There are two kinds of people who don\u2019t hang pictures on their walls: minimalists, and people who live directly above a fault line.<\/p>\n
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Alex\u00a0Cully is the latter. From 2016 to 2017, Cully rented an apartment in the Hayward<\/a> Hills, near Garin Regional Park, that was directly on the Hayward Fault. Because two continental plates were having a shoving fight beneath the floorboards, Cully had started to forgo the normal interior decor.<\/p>\n \u201cI never put up photos on the walls, and kept everything fragile either in a box or somewhere that falling wouldn\u2019t break them,\u201d\u00a0Cully said in an email.<\/p>\n Article continues below this ad<\/p>\n But that wasn\u2019t the worst of it.<\/p>\n Everyone in the San Francisco Bay Area knows we live in a geologically active region. Lest you forget, small reminders poke out everywhere: tsunami warning signs, earthquake insurance fees, triangular crossbeams that gird earthquake-retrofitted buildings, and our noticeable lack of brick construction.<\/p>\n Make SFGATE a preferred source so your search results prioritize writing by actual people, not AI.<\/p>\n <\/p>\n Add Preferred Source<\/p>\n <\/a><\/p>\n But then there are the brave Bay Area residents who live directly on top of the boundary between two tectonic plates \u2014 what, in common parlance, we call a fault line. For them, the existential threat presents itself in small, and sometimes big, ways on a weekly basis. Plate tectonics is not a slow process but something that plays out constantly on their property.\u00a0<\/p>\n Article continues below this ad<\/p>\n An aerial view of UC Berkeley\u2019s California Memorial Stadium in Berkeley, Calif.\u00a0<\/p>\n Steve Proehl\/Getty Images\/Corbis Unreleased<\/p>\n Many prominent properties in the Bay are built atop faults<\/a>: UC Berkeley\u2019s California Memorial Stadium; much of Cal\u2019s adjacent frat row; the Oakland Zoo<\/a>; and a long swath of Skyline Boulevard on the Peninsula are all bisected by either the Hayward or San Andreas faults. Moreover, hundreds of single family-homes on both sides of the Bay sit atop a fault line.\u00a0<\/p>\n And if you\u2019ve ever wondered what it\u2019s like for the people who live atop such geologic hazards\u00a0\u2014 boy, do they have stories.<\/p>\n What\u2019s happening geologically\u00a0<\/p>\n The Bay Area is one of the most seismically active urban areas in the whole world. In terms of natural beauty, that\u2019s a boon: vast mountain ranges, dramatic coastlines and San Francisco\u2019s\u00a0legendary hills<\/a> all owe their existence to our geologically active region.\u00a0 Article continues below this ad<\/p>\n An illustration shows the major fault lines in the San Francisco Bay Area.\u00a0<\/p>\n Getty Images<\/p>\n Specifically, the treacherous Hayward Fault is a \u201csecondary strand\u201d of the San Andreas Fault system, Roland B\u00fcrgmann\u00a0told SFGATE in a phone interview. B\u00fcrgmann, a professor of geophysics at the Berkeley Seismological Laboratory, studies active tectonics, including the Hayward Fault.\u00a0<\/p>\n To visualize the relationship between the San Andreas and Hayward faults,\u00a0B\u00fcrgmann\u00a0likened it to slices of cake. The wedge of cake bound by the Hayward and San Andreas faults is moving a little faster than the plate to its east, and the (mostly oceanic) plate west of the San Andreas Fault is moving faster than either of those.\u00a0<\/p>\n Meanwhile, some fault systems abut and push into each other, producing mountains.<\/p>\n Article continues below this ad<\/p>\n That\u2019s not what ours does.<\/p>\n Our fault system is what is known as a \u201cslip-strike\u201d fault,\u00a0B\u00fcrgmann said \u2014 meaning these tectonic plates \u201cmove horizontally\u201d against each other.\u00a0<\/p>\n \u201cIn this case, the Pacific plate moves towards the northwest and relative to North America,\u201d he added. B\u00fcrgmann\u00a0said the Hayward Fault moves about 10 millimeters a year, while the San Andreas moves about 20 millimeters. (That motion is relative to either side of the fault.)<\/p>\n FILE: A bridge crosses over the San Andreas Fault from the Pacific to the North American tectonic plates near Parkfield, Calif.