Current Projects

Analysis of Patterns of Earthquakes

Using data analysis methods to examine the spatial and temporal relationships of earthquakes, mostly in the Pacific Northwest.

Deformation in the Cascadia Region

Working with Dr. Curt Peterson (PSU) on coastal deformation, and using continuously operating GPS stations (with Dr.Jake Griffiths, NOAA - NGS) .

Ross Ice Shelf, Antarctica

Fracturing in ice shelves, as well as deormation across grounding lines. With Dr. Christina Hulbe (PSU) and Dr. Ginny Catania (UT Austin)

Past Projects

Below are brief summaries of some of the recent project I have worked on. There are some links to online manuscripts.

Analysis of a Kink-like fold in the Oregon-Idaho Graben, Malheur County, Oregon

With graduate student Jake Griffiths. See Jakes Thesis

Dodson debris flow

In February 1996 a series of debris flows occurred near Dodson in the Columbia River Gorge, about 35 miles east of Porland, Oregon. These flows derailed a train, and blocked both directions of Interstate 84 for five days. One of these flows passed through a house, filling the lower floor with mud and debris.

Click here for maps, photographs, and more details on the flow.

Gravity through the Portland Hills

The Department of Geology at Portland State University in collaboration with the U.S. Geological Survey and with the cooperation of Tri-Met conducted a gravity survey in the northern light-rail tunnel through the Portland Hills. The data gathered is available through the Pacific Northwest Geologic Data Clearinghouse.

Stability of Borax Lake

With Ansel Johnson, Michael Cummings and graduate student Sean Wilson. See Sean's thesis for details

Borax lake is a hot spring located a few km from Fields in SE Oregon, in the Alvord Desert. Borax Lake is a located atop a small mound. The mound is an erosion feature -- the surrounding area has been deflated. The area around the hot spring has been armored with sinter and so now stands as a topographic high. Under the sinter is a diatomaceous material with very low remolded strength. Borax Lake contains a unique species of chub that is on the endangered species list. In order to help the chub survive water levels in the lake were raised (by damming outlets). This gives the fish a wider range of water temperatures and helps keep the average temperature more stable. Increasing the water level has also increased some spring activity on the flanks of the mound. The morphology of the mound also suggest that there is some downslope movement of the flanks.

Thus Borax lake is a saturated mound of poorly consolidated material, with very little remolded strength. Should the flanks of Borax Lake begin to move the material may remold, there would be a catastrophic loss of strength in the material, and a section of the flank could rapidly fail (i.e., within a few minutes). This would either cause the lake to drain, or the volume of water to be reduced such that there would be a significant rise in temperature. The catastrophic loss of strength could result from natural movement of the slope, or by earthquake-induced shaking.

To look for any movement on the mound we have installed a series of benchmarks which have been precisely surveyed. These monuments will be resurveyed at a later date to look for any changes in angles or distances between monuments. The monuments were laid out as a series of braced quadrilaterals. This allows us to determine the magnitude and direction of any strains. Strains of 10-3 can be detected in this way. A map of the quadrilaterals is shown below.

Map of quadrilaterals at Borax lake. The benchmarks marked D, E, F, ... II, JJ, KK, ring the lip of Borax lake. The blue lines represent distances measured. All angles between the blue lines were measured using a 1-second total station. Several of the benchmarks on the south side of the lake were tied to a stable ridge of ground to the SW . Grid spacing is 50 meters.

Forms of folds in Roseburg formation along the Umpqua River, Southern Oregon

With graduate student Carol Stack. See Carols Thesis

Engineering Geology of the Newell Canyon area, Oregon City.

With graduate student Bill Burns. See Bills Thesis

Surface deformation 1994 Northridge, CA, earthquake

K.M. Cruikshank, Arvid M. Johnson, & Robert W. Fleming

The research will determine whether areas of concentrated damage to houses, roads and other structures can be ascribed to areas of localized ground deformation along buried faults during the 17 January, 1994 Northridge earthquake in San Fernando Valley, California. The research addresses whether localized damage is due to ground deformation as opposed to some other mechanism such as shaking in valley fill or in-phase surface waves. Our preliminary field investigations identified a zone of fracturing trending NE-SW about 100 m long in the vicinity of Tampa Avenue in Reseda, another trending NW-SE at Tampa Avenue just south of the Simi Valley Freeway, and a third at Balboa Avenue north of the Simi Valley Freeway in Granada Hills. A compilation of building damage has since suggested that the zone in Reseda is part of a band of localized damage several blocks wide and about 12 km long extending from Northridge SW through Canoga Park to Hidden Hills.

