Right-lateral Shear Stress Research Articles

Passive crustal clockwise rotational deformation of the Sichuan Basin since the Miocene and its relationship with the tectonic evolution of the fault systems on the eastern edge of the Tibetan Plateau

Research Article| August 15, 2018 Passive crustal clockwise rotational deformation of the Sichuan Basin since the Miocene and its relationship with the tectonic evolution of the fault systems on the eastern edge of the Tibetan Plateau Yabo Tong; Yabo Tong † 1Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China2Key Laboratory of Paleomagnetism and Tectonic Reconstruction, the Ministry of Land and Resources, Beijing 100081, China †tyb816@163.com Search for other works by this author on: GSW Google Scholar Yujun Sun; Yujun Sun 1Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China Search for other works by this author on: GSW Google Scholar Zhonghai Wu; Zhonghai Wu 1Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China Search for other works by this author on: GSW Google Scholar Changping Mao; Changping Mao 3School of Earth Sciences and Engineering, Hohai University, Nanjing 210098, China Search for other works by this author on: GSW Google Scholar Junling Pei; Junling Pei 1Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China2Key Laboratory of Paleomagnetism and Tectonic Reconstruction, the Ministry of Land and Resources, Beijing 100081, China Search for other works by this author on: GSW Google Scholar Zhenyu Yang; Zhenyu Yang 4College of Resources, Environment and Tourism, Capital Normal University, Beijing 100048, China Search for other works by this author on: GSW Google Scholar Zongwen Pu; Zongwen Pu 1Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China Search for other works by this author on: GSW Google Scholar Yue Zhao; Yue Zhao 1Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China2Key Laboratory of Paleomagnetism and Tectonic Reconstruction, the Ministry of Land and Resources, Beijing 100081, China Search for other works by this author on: GSW Google Scholar Hao Xu Hao Xu 1Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China Search for other works by this author on: GSW Google Scholar GSA Bulletin (2019) 131 (1-2): 175–190. https://doi.org/10.1130/B31965.1 Article history received: 07 Nov 2017 rev-recd: 13 Jun 2018 accepted: 15 Jul 2018 first online: 15 Aug 2018 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Yabo Tong, Yujun Sun, Zhonghai Wu, Changping Mao, Junling Pei, Zhenyu Yang, Zongwen Pu, Yue Zhao, Hao Xu; Passive crustal clockwise rotational deformation of the Sichuan Basin since the Miocene and its relationship with the tectonic evolution of the fault systems on the eastern edge of the Tibetan Plateau. GSA Bulletin 2018;; 131 (1-2): 175–190. doi: https://doi.org/10.1130/B31965.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract We conducted a paleomagnetic study of the Upper and Lower Cretaceous red-beds in the Yibin area, in the southern part of the Sichuan Basin. High-temperature magnetic components were isolated between 580 °C and 695 °C. An ambiguous fold test resulted in alternative interpretations of the Cretaceous primary magnetization or Oligocene-Miocene remagnetization. Nevertheless, the two different interpretations of the paleomagnetic data consistently show that the Yibin area on the southern edge of the Sichuan Basin experienced clockwise rotation, relative to the eastern edge of the South China Block and Europe. A comparison with the Cretaceous and Paleogene paleomagnetic data from the northern and western part of the Sichuan Basin indicates that, except for the southeastern corner of the Sichuan Basin, the crust of the Sichuan Basin generally experienced significant clockwise rotational deformation since the early Miocene. The northeastward escape of the Songpan-Ganzi Terrane and the counterclockwise rotation of the Yangtze Fold Belt applied a right-lateral shear stress to the region surrounding the Sichuan Basin since the Miocene, which induced the passive crustal clockwise rotational deformation of the Sichuan Basin. Subsequently, the non-synchronous crustal rotational deformation of the Sichuan Basin and its surrounding blocks controlled the tectonic evolution of their boundary tectonic belts: for example, the right-lateral strike-slip movement of the Longmenshan fault belt and the southeastward extension of the Xianshuihe strike-slip fault since the Miocene. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Tidal triggering of low frequency earthquakes near Parkfield, California: Implications for fault mechanics within the brittle‐ductile transition