\u00a0<\/p>\n Frederic J. Brown\/AFP via Getty<\/p>\n This explains what was going on in\u00a0Cully\u2019s apartment complex in Hayward. The western half of the apartment was moving northwest relative to the eastern half. And since buildings are designed to be, well, immobile, that didn\u2019t exactly have positive consequences for Cully\u2019s photos on her wall \u2014 or the rest of her building, as she\u2019ll explain soon.\u00a0<\/p>\n Article continues below this ad<\/p>\n When a fault line suddenly slips<\/p>\n For an example of the effects of the Hayward Fault on human-made structures, take a stroll around\u00a0UC Berkeley\u2019s California Memorial Stadium. Home to Cal\u2019s football team, the Golden Bears, the stadium also happens to bisect the Hayward Fault.\u00a0<\/p>\n In 2008, the university initiated a nine<\/a>-figure renovation to seismically retrofit the stadium. As Carolyn Jones wrote for SFGATE at the time, the plan called for \u201cportions of the stadium to be sliced into blocks that will rest on plastic sheets. When the earth ruptures, the soil will move under the sheets but, engineers hope, will leave the blocks intact.\u201d<\/p>\n While the structure itself is safe(ish) by virtue of these retrofits, you can see the dramatic effects of what the fault is doing to the surrounding environment. Where the exterior stairs touch the stadium, cracks in the concrete reveal that it is pulling away from the structure. Grout in the sidewalk adjoining the stadium and sidewalk is inches apart from where it clearly used to be. Walk about a hundred feet from the stadium\u2019s south entrance and kneel, and you can see a rippling in the cinder block steps that form the walkway \u2014 an ominous reminder from the Earth that, yes, it is alive, and there\u2019s stuff happening down there.<\/p>\n Article continues below this ad<\/p>\n Buckling cobblestones in the sidewalk outside UC Berkeley\u2019s California Memorial Stadium in Berkeley, Calif.,\u00a0on March 1, 2026. The Hayward Fault runs directly beneath the stadium.<\/p>\n Keith A. Spencer<\/p>\n But these literal cracks in the facade are better than the alternative, it turns out \u2014 not all faults are so gracious.\u00a0<\/p>\n \u201cThere are essentially two major ways in which faults slip,\u201d B\u00fcrgmann explained. \u201cOne is suddenly \u2014 in an earthquake, going fast enough that it also produces seismic shaking.\u201d<\/p>\n \u201cAnd the other would be this slow sliding\u201d \u2014 what is known as creep or slow slip, he said. The land around Cal\u2019s stadium is doing the slow sliding, fortuitously.<\/p>\n Article continues below this ad<\/p>\n B\u00fcrgmann also said that the Hayward Fault in particular has \u201clittle, slow, so-called creep events. Those are much slower than earthquakes.\u201d<\/p>\n And that creep is visible in the concrete and grout that\u2019s slowly separating around the Berkeley stadium.<\/p>\n Steve Graham, a geology professor in the Department of Earth and Planetary Sciences at Stanford University, explained in a phone interview that creep is preferable to the sudden release of energy that accompanies an earthquake. Creep means that the energy from the fault is coming out slowly rather than all at once. (Though that \u201cdoesn\u2019t preclude a larger earthquake happening along a creeping section,\u201d Graham clarified.)<\/p>\n And if you live on a fault line that suddenly slips?\u00a0<\/p>\n Article continues below this ad<\/p>\n The author\u2019s foot is seen next to the drainage grate, left, on the sidewalk abutting the California Memorial Stadium; grout and the sidewalk, at right, are separating from the California Memorial Stadium in Berkeley, Calif.<\/p>\n Keith A. Spencer<\/p>\n \u201cThere\u2019s little that could be worse than living exactly on a break or a fault, because if it slips 15 feet suddenly in an event, your house is going to be ripped asunder,\u201d Graham said.\u00a0<\/p>\n Graham mentioned the\u00a0Kaikoura earthquake<\/a> that struck New Zealand in 2016. One of his Ph.D. advisees was working in the area near a house that was \u201cbuilt exactly where that fault actually breached the surface in this earthquake.\u201d<\/p>\n \u201cAnd there\u2019s a very dramatic aerial view of the house that actually was fully twisted off of its foundation and the driveway offset by 15 feet in a lateral movement,\u201d Graham added.