The night Bucharest fell down

The instrument at INCERC recorded more than a minute of shaking. On the north–south line, the fragment recorded there is dominated by a single jolt.

The instrument was a Japanese SMAC-B accelerograph, set in the basement of a light, single-storey building at INCERC, the Building Research Institute on Pantelimon Road. Three pendulums wrote their motion on a strip of waxed paper: one for north–south, one for east–west, one for up–down. The Romanian Academy's 1982 monograph treats it as a record of ground motion largely unaffected by the building. It is the only complete three-component accelerogram available from this earthquake.

The strip ran for more than a minute. In the monograph's description, the first 18 seconds or so brought P waves, small and quick, mostly vertical, below 0.5 m/s². Then the S waves arrived, bringing large, mostly horizontal motion. The strong phase lasted only 10–15 seconds. After 30–40 seconds came long, weak waves.

The strong phase was digitised and survives as numbers in ESM, the European strong-motion database: about 16 seconds in each direction. The ESM files do not contain the rest of the strip and give no valid clock time for the first point, so the seconds in the drawing above count from the start of the fragment.

On the north–south line the acceleration peaked at 1.94 m/s², about a fifth of the acceleration of free fall, and the ground's speed at 74 centimetres a second. East–west: 1.67 m/s²; vertical: 1.03 m/s². The monograph, working from an uncorrected digitisation, gives 2.1–2.2 m/s² north–south, 1.6–1.7 east–west and 1.1–1.2 vertical.

The monograph described a single large, almost sinusoidal cycle at the start of the north–south strong phase. In the digitised fragment, that cycle is nearly everything: the strongest two seconds carried 75% of the north–south shaking. The ground moved 19 centimetres one way and then, in less than a second, 20 centimetres the other.

The jolt had a long beat. A pendulum with 5% damping responds to this motion most strongly when it swings to and fro once every 1.3–1.6 seconds: there the response reaches 6.3 m/s², more than three times the ground's acceleration. Tall blocks built between the two world wars had natural beats close to that range. For a low house, which sways once every fifth of a second, the response is 2.4 m/s². Further down, the same record shakes a street.

The SMAC-B record from INCERC, the digitised strong phase, from the European strong-motion database ESM (manual processing, filtered between 0.2 and 25 Hz). All three lines share one scale.

In the ROMPLUS catalogue of Romania's Institute of Earth Physics, the rupture began 94 kilometres beneath Vrancea, a mountain region north-east of Bucharest, with its epicentre 158 kilometres from the city centre. But an epicentre marks only where a rupture begins, and the 1977 earthquake was not a single jolt.

In 1978 the seismologists Müller, Bonjer, Stöckl and Enescu analysed the waveforms and found a series of shocks moving south-west; in 2007 two seismologists at Romania's Institute of Earth Physics again described it as a foreshock followed by at least three main shocks. Mihail Ifrim's 1984 textbook on structural dynamics lists them in Table 7.8: a first shock of magnitude 5, then two of 6.5 at 4.7 and 12.3 seconds, and the strongest, 7.2, starting 19.2 seconds after the first and 109 kilometres down.

The big shock started 62 kilometres south-west of the first. From there the horizontal distance to central Bucharest was 102 kilometres, against 159 for the first shock; Focșani, the city nearest the epicentre, was 79 kilometres away. Measured from the catalogue epicentre, Bucharest is 4.7 times as far as Focșani (158 against 34 kilometres); measured from the big shock, it is less than a third farther. In 1977 the intensity was higher in Bucharest than in Focșani: VIII against VII on the MSK scale.

The digitised INCERC fragment has no valid clock time, so it cannot be lined up directly with the moments of the four shocks. A standard model of wave speeds through the Earth (ak135) puts the S wave of the big shock in Bucharest about 11 seconds after the S wave of the first. The calculation is explained on the page about how many seconds each place gets before the strong wave.

In the Mica-Nestor building on Calea Victoriei, the painter Nicolae Stanciu ran for the stairs with his neighbours. “And I felt them sink away with us. When we came to, we were in darkness, in a narrow space that only let us crouch.”

By the Bucharest Museum's 2017 study, the earthquake lasted 55–56 seconds; it measured 7.2 on the Richter scale. The epicentre was in Vrancea. The wave reached Bucharest and shook the city horizontally and vertically, travelling from north-east to south-west.

On a city rooftop, the sentry Mircea Nemigean watched the blocks sway “like a forest driven by the most terrible storm”. A strong wind came, then a heavy smell of burning. The lights went out. “That's it, I think the city is done for,” he said to himself.

