Harold Mofjeld

Harold Mofjeld
University of Washington Seattle | UW · School of Oceanography

PhD

About

87
Publications
21,593
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
3,613
Citations
Citations since 2017
1 Research Item
875 Citations
2017201820192020202120222023050100150
2017201820192020202120222023050100150
2017201820192020202120222023050100150
2017201820192020202120222023050100150

Publications

Publications (87)
Article
A performance measure for a DART tsunami buoy network has been developed. The measure is based on a statistical analysis of simulated forecasts of wave heights outside an impact site and how much the forecasts are degraded in accuracy when one or more buoys are inoperative. The analysis uses simulated tsunami height time series collected at each bu...
Article
In response to hazards posed by earthquake-induced tsunamis, the National Oceanographic and Atmospheric Administration developed a system for issuing timely warnings to coastal communities. This system, in part, involves matching data collected in real time from deep-ocean buoys to a database of precomputed geophysical models, each associated with...
Article
Full-text available
U.S. Tsunami Warning Centers use real-time bottom pressure (BP) data transmitted from a network of buoys deployed in the Pacific and Atlantic Oceans to tune source coefficients of tsunami forecast models. For accurate coefficients and therefore forecasts, tides at the buoys must be accounted for. In this study, five methods for coefficient estimati...
Article
Full-text available
We have developed a method to compute the total energy transmitted by tsunami waves, to the case where the earthquake source is unknown, by using deep-ocean pressure measurements and numerical models (tsunami source functions). Based on the first wave recorded at the two closest tsunameters (Deep-Ocean Assessment and Reporting of Tsunamis (DART)),...
Article
Full-text available
The ability to accurately forecast potential hazards posed to coastal communities by tsunamis generated seismically in both the near and far field requires knowledge of so-called source coefficients, from which the strength of a tsunami can be deduced. Seismic information alone can be used to set the source coefficients, but the values so derived r...
Article
A methodology for probabilistic tsunami hazard assessment (PTHA) will be described for multiple near- and far-field seismic sources. The method integrates tsunami inundation modeling with the approach of probabilistic seismic hazard assessment (PSHA). A database of inundation simulations is developed, with each simulation corresponding to an earthq...
Article
Full-text available
A major difficulty in investigating the nature of interdecadal variability of climatic time series is their shortness. An approach to this problem is through comparison of models. In this paper a first-order autoregressive [AR(1)] model is contrasted with a fractionally differenced (FD) model as applied to the winter-averaged sea level pressure tim...
Article
Full-text available
The first probabilistic tsunami flooding maps have been developed. The methodology, called probabilistic tsunami hazard assessment (PTHA), integrates tsunami inundation modeling with methods of probabilistic seismic hazard assessment (PSHA). Application of the methodology to Seaside, Oregon, has yielded estimates of the spatial distribution of 100-...
Article
Full-text available
This study applies tsunami forecast models developed for NOAA's Tsunami Warning and Forecast System to investigate the May 2006 Tonga Tsunami. Inversion of the Deep-ocean Assessment and Reporting of Tsunamis (DART) measurements estimates a tsunami magnitude equivalent to an earthquake moment magnitude of 8.0. The DART-constrained modeling forecasts...
Article
This study describes winter climate during the last 500 yr for the greater Baltic Sea region through an examination of well-documented time series of ice cover, sea level pressure, and winter surface air temperatures. These time series have been the focus of previous studies, but here their covariation over different time scales is analyzed based o...
Article
Full-text available
A theoretical study was carried out to understand how the probability distribution for maximum wave heights (ηm) during tsunamis depends on the initial tsunami amplitude (A) and the tides. It was assumed that the total wave height is the linear sum of the tides and tsunami time series in which the latter is decaying exponentially in amplitude with...
Article
Full-text available
This study develops a method for estimating the number of casualties that may occur while people evacuate from an inundation zone when a tsunami has inundated an area. The method is based on a simple model of hydrodynamic forces as they affect the human body. The method uses a Tsunami casualty index (TCI) computed at each grid point of a numerical...