<\/p>\n Article continues below this ad<\/p>\n That now-iconic photo<\/a> from that earthquake shows the house on one side of the fault and its foundation on the other \u2014 as though a magician performed a tablecloth trick on the house. A seam like a scar runs across the two, the product of the fault below.<\/p>\n Because the Bay Area has the same kind of strike-slip faults, this is what could happen in a big quake if you were living right on a fault line. The most dangerous apartment in the East Bay?<\/p>\n In the year she lived in the fault-overlapping Hayward apartment,\u00a0Cully never saw something as dramatic as the building getting ripped off its foundation. But she observed the effects of the fault all the time. And they kept escalating.\u00a0<\/p>\n Article continues below this ad<\/p>\n \u201cAsphalt constantly cracked,\u201d\u00a0Cully said. Her water pipes \u201cwere breaking regularly in the same areas.\u201d Wooden railings would separate from the walls as cracks formed between wood and concrete. The sidewalk was pushed up in random spots. And cracks appeared in the road and parking lot \u2014 cracks that grew regularly, she noted. \u00a0<\/p>\n FILE: Contra Costa College in San Pablo, Calif,. sits near the Hayward Fault. Bricks at the Campus Circle courtyard on the campus\u2019s north side appear to have shifted into an S-alignment.<\/p>\n John Dvorak\/Getty Images<\/p>\n The apartment\u2019s parking lot was\u00a0repaved while Cully lived there and immediately began deteriorating. \u201cBy the time I moved out, there was 1.5 inches of dip from the main road, and the center had begun to sink,\u201d\u00a0Cully said.<\/p>\n As Graham noted,\u00a0Cully was observing not only creep but the more dramatic, sudden \u201cslip\u201d effects from small earthquakes, too.\u00a0<\/p>\n Article continues below this ad<\/p>\n \u201cThere was one particular 3.0-plus [quake] that made the whole building creak and shift. It was very scary,\u201d Cully said. \u201cAfter that, the walls had deep cracks going horizontal, showing that the foundation had tilted and the drywall separated. This wasn\u2019t relative to just our unit. Lower down the hill, the roadway began to split into deep convex fissures.\u201d\u00a0<\/p>\n \u201cSeeing the walkways constantly disintegrate was concerning,\u201d\u00a0Cully added. \u201cI worried about our parking situation going downhill \u2014 literally.\u201d Eventually,\u00a0Cully had to adapt to life on a fault. Besides forgoing hanging art, she also stopped using the \u201cbad side\u201d of her patio because it was splitting off from the main building.<\/p>\n Living on the fault in a less urban area is a very different experience compared to Cully\u2019s apartment situation. Carrie Coe\u00a0has lived for 30 years on a fork of the San Andreas Fault in San Benito County. Coe\u00a0said that she \u201crarely worries about the San Andreas.\u201d<\/p>\n Article continues below this ad<\/p>\n \u201cThis property survived the quake of \u201989,\u201d meaning the\u00a0Loma Prieta quake, she said over email. That quake, a magnitude 6.9 event, devastated nearby Santa Cruz, wrecked the Embarcadero Freeway and severed a deck segment of the Bay Bridge.\u00a0<\/p>\n \u201cI figure if it survived that, we\u2019re probably okay,\u201d Coe added. \u201cIf we get a quake bigger than that I think everyone will be in trouble.\u201d<\/p>\n She said that she feels earthquakes \u201cfrequently\u201d on the property. \u201cWe had a doozy on Thanksgiving,\u201d she noted. \u201cThey freak out people from the East Coast, but us locals are used to them.\u201d<\/p>\n But excepting the so-called Big One, Coe is worried more about other natural disasters.<\/p>\n Article continues below this ad<\/p>\n \u201cHonestly, El\u00a0Ni\u00f1o is what scares me,\u201d she said. The fault line creates hilly topography on her property, which \u201cmeans we get mudslides when we get too much rain.\u201d<\/p>\n FILE: The remains of the Cypress Freeway, which ran through the center of Oakland, Calif., following the Loma Prieta earthquake in 1989.\u00a0<\/p>\n Jim Sugar\/Corbis via Getty Images<\/p>\n Who wants to live on a fault line?<\/p>\n So, how dangerous is it actually living on a fault line, as Carrie Coe,\u00a0Alex Cully and thousands of locals do? And how does that compare to living near one, as hundreds of thousands of us do?\u00a0<\/p>\n Article continues below this ad<\/p>\n Geologists I spoke with said that\u2019s hard to assess \u2014 but living directly on a fault line would be inadvisable.