Ghost forest on Washington state's Copalis River during a very high fair-weather tide in December 1997. Photo courtesy of the USGS public domain

If a megathrust earthquake struck the modern world, most of us would know about it within seconds. Bill Steele, Director of Information Services at the Pacific Northwest Seismic Network, would get a detailed account from an extensive array of seismometers located around the globe. Regular citizens would probably get an email, tweet, or Facebook note from a friend.

But what if the quake hit hundreds of years ago? How were scientists able to determine that a Cascadia Subduction Zone megathrust trembler hit sometime between 9:00 and 10:00 p.m. on January 26, 1700?

The story starts in the 1980s when geologist Brian Atwater, dendrochronologist David Yamaguchi, and others began to investigate the Pacific coast of Oregon and Washington. Traveling by foot and boat through the region’s many bays and river mouths, the scientists examined thousands of dead western red cedar and Sitka spruce. The trees had not fallen to the ground but stuck upright out of the sand in great groves, known as ghost forests.

Intriguingly, James Graham Cooper, a naturalist living on the Washington coast in 1853-1854, had noticed the dead trees, too. He thought they had died slowly, sinking into quicksand. Atwater, however, knew differently. When a magnitude 9.5 earthquake hit Chile in 1960, coastal marshes had dropped several feet, allowing sea water to flow in and quickly kill the trees.

Because the spruce and cedar still stood in place, Atwater and Yamaguchi realized they had a clock that would tell precisely when the trees died. All they had to do was look at the trees’ growth rings. Those rings would reveal how the trees had lived and when they had died.

Tree ring analysis, or dendrochonology, is based on the fact that trees add new material each year: early, lighter-colored cells followed by darker cells. Each set is known as a tree, annual, or growth ring. Width depends on the climatic conditions with wider rings in a good growing season.

Yamaguchi found that the trees had wide rings right up until the time they died. This indicated that disease had not killed the trees. He and other researchers then compared the rings of the dead trees with those living nearby. These trees spanned nearly a thousand years of time, from 993 to 1986. Using this data, they tried to match the growth rings of the living trees with the growth ring of the dead trees. A match would tell when the ghost forest trees died.

They had a problem, though. Erosion of the tree’s trunks had obliterated the final rings. Fortunately, in 1996, they dug up eight stumps whose roots had not decayed. In all but one case the rings showed the trees had died between August 1699 and May 1700. Narrowing the timing down to January 26 required another line of evidence, and the assistance of colleagues and documents from Japan.

Proposed tower and berm structure by Ronald Kasprisin. Image courtesy of the Washington Emergency Management Division.

CAMP MURRAY, WASHINGTON- When natural disaster strikes, most of us instinctively run for the hills. But what if you live in the flats, and can't outrun or even out-drive a fast-approaching tsunami wave?

The low-lying coast on the west coast of Washington state is one such region. Residents face both the risk of a major earthquake from the Cascadia fault, and tsunami waves predicted to pummel the shore only 30-40 minutes after the quake. John Schelling, Earthquake Program Manager at the Washington State Emergency Management Division, claims that when a tsunami is approaching, residents need to be prepared to evacuate—vertically.

Schelling worked with a team of engineers to plan a series of towers, buildings and berms to provide a vertical escape option that is easily accessible and can withstand the massive force of a tsunami. The proposal, dubbed "Project Safe Haven," is well underway in Washington's coastal communities, including Ocean Shores and Westport where community members have come together to figure out what “heading for higher ground” will look like for them.

“The community members themselves have been the drivers for a lot of the effort that’s gone on in the Safe Haven Project,” says Schelling. “We’ve tried to make sure all of these are multipurpose so that people interact with them on a daily basis.”

But there will be much more physics and engineering going into these buildings than meets the eye.

Locations on Washington coast for proposed vertical evacuation structures. Image courtesy of the Washington Emergency Management Division.

“The structures themselves have to be designed to withstand at least a magnitude 9 earthquake,” says Schelling. “You’re talking about a significant amount of geotechnical engineering and analysis to make sure the footings that are placed support the weight of the structure, as well as account for the forces that are coming.”