Ground deformation will be determined with pre- and post-earthquake ground surveys and aerial photographs. We will measure changes in lengths of various lines defined by connecting identifiable points such as manhole covers, fire hydrants, and other recognizable features. The strains can be obtained by comparing direct measurements of line lengths. Multiple strain measurements in a small area will allow strain ellipses to be determined at points.

Identifying the mechanism responsible for localized damage will help in formulating construction guidelines and zoning in the San Fernando Valley, and aid in planning for the occurrence of major earthquakes near the Los Angeles basin. If localized structural damage can be ascribed to surface deformation resulting from movement on buried faults, then this information will help in evaluating the seismic hazard in other areas containing buried faults, such as the remainder of the Los Angeles basin.

Project Update

The City of Los Angeles, Office of Surveys, Department of Public Works, is currently re-surveying selected in area in the epicentral area. The surveys should reveal the nature of the ground deformation at the city-block scale.

USGS Open-File Report 96-523 Coactive fault of the Northridge earthquake - Granada Hills, California
USGS Open-File Report 96-698 Coactive fault of the Northridge earthquake - Winnetka area, California

Surface fracturing and ground deformation 1992 Landers, CA, earthquake

Arvid M. Johnson, Robert W. Fleming, & K.M. Cruikshank

Surface rupturing during the 28 June 1992, Landers, California earthquake, east of Los Angeles, accommodated right-lateral offsets up to about 6 m along segments of distinct, en echelon fault zones with a total length of 80 km. The offsets were accommodated generally not by faults-distinct slip surfaces-but rather by shear zones, tabular bands of localized shearing. Along simple stretches of fault zones at Landers the rupture is characterized by telescoping of shear zones and intensification of shearing: broad shear zones of mild shearing, containing narrow shear zones of more intense shearing, containing even-narrower shear zones of very intense shearing, which may contain a fault. Thus the ground ruptured across broad belts of shearing with clearly-defined, subparallel walls, oriented NW. Each broad belt consists of a broad zone of mild shearing, extending across its entire width (50 to 200 m), and much narrower (a few m wide) shear zones that accommodate most of the offset of the belt and are portrayed by en echelon tension cracks. In response to right-lateral shearing, the slices of ground bounded by the tension cracks rotated in a clockwise sense, producing left lateral shearing, and the slices were forced against the walls of the shear zone, producing thrusting. Even narrower shear zones formed within the narrow shear zones. Although these probably are guides to right-lateral fault segments below, the surface rupturing during the earthquake is characterized not by faulting, but by the formation of shear zones at various scales.

Online version of Bulletin of the Seismological Society of America paper

Online version of United States Geological Survey Open-file Report OF-93-348

Project Update

Current work is focused on using pre- and post-earthquake photogrammetry to measure distances between identifiable points. This is allowing detailed deformation fields to be determined for a portion of the Emerson Fault. This portion of the rupture also passed through a control network established in the mid 1970's by Southern California Edison. The control network was surveyed for a potential power plant site. The original survey data has been obtained, and the network is being re-surveyed, and re-leveled. This should provide a good picture of the deformation in the area of the Emerson Fault. The results will be posted here as they are written up.

