Geology topics

Jian Lin

Publications and source records attributed to Jian Lin.

9 recordsLinked to original sources

USGS2012

Three-dimensional modeling of pull-apart basins: implications for the tectonics of the Dead Sea Basin

We model the three-dimensional (3-D) crustal deformation in a deep pull-apart basin as a result of relative plate motion along a transform system and compare the results to the tectonics of the Dead Sea Basin. The brittle upper crust is modeled by a boundary element technique as an elastic block, broken by two en echelon semi-infinite vertical faults. The deformation is caused by a horizontal displacement that is imposed everywhere at the bottom of the block except in a stress-free “shear zone” in the vicinity of the fault zone. The bottom displacement represents the regional relative plate motion. Results show that the basin deformation depends critically on the width of the shear zone and on the amount of overlap between basin-bounding faults. As the width of the shear zone increases, the depth of the basin decreases, the rotation around a vertical axis near the fault tips decreases, and the basin shape (the distribution of subsidence normalized by the maximum subsidence) becomes broader. In contrast, two-dimensional plane stress modeling predicts a basin shape that is independent of the width of the shear zone. Our models also predict full-graben profiles within the overlapped region between bounding faults and half-graben shapes elsewhere. Increasing overlap also decreases uplift near the fault tips and rotation of blocks within the basin. We suggest that the observed structure of the Dead Sea Basin can be described by a 3-D model having a large overlap (more than 30 km) that probably increased as the basin evolved as a result of a stable shear motion that was distributed laterally over 20 to 40 km.

Dead Sea Basin↗

USGS2011

Using the 2011 M w 9.0 Tohoku earthquake to test the Coulomb stress triggering hypothesis and to calculate faults brought closer to failure

The 11 March 2011 Tohoku Earthquake provides an unprecedented test of the extent to which Coulomb stress transfer governs the triggering of aftershocks. During 11-31 March, there were 177 aftershocks with focal mechanisms, and so the Coulomb stress change imparted by the rupture can be resolved on the aftershock nodal planes to learn whether they were brought closer to failure. Numerous source models for the mainshock have been inverted from seismic, geodetic, and tsunami observations. Here, we show that, among six tested source models, there is a mean 47% gain in positively-stressed aftershock mechanisms over that for the background (1997-10 March 2011) earthquakes, which serve as the control group. An aftershock fault friction of 0.4 is found to fit the data better than 0.0 or 0.8, and among all the tested models, Wei and Sladen (2011) produced the largest gain, 63%. We also calculate that at least 5 of the seven large, exotic, or remote aftershocks were brought ≥0.3 bars closer to failure. With these tests as confirmation, we calculate that large sections of the Japan trench megathrust, the outer trench slope normal faults, the Kanto fragment beneath Tokyo, and the Itoigawa-Shizuoka Tectonic Line, were also brought ≥0.3 bars closer to failure.

Earth, Planets and Space↗

USGS2011

Coulomb 3.3 Graphic-rich deformation and stress-change software for earthquake, tectonic, and volcano research and teaching-user guide

Coulomb is intended both for publication-directed research and for college and graduate school classroom instruction. We believe that one learns best when one can see the most and can explore alternatives quickly. So the principal feature of Coulomb is ease of input, rapid interactive modification, and intuitive visualization of the results. The program has menus and check-items, and dialogue boxes to ease operation. The internal graphics are suitable for publication, and can be easily imported into Illustrator, GMT, Google Earth, or Flash for further enhancements. Coulomb is designed to let one calculate static displacements, strains, and stresses at any depth caused by fault slip, magmatic intrusion, or dike expansion/contraction. One can calculate static displacements (on a surface or at GPS stations), strains, and stresses caused by fault slip, magmatic intrusion, or dike expansion. Problems, such as how an earthquake promotes or inhibits failure on nearby faults, or how fault slip or dike expansion will compress a nearby magma chamber, are germane to Coulomb. Geologic deformation associated with strike-slip faults, normal faults, or fault-bend folds is also a useful application. Calculations are made in an elastic halfspace with uniform isotropic elastic properties following Okada (1992)-see list of key papers in section 1.9. There is substantial evidence to support the hypothesis that faults interact by the transfer of stress, both on the time scales of earthquake sequences and aftershocks and on longer time scales associated with the interevent time of the largest shocks that occur in a given region. There is also evidence that faults and magmatic systems interact as well, and that static stress changes influence intrusions and eruptions. Processes not included in Coulomb are also important, such as dynamic stresses, pore-fluid diffusion, and viscoelastic rebound. Further, elastic stiffness differences between basins and crustal layering modify the stresses in comparison to the elastic halfspace implemented in Coulomb. Nevertheless, we believe that a simple tool that permits exploration of a key component of earthquake interaction has great value for understanding and discovery. To download the software (a MATLAB application) and tutorial files, please go to http://www.coulombstress.org

Open-File Report↗

USGS2010

USGS-WHOI-DPRI Coulomb Stress-Transfer Model for the January 12, 2010, MW=7.0 Haiti Earthquake

Using calculated stress changes to faults surrounding the January 12, 2010, rupture on the Enriquillo Fault, and the current (January 12 to 26, 2010) aftershock productivity, scientists from the U.S. Geological Survey (USGS), Woods Hole Oceanographic Institution (WHOI), and Disaster Prevention Research Institute, Kyoto University (DPRI) have made rough estimates of the chance of a magnitude (Mw)=7 earthquake occurring during January 27 to February 22, 2010, in Haiti. The probability of such a quake on the Port-au-Prince section of the Enriquillo Fault is about 2 percent, and the probability for the section to the west of the January 12, 2010, rupture is about 1 percent. The stress changes on the Septentrional Fault in northern Haiti are much smaller, although positive.