Studies of nonvolcanic tremor (NVT) have established the significant impact of small stress perturbations on NVT generation. Here we analyze the influence of the solid earth and ocean tides on a catalog of ∼550,000 low frequency earthquakes (LFEs) distributed along a 150 km section of the San Andreas Fault centered at Parkfield. LFE families are identified in the NVT data on the basis of waveform similarity and are thought to represent small, effectively co‐located earthquakes occurring on brittle asperities on an otherwise aseismic fault at depths of 16 to 30 km. We calculate the sensitivity of each of these 88 LFE families to the tidally induced right‐lateral shear stress (RLSS), fault‐normal stress (FNS), and their time derivatives and use the hypocentral locations of each family to map the spatial variability of this sensitivity. LFE occurrence is most strongly modulated by fluctuations in shear stress, with the majority of families demonstrating a correlation with RLSS at the 99% confidence level or above. Producing the observed LFE rate modulation in response to shear stress perturbations requires low effective stress in the LFE source region. There are substantial lateral and vertical variations in tidal shear stress sensitivity, which we interpret to reflect spatial variation in source region properties, such as friction and pore fluid pressure. Additionally, we find that highly episodic, shallow LFE families are generally less correlated with tidal stresses than their deeper, continuously active counterparts. The majority of families have weaker or insignificant correlation with positive (tensile) FNS. Two groups of families demonstrate a stronger correlation with fault‐normal tension to the north and with compression to the south of Parkfield. The families that correlate with fault‐normal clamping coincide with a releasing right bend in the surface fault trace and the LFE locations, suggesting that the San Andreas remains localized and contiguous down to near the base of the crust. The deep families that have high sensitivity to both shear and tensile normal stress perturbations may be indicative of an increase in effective fault contact area with depth. Synthesizing our observations with those of other LFE‐hosting localities will help to develop a comprehensive understanding of transient fault slip below the “seismogenic zone” by providing constraints on parameters in physical models of slow slip and LFEs.

相模トラフ北部の海底地形と断層系の形成―５系統の断層発達史―

This paper describes topographic and geologic features of the northern part of the Sagami Trough and surrounding areas, off central Japan, and discusses the role of the Philippine Sea plate in the development of the trough's topography and fault systems. In the study area, the Okinoyama Bank Chain, Miura Basin Chain, and several spurs are aligned NW-SE parallel to the axis of the Sagami Trough. We examine the lithological compositions of rock and piston-core samples collected from the R/V Hyper Dolphin during Japan Agency for Marine-Earth Science and Technology dives 906 and 907, and rock samples dredged during Ocean Research Institute of the University of Tokyo cruise KT88. These samples represent mainly volcaniclastic rocks derived from the volcanoes of the Izu arc and subordinate amounts of terrigenous sediment interpreted as derived from the Sagami and Sakawa Rivers. The topographic and geologic data define five fault systems in the eastern part of the northern Sagami Trough. We interpret the Okinoyama Bank Chain as an elevated outer-ridge belt developed at the landward slope of the plate boundary, which is represented by NW-SE trending right-lateral reverse faults (F1). At the northeast side of the Okinoyama Bank Chain, NW-SE trending normal faults (F2) formed and the Miura Basin Chain developed. The cutting relationship between these fault sets suggests that the collision of the Izu arc with the Honshu arc imposed a right-lateral shear stress field on the Okinoyama Bank and Miura Basin Chains. This shear stress may have led to clockwise rotation of these tectonic blocks formation of a set of NE-SW trending left-lateral reverse faults (F3). The initiation of the Izu block collision is interpreted as a turning point after which the northward motion of the Philippine Sea plate abruptly changed to NW and the Sagami Bay area came under a NW-SE compressional stress field, which resulted in the development of E-W trending right-lateral faults (F4) in the narrow shelf off the Miura Peninsula. A number of spurs subsequently developed along these faults. Finally, NNE-SSW trending right-lateral normal faults (F5) developed under an E-W extensional stress field, which caused the formation of N-S trending topographic depressions such as Tokyo Canyon and submarine highs such as Okinoyama and Oiso Spur.