Designing a structure to withstand an earthquake of that size is a task in itself, but these buildings and towers will also then need to withstand the force of the approaching tsunami wave. The engineering answer to this challenge? “The ground floor would be sacrificial, the walls are designed to wash away, and allow water to flow in and out,” says Schelling. Meanwhile, the top floors, where the evacuees would be gathered, are left intact.

It’s a different design concept than berms which are essentially small, hollow hills that can be easily accessed, including by those people who may have trouble quickly climbing to safety in towers or buildings. These structures will be strategically placed throughout the communities most vulnerable to a tsunami. The goal is not only to get as many people to safety as possible; it’s to get as many people to safety as quickly as possible.

While the berms would have the largest foot print on the landscape, they will be able to hold anywhere from 100 to 10,000 people above the water. The outer mound will be constructed from soil to provide a natural slope that can easily be climbed. Schelling says the inside will be a “reinforced concrete core” to keep the berm from collapsing during an earthquake and steady as the tsunami waves hit the coast.

The other benefit to berms is that the mound of earth, similar to the one in Gasworks Park in Seattle, can provide safety without looking too man-made and disrupting the natural environment. “It’s designed to blend in and provide a nice aesthetic to the natural and built environment that people love about the coast,” says Schelling.

For these safe havens, the sky is the limit.

Additional Links

• Project Safe Haven: Tsunami Vertical Evacuation on the Washington Coast on Facebook
• Washington Military Department: Emergency Management Division's Tsunami Evacuation Tips

Colette Kent, intern at KCTS 9 and student at George Washington University, contributed to this blog.

Ernie Majer, a staff scientist with the Lawrence Berkeley National Laboratory, tests seismic monitoring equipment.

In California, more renewable energy comes from geothermal energy than solar and wind, combined. Today, a new technology known as Enhanced Geothermal Systems has the potential to extract even more heat and consequently energy to power steam turbines, but it’s not without challenges, including man-made earthquakes which are a consequence of breaking up rock more than a mile below the earth’s surface. Such earthquake activity is referred to as "induced seismicity" and can occur in other fields of energy production, including oil and natural gas production and hydropower.

Although most of these earthquake events are miniscule, registering less than a 2.0 in magnitude, occasionally, they can result in larger magnitude earthquakes, especially when the engineering activity which precipitates them occurs within the proximity of active fault zones.

In the U.S., the buzz over Enhanced Geothermal Systems (EGS) started ratcheting up after the publication of a 2006 Department of Energy study investigating its potential, spearheaded by researchers at M.I.T. Among their findings was that EGS could meet 10% of the U.S.' electricity supply by 2050. Ten percent doesn't seem to be that much but it would represent a 40-fold increase over the current amount of geothermal power being harnessed nationally and if realized, it could significantly boost the nation's efforts to wean itself off its carbon-heavy diet, with more than 60% of energy consumption in the U.S. currently coming from coal and petroleum.

Today, the Department of Energy is spending millions of dollars to fund seven demonstration EGS projects, including a grant of $5.5 million Calpine's to develop the EGS field featured in our QUEST story on induced seismicity. Calpine has invested $9.5 million of its own money on the project, an impressive sum it's willing to spend to demonstrate the success of this green, renewable technology.

Here is how Calpine Senior Vice President Mike Rogers described the project's energy potential to me: "We expect to produce between 5 to 7 megawatts of additional steam (which is) enough for a small city, say, 6,000 people (and) depending on what we find, possibly up to 50 megawatts in that part of the field." Calpine has measured a temperature of 725 degrees Fahrenheit at a depth of 11,000 feet at their new enhanced geothermal project site. That's roughly 300 degrees warmer than their other geothermal fields at the Geysers, and with more heat comes more energy potential.

Calpine is working with Ernie Majer of the Lawrence Berkeley National Laboratory to monitor the risk of induced seismicity with additional, around-the-clock seismic monitoring next to their EGS production and injection wells located in the northwestern region of the Geysers.

The company is proud of their efforts to reach out to nearby communities such as the town of Anderson Springs that are impacted by the year-round geothermal activities at the Geysers. Not only has Calpine created a seismic monitoring committee comprised of representatives from the Lawrence Berkeley National Laboratory, USGS and community members to review recent earthquake activity in the vicinity of the Geysers, they also have set up a hotline to report earthquake activity and an annual fund which communities can use to pay for repairs to buildings and homes possibly damaged by earthquakes.

