Full Moment Tensor Variations and Isotropic Characteristics of Earthquakes in the Gulf of California Transform Fault System

2013 ◽  
Vol 171 (10) ◽  
pp. 2805-2817 ◽  
Author(s):  
Roberto Ortega ◽  
Luis Quintanar ◽  
Luis Rivera
Keyword(s):  
Gulf Of California ◽  
Moment Tensor ◽  
Fault System ◽  
Transform Fault ◽  
Full Moment Tensor

The 4 January 2006 (Mw 6.6), San Pedro Martir Earthquake: Example of an Earthquake for Calibrating Excitation and Attenuation Studies

2019 ◽  
Vol 109 (6) ◽  
pp. 2399-2414 ◽  
Author(s):  
Luis Quintanar ◽  
Roberto Ortega ◽  
Héctor E. Rodríguez‐Lozoya ◽  
Tonatiuh Domínguez‐Reyes
Keyword(s):  
Gulf Of California ◽  
Moment Tensor ◽  
Near Field ◽  
Scaling Law ◽  
Rate Function ◽  
Transform Fault ◽  
High Frequencies ◽  
Stress Parameter ◽  
Rupture Area ◽  
San Pedro

Abstract An earthquake of magnitude 6.6 occurred on 4 January 2006, at 28.081° N and 112.381° W along a transform fault that joins the San Pedro Martir and the Guaymas basins in the Gulf of California extensional province. We located 17 foreshocks and 38 aftershocks. The foreshocks occurred on a fault perpendicular to the transform fault, where the main event occurred. The aftershocks were located along a fault length of approximately 18 km with a northwest–southeast trend. The average Brune static stress drop of the San Pedro Martir event was 8 MPa. From a time‐domain moment tensor inversion, we obtained the fault geometry given by strike of 129°±1°, dip of 86°±4°, and rake of 168°±12°, which was constrained to have a nonisotropic component and a source depth of 6±2  km. We used the inversion code from Yagi et al. (1999) to invert near field and teleseismic P waves to obtain the spatial slip distribution over the fault. The event had a single source and a moment rate function (MRF) displaying a triangular shape with a duration of 12 s. The rupture propagated toward the northwest from the hypocenter over a rupture area of 28×12  km2 with a maximum slip displacement of 2.3 m and a seismic moment of 8.79×1018  N·m. The directivity confirmed that the rupture propagated from the southeast to the northwest. Few aftershocks were located in the rupture area obtained from the inversion. Most aftershocks occurred toward the southeast of the epicenter. All these source analyses were performed to have a well‐calibrated excitation term for future regional modeling of ground‐motion parameters. The magnitudes of the foreshocks preceding this peculiar earthquake were higher than those of the aftershocks. Our results show that earthquakes with magnitudes of five or higher present a simple and self‐scaling law using a constant stress parameter, but for earthquakes with magnitudes lower than five, the high frequencies are depleted, and the earthquake can be replicated by a low‐stress parameter of 0.28 MPa. We also observed that the aftershocks and foreshocks differ in their frequency content. Although the foreshocks follow Brune’s omega‐squared source term, the aftershocks have larger contents of high frequencies.

Analysis of the 15 December 2017 Mw 6.5 and the 23 January 2018 Mw 5.9 Java Earthquakes

2020 ◽  
Vol 110 (6) ◽  
pp. 3050-3063
Author(s):  
Anne Meylani Magdalena Sirait ◽  
Anne S. Meltzer ◽  
Felix Waldhauser ◽  
Joshua C. Stachnik ◽  
Daryono Daryono ◽  
...  
Keyword(s):  
Moment Tensor ◽  
Fluid Pressure ◽  
Fault System ◽  
Double Difference ◽  
Northern Coast ◽  
Eurasian Plate ◽  
Slab Geometry ◽  
Plate Interface ◽  
Upward Migration ◽  
Ground Shaking