Interactions between the Landers and Hector Mine, California, Earthquakes from Space Geodesy, Boundary Element Modeling, and Time-Dependent Friction

The M w 7.1 Hector Mine earthquake happened 7 years after the 1992 M w 7.3 Landers earthquake, within a system of right-lateral strike slip faults comprising the Eastern California Shear Zone. Because estimates of recurrence intervals of M 7 earthquakes on these faults range anywhere from 1500 to 50,000 years, the close temporal spacing of these two earthquakes suggests that there is some interaction between the two. Current models of simple Coulomb static stress interactions between the earthquake ruptures do not predict an obvious cause-and-effect relationship. The interaction between the computed normal and right-lateral shear stress reductions induced by the Landers earthquake at the Hector Mine hypocenter is unclear. We use a combination of space geodesy, boundary element modeling, and computer modeling of time-dependent fault friction to investigate the interaction between the two earthquakes. We compare stress changes on the Hector Mine rupture plane induced by the Landers earthquake with the detailed slip distribution inferred using a combination of GPS and InSAR data. The slip distributions of both earthquakes are also used to infer the magnitude of the shear stress drop on each earthquake rupture and the orientation of the remote background stress consistent with these two recent events. For each earthquake the azimuth of the remote maximum compressive stress was approximately 17° ± 6°, and the magnitude of the shear stress drop was 8 ± 1 MPa on the Landers rupture and 10 ± 2 MPa on the Hector Mine rupture. Using a simple spring-and-slider model as a proxy for the rate-and-state frictional response of the Hector Mine faults to Landers earthquake-imposed stress steps, we find that, while a decrease in normal stress at the Hector Mine hypocenter would, by itself, have caused the Hector Mine earthquake to nucleate immediately, the simultaneous decrease in shear stress may have caused a delay in the peak shear loading. Consideration of an acceptable range of rate-and-state friction parameters, secular strain rates, and crustal stiffnesses leads us to conclude that this delay could have been 0 to 40 years.

In situ stress measurements to 3.5 km depth in the Cajon Pass Scientific Research Borehole: Implications for the mechanics of crustal faulting

Measurements of in situ stress orientation and magnitude at the site of the Cajon Pass research borehole have been made from depths of 0.9–3.5 km using the hydraulic fracturing technique and analysis of stress‐induced well bore breakouts. The results of these measurements support two important conclusions about the mechanics of crustal faulting. First, the magnitudes of measured in situ stresses indicate ratios of shear to normal stress on favorably oriented fault planes that are consistent with predictions based on Mohr‐Coulomb theory and laboratory‐determined coefficients of friction in the range of 0.6–1.0 assuming hydrostatic pore pressure (this is commonly known as Byerlee's law). Thus the stress measurements indicate that the frictional strength of the crust adjacent to the San Andreas fault is high (i.e., consistent with laboratory‐derived friction values) and that the level of shear stress in the crust adjacent to the San Andreas is principally controlled by its frictional strength. However, data on the orientation of maximum horizontal compression in the borehole from 1.75 to 3.5 km (N57°E ± 19°) indicate that the San Andreas must be quite weak as a complete absence of right‐lateral shear stress resolved on planes parallel to the ∼N60°W striking San Andreas fault is observed. The lack of right‐lateral shear stress on planes parallel to the San Andreas fault at this site is especially surprising as Cajon Pass is located along a section of the San Andreas which has not had a major earthquake since 1812 and is thus presumably quite “late” in the earthquake cycle. Nevertheless, both the orientation and magnitudes of stresses measured in the well are consistent with the style of active faulting in the area surrounding the drill site, most notably normal faulting and Quaternary age left‐lateral slip on the Cleghorn fault that parallels the San Andreas in the vicinity of the drill site (Meisling and Weldon, 1982; Weldon, 1986; R. J. Weldon et al., unpublished report, 1981). We argue that the stress state (and Quaternary fault offsets) observed in the Cajon Pass area could exist only if the San Andreas moved at low shear stresses comparable to seismic stress drops rather than the much higher values predicted by Byerlee's law, a conclusion consistent with the lack of frictionally generated heat flow along the San Andreas system (e.g., Brune et al., 1969; Henyey and Wasserburg, 1971; Lachenbruch and Sass, 1973, 1980). Taken together, the Cajon Pass in situ stress and heat flow measurements (Lachenbruch and Sass, this issue) support a conceptual model of the San Andreas system in which the San Andreas is extremely weak with respect to the surrounding crust.

