Geology topics

A. T. Linde

Publications and source records attributed to A. T. Linde.

6 recordsLinked to original sources

USGS2012

Short-period strain (0.1–105 s): Near-source strain field for an earthquake (ML 3.2) near San Juan Bautista, California

Measurements of dilational earth strain in the frequency band 25–10 −5 Hz have been made on a deep borehole strainmeter installed near the San Andreas fault. These data are used to determine seismic radiation fields during nuclear explosions, teleseisms, local earthquakes, and ground noise during seismically quiet times. Strains of less than 10 −10 on these instruments can be clearly resolved at short periods (< 10 s) and are recorded with wide dynamic range digital recorders. This permits measurement of the static and dynamic strain variations in the near field of local earthquakes. Noise spectra for earth strain referenced to 1 (strain) 2 /Hz show that strain resolution decreases at about 10 dB per decade of frequency from −150 dB at 10 −4 Hz to −223 dB at 10 Hz. Exact expressions are derived to relate the volumetric strain and displacement field for a homogeneous P wave in a general viscoelastic solid as observed on colocated dilatometers and seismometers. A rare near-field recording of strain and seismic velocity was obtained on May 26, 1984, from an earthquake ( M L 3.2) at a hypocentral distance of 3.2 km near the San Andreas fault at San Juan Bautista, California. While the data indicate no precursory strain release at the 5 × 10 −11 strain level, a coseismic strain release of 1.86 nanostrain was observed. This change in strain is consistent with that calculated from a simple dislocation model of the event. Ground displacement spectra, determined from the downhole strain data and instrument-corrected surface seismic data, suggest that source parameters estimated from surface recordings may be contaminated by amplification effects in near-surface low-velocity materials.

California↗

USGS2007

Borehole observations of continuous strain and fluid pressure: Chapter 9

Strain is expansion, contraction, or distortion of the volcanic edifice and surrounding crust. As a result of magma movement, volcanoes may undergo enormous strain prior to and during eruption. Global Positioning System (GPS) observations can in principle be used to determine strain by taking the difference between two nearby observations and dividing by the distance between them. Two GPS stations 1 km apart, each providing displacement information accurate to the nearest millimeter, could detect strain as small as 2 mm km -1 , or 2 × 10 -6 . It is possible, however, to measure strains at least three orders of magnitude smaller using borehole strainmeters. In fact, it is even possible to measure strains as small as 10 -8 using observations of groundwater levels in boreholes.

Book chapter↗

USGS2006

Continuous borehole strain and pore pressure in the near field of the 28 September 2004 M 6.0 Parkfield, California, earthquake: Implications for nucleation, fault response, earthquake prediction and tremor

Near-field observations of high-precision borehole strain and pore pressure, show no indication of coherent accelerating strain or pore pressure during the weeks to seconds before the 28 September 2004 M 6.0 Parkfield earthquake. Minor changes in strain rate did occur at a few sites during the last 24 hr before the earthquake but these changes are neither significant nor have the form expected for strain during slip coalescence initiating fault failure. Seconds before the event, strain is stable at the 10 −11 level. Final prerupture nucleation slip in the hypocentral region is constrained to have a moment less than 2 × 10 12 N m ( M 2.2) and a source size less than 30 m. Ground displacement data indicate similar constraints. Localized rupture nucleation and runaway precludes useful prediction of damaging earthquakes. Coseismic dynamic strains of about 10 microstrain peak-to-peak were superimposed on volumetric strain offsets of about 0.5 microstrain to the northwest of the epicenter and about 0.2 microstrain to the southeast of the epicenter, consistent with right lateral slip. Observed strain and Global Positioning System ( gps ) offsets can be simply fit with 20 cm of slip between 4 and 10 km on a 20-km segment of the fault north of Gold Hill ( M 0 = 7 × 10 17 N m). Variable slip inversion models using gps data and seismic data indicate similar moments. Observed postseismic strain is 60% to 300% of the coseismic strain, indicating incomplete release of accumulated strain. No measurable change in fault zone compliance preceding or following the earthquake is indicated by stable earth tidal response. No indications of strain change accompany nonvolcanic tremor events reported prior to and following the earthquake.