It should also be noted that Calpine has the support of some prominent members of Anderson Springs for the development of their EGS demonstration project. Jeff Gospe, the President of Anderson Springs Community Alliance, wrote a letter of support for the project in September 2010 to Sonoma County District Supervisor Paul Kelly. Although Jeff and other community members still have concerns about seismicity in the southern portion of the Geysers, Jeff maintains that the work on the EGS demonstration project is an example of "pro-community geothermal development" that is far enough away to pose little risk to residents of the town.

In the course of my research on the story, I discovered several international EGS projects, including two that are online in France and Germany. Given the concern with nuclear energy in the wake of the Fukushima Daiichi disaster in Japan, and the phasing out of nuclear energy programs in Germany, Italy and Switzerland, the need for more renewable energy sources like geothermal power becomes more pressing.

But as nuclear energy also reveals, no matter how green the energy source is, its exploitation must be safe for the public to get behind it.

As Ernie Majer of Lawrence Berkeley National Laboratory told me, "Over the past 20 years, it started out as the (geothermal energy) industry almost ignored induced seismicity. But as the recent issues have come up, the industry has finally said, 'Alright, we need to deal with this properly and we need to take it very seriously.'"

The gist of the 2008 TV story was that geologists are now able to use special paleoseismic techniques to analyze earthquake faults and determine their seismic history over several thousand years. By noticing patterns in earthquake activity over long periods of time, they can also make predictions about when major events are likely to happen in the future. They determined that a major event of 6.8 or higher happens every 140 years or so on the Hayward Fault. It's been 143 since the last one.

Engineer Khalid Mosalam

A 2003 report by the USGS found that there is a 62% probability of at least one magnitude 6.7 or greater earthquake in the 3-decade interval 2003-2032 within the San Francisco Bay region. With odds like this, I'm grateful that there are people like Khalid Mosalam and his colleagues at the Pacific Earthquake Engineering Research Center's Shaking Table Laboratory who dedicate their careers to learning how to make the built environment that we live in, work in and travel on more safe in an earthquake.

I'd included about a minute of video from the Shaking Table Lab in the 2008 piece but I always regretted that I wasn't able to show more of this facility. So when we started putting together an entire episode focused around the theme of earthquakes, I thought a short segment about the Shaking Table would be perfect for this show.

Substation equipment getting shaken up on the table

When we were there shooting in 2008, they were testing some electrical substation switches which were interesting but definitely not as dramatic as some of the other structures they build and shake in three axes, often until collapse. The generous engineers at PEER were able to provide us some videos of other structures they tested including a two story house, a masonry wall and a bridge pier support. The 20' x 20' table is one of the largest in the world to be able to move in three directions (translation and rotation) so, according to Mosalam, it's an extremely important piece of equipment at UC Berkeley and has contributed to important research that will result in people being safer when the next 'big one' hits.

 Megathrust Earthquakes Educator Guide

With recent lessons from Japan in mind, I wanted to look at what might happen if an earthquake struck the Cascadia Zone. However, an in-depth look at megathrust quakes has a unique set of challenges because one can’t snap their fingers and inspire nature to shake the ground. As a television journalist I have to be slightly obsessive about capturing enough footage to cover a story because a bunch of talking heads will put the audience to sleep. It’s easy to end up with a bunch of lackluster clips from expert interviewees strung together in a timeline. Fortunately, my early research revealed that the last megathrust earthquake in 1700 left behind some very interesting visuals.

Until recently, Cascadia did not have any written records of local earthquakes larger than magnitude 7.5, nor of transpacific tsunamis. However, in the early 1980’s earth scientists began looking a little closer. Hints from oral histories of native peoples were analyzed in detail, and geologists began uncovering unusual and exciting physical clues, both suggesting that very large earthquakes had struck the Pacific Northwest.

Two of the detectives who pinpointed the timing of the 1700 quake were geologist, Brian Atwater, and tree ring scientist, Dave Yamaguchi. Our camera crew joined this duo for a day in the field on a sunny June morning. Videographer, Tim Griffis, and I followed Atwater a few hundred feet up a stream near Discovery Bay on Washington’s Olympic Peninsula. Atwater scraped away at the riverbank to reveal a light grey layer of sand filled with microscopic siliceous shells of marine diatoms. According to Atwater, the simplest explanation for this unique sand layer is a tsunami from an earthquake in which a tectonic plate, in a seismic shift, abruptly displaced the sea while lowering the adjoining coast.