\u00a0<\/p>\n \u201cIf you\u2019re right on the fault, nothing good is going to come out of that,\u201d Graham said.\u00a0<\/p>\n \u201cYou don\u2019t want to live right on the fault,\u201d B\u00fcrgmann concurred.\u00a0<\/p>\n FILE: The\u00a0Carrizo Plain in eastern San Luis Obispo County, Calif., contains the most strikingly visual portion of the San Andreas Fault.<\/p>\n Lloyd Cluff\/Getty Images<\/p>\n However, risk is \u201cnot as simple as distance from the fault,\u201d B\u00fcrgmann\u00a0said. \u201cLow-lying areas along the bay that are built on bay mud or reclaimed land experience much more shaking than locations that are closer to the fault but are on solid bedrock,\u201d he noted.\u00a0<\/p>\n Article continues below this ad<\/p>\n \u201cIt depends so much on construction of your home and specifically what it was built on,\u201d Graham said. \u201cWas it built on soft sand like in the Marina District, where buildings subsided where the old sand dunes foundered? Or is it built on and tied into bedrock?\u201d<\/p>\n Bedrock, of course, is the safest option.\u00a0<\/p>\n \u201cIf you\u2019re built on bedrock and tied into it structurally, you\u2019re going to shake with the earth instead of\u00a0disharmoniously, and that\u2019s going to greatly reduce the damage to your house\u00a0\u2014 in principle,\u201d Graham added.\u00a0<\/p>\n Meanwhile, neighborhoods like the Marina, despite being several miles from the San Andreas Fault line, are apt to be the most decimated. That\u2019s because the Marina is built on artificial landfill \u2014 a mix of sand and debris from the 1906 earthquake.\u00a0<\/p>\n Article continues below this ad<\/p>\n FILE: An apartment in San Francisco\u2019s Marina District appears heavily damaged following the 1989 Loma Prieta earthquake.\u00a0<\/p>\n Jim Sugar\/Getty Images<\/p>\n And B\u00fcrgmann\u00a0is putting his faith in science to the test. He said that he lives two blocks from the Hayward Fault. But his house is on solid ground and has the most modern earthquake-proof construction techniques.<\/p>\n \u201cI think I live in a pretty well constructed home, but in a zone that could see quite intense shaking. So we will find out.<\/p>\n \u201cWe do have earthquake insurance,\u201d he added.\u00a0<\/p>\n Article continues below this ad<\/p>\n Regardless of your proximity to either fault, the Hayward Fault is considered one of the most dangerous fault lines in the world. Part of that is the probability of a quake, and another part of that is how urbanized the land around it is.<\/p>\n B\u00fcrgmann said that his colleagues at the United States Geological Survey have data \u201cgoing back 2,000 years or so\u201d on when big earthquakes occurred. According to B\u00fcrgmann,\u00a0scientists estimated that between 2013 and 2043, there is a 30% probability of a 6.7 magnitude or greater earthquake occurring on either the San Andreas or Hayward Fault. And for that one, you probably don\u2019t want to be living directly above it.\u00a0<\/p>\n Article continues below this ad<\/p>\n<\/p>\n
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In other words, the Bay\u2019s famous topography is the result of a few major fault lines, including the San Andreas Fault, which runs south by southeast from Daly City down through San Juan Bautista (and ultimately down to SoCal), and the Hayward Fault, which runs parallel from Richmond and through Morgan Hill. There are other fault lines in the area, too \u2014 among them are the Calaveras Fault and the Rodgers Creek Fault. But technically, these are all part of the same fault system, experts said.<\/p>\n<\/p>\n
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Cully found this out firsthand.<\/p>\n<\/p>\n
In practical terms, what was happening was that the western side of this apartment complex was moving north relative to the eastern half \u2014 by a staggering 10 millimeters a year. That might sound small, but modern buildings built to exact specifications aren\u2019t typically designed to have their opposite ends move 4 inches apart every decade.\u00a0<\/p>\n<\/p>\n
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\u201cThose data suggest, on average, the Hayward Fault can have an earthquake every 150, 260 years,\u201d B\u00fcrgmann\u00a0noted. \u201cAnd that\u2019s just about as long as it\u2019s been since the last one,\u201d referring to the 1868 Hayward earthquake<\/a>.<\/p>\n