California↗

USGS2002

36 - Implications of crustal strain during conventional, slow, and silent earthquakes

Uniform block-slip motion consistent with simple shear on locked fault segments is the primary feature apparent in geodetic measurements of strain accumulation along plate boundaries (Savage, 1983). However, almost every aspect of fault failure is nonlinear in character. This premise derives from theoretical models (Kostrov, 1966; Richards, 1976; Andrews, 1976; Freund, 1979; Rice and Rudnicki, 1979; Rice, 1983, 1992; Stuart, 1979, Stuart and Mavko, 1979; Das and Scholz, 1981; Rundle et al., 1984; Tse and Rice, 1986; Lorenzetti and Tullis, 1989; Segall and Rice, 1995; Shaw, 1997; Miller et al., 1999) and laboratory-generated frictional failure of crustal materials (Dieterich, 1979, 1981; Mogi, 1981; Mogi et al., 1982) which predict accelerating deformation will occur before dynamic slip instabilities, better known as earthquakes.

International Geophysics↗

USGS1994

Continuous borehole strain in the San Andreas fault zone before, during, and after the 28 June 1992, MW 7.3 Landers, California, earthquake

High-precision strain was observed with a borehole dilational strainmeter in the Devil's Punchbowl during the 11:58 UT 28 June 1992 M W 7.3 Landers earthquake and the large Big Bear aftershock ( M W 6.3). The strainmeter is installed at a depth of 176 m in the fault zone approximately midway between the surface traces of the San Andreas and Punchbowl faults and is about 100 km from the 85-km-long Landers rupture. We have questioned whether unusual amplified strains indicating precursive slip or high fault compliance occurred on the faults ruptured by the Landers earthquake, or in the San Andreas fault zone before and during the earthquake, whether static offsets for both the Landers and Big Bear earthquakes agree with expectation from geodetic and seismologic models of the ruptures and with observations from a nearby two-color geodimeter network, and whether postseismic behavior indicated continued slip on the Landers rupture or local triggered slip on the San Andreas. We show that the strain observed during the earthquake at this instrument shows no apparent amplification effects. There are no indications of precursive strain in these strain data due to either local slip on the San Andreas or precursive slip on the eventual Landers rupture. The observations are generally consistent with models of the earthquake in which fault geometry and slip have the same form as that determined by either inversion of the seismic data or inversion of geodetically determined ground displacements produced by the earthquake. Finally, there are some indications of minor postseismic behavior, particularly during the month following the earthquake.

California↗

USGS1987

Fault failure with moderate earthquakes

High resolution strain and tilt recordings were made in the near-field of, and prior to, the May 1983 Coalinga earthquake ( M L = 6.7, Δ = 51 km), the August 4, 1985, Kettleman Hills earthquake ( M L = 5.5, Δ = 34 km), the April 1984 Morgan Hill earthquake ( M L = 6.1, Δ = 55 km), the November 1984 Round Valley earthquake ( M L = 5.8, Δ = 54 km), the January 14, 1978, Izu, Japan earthquake ( M L = 7.0, Δ = 28 km), and several other smaller magnitude earthquakes. These recordings were made with near-surface instruments (resolution 10 −8 ), with borehole dilatometers (resolution 10 −10 ) and a 3-component borehole strainmeter (resolution 10 −9 ). While observed coseismic offsets are generally in good agreement with expectations from elastic dislocation theory, and while post-seismic deformation continued, in some cases, with a moment comparable to that of the main shock, preseismic strain or tilt perturbations from hours to seconds (or less) before the main shock are not apparent above the present resolution. Precursory slip for these events, if any occurred, must have had a moment less than a few percent of that of the main event. To the extent that these records reflect general fault behavior, the strong constraint on the size and amount of slip triggering major rupture makes prediction of the onset times and final magnitudes of the rupture zones a difficult task unless the instruments are fortuitously installed near the rupture initiation point. These data are best explained by an inhomogeneous failure model for which various areas of the fault plane have either different stress-slip constitutive laws or spatially varying constitutive parameters. Other work on seismic waveform analysis and synthetic waveforms indicates that the rupturing process is inhomogeneous and controlled by points of higher strength. These models indicate that rupture initiation occurs at smaller regions of higher strength which, when broken, allow runaway catastrophic failure.

California↗