FIELD NOTE · SUPPLEMENTAL SET
Not fully anchored: what actually came down in Uptown Whittier
ISSUEDJULY 11, 2026DRAWN BY THE NIGHTLY SWEEP
Earthquake damage to a building on Philadelphia Street in Whittier. Photo by Whittier Museum, 1987 CC BY-SA 4.0
Brick did not fail in Whittier. The connection did.
The Caltech record of the Whittier Narrows earthquake says it in one clause, about the houses. They were constructed of masonry, were not fully anchored to foundations, or were houses built over garages with large door openings. Not fully anchored. That is the condition, and it is not a property of the brick.
An unreinforced masonry building carries its floors on its walls. The joists run into pockets in the masonry and bear there. Nothing ties them together. Gravity holds the whole arrangement in place and gravity works only in one direction.
Shake it sideways and the wall leans out. The joist ends slide off their bearing. The wall keeps going.
That is not a large earthquake. It emptied three downtowns.
Caltech names them: the most severe damage occurred in the Uptown district of Whittier, the old downtown section of Alhambra, and the Old Town section of Pasadena. The reason it gives is the building stock. These communities had high concentrations of unreinforced masonry buildings.
And the control case is in the same record. Wood frame residences sustained relatively little damage. No severe structural damage to high-rise structures in downtown Los Angeles was reported. Many chimneys collapsed. A wood frame house is nailed together at every crossing, so the walls and the floors are one object. A brick wall with a joist resting in it is two objects leaning on each other.
October 1 1987 THE MORNING IT HAPPENED 5.9 MAGNITUDE ON THE CALTECH RECORD 14.6 km DEEP, ON A FAULT NOBODY HAD MAPPED $358 million IN PROPERTY DAMAGE
Appendix Chapter A1 covers seismic strengthening for unreinforced masonry bearing wall buildings, and the 2025 California Existing Building Code carries it in its appendix. It reaches existing buildings up to six stories with at least one unreinforced masonry bearing wall. Its stated purpose is narrow and worth reading as written: to promote public safety and welfare by reducing the risk of death or injury that may result from the effects of earthquakes on existing unreinforced masonry bearing wall buildings.
Not to save the building. To stop it killing anybody.
The core of it is anchorage. A1 puts anchors through the wall into the floor and roof framing at a maximum spacing of 6 feet, and sizes each one for the greater of 0.9 times SDS times the tributary weight or 200 pounds per linear foot, acting normal to the wall.
Normal to the wall. That is the direction the wall wants to go, and until somebody bolts it, nothing resists it.
A1 treats it separately for that reason. Parapets get braced back to the roof framing, and the code sets a minimum parapet height above the wall anchor of 12 inches, or 6 inches where a reinforced concrete beam does the work.
Twelve inches. That is the dimension between an anchor that works and an anchor with nothing above it to hold.
Senate Bill 547 supplied both in 1986, the year before Whittier Narrows. It declared unreinforced masonry buildings a potential hazard and required local governments in the highest seismic zone to inventory their URM stock, adopt a loss reduction program, and report progress to the state. The earthquake arrived fourteen months later and made the case the statute had already made on paper.
The inventories are the useful artifact for a contractor. A URM building in Whittier or any older city around it is not a hypothesis. It is a named address on a list somebody in a building department maintains, with a wall thickness and a story count attached to it.
What that owner does next is constrained by more than structure. A brick building in a historic district is also governed by what the district permits, the same collision a Bungalow Heaven reroof runs into when a fire rule meets an appearance rule. Filings scored nightly for structural contractors show the masonry buildings reaching permit while the retrofit scope is still open.
The blind spot in all of this is that the brick is what people love and the brick is not what fails. An owner will spend to keep the facade and balk at the bolts behind it. The bolts are the part that decides whether the facade is still there in thirty years.
A wall tied to its floors at six feet on centre is a building. A wall with joists resting in it is a stack of brick with a floor leaning on it, and the ground gets a vote every few decades.
Brick did not fail in Whittier. The connection did.
The Caltech record of the Whittier Narrows earthquake says it in one clause, about the houses. They were constructed of masonry, were not fully anchored to foundations, or were houses built over garages with large door openings. Not fully anchored. That is the condition, and it is not a property of the brick.