Numerical Simulation of High-Amplitude Folding

High-amplitude folding of viscous multilayers during shortening can be analyzed with a theoretical solution motivated by first-order theoretical analysis of folding by Raymond Fletcher and Ronald Smith. The solution method can better match boundary conditions along irregular interfaces than the first-order method, so it increases the range of slopes over which linear-viscous folding theory can be applied. In our method, rather than solving algebraically for a small number of constants in the flow equations, we numerically solve for a large number of constants, the values of which are chosen so that they minimize errors in matching conditions at the interfaces in a least-squares sense. A similar method has been applied to problems of density instability involving a single deformable interface with bonded contacts, however, we extend the method to include shortening parallel to interfaces and many deformable interfaces so that we can deal with problems of multilayer folding. Contacts between the layers can be firmly bonded, slip freely, or slip with viscous resistance. We use the solution to produce high-amplitude folds in single layers embedded in soft media, and in simple repetitive multilayers confined above and below by stiff or soft media. We show that the folding of linear-viscous multilayers can largely reproduce the gross forms of some small folds in the Huasna syncline in the central California Coast Range as well as the Berry-Buffalo syncline in the central Pennsylvania Appalachians. However, the sharp, chevron-like forms in these natural examples are notably missing in the simulations based on linear-viscous theory.

Online version of Journal of Structural Geology paper on high-amplitude folding

Project Update

Work is currently under way to incorporate nonlinear "frictional" contacts between the layers, and the addition of layer-parallel shearing.

Fold Simulations

There are a number of simulations available. The fold program recorded the coordinates of points at each stage in the evolution of the numerical fold. These results can then be played back using a simple viewer. Sometime soon, I should get to writing a Microsoft Windows viewer. Click here to download simulation files and a MS DOS viewer. You can also download programs to produce AutoCAD DXF, PostScript, and HP-GL files from the simulation files.

Joint Patterns at Arches National Park

This is part of project to understand the fracturing history of the Salt Valley Anticline in Utah. The project has evolved from a detailed analysis of individual fractures, to interpreting the history of the fracture patterns over several kilometers. The work has focused on the SW limb of the anticline, and will soon progress to the NE limb, where the fracture patterns are different.

  • Analysis of minor fractures associated with joints and faulted-joints

Online version of Journal of Structural Geology paper.

  • Duplex structures along deformation bands in Entrada Sandstone

Online version of Journal of Structural Geology paper.

  • Role of fractures in the formation of arches at Arches National Park

Spectacular rock fins on the flanks of Salt Valley anticline in southeast Utah are formed by erosion along zones of joints. Within a rock fin arches form where intense fracturing is localized. Fracture localization is controlled by shear displacement along existing horizontal or vertical discontinuities. Horizontal discontinuities may be shale layers, shale lenses, or bedding planes, whereas vertical discontinuities are usually pre-existing joint segments. The roof and overall shape of an arch is controlled either by existing shale layers, interfaces between sandstones of different properties, or secondary fractures due to shear on vertical joints. Joints that bound rock fins are related to the formation of the diapir-cored Salt Valley anticline. Shear displacement along existing discontinuities, which localizes intense fracturing, is probably related to the growth of Salt Valley anticline and its subsequent collapse due to dissolution of the anticlines salt core.

Online version of Geological Society of America Bulletin paper.

List of arches and their locations (Microsoft Excel 5.0 file)

  • Joint Networks

On the southwest limb of Salt Valley Anticline are three sets of joints in the Entrada Sandstone covering an area of about 6 km2. Within the 20 m thick Moab Member, a single joint set is found in three distinct areas, separated by a second set of joints, at a 35� angle to the first. Joint interaction features show that the second set is younger than the first. This illustrates that joints of a single set do not have to fill the entire area across which the stresses that formed the joints were acting. The underlying Slickrock Member contains the third set of joints, which is at an angle of 5�-35� to joints in the Moab Member. The Slickrock set nucleated from the lower edges of joints of all orientations in the overlying Moab Member. Thus, the fracture pattern evolved both horizontally, within the same unit, and vertically between units. The sequence of jointing is determined by establishing the relative ages of each joint set. Each joint orientation is best interpreted as representing a direction of maximum compression, ruling out the possibility that the joints are a conjugate set. The joints, and an earlier set of deformation bands, record a 95� counterclockwise rotation of the direction of maximum compression.

Online version of Journal of Structural Geology paper.

  • Mobius Joints

Cross-joints which do not intersect the through-going joints confining their development are, in fact, the same joint surface as those through-going joints, as documented by three-dimensional exposures at Arches National Park.

<Online Document>