Article
Full-text available
Tsunamis are an ever-present threat to lives and property along the coasts of most of the world's oceans. As the Sumatra tsunami of 26 December 2004 reminded the world, we must be more proactive in developing ways to reduce their impact on our global society. This article provides an overview of the state of knowledge of tsunamis, presents some cha...
Article
Regimes and regime shifts are important concepts for understanding decadal variability in the physical system of the North Pacific because of the potential for an ecosystem to reorganize itself in response to such shifts. There are two prevalent senses in which these concepts are taken in the literature. The first is a formal definition and posits...
Article
Surface air temperatures (SAT) from three Alaskan weather stations in a north–south section (Barrow, Nome, and St. Paul) show that on a decadal scale, the correlation among the stations changed during the past century. Before the 1960s, Barrow and Nome were dominated by Arctic air masses and St. Paul was dominated by North Pacific maritime air mass...
Chapter
The Hazard Assessment component of the U.S. National Tsunami Hazard Mitigation Program has completed 22 modeling efforts covering 113 coastal communities with an estimated population of 1.2 million residents that are at risk. Twenty-three evacuation maps have also been completed. Important improvements in organizational structure have been made wit...
Article
Numerical model simulations, combined with tide-gauge and satellite altimetry data, reveal that wave amplitudes, directionality, and global propagation patterns of the 26 December 2004 Sumatra tsunami were primarily determined by the orientation and intensity of the offshore seismic line source and subsequently by the trapping effect of mid-ocean r...
Article
Full-text available
A new method for real-time tsunami forecasting will provide NOAAs Tsunami Warning Centers with forecast guidance tools during an actual tsunami event. PMEL has developed the methodology of combining real-time data from tsunameters with numerical model estimates to provide site- and event-specific forecasts for tsunamis in real time. An overview of...
Article
Full-text available
A tsunameter (soo-NAHM-etter) network has been established in the Pacific by the National Oceanic and Atmospheric Administration. Named by analogy with seismometers, the NOAA tsunameters provide early detection and real-time measurements of deep-ocean tsunamis as they propagate toward coastal communities, enabling the rapid assessment of their dest...
Article
A tsunameter (soo-NAHM-etter) network has been established in the Pacific by the National Oceanic and Atmospheric Administration. Named by analogy with seismometers, the NOAA tsunameters provide early detection and real-time measurements of deep-ocean tsunamis as they propagate toward coastal communities, enabling the rapid assessment of their dest...
Article
The tides along the U.S. West Coast are large enough to have a major impact on tsunami inundation. An analysis of the first-order linear effects of tides on the total tsunami wave heights has been carried out for Seaside, Oregon, as part of the FEMA FIRM Pilot Study (Gonzalez et al., this session). Since the tsunami may arrive at a random time rela...
Article
Full-text available
Instrumental surface air temperature (SAT) records beginning in the late 1800s from 59 Arctic stations north of 64°N show monthly mean anomalies of several degrees and large spatial teleconnectivity, yet there are systematic seasonal and regional differences. Analyses are based on time longitude plots of SAT anomalies and principal component analys...
Article
Introduction Tectonic processes in the deep ocean occur over an immerse range of temporal and spatial scales. The shortest in time are from seconds to minutes during which earthquakes and landslides occur. The recurrence interval between earthquakes, submarine landslides, and volcanic eruptions may be tens, hundreds, or thousands of years. At the f...
Article
Full-text available
We present a case studyin modeling the North Pacific (NP) index, which is a time series related to atmospheric pressure variations at sea level. We con- sider three statistical models, namely, a Gaussian stationary autoregressive process, a Gaussian stationaryfractionallydifferenced (FD) process, and a 'signal plus noise' pro- cess consisting of a...
Article
The harmonic constant datum (HCD) method is a computationally efficient way of estimating tidal datums relative to mean sea level, without the need to compute long time series. However, datum discontinuities can occur between mixed and diurnal tidal regimes using this method. Solutions to this problem are investigated, with a hypothetical strait th...
