“The Landers earthquake, which had a moment magnitude (Mw) of 7.3, was the largest earthquake to strike the contiguous United States in 40 years. This earthquake resulted from the rupture of five major and many minor right-lateral faults near the southern end of the eastern California shear zone.”
—Kerry Sieh et al., Science, v 260, issue 5105, 171-176.
Staying Safe Where the Earth Shakes
Staying Safe Where the Earth Shakes is a booklet that includes the “Seven Steps to Earthquake Safety” – basic guidelines for what to do before, during, and after a damaging earthquake.
When the Landers earthquake struck on the morning of June 28, 1992, it immediately grabbed the attention of earthquake scientists due to not only its large magnitude, but also the wealth of data that was collected. At magnitude 7.3, it was the largest earthquake in the contiguous United States in 40 years, leaving a dramatic surface break through the Mojave desert.
Damage was light relative to the magnitude due to the sparsely populated location of the earthquake, but local desert communities experienced very strong shaking, and one child was killed by the collapse of a stone fireplace. It was also the first large earthquake following the establishment of the National Earthquake Hazards Reduction Program in 1977, which greatly expanded seismic monitoring led by the US Geological Survey in partnership with academic institutions.
From the earliest observations onward, it became clear that this was a complex sequence that included the primary mainshock (the M 7.3 Landers earthquake), a large foreshock (the M 6.1 Joshua Tree earthquake), many aftershocks including the M6.3 Big Bear event, and distant events that scientists dubbed remotely triggered earthquakes: “The magnitude 7.3 Landers earthquake of 28 June 1992 triggered a remarkable sudden and widespread increase in earthquake activity across much of the western United States. The triggered earthquakes, which occurred at distances of up to 1250 kilometers (17 source dimensions) from the Landers mainshock, were confined to areas of persistent seismicity and strike-slip to normal faulting” —David Hill et al., Science, v 260, issue 5114, 1617-1623
Computer technologies were relatively limited in 1992: with the web barely in its infancy, researchers had less sophisticated tools than they do now to analyze data and share results. Researchers rushed to their offices to analyze the quake, relying on paper topo maps to interpret data and plan fieldwork. The launch of the USGS Did You Feel It? system was still seven years away (although observations of the earthquake can now be contributed retroactively!).
In spite of these limitations, the Landers earthquake produced a bounty of new data. Over the weeks, months, and years that followed, researchers exploited the rich data sets collected from traditional networks, boots-on-the-ground mapping, portable instruments, and remote sensing imagery. Seismology is a data-driven science, often fueled by observations of notable earthquakes. Using the wealth of data it generated, the Landers sequence had many important lessons for earthquake science, lessons regarding the potentially complex nature of large earthquake ruptures, and how earthquakes trigger other earthquakes at both near and far distances.
The Landers mainshock was followed by many thousands of recorded aftershocks. Those aftershocks tapered off over time, but in the decades that followed, it became clear that the Joshua Tree-Landers-Big Bear sequence was only the beginning of a period of heightened regional activity in the area known as the Eastern California Shear Zone.
On 16 October 1999, the M7.1 Hector Mine earthquake—another complex large earthquake in a remote part of the Mojave desert—struck to the west/northwest of the Landers rupture. Then in 2019, the Ridgecrest area to the north of Landers was jolted by a M6.4 earthquake on 4 July, followed by a M7.1 earthquake on 5 July. The Ridgecrest earthquakes in particular generated another bounty of data from monitoring networks that have grown more sophisticated since 1992.
Thus, from 1992 onward, the eastern part of California has been especially seismically active. Thanks to modern data availability and innovative analysis, the Landers earthquake, and the large earthquakes that followed, contributed important lessons to our understanding of earthquake ruptures and the complex interactions between earthquakes and faults. These scientific developments continue to contribute directly to improved understanding of seismic hazard in southern California and beyond.
Science
The 1992 Landers-Big Bear Earthquakes
Articles from CALIFORNIA GEOLOGY™ magazine about the earthquake sequence and its effects, including numerous photos.
Scientific overview of the earthquake from Southern California Earthquake Data Center, including photos of the fault rupture.
Lectures
Earthquake Storms by Sue Hough
OCTOBER 27, 2005
Where Earthquakes Hide in the Desert by Austin Elliot
MAY 27, 2021
Webinar
Lessons, Lore, and Legacies of the 1992 Landers Earthquake
June 28, 2022
Sounds
Listen to the shaking of the Landers Earthquake captured by seismometers in Parkfield, CA and Long Valley Caldera near Mammoth Lakes, CA.
Parkfield
Long Valley Caldera
1992 Joshua Tree-Landers-Big Bear, California Earthquake Sequence
All earthquakes magnitude 2 or greater in the region of the 1992 Joshua Tree-Landers-Big Bear sequence from April 22 to July 15 are shown as gray circles. The mainshocks for each of the 3 main sequences are shown as red stars.
- Overview
“The Landers earthquake, which had a moment magnitude (Mw) of 7.3, was the largest earthquake to strike the contiguous United States in 40 years. This earthquake resulted from the rupture of five major and many minor right-lateral faults near the southern end of the eastern California shear zone.”
—Kerry Sieh et al., Science, v 260, issue 5105, 171-176.
Staying Safe Where the Earth ShakesStaying Safe Where the Earth Shakes is a booklet that includes the “Seven Steps to Earthquake Safety” – basic guidelines for what to do before, during, and after a damaging earthquake.