Open-File Report↗

USGS2006

Seismic constraints and Coulomb stress changes of a blind thrust fault system, 1: Coalinga and Kettleman Hills, California

This report reviews the seismicity and surface ruptures associated with the 1982-1985 earthquake sequence in the Coalinga region in California, and the role of Coulomb stress in triggering the mainshock sequence and aftershocks. The 1982-1985 New Idria, Coalinga, and Kettleman Hills earthquakes struck on a series of west-dipping, en echelon blind thrust faults. Each earthquake was accompanied by uplift of a Quaternary anticline atop the fault, and each was accompanied by a vigorous aftershock sequence. Aftershocks were widely dispersed, and are seen above and below the thrust fault, as well as along the up-dip and down-dip projection of the main thrust fault. For the Coalinga and Kettleman Hills earthquakes, high-angle reverse faults in the core of the anticlines are evident in seismic reflection profiles, and many of these faults are associated with small aftershocks. The shallowest aftershocks extended to within 3-4 km of the ground surface. There is no compelling evidence for aftershocks associated with flexural slip faulting. No secondary surface rupture was found on any of the anticlines. In contrast, the 1983 Nuñez rupture struck on a high-angle reverse fault 10 km west of the Coalinga epicenter, and over a 40-80-day period, up to 1 m of oblique surface slip occurred. The slip on this Holocene fault likely extended from the ground surface to a depth of 8-10 km. We argue that both the Nuñez and Kettleman earthquakes were triggered by stresses imparted by the Coalinga mainshock, which was the largest of the four events in the sequence.

California↗

USGS2006

Seismic constraints and coulomb stress changes of a blind thrust fault system, 2: Northridge, California

We review seismicity, surface faulting, and Coulomb stress changes associated with the 1994 Northridge, California, earthquake. All of the observed surface faulting is shallow, extending meters to tens of meters below the surface. Relocated aftershocks reveal no seismicity shallower than 2 km depth. Although many of the aftershocks lie along the thrust fault and its up-dip extension, there are also a significant number of aftershocks in the core of the gentle anticline above the thrust, and elsewhere on the up-thrown block. These aftershocks may be associated with secondary ramp thrusts or flexural slip faults at a depth of 2-4 km. The geological structures typically associated with a blind thrust fault, such as anticlinal uplift and an associated syncline, are obscured and complicated by surface thrust faults associated with the San Fernando fault that overly the Northridge structures. Thus the relationship of the geological structure and topography to the underlying thrust fault is much more complex for Northridge than it is for the 1983 Coalinga, California, earthquake. We show from a Coulomb stress analysis that secondary surface faulting, diffuse aftershocks, and triggered sequences of moderate-sized mainshocks, are expected features of moderate-sized blind thrust earthquakes.

California↗

USGS2004

Preliminary report on the 22 December 2003, M 6.5 San Simeon, California earthquake

The M w 6.5 San Simeon earthquake struck the central California coast on 22 December 2003 at 19:15:56 UTC (11:15:56 am local time.) The epicenter was located 11 km northeast of the town of San Simeon, and 39 km west-northwest of Paso Robles ( Figure 1 ), as reported by the California Integrated Seismic Network (CISN, the California region of the Advanced National Seismic System [ANSS]). The mainshock nucleated at 35.702°N, 121.108°W and a depth of 7.1 km, and the rupture propagated unilaterally to the southeast. The strong directivity of the rupture resulted in a concentration of damage and aftershock activity to the southeast of the hypocenter. The worst earthquake damage occurred in Paso Robles, where two people died in the collapse of an unreinforced masonry building. The accurate and rapid earthquake information provided in near real-time by CISN/ANSS to the Governor's Office of Emergency Services made it possible to focus emergency response in the source area, although the earthquake was felt from San Francisco to Los Angeles. The San Simeon earthquake occurred on a reverse fault striking northwest and most likely dipping to the northeast. Although motion along the Pacific-North America plate boundary in California is dominantly strike-slip, there is a small compressional component through central California. Repeated thrust earthquakes such as the San Simeon event accommodate this compression and build the Coast Ranges. Other recent thrust earthquakes in central California include the 1983 Coalinga (M 6.4) and the 1985 Kettleman Hills (M 6.0) earthquakes. Prior earthquakes in the vicinity of the San Simeon event include a M 5-6 earthquake in 1853, a M 5.7 earthquake in 1906, and the M L 6.2 Bryson earthquake of 1952 ( Figure 1 ) ( McLaren and Savage, 2001 .) The San Simeon earthquake occurred on a previously unknown blind thrust fault. No surface rupture associated with the earthquake has been identified. A number of roads, including State Highway 46, buckled due to the earthquake, but this deformation appears mainly to be failure of road fill due to ground shaking and not the result of tectonic surface rupture. Extrapolation of the fault plane to the surface would roughly align with the surface trace of the Oceanic Fault, but this is thought to be a vertical strike-slip fault. Two models for the kinematics of the region have previously been proposed. The first is a fault-propagation fold model developed by Namson and Davis ( 1990 ) for the Santa Lucia mountains ∼30 km to the southeast of the San Simeon sequence. The mainshock geometry is similar to, although more steeply dipping than, the main blind thrust of this model, implying that this model may be applicable to the San Simeon region as well. The second is the model of McLaren and Savage ( 2001 ), in which the region is dominated by strike-slip faulting with shortening on high-angle reverse faults. This model also may be applicable, although the dip of the San Simeon mainshock is shallower than predicted. The San Simeon earthquake was followed by a vigorous aftershock sequence, with 165 events above M 3 reported by CISN within the first week of the mainshock. Although the event triggered many aftershocks, it did not significantly impact the seismicity rates of other nearby faults such as the San Andreas Fault and the San Simeon-Hosgri fault zone. The only triggered seismicity seems to be a few small events within the mainshock coda at the Geysers geothermal area, north of San Francisco. The San Simeon earthquake did, however, trigger shallow creep on the San Andreas Fault at Parkfield and hydrologic changes in hot springs in Paso Robles.