Hydraulic fracturing in situ stress measurements to 2.1 km depth at Cajon Pass, California

Stress measurements to 2.1 km reveal stress changes with depth that cannot be explained by an elastic response to uniform crustal strain. The data at about 1 km depth suggest that the stress is limited by the frictional strength of rock and is perturbed at greater depths by faults which intersect the borehole. The stress data indicate that there is little or no right‐lateral shear stress acting on planes parallel to the San Andreas fault.

New Evidence on the State of Stress of the San Andreas Fault System

Contemporary in situ tectonic stress indicators along the San Andreas fault system in central California show northeast-directed horizontal compression that is nearly perpendicular to the strike of the fault. Such compression explains recent uplift of the Coast Ranges and the numerous active reverse faults and folds that trend nearly parallel to the San Andreas and that are otherwise unexplainable in terms of strike-slip deformation. Fault-normal crustal compression in central California is proposed to result from the extremely low shear strength of the San Andreas and the slightly convergent relative motion between the Pacific and North American plates. Preliminary in situ stress data from the Cajon Pass scientific drill hole (located 3.6 kilometers northeast of the San Andreas in southern California near San Bernardino, California) are also consistent with a weak fault, as they show no right-lateral shear stress at approximately 2-kilometer depth on planes parallel to the San Andreas fault.

Geology, petrography, and geochemistry of the volcanic islands of Tonga

The South Pacific Ocean is an ideal area in which to test some of the compositional implications of plate tectonics and sea-floor spreading. The island arc of Tonga marks an active zone of seismic disturbances and volcanic activity that may be related to thrusting of the oceanic crust beneath the marginal crustal plate on which the islands are constructed. This marginal plate appears to be of oceanic character in the vicinity of Tonga, and the Tongan volcanoes thus provide an opportunity to examine the nature of magmas of a typical circum-Pacific orogenic zone located within an oceanic crustal regime. Volcanic eruptions in the Tonga Islands have averaged about one every four years during the present century, and milder submarine eruptions may have escaped notice. The submarine volcanoes and volcanic islands appear to be located along en-echelon fractures that strike slightly east of the general trend of the islands. These fractures would tend to open under right-lateral shear stress in the sense of the New Zealand Alpine fault and would tend to close under compression directed perpendicular to the island arc from the Pacific side. Thus, the relative amount and direction of movement of crustal plates on either side of the island arc may control the frequency and intensity of volcanic eruptions. The active volcanic islands and sea mounts are along a submarine ridge about 200 km west of the axis of the Tonga trench. The youthful constructional volcanic topography and limited paleomagnetic data indicate a very recent age for the volcanic activity. The rocks of these islands are basaltic andesite, andesite, and dacite, with the exception of Niuafo'ou, from which only basalt has been reported. These rocks differ from most other circum-Pacific andesite-dacite suites in their very low content of alkali, especially low K2O, although similar rocks have been reported from a few other island arcs, such as the Izu peninsula of Japan, the Marianas, and the South Sandwich Islands. The chemical peculiarities are represented modally by exceptionally calcic plagioclase and near absence of alkali feldspar. Pre-late Eocene basalt and uralitized gabbro on Eua Island at the southeast end of the group may represent uplifted pre-arc sea floor. These rocks are high in Al2O3 and are especially poor in K2O. The variation in K2O and total alkalies across the Tonga arc is similar to that observed in other circum-Pacific island arcs. The volcanic rocks show moderately strong iron enrichment, the highest Fe/Mg ratios appearing in the more siliceous andesites and dark dacites. This iron enrichment should not be regarded as evidence for a tholeiitic affinity for these rocks. Trace element abundances are similar to those of many other calcalkaline island arc lavas and apparently are consistent with a genetic evolution of the lavas by fractional crystallization. Bouger gravity anomalies decrease from south to north, from a high of +243 mgal on Eua to a low of +122 mgal on Fonualei. This decrease in gravity is matched by a slight increase in potash content in lavas of otherwise comparable composition, implying a change in the composition of the deep crust or mantle from which the lavas are derived. However, the most important compositional changes along the Tonga-Kermadec-New Zealand volcanic line occur between the Kermadecs and New Zealand, and probably reflect the influence of crustal contamination beneath the North Island.