When the Landers earthquake struck on the morning of June 28, 1992, it immediately grabbed the attention of earthquake scientists due to not only its large magnitude, but also the wealth of data that was collected. At magnitude 7.3, it was the largest earthquake in the contiguous United States in 40 years, leaving a dramatic surface break through the Mojave desert.
Sources/Usage: Public Domain.The Landers earthquake ruptured segments of multiple faults that had previously been mapped as separate structures. The most dramatic scarp, including a component of vertical as well as horizontal motion, was on the Emerson fault in a remote part of the Mojave desert. (Photograph: Susan E. Hough, USGS) Damage was light relative to the magnitude due to the sparsely populated location of the earthquake, but local desert communities experienced very strong shaking, and one child was killed by the collapse of a stone fireplace. It was also the first large earthquake following the establishment of the National Earthquake Hazards Reduction Program in 1977, which greatly expanded seismic monitoring led by the US Geological Survey in partnership with academic institutions.
Sources/Usage: Public Domain.Damage from the Landers earthquake was relatively light given the magnitude (7.3) because the strongest shaking was concentrated in a relatively remote part of the Mojave Desert. Structures in the desert near the town of Landers did, however, sustain serious damage. Shaking at this location was likely especially strong due to the proximity to the surface rupture and the local topography, which is known to amplify shaking. (Photograph: Susan E. Hough, USGS) From the earliest observations onward, it became clear that this was a complex sequence that included the primary mainshock (the M 7.3 Landers earthquake), a large foreshock (the M 6.1 Joshua Tree earthquake), many aftershocks including the M6.3 Big Bear event, and distant events that scientists dubbed remotely triggered earthquakes: “The magnitude 7.3 Landers earthquake of 28 June 1992 triggered a remarkable sudden and widespread increase in earthquake activity across much of the western United States. The triggered earthquakes, which occurred at distances of up to 1250 kilometers (17 source dimensions) from the Landers mainshock, were confined to areas of persistent seismicity and strike-slip to normal faulting” —David Hill et al., Science, v 260, issue 5114, 1617-1623
Computer technologies were relatively limited in 1992: with the web barely in its infancy, researchers had less sophisticated tools than they do now to analyze data and share results. Researchers rushed to their offices to analyze the quake, relying on paper topo maps to interpret data and plan fieldwork. The launch of the USGS Did You Feel It? system was still seven years away (although observations of the earthquake can now be contributed retroactively!).
In spite of these limitations, the Landers earthquake produced a bounty of new data. Over the weeks, months, and years that followed, researchers exploited the rich data sets collected from traditional networks, boots-on-the-ground mapping, portable instruments, and remote sensing imagery. Seismology is a data-driven science, often fueled by observations of notable earthquakes. Using the wealth of data it generated, the Landers sequence had many important lessons for earthquake science, lessons regarding the potentially complex nature of large earthquake ruptures, and how earthquakes trigger other earthquakes at both near and far distances.
The Landers mainshock was followed by many thousands of recorded aftershocks. Those aftershocks tapered off over time, but in the decades that followed, it became clear that the Joshua Tree-Landers-Big Bear sequence was only the beginning of a period of heightened regional activity in the area known as the Eastern California Shear Zone.
On 16 October 1999, the M7.1 Hector Mine earthquake—another complex large earthquake in a remote part of the Mojave desert—struck to the west/northwest of the Landers rupture. Then in 2019, the Ridgecrest area to the north of Landers was jolted by a M6.4 earthquake on 4 July, followed by a M7.1 earthquake on 5 July. The Ridgecrest earthquakes in particular generated another bounty of data from monitoring networks that have grown more sophisticated since 1992.
Thus, from 1992 onward, the eastern part of California has been especially seismically active. Thanks to modern data availability and innovative analysis, the Landers earthquake, and the large earthquakes that followed, contributed important lessons to our understanding of earthquake ruptures and the complex interactions between earthquakes and faults. These scientific developments continue to contribute directly to improved understanding of seismic hazard in southern California and beyond.
Science
The 1992 Landers-Big Bear Earthquakes
Articles from CALIFORNIA GEOLOGY™ magazine about the earthquake sequence and its effects, including numerous photos.
Scientific overview of the earthquake from Southern California Earthquake Data Center, including photos of the fault rupture.
Lectures
Earthquake Storms by Sue Hough
OCTOBER 27, 2005
Where Earthquakes Hide in the Desert by Austin Elliot
MAY 27, 2021
Webinar
Lessons, Lore, and Legacies of the 1992 Landers Earthquake
June 28, 2022
Sounds
Listen to the shaking of the Landers Earthquake captured by seismometers in Parkfield, CA and Long Valley Caldera near Mammoth Lakes, CA.
Parkfield
Sound recorded from the Parkfield, CA area during the 1992 M7.3 Landers earthquake event. Long Valley Caldera
Sound recorded from the Long Valley, CA area during the 1992 M7.3 Landers earthquake event. - Multimedia
1992 Joshua Tree-Landers-Big Bear, California Earthquake Sequence
All earthquakes magnitude 2 or greater in the region of the 1992 Joshua Tree-Landers-Big Bear sequence from April 22 to July 15 are shown as gray circles. The mainshocks for each of the 3 main sequences are shown as red stars.
- Publications