When a megathrust earthquake strikes, the land can drop by five feet or more. Imagine a tsunami wave powerfully driving towards a shoreline. Sand from the sea is swept up into the current and carried far inland and then deposited, coating the land with a fresh layer of sand.

Once Atwater concluded that the sand layers likely revealed evidence of past tsunamis, he recruited tree ring scientist, Dave Yamaguchi to help him pinpoint when the last giant quake struck. Yamaguchi suggested they look to trees that were drowned by incoming waters from the past giant tsunami. He pointed to ghost forests—groves of weather-beaten tree trunks in tidal marshes and meadows in southern Washington.

When incoming waters from a tsunami rush inland the bases of trees are submerged underwater and the trees are killed. Thousands of rotting stumps can be seen along the banks of tidal streams up and down the west coast. By dating the final ring on one of these trees Yamaguchi determined the past giant quake happened in 1700. According to Yamaguchi, “It’s important for us to know how big the earthquakes in the past have been in this region because the past tells us what can happen in the future.”

Knowing the Cascadia fault is susceptible to giant quakes allows engineers to plan ahead and construct structures to withstand that kind of force.

Although footage from the Tōhoku quake was the primary footage used to illustrate our story about megathrust quakes, my favorite visuals revealed the signs of an earthquake that hit over three hundred years ago. Not only did we witness unique science in action, we shared in the joy of two scientists who clearly love connecting the dots between geologic evidence and history. Plus, it was obvious they enjoyed striding through tidal muck in hip waders giddily digging away the shoreline to reveal an unusual and important discovery.

Additional Links

• Pacific Northwest Seismic Network Homepage
• PNSN Deep Quakes in Washington and Oregon
• USGS Pacific Northwest Hazards and Preparedness
• USGS Liquefaction information in coordination with the California Geological Survey
• NOAA Center for Tsunami Research Animations
• The Burke Museum online exhibit on the geological evolution of Washington

Another 7.4 aftershock has occurred in Japan following the 9.0 earthquake that the country a month earlier.

If you'd like to learn more about these geologic events, QUEST has produced many stories about earthquakes over the years, from videos about the Bay Bridge receiving an earthquake makeover and an in-depth look at The Hayward Fault.

There's also radio stories that have covered earthquake prediction, along with building infrastructure lessons learned from the earthquake in Chile last year.

Our bloggers have written about earthquake preparedness, what went wrong with the buildings after the Haitian earthquake, faults in the Bay Area, even earthquake warnings that can be found in tiny fossils.

There's also an earthquake educator guide for teachers and a science hike of the San Andreas Fault in the Midpeninsula Regional Open Space District.

Check out the QUEST story, "Breaking New Ground" and search kqed.org/quest for more related content.

QUEST on KQED Public Media.

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"Minuscule" amounts of iodine-131 was found in milk from Washington state. Image courtesy of stevoarnold.

Reuters reports that trace amounts (0.8 pCi/L) of radioactive iodine-131 was found in milk from cows in Washington state, though officials stress this is nothing to be alarmed about.

"These types of findings are to be expected in the coming days and are far below levels of public health concern, including for infants and children," said the Food and Drug Administration and the Environmental Protection Agency in a joint statement.

Though the levels found in the US are 5,000 times below the FDA's standard, this particular isotope of iodine is not normally present in milk. When milk is contaminated, iodine-131 can accumulate in the thyroid and lead to cancer.

US officials have been monitoring radiation levels in milk and drinking water since the radiation leak at Japan's Fukushima Daiichi nuclear plant after the March 11 earthquake.

Fortunately the half life of iodine-131 is quite short, only 8 days, meaning the vast majority of the dangerous isotope should be degraded in 2 weeks time so long as there is not additional exposure.

US citizens are at extremely low risk of radiation exposure due to the events in Japan, but officials will continue to monitor the situation.