Article
The National Tsunami Hazard Mitigation Program (NTHMP) seeks to develop and implement tsunami forecast guidance tools for NOAA's Tsunami Warning Centers (TWCs) by integrating two technologies: tsunami numerical modeling and real-time measurement systems. In recent years, tsunami modeling has developed into a mature technology. Consistent simulation...
Article
We present a case study in modeling the North Pacific (NP) index, a time series of the wintertime Aleutian low sea level pressure from 1900 to 1999. We consider three statistical models, namely, a Gaussian stationary autoregressive process, a Gaussian fractionally difference (FD) or ``long-memory" process, and a ``signal plus noise" process consist...
Article
We use a scattering index to identify the regions in the Pacific Ocean where topographic features scatter significant tsunami energy. Based on linear wave theory, the index is computed from the Smith/Sandwell topography. Consistent with numerical simulations, it shows that there is a narrow band of strong scatterers running across the ocean from th...
Article
Full-text available
A project is underway to assess the tsunami hazards that threaten Puget Sound communities and to provide information for tsunami planning and mitigation. It is one of the Tsunami Inundation Modeling Efforts within the National Tsunami Hazard Mitigation Program. It is recognized that the Seattle Fault zone and other active faults in this region have...
Article
Full-text available
Since 1997, PMEL has been involved in the R’D effort to provide tsunami-forecasting capabilities for the Pacific Disaster Center (PDC) in Hawaii. As a part of this effort, modeling tools for the short-term forecasting, and assessing the risk of tsunami inundation have been developed. The Short-term Inundation Forecasting for Tsunamis (SIFT) will in...
Chapter
This paper describes a Research and Development activity to develop tsunami forecasting tools for the Pacific Disaster Center (PDC). The activity included analytical and numerical sensitivity studies of tsunami wave characteristics offshore of Hawaii, for ranges of earthquake source parameters in the Alaska-Aleutian Subduction Zone (AASZ). This reg...
Article
The small amount of North Pacific SST variance explained by the first two organized modes, as well as the irregular nature of the decadal-interdecadal variability of SSTs and spatial atmos-pheric forcing, suggest that a low order, nonlinear, chaotic system of atmospheric/oceanic variability may be acting in the North Pacific. Systems, which visit m...
Article
Full-text available
A method is derived to forecast theextreme heights of later waves in Pacific-widetsunamis, for locations in the vicinity of real-timereporting tide gages. The forecast for wave peaks hasthe form F(t) = B(t) + e(t),where e = A exp [- (t - to)/ ]. Here, the forecast begins attime t = to, which is 4 h after tsunamidetection at a tide gage, is the stan...
Conference Paper
Summary form only given. NOAA has a goal to mitigate the tsunami hazard to Hawaii, California, Oregon, Washington, Alaska, and U.S. possessions in the Pacific region. Fulfilling this goal requires research, development and implementation of tsunami forecasts (with increased accuracy and speed) and the creation of state-of-the-art inundation maps. T...
Article
Full-text available
this paper, we demonstrate that wavelet analysis based on the maximal overlap discrete wavelet transform (MODWT) is an e#ective technique for quantifying the nonstationary characteristics of subtidal sea level fluctuations as measured by the tide gauge at Crescent City, California. This site is of particular interest because Crescent City has a wel...
Article
Full-text available
Low, neap tides occurred along the West Coast of the United States and Canada around 0500 UT January 27, 1700, a time for the last major Cascadia earthquake/tsunami based on teletsunami arrival times in Japan [Satake et al., 1996]. However, high-range perigean spring tides occurred only a week later, illustrating how accurately occurrence times mus...
Chapter
It is found empirically that, at tide gauges in the eastern North Pacific, later waves in a teletsunami are bounded in amplitude by envelopes that can be determined from observations of earlier waves at the same site. This is illustrated using the teletsunami generated by the 4 October 1994 Shikotan earthquake. The envelopes have the form η(t)=AσT...