An unreinforced masonry building carries its floors on its walls. The joists run into pockets in the masonry and bear there. Nothing ties them together. Gravity holds the whole arrangement in place and gravity works only in one direction.
Shake it sideways and the wall leans out. The joist ends slide off their bearing. The wall keeps going.
What the record blames
The earthquake was October 1, 1987. Magnitude 5.9 on the Caltech record, 14.6 kilometres deep, centred about 11 kilometres southeast of Pasadena on a concealed thrust fault nobody had mapped. Eight people died. Property damage came to $358 million.That is not a large earthquake. It emptied three downtowns.
Caltech names them: the most severe damage occurred in the Uptown district of Whittier, the old downtown section of Alhambra, and the Old Town section of Pasadena. The reason it gives is the building stock. These communities had high concentrations of unreinforced masonry buildings.
And the control case is in the same record. Wood frame residences sustained relatively little damage. No severe structural damage to high-rise structures in downtown Los Angeles was reported. Many chimneys collapsed. A wood frame house is nailed together at every crossing, so the walls and the floors are one object. A brick wall with a joist resting in it is two objects leaning on each other.
October 1 1987 THE MORNING IT HAPPENED 5.9 MAGNITUDE ON THE CALTECH RECORD 14.6 km DEEP, ON A FAULT NOBODY HAD MAPPED $358 million IN PROPERTY DAMAGE
Six feet, and two hundred pounds
The retrofit standard is the inverse of that Caltech clause, and it is dull in the way good engineering is dull.Appendix Chapter A1 covers seismic strengthening for unreinforced masonry bearing wall buildings, and the 2025 California Existing Building Code carries it in its appendix. It reaches existing buildings up to six stories with at least one unreinforced masonry bearing wall. Its stated purpose is narrow and worth reading as written: to promote public safety and welfare by reducing the risk of death or injury that may result from the effects of earthquakes on existing unreinforced masonry bearing wall buildings.
Not to save the building. To stop it killing anybody.
The core of it is anchorage. A1 puts anchors through the wall into the floor and roof framing at a maximum spacing of 6 feet, and sizes each one for the greater of 0.9 times SDS times the tributary weight or 200 pounds per linear foot, acting normal to the wall.
Normal to the wall. That is the direction the wall wants to go, and until somebody bolts it, nothing resists it.
The parapet comes first
Above the roof line the wall stops being structure and becomes a cantilever. There is no diaphragm up there to brace it. So the parapet is the first thing off a URM building in any earthquake, and it lands on the sidewalk, which is where people are.A1 treats it separately for that reason. Parapets get braced back to the roof framing, and the code sets a minimum parapet height above the wall anchor of 12 inches, or 6 inches where a reinforced concrete beam does the work.
Twelve inches. That is the dimension between an anchor that works and an anchor with nothing above it to hold.
A law that made a list
The engineering was understood well before 1987. What was missing was a list of buildings and somebody obliged to keep it.Senate Bill 547 supplied both in 1986, the year before Whittier Narrows. It declared unreinforced masonry buildings a potential hazard and required local governments in the highest seismic zone to inventory their URM stock, adopt a loss reduction program, and report progress to the state. The earthquake arrived fourteen months later and made the case the statute had already made on paper.
The inventories are the useful artifact for a contractor. A URM building in Whittier or any older city around it is not a hypothesis. It is a named address on a list somebody in a building department maintains, with a wall thickness and a story count attached to it.
What that owner does next is constrained by more than structure. A brick building in a historic district is also governed by what the district permits, the same collision a Bungalow Heaven reroof runs into when a fire rule meets an appearance rule. Filings scored nightly for structural contractors show the masonry buildings reaching permit while the retrofit scope is still open.
The blind spot in all of this is that the brick is what people love and the brick is not what fails. An owner will spend to keep the facade and balk at the bolts behind it. The bolts are the part that decides whether the facade is still there in thirty years.
A wall tied to its floors at six feet on centre is a building. A wall with joists resting in it is a stack of brick with a floor leaning on it, and the ground gets a vote every few decades.