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Courtesy of NASA

On March 12, a one-foot tidal wave was filmed as it slowly surged across the San Francisco Bay. The wave traveling 5000 miles from Japan started out as a 23-foot tsunami off the Japanese coast. It was created by a devastating earthquake with a magnitude of 9.0. The earthquake was the largest earthquake in Japan’s history and the fourth largest earthquake since 1900. It shifted the planet’s axis and opened a rift that moved Japan closer to the United States by thirteen feet.

We were lucky to have such a slight nudge from such a devastating natural disaster. Crescent City was not so lucky. Six to eight foot surges hit the harbor of Crescent City creating flooding, splintered docks, and damage to boats and marinas alike.

Crescent City’s claim to fame is it the only town in the continental US where a tsunami has killed residents. On March 28, 1964, a 21-foot tsunami wave created by a earthquake in nearby Alaska surged into the town of 7,500 doing extensive damage and killing 11 people. Underwater topography can tunnel these massive waves to direct them towards a certain point, which increases the power by centralizing their force. Such was the case with the wave that hit Crescent City; the underwater topography leading to Crescent City created a funnel for the wave in 1964.

With such a powerful wave, it is a blessing that more people were not killed. Early sirens warned of the wave and many residents retreated to higher ground. UGGS put out a report in 2005 of how to survive a tsunami taking much information from the survivors of Tsunamis in Chile, Hawaii and Japan. From their extensive research, the following points were given:

• Many will survive the earthquake that will later trigger a tsunami

• Look for natural warnings; An earthquake or rise and fall of coastal waters may serve as an early warning as well as wildlife heading for higher ground

• Listen for official warnings; Take sirens and evacuation notices seriously

• There is usually not just one wave; Generally small waves are then followed by higher intensity waves

• Head for higher ground and stay put; It may take several hours for the Tsunami force wave to hit

• Abandon belongings; Many people died concerning themselves with belonging rather than heading to higher ground

• Roads may not be an escape route; They might be made impassable by earthquakes or earlier waves

• If getting to higher ground is not an option:
Go to an upper floor or roof of a building; Climb a tree; If you are near wave, find something that can act as a raft

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It feels like the world is still shaking from the earthquake and ensuing tsunami that hit northern Japan on Friday. The 8.9 magnitude quake created enormous waves of water, which moved quickly through the ocean and hit the coast of Japan with waves that in some areas were over 10 feet high. This animation shows how earthquakes give rise to tsunamis. When tsunamis hit shore, they can carry with them sediment that they’ve picked up from the bottom of the ocean. This sediment differs from the sediment close to shore, leaving a long-term record of the tsunami’s occurrence.

Paleontologists can look at the layers of sediment along the coast and see records of past tsunamis. They can also see that before tsunamis occur, the land along the coast often starts to subside, as one tectonic plate slips underneath another. The clue that tells paleontologists that the coastline tilts before an earthquake is a group of tiny marine organisms, called foraminifera. By studying these organisms in the sediment along the shore of the West Coast, scientists can learn how frequently tsunamis occurred here in the past, and whether we can predict a big quake in the future.

The tiny marine organisms in the sediment are called foraminifera, or forams for short. They are protists—neither animals nor plants, protists are a grab bag of simple organisms that includes amoebas, seaweeds, and single-celled algae. Forams are unicellular, and they build a shell, called a test, out of calcium carbonate. The test has little opening from which pseudopods—thin strands of the cell’s cytoplasm—protrude. The pseudopods help the forams move around. However, it is the calcium carbonate tests that make forams so useful as records of geological events.

The tests of foraminifera are often well preserved in marine sediment, as fossils. Forams evolve relatively quickly, so micropaleontologists (folks who study tiny fossils) can determine the age of the sediment by identifying the species of foram that is preserved. Also, each species of foram can survive only in a narrow range of environmental conditions. If the water is too salty, a given species can’t survive; if the water is too fresh, that species won’t survive either. The salinity of the water has to be just right. This means that micropaleontologists can use foram fossils to estimate the salinity of the water in the past. (For similar reasons, forams are also good indicators of the proximity of oil deposits, and a good proxy for past climates.)

A few years ago, UC Berkeley Professor Emeritus Jere Lipps and a few colleagues, including Dalhousie University professor David Scott, travelled along the coast from Alaska to Baja, taking cores of coastal sediment along the way. They found that several years before a big earthquake and tsunami, the foram composition in the sediment changed slightly. The forams shifted from species that live in very slightly salty water to species that live in water that is even saltier. This is a sign that the land had begun to tilt downward towards the ocean.