How strong was it, exactly?

• 7.2Richter degrees — the number spoken at the time, still used in Romania
• 7.4 Mwseismic moment from INCDFP
• 7.5 Mwseismic moment from the ISC/USGS catalogue

Inside, people heard the roar of the earth and the howl of collapses: “a muffled sound, a dry sound, coming from everywhere at once”. Fires broke out, windows shattered, branches snapped in calm air, bells rang. Some stayed paralysed in their homes. Others rushed down the stairs in pyjamas and gowns, bleeding from shards of glass.

The 7.2 is the local magnitude, the one read on the radio at the time. Today's seismologists give the seismic moment: 7.4 from the National Institute for Earth Physics, 7.5 from the American catalogue. The modern depth is 94 kilometres; older studies wrote 110.

On the left, a two-storey house. In the middle, an 11-level block with reinforced-concrete walls, the stiff kind raised in the decades before 1977. On the right, an interwar block, also 11 levels, with shops on the ground floor and a concrete frame. The same ground moves all three.

Grab the street and drag it left and right, or pick a beat. Each building has its own beat: it sways there and back once every so many seconds. When the ground pushes it at that same beat, the sway grows from one push to the next, until damping holds it in check.

Next to INCERC, on Pantelimon Road, the borehole found 128 metres of sands and clays down to the Frățești complex, which the authors take as the base. Waves cross them at about 400 m/s. A layer like that sways on its own once every 1.28 seconds. On the night of 4 March the recording showed 1.5–1.6 seconds: treating the layer as uniform, the authors infer from the difference that under such violent shaking the ground softened, and waves crossed it 15–20% more slowly.

Ambraseys thought the blocks slowed too. He wrote in 1977 that the old reinforced-concrete blocks had beats of 0.7–1.6 seconds, and that damage during the shaking should have lengthened their period and raised the forces on them. By that reasoning, a block that was cracking drew closer, second by second, to the beat of the ground.

The survey carried out across Bucharest after the quake sorted buildings by their own beat and found the same thing across the districts it studied: damage rises with the building's period. Low houses, with beats under a quarter of a second, got off lightest.

Of the roughly 300 old blocks of more than 8 levels, 25 collapsed, all in the centre and nearly all on street corners. Another 3 were demolished afterwards, and about 100 were left gravely damaged. The authors of the 1982 monograph list, beside the technical causes, precisely the closeness between the ground's beat and the beat of these flexible structures.

The number went into the law. The 2006 seismic design code gives Bucharest a corner period of 1.6 seconds and shows in its annex the spectra of the INCERC recordings of 1977 and 1986. New blocks in the city are designed with the beat of that night in mind.

The INCERC instrument's paper, drawn at the top of this page, was also processed in Japan into a 254-page report. It remains the truest witness of the minute: the wave had come from under Vrancea, from almost a hundred kilometres down.

Vrancea quakes are born 60–200 kilometres deep, in a tight nest a few tens of kilometres across (40 by 90 in a 2005 study, 30 by 70 in others), under the south-eastern corner of the Carpathian arc. There is no plate boundary there today; seismologists speak of an ancient subduction zone. The hypocentres line up on a near-vertical plane striking north-east to south-west.

According to the catalogue of Romania's National Institute for Earth Physics, the 1977 rupture began 94 kilometres down, 158 kilometres from central Bucharest. A 2005 conference abstract proposes a model in which it started deeper, at 125 kilometres, and climbed through the seismic plane; the largest aftershock, of magnitude 4.7, came from 48 kilometres down. The strongest of the four shocks, though, started only 102 kilometres, measured horizontally, from central Bucharest.

How far it was felt

• 1.3 million km²the area over which the quake was felt
• 80,000 km²the area with damage
• 23 of 40counties strongly affected, Bucharest first

Vrancea had struck before. On 10 November 1940 a magnitude 7.7 quake from about 150 kilometres down (a 2012 study gives 140), felt across 2 million square kilometres, brought down the Carlton block in Bucharest and badly damaged other tall blocks: Belvedere, Wilson, Lengyel, Pherekide, Broșteni, Gălășescu. In 1838 the capital's police counted 8 dead, 14 injured and 36 collapsed buildings. In 1829 the magnitude had reached 7.3.

At the Scala confectionery, Florica Iordache was washing the customers' plates when the wave struck. The block above — Nicolae Bălcescu Boulevard, corner of C. A. Rosetti — turned into a heap of rubble. By Sunday night 108 dead and 6 living had been pulled from under it. She was found on Monday at dawn, wedged between fallen slabs.