California↗

USGS1996

Three-dimensional models of deformation near strike-slip faults

We use three-dimensional elastic models to help guide the kinematic interpretation of crustal deformation associated with strike-slip faults. Deformation of the brittle upper crust in the vicinity of strike-slip fault systems is modeled with the assumption that upper crustal deformation is driven by the relative plate motion in the upper mantle. The driving motion is represented by displacement that is specified on the bottom of a 15-km-thick elastic upper crust everywhere except in a zone of finite width in the vicinity of the faults, which we term the “shear zone.” Stress-free basal boundary conditions are specified within the shear zone. The basal driving displacement is either pure strike slip or strike slip with a small oblique component, and the geometry of the fault system includes a single fault, several parallel faults, and overlapping en echelon faults. We examine the variations in deformation due to changes in the width of the shear zone and due to changes in the shear strength of the faults. In models with weak faults the width of the shear zone has a considerable effect on the surficial extent and amplitude of the vertical and horizontal deformation and on the amount of rotation around horizontal and vertical axes. Strong fault models have more localized deformation at the tip of the faults, and the deformation is partly distributed outside the fault zone. The dimensions of large basins along strike-slip faults, such as the Rukwa and Dead Sea basins, and the absence of uplift around pull-apart basins fit models with weak faults better than models with strong faults. Our models also suggest that the length-to-width ratio of pull-apart basins depends on the width of the shear zone and the shear strength of the faults and is not constant as previously suggested. We show that pure strike-slip motion can produce tectonic features, such as elongate half grabens along a single fault, rotated blocks at the ends of parallel faults, or extension perpendicular to overlapping en echelon faults, which can be misinterpreted to indicate a regional component of extension. Zones of subsidence or uplift can become wider than expected for transform plate boundaries when a minor component of oblique motion is added to a system of parallel strike-slip faults.

Journal of Geophysical Research B: Solid Earth↗

USGS1994

Static stress changes and the triggering of earthquakes

To understand whether the 1992 M = 7.4 Landers earthquake changed the proximity to failure on the San Andreas fault system, we examine the general problem of how one earthquake might trigger another. The tendency of rocks to fail in a brittle manner is thought to be a function of both shear and confining stresses, commonly formulated as the Coulomb failure criterion. Here we explore how changes in Coulomb conditions associated with one or more earthquakes may trigger subsequent events. We first consider a Coulomb criterion appropriate for the production of aftershocks, where faults most likely to slip are those optimally orientated for failure as a result of the prevailing regional stress field and the stress change caused by the mainshock. We find that the distribution of aftershocks for the Landers earthquake, as well as for several other moderate events in its vicinity, can be explained by the Coulomb criterion as follows: aftershocks are abundant where the Coulomb stress on optimally orientated faults rose by more than one-half bar, and aftershocks are sparse where the Coulomb stress dropped by a similar amount. Further, we find that several moderate shocks raised the stress at the future Landers epicenter and along much of the Landers rupture zone by about a bar, advancing the Landers shock by 1 to 3 centuries. The Landers rupture, in turn, raised the stress at site of the future M = 6.5 Big Bear aftershock site by 3 bars. The Coulomb stress change on a specified fault is independent of regional stress but depends on the fault geometry, sense of slip, and the coefficient of friction. We use this method to resolve stress changes on the San Andreas and San Jacinto faults imposed by the Landers sequence. Together the Landers and Big Bear earthquakes raised the stress along the San Bernardino segment of the southern San Andreas fault by 2 to 6 bars, hastening the next great earthquake there by about a decade.

Bulletin of the Seismological Society of America↗