A few events took place at the boundary between the coastal ranges and the central valley. Well constrained fault plane solutions could be computed for 32 of the 240 well located events. Most of the earthquakes located on the Wadati-Benioff zone had "slab-pull" fault mechanism due to tensional stresses sub-parallel to the downgoing slab. This "slab-pull" mechanism is the same as that of eight earthquakes of magnitude around 6 that are listed in the CMT catalog of Harvard University for the period 1980-1998. This is also the mechanism inferred for the large 1939 Chilean earthquake. A very small number of events in the Benioff zone had "slab-push" mechanisms, that is events whose pressure axis is aligned with the slab. These events are found in double layered Wadati-Benioff zones, such as in northern Chile or Japan. Our spatial resolution is not good enough to detect the presence of a double layer, but we suspect there may be one.
Geophysical Journal International, 2010
Geophysical Journal International, 2010
We study a large M w = 7.6 earthquake that occurred on 2007 November 14 in the Northern Chile sei... more We study a large M w = 7.6 earthquake that occurred on 2007 November 14 in the Northern Chile seismic gap near the city of Tocopilla. Using a variety of seismic data we show that this earthquake ruptured only the lower part of the interplate seismic zone and generated a series of plate interface aftershocks. Two large aftershocks on 2007 November 15 ruptured the interplate zone oceanwards of the Mejillones Peninsula, a major geographical feature in the Antofagasta region. On 2007 December 16, a large M w = 6.8 aftershock, that occurred near the southern bottom of the fault plane of the main event, is shown to be a slab-push earthquake located inside the subducted Nazca Plate and triggered by along slab compression. Aftershocks of this event demonstrate that it occurred on an almost vertical fault. The Tocopilla earthquake took place just after the installation of a new seismological network by Chilean, German and French researchers. The accelerometric data combined with far field seismic data provide a quite complete and consistent view of the rupture process. The earthquake broke a long (130 km) and narrow (about 30-50 km) zone of the plate interface just above the transition zone. Using a non-linear kinematic inversion method, we determined that rupture occurred on two well-defined patches of roughly elliptical shape. We discuss the consequences of this event for models of gap filling earthquakes in Chile proposed in the 1970s.
Science, 2010
It has been known for 10 years that the site of the Maule mega-earthquake of 27 February 2010 was... more It has been known for 10 years that the site of the Maule mega-earthquake of 27 February 2010 was fully locked and ready to break.
Unlike inertial sensors, GPS should reliably record both the dynamic (far-field) and static (near... more Unlike inertial sensors, GPS should reliably record both the dynamic (far-field) and static (near-field) displacements because of earthquakes. In 2002, high-rate (1-Hz and higher) GPS was first used to measure seismic waves from a large earthquake (M7.9 Denali); but nearly all the stations were in the far field. In 2004, the dense GPS network (GEONET) on Hokkaido measured large displacements
The 2010 Maule earthquake is one of the largest events ever recorded with modern instruments. We ... more The 2010 Maule earthquake is one of the largest events ever recorded with modern instruments. We used the continuous GPS (cGPS) records to invert for the kinematic rupture process using an elliptical sub-patch approximation. In agreement with previous inversions, the largest slip is found in the northern part of the rupture zone. By cross-correlating signals from cGPS and strong motion records (SM) located in the northern part of the rupture zone, we identified two distinct seismic pulses. Using the arrival time of these pulses, we propose a short-period (<20 s) rupture process, the zone where these pulses are generated is situated near 35.5°S, in agreement with the area with the highest seismic slip and maximum observed intensity. Finally, we compare the strong motion records at the same sites for the 1985 M w 8 Valparaíso earthquake and the Maule earthquake. We found that spectral contents and duration of the records of these two events were very similar. Thus, at least in the northern part of the rupture, the Maule earthquake radiated high frequency waves like an M w 8 earthquake.
Three campaigns of Global Positioning System (GPS) measurements were carried out in the Concepcio... more Three campaigns of Global Positioning System (GPS) measurements were carried out in the Concepcion-Constitucion seismic gap in South Central Chile in 1996, 1999, and 2002. We observed a network of about 40 sites, made of 2 east-west transects roughly perpendicular to the trench ranging from the coastal area to the Argentina border and 1 north-south profile along the coast. Data sets were processed with MIT's GAMIT/GLOBK package. Horizontal velocities have formal uncertainties around 1 to 2 mm/yr in average. Vertical velocities are also determined and have uncertainties around 2 to 5 mm/yr. We find that the convergence between Nazca and South-America plates better matches the pole previously estimated by (Larson et al, 1997) than the Nuvel-1A estimate. Our estimate predicts a convergence of 72 mm/yr at N70 to be compared with Nuvel-1A 80 mm/yr at N79. With respect to stable South America, horizontal velocities decrease from 35 mm/yr on the coast to 14 mm/yr in the Cordillera. Vertical velocities help constraint lithospheric flecture. Partionning of the slightly oblique convergence will be investigated. The gradient of convergent parallel velocities reflects aseismic elastic loading on a zone of about 400 km width. Interestingly enough, this gradient exhibit a linear pattern, marginally compatible with the expected arctangent shape. 70 mm/yr of motion accumulated since the last big event in this area (1835 Earthquake described by Darwin) represent more than 10 m of displacement. Therefore, this area is probably mature for a next large earthquake, the magnitude of which could reach 8.5.
Pure and Applied Geophysics
Bulletin of the Seismological Society of America
The large number of high-quality stations from global networks (e.g., IRIS, GEOSCOPE) allows for ... more The large number of high-quality stations from global networks (e.g., IRIS, GEOSCOPE) allows for rapid and robust recovery of source parameters of large earthquakes. We present a self-consistent analysis of surface waves in terms of directivity parameters. The boxcar is often used to recover source parameters but is rarely a faithful representation of an event's time function. We demonstrate that more reliable estimates of directivity parameters can be obtained when we take into account the source time function (STF) of the event. A low-frequency STF is obtained from first (R1) and second (R2) orbit Rayleigh waves in the range 2 to 15 mHz, with a spectral synthesis and inversion method. We measure the differential amplitudes between data and 3D synthetics. We use the R1/R2 ratio of differential amplitudes to invert, in a single narrow-frequency band, for the event's apparent rupture azimuth and velocity. For the Mw 8.1 Chile 1995 event, data are consistent with unilateral so...
International Journal of Disaster Risk Reduction
Seismological Research Letters
Seismological Research Letters
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Papers by Jaime CAMPOS M.