Off the map, in Militari: the new OD16 block at 16 Păcii Blvd, with concrete walls, had six sections of 44 flats each, plus a block joined on at each end. The last section before the end block collapsed completely, toppling into the middle of the boulevard. The inquiry found concrete at or even below the permitted strength, segregated especially at the ends of the walls, and badly treated pour joints, in a block with a single lengthwise wall that had been loaded after design with longer balconies and concrete planters full of soil. What is left of OD16, now at 57 Iuliu Maniu Blvd, is on the seismic-risk list, in class II.

Most fallen blocks were interwar, raised with no seismic rules. The 1935 city plan had pushed the tallest buildings into the very centre: 6–7 full storeys plus 2–3 set back. That is why 29 of the 32 collapsed tall buildings stood in the city centre.

The ledger of the streets

Addresses and heights come from the Academy's 1982 monograph; years from the monograph, Agerpres and urban-history press; the dead and the rescues from the Bucharest museum's 2017 study.

Three weaknesses condemned them. The open ground floor, with shops and no walls between columns, left the block soft at its base. In many of them, the 1940 quake had already cracked the frames. And their concrete measured 100–200 daN/cm², a weak concrete. What fell above all were the old flexible blocks of 6–12 storeys.

The contrast condemns and absolves the builders at once. Rigid large-panel or shear-wall buildings of the same height suffered little damage. So did 1–3-storey masonry houses. The danger lay in the combination of height, age and design with no seismic rules.

The official list of May 2026 holds 415 buildings in seismic risk class I, 141 of them built by 1940 with at least four floors.

“A little hand pierces the layer of rubble, and moments later the soldiers lift a small girl into the light. She is crouched, kept in the position in which she had stayed for 62 hours.” Gabriela Doina Corduneanu, a first-grade pupil, found her father again on 7 March at 11:30.

Under the Continental rubble also lay Toma Caragiu, Alexandru Bocăneț, Doina Badea with her family, Anatol E. Baconsky, Mihai Gafița, Veronica Porumbacu and Mihail Petroveanu. From the same heap the writer Romulus Rusan came out alive: the quake had caught him with the telephone in his hand, and the bed had slid with him “like a sledge” down seven floors. A 30-year-old, Bucur Gabriel, saved him at 00:05.

The record went to Sorin Crainic Ivan, 19: pulled out after 251 hours, eleven nights, he answered from under the rubble “I am a man from the evening of the 4th…”. He beat the nine days of Agadir, the longest survival known until then.

On the morning of 5 March the first toll said 508 dead and 2,600 injured (secondary source). Work to bring back water, gas, power and telephones had already begun (secondary source). Beside soldiers and firefighters, the Buftea stuntmen, doctors and many volunteers went under the rubble (secondary source).

The Enei church near the University, damaged, never got its consolidation: it was demolished, with the neo-Gothic house of the architect Cerchez and the merchant houses on I. C. Brătianu. Under the pretext of the quake's aftermath, the abusive demolitions began.

On the empty sites new buildings grew: nine storeys on the Scala site, a plain building on the Casata site, three blocks on the Dunărea site, the București hotel complex on the Nestor site, a sober edifice on the Continental site.

On 30 March 1977 the state set the consolidation strategy: old buildings had to be brought back to their pre-1940 strength. After the quake came the order for the capital's new political-administrative centre: for the People's House, the Brâncovenesc hospital and the State Archives in the Mihai Vodă precinct disappeared.

The lessons stayed on paper longer than in the walls. Specialists had asked since 1977 for every building raised without seismic rules to be assessed. In 2026 the official list holds 415 buildings in risk class I, 383 of them built by 1940.

Bucharest City Hall keeps the list of buildings assessed for seismic risk. The table updated on 19 May 2026 holds 2,796 buildings. It holds 415 in class I, the buildings “at high risk of collapse under the design earthquake”. Of those, 383 were built by 1940, and 141 of those have at least four floors above the ground floor.

On Ion Ghica Street, at whose corner the Continental fell, a different building, at number 3, raised in 1938 with eight floors, is in class I. Class I is not the whole list: another 1,453 buildings sit in the emergency category with no risk class, and a building missing from the list may never have been assessed.

Source: Bucharest municipal agency for strengthening buildings at seismic risk (AMCCRS), “Listă imobile expertizate”, table updated 19 May 2026. The official list