Article
Since September 1987, bottom pressure (BP) has been observed at Axial Seamount (45°57.5'N, 130°00.3'W 1540-m depth), located 450 km off the Oregon Coast on the Juan de Fuca Ridge. Observations from 1987 to 1992 show that subtidal Axial BP is dominated by barotropic 2- to 5-mbar fluctuations with frequencies =0.5), except at intraseasonal frequencie...
Article
Full-text available
The 25 April 1992 Cape Mendocino earthquake generated a tsunami characterized by both coastal trapped edge wave and non-trapped tsunami modes that propagated north and south along the U.S. West Coast. Both observed and synthetic time series at Crescent City and North Spit are consistent with the zero-order edge wave mode solution for a semi-infinit...
Article
A comparison of bottom pressure observations and global tide models shows that the regional distributions of the diurnal and semidiurnal tides off the Oregon and Washington shelves are determined mainly by the large-scale amphidromic systems in the North Pacific Ocean. These cause the tidal amplitudes to increase toward the northeast and the phase...
Article
A cross-spectral analysis is made of subtidal (0.01-0.5 cpd) sea level (SSL), atmospheric pressure and wind fluctuations observed during 1966-1988 in the southern reaches of the fjord system formed by the Straits of Juan de Fuca/Georgia and Puget Sound. It shows that observed SSL can be largely explained by quasi-steady inverse barometer compensati...
Article
A level 2½ turbulence closure model is used to investigate the dependence on water depth H of bottom stress τb and quadratic drag coefficient Cd for a steady barotropic pressure-driven current in unstratified water when the current is the primary source of turbulence. For spatially uniform pressure gradient and bottom roughness z0 the magnitude |τb...
Article
The emphasis here is on work published since 1966, though the most important earlier work is also included. The focus is on abiotic, noncohesive sediments; however, a few papers on cohesive sediments are also included that bear on the threshold issue. Important publications related to turbulence phenomena in boundary layers have not been overlooked...
Article
The concept of critical stress for the initial motion of noncohesive sediment beds under turbulent flow conditions is reviewed. Observational definitions of incipient motion are many and not entirely compatible. Some laboratory flume observations of sediment movement suggest that no true threshold exists. Current understanding of turbulent fluid mo...
Article
Bottom pressure observations (November 1981 to August 1982) show that the diurnal tides dominate the outer reaches of the northeastern Bering Sea shelf. The diurnal tides decrease inshore from the shelf break (maximum K1 amplitude of 38 cm) and appear to be evanescent Sverdrup (Poincare) waves on the outer shelf. The K1 amplitude (2.3 cm) in the Be...
Article
Frequently the mixing length l in second-order closure models is assumed to have a constant value l0 = γL at large distances from the bottom with a magnitude proportional to the first moment L of turbulent intensity. Although it is often stated that turbulence closure model results are relatively insensitive to the value of mixing length parameter...
Article
Near-bottom current and particulate concentration data and a theoretical model of sediment resuspension together have led to inferences about the erosional response of a fine-grained sediment to bottom stress. Tidal boundary layer observations, made 5 m from the bottom in the main basin of Puget Sound, Washington, show that currents with speeds exc...
Article
The free-drift equations are solved for ice floes in a shallow sea of neutral stratification, typical of many high-latitude continental shelves. Solutions for ice drift and current velocity are obtained as a function of wind stress, ice thickness, and water depth. The ocean is modeled by second-order closure, which allows continuous solutions from...
Article
A semianalytic model of a time-dependent bottom boundary layer has been constructed in which flow and time-variable eddy viscosity are interdependent. Evaluated in the case of oscillatory forcing at tidal frequencies, the model shows that neglecting time variations in viscosity results in underestimates of maximum bottom stress and distortion of th...
Article
Full-text available
We study theoretically the effects of linear (Rayleigh) friction on free internal waves in the equatorial wayeguide. The waves may be vertically propagating or in standing vertical modes. Analytic solutions on a beta-plane show that the meridional scale of the wayeguide becomes significantly larger than the inviscid value only when the frequency is...