The Pacific plate is slowly sliding underneath the North American plate. But the plates stick together, and the edge of the North American plate gets pulled down slightly along with the Pacific plate. Suddenly, the plates will un-stick; the North American plate will release and move upwards again, and the Pacific plate will slide underneath. This kind if quake is called a megathrust earthquake. Dr. Lipps and his colleagues found that there have been three megathrust earthquakes, preceded by a tilt in the coastline, over the past 3000 years.

Forams are good measurements of past coastline tilt. But to measure coastlines in real time today, scientists can deploy seismometers. By placing seismometers in areas that have undergone a pre-earthquake tilt in the past, we may be able to detect early warning signs of potentially destructive megathrust earthquakes and resultant tsunamis.

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_{The Hayward fault crosses Oakland's Temescal Regional Park. Photo courtesy Andrew Alden}

Earthquakes will never be as predictable as the weather, I think it's safe to say, but if you get to know your nearest faults then earthquakes will be less of a surprise. When our local faults rupture, you will be less likely to panic and more likely to get through the event unscathed. So when I urge you to friend a fault, it's not to infect you with a scientific hobby but to bring you a lasting practical benefit.

A fault is a crack that has had movement along it. Geologists find them everywhere, and geologic maps are festooned with them. Almost all of them are inactive, though, and they're generally obscure even to practiced eyes. You can see what I mean on the U.S. Geological Survey's zoomable geologic map of the Bay Area.

_{US Geological Survey image}

Here's a part of it showing the area around Fremont. We can't be expected to worry about every heavy line, can we? Thankfully, no; and not the colors and symbols either. That's geology stuff: bedrock and contacts between stratigraphic units. But the two heaviest lines are important. On the left is the Hayward Fault and on the right is the Calaveras fault, both capable of major shocks.

_{US Geological Survey image}

Another USGS map called the Quaternary map focuses on just the active faults—well, the sort-of active ones that have moved during the Quaternary Period. You need to know only two things about the Quaternary: it's pronounced "qua-TERN-ary" and for our purposes it includes the last 1.8 million years of geologic time. Now a fault that hasn't moved in a million years, like a volcano that hasn't erupted in a million years, is not much of a threat. The color codes on the faults match the time of the latest fault movement, angry red being historic time (namely, 1868).

There are two good ways to visit our local faults. One is visiting them in parks (see the list below), and the other is the freelance approach of tracking them through the neighborhood. For that, the best tool is the State of California's Alquist-Priolo Earthquake Zone Maps, which have just been placed online by the California Geological Survey. Mandated by the Alquist-Priolo Act of 1972, these maps display the locations of faults that have ruptured during Holocene time, which is geologese for the last 11,000 years. Unlike Quaternary faults, activity on these Holocene faults is a pretty sure thing. And the maps display the detailed fault traces as mapped by geologists, superimposed on a high-quality topographic map.

With these, you can drive or stroll an area and assess the land for yourself. In places like downtown Hayward, the signs are plain and plentiful. In many others, you'll wonder what the heck those geologists were seeing. (The answer is that they were looking at historical aerial photos and data, finding subtle clues on the ground, and doing a lot of connecting dots.) You'll have a head-scratching good time, and you won't see your landscape the same way again.

Visit the San Andreas fault:
Fort Ross—Take Fort Ross Road east about 0.5 mile and spot the painted line across the road; an interpretive trail is nearby.
Olema—Take the Earthquake Trail near the Bear Valley Visitor Center in Point Reyes National Seashore.
Los Trancos Ridge—This ridgetop park above Palo Alto has an earthquake trail along the fault.
Sanborn County Park—South of Cupertino in the Santa Cruz Mountains is this park with the 2.5-mile San Andreas trail along the fault trace.
San Juan Bautista—The fault runs just yards east of the mission here.

Visit the Hayward fault:
Berkeley—Tour the fault in "Bear territory" including the infamous football stadium built across the fault in 1923.
Oakland—Lake Temescal park displays the fault in several places.
Hayward—The historic downtown and old City Hall straddle the fault, and signs of steady (aseismic) creep are abundant here.

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