ABSTRACT The west part of Java sits at the transition from oblique subduction of the Australian plate under the Sunda block of the Eurasian plate along Sumatra to orthogonal convergence along central and eastern Java. This region has experienced several destructive earthquakes, the 17 July 2006 Mw 7.7 earthquake and tsunami off the coast of Pangandaran and the 2 September 2009 Mw 7 earthquake, located off the coast of Tasikmalaya. More recently, on 15 December 2017, an Mw 6.5 earthquake occurred off the coast near Pangandaran, and, on 23 January 2018, an Mw 5.9 earthquake occurred offshore Lebak, between Pelabuhan Ratu and Ujung Kulon. Ground shaking and damage occurred locally and in Jakarta on the northern coast of Java. In this study, we use the double-difference technique to relocate both mainshocks and 10 months of seismicity (228 events) following the earthquakes. The relocation result improved the mainshock locations and depth distribution of earthquakes. Moment tensor of the December 2017 event located the hypocenter at ∼108  km depth within the subducting slab. The best-fit relocation places the depth at 61 km, close to the slab interface. Aftershocks occur between 68 and 86 km depth and align along a steeper plane than slab geometry models. The January 2018 event is located at ∼46  km depth. Aftershocks form a near-vertical, pipe-like structure from the plate interface to ∼10  km depth. A burst of aftershocks immediately following the mainshock shows a shallowing upward trend at a rate of ∼2  km/hr, suggesting that a fluid pressure wave released from the oceanic crust is causing brittle failure in the overriding plate, followed by upward migration of fluids. Five months later, shallow (<25  km) seismicity collocates with background seismicity, suggesting the January 2018 event activated the Pelabuhan Ratu fault system close to the coast.

The geology and evolution of the Pinchi Fault Zone at Pinchi Lake, central British Columbia

1977 ◽  
Vol 14 (6) ◽  
pp. 1324-1342 ◽  
Author(s):  
I. A. Paterson
Keyword(s):  
Fault Zone ◽  
Subduction Zones ◽  
High Pressures ◽  
Metamorphic Grade ◽  
Fault System ◽  
Late Triassic ◽  
Transform Fault ◽  
The West ◽  
Early Mesozoic ◽  
Complex Fault

At Pinchi Lake, the Pinchi Fault Zone separates the early Mesozoic Takla Group to the east from the late Paleozoic Cache Creek Group to the west. Between these regions a complex fault system involves a series of elongate fault-bounded blocks of contrasting lithology and metamorphic grade. These blocks consist of: (a) highly deformed aragonite–dolomite limestone and blueschist, (b) pumpellyite–aragonite greenstone, (c) a harzburgite–gabbro–diabase–basalt ophiolite sequence, (d) serpentinized alpine ultramafite, and (e) Cretaceous (?) conglomerate. The blueschist probably formed at 8–12 kbar (8 × 105–12 × 105 kPa) and 225–325 °C during a penetrative early deformation which was closely followed by a later deformation associated with a Late Triassic uplift and cooling event. The ophiolite sequence is overlain by Late Triassic sediments which locally contain aragonite suggesting that at least part of the Takla Group may have also undergone high pressure – low temperature metamorphism.The evolution of the 450 km fault zone is discussed and a model is proposed which involves right lateral transform faulting on the Pinchi Fault and underthrusting along northerly dipping subduction zones during the Late Triassic. The blueschist formed at high pressures in such a subduction zone and leaked to the surface in zones of low pressure along an active transform fault.

scholarly journals Automated full moment tensor inversion of coal mining-induced seismicity

2013 ◽  
Vol 195 (2) ◽  
pp. 1267-1281 ◽  
Author(s):  
Ali Tolga Sen ◽  
Simone Cesca ◽  
Monika Bischoff ◽  
Thomas Meier ◽  
Torsten Dahm
Keyword(s):  
Coal Mining ◽  
Induced Seismicity ◽  
Moment Tensor ◽  
Moment Tensor Inversion ◽  
Mining Induced Seismicity ◽  
Full Moment Tensor
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