Article
Full-text available
On 10 August 1976 Hurricane Belle passed rapidly over the highly stratified shelf of the New York Bight. Records from Aanderaa current-meter moorings show that the response to the hurricane depended strongly on bathymetry. At deeper stations (∼70 m depth), intense, first-mode, internal near-inertial oscillations were generated at frequencies ∼1% le...
Article
Current, salinity, and temperature data obtained from lower Cook Inlet during May-September 1973 have been analyzed. These data define a regional mean circulation whose main features are (1) a concentrated southward flow along the western shore of lower Cook Inlet of water from upper Cook Inlet which has been diluted by river input, (2) an intense...
Article
During 1971 to 1974, offshore pressure gages were developed in the Gulf of Mexico and the Caribbean Sea to measure tides and bottom pressure continuum. The observations indicate that the Gulf of Mexico has a Helmholtz resonance with a period of 1.56d. While the lack of confidence limits on theoretical cotidal charts hinders the comparison between t...
Article
Five bottom pressure gages wer deployed in the Middle-Atlantic Bight during the late winter of 1974. Analysis of the resulting pressure series and neighboring coastal tide gage series shows that tides are the dominant pressure signal in this section of the continental shelf. Most of the remaining pressure fluctuations appear to be forced by meteoro...
Article
The behavior of a barotropic Rossby wave in a zonal current is studied theoretically using a beta-plane ocean of constant depth in which the current depends only on latitude. The wave may be reflected or absorbed, depending on whether the relative frequency as detected in the moving water increases or decreases, respectively, as the wave penetrates...
Article
Full-text available
Pressure fluctuations on the deep seafloor at frequencies below inertial and tidal have been measured. Between 0.1 and 1 cycle per day the variance is about 2 mb², spectra diminish with increasing frequency as ω⁻ⁿ, n=1.5 to 2, and a signal-to-instrument noise ratio of 10 dB is achieved. Fluctuations are in phase and highly coherent within the MODE...
Article
Full-text available
3. Freeze frames of animation of modeled tsunami at 30-second intervals (from left to right). The wave crest is colored pale blue. Note that because Harbor Island is uplifted by the earthquake, the Duwamish Waterway initially drains rapidly before the wave reflects off the north side of the bay and then inundates the Harbor Island area. WASHINGTON...
Article
Full-text available
Over the period October 1999–January 2001, there were four separate occasions in which real-time reporting tsunami DART systems, deployed by NOAA in the North Pacific, were set into tsunami event reporting mode by regional earthquakes. Fortunately, none of these generated a dangerous tsunami. To go into event mode, the high-frequency fluctuations i...
Article
Full-text available
This study aims to reproduce the tsunami that occurred 1100 years ago in Puget Sound reported by recent paleoseismological studies, using a finite difference model based on nonlinear shallow water theory. The study refines the estimates of run-up height, flow depth, and current velocity at these sites made by Moore (1993) and Dinkelman and Holmes (...
Article
Full-text available
The U.S. National Tsunami Hazard Mitigation Program (NTHMP) was established in Fiscal Year 1997, and is now in its fifth year of operation. This report provides a review of NTHMP Inundation Mapping Program activities during the first 5 years, 1997–2001. Accom-plishments include the establishment of a tsunami modeling infrastructure and the producti...
Article
Full-text available
Abstract Matching pursuit was originally formulated as a technique for identifying the time/frequency content of a time series whose spectral properties evolve over time. The basic idea was to construct a large ‘dictionary’ of explanatory vectors that are lo- calized both in time and in frequency and then to analyze a time series by projecting it a...
Article
Full-text available
The computed tsunami inundation is shown on the map in three color-coded depth ranges: 0-0.5 m, 0.5-2 m, and greater than 2 m. These depth ranges were chosen because they are approximately knee-high or less, knee-high to head-high, and more than head-high and so approximately represent the degree of hazard for life safety. The greatest tsunami floo...