domingo, 24 de noviembre de 2013

The May 7, 1822 earthquake (part II)



The May 7, 1822 earthquake (part II)

Eduardo Camacho and Vilma Víquez, publicado en la Revista Geológica de América Central, 15:49-64, 1993

The part I (in spanish) was published in this blog on January 24, 2013.

Montero et al., affirm that historical accounts suggest that this event is similar to the Limón Earthquake of April 22, 1991, which occurred in the southeast Caribbean region of Costa Rica, near the Panamá border.

According to Cleto Gonzalez Viquez, Raimundo Calvo declared to the City Council of Cartago: “In Matina three violent shocks were felt, as no neighbor remembers to have ever felt; that the shakes lasted almost with no interruption for twenty four hours; that the ground cracked in several sites, leaving deep fissures from which salty water and black sand erupted; the rivers and bays grew and caused floods and the neighbors decided to leave for Cartago; at Hondo River, near Matina they met Father Don Tomás Prieto, who once informed on the earthquakes took all the people to Pacuare River. The tremor lasted several days, because on May 15 the Cartago Council declares that due to the ruin of the City Hall in the morning of the seven it was necessary to freed the criminals and other inmates of the jail, because the earthquakes has not ceased. In September of the same year the Major of Ujarras asked permission to take the timber and the tile from the ruined church to build a new hermit to Our Lady of the Rescue. On 1829 the Prefect of Missions Friar Pedro Moreno requested from the Executive permission to rebuild the church of San Francisco de Terraba, which was destroyed by the May 7, 1822 earthquake. In Cartago as well in the capital San Jose, it caused great damage, because there it ruined many houses and walls, which the authorities almost immediately order to be demolished”.

Ricardo Fernandez Guardia reports in 1937: “Our Lady of the Conception had her sanctuary in the town of Ujarraz, this beautiful temple was built by the Governor Don Miguel Gomez de Lara at the end of the XVII Century and its ruins, caused by the 1822 earthquake, can be admired today in the beautiful valley”.

A chilean newspaper “El Mercurio de Chile” reproduces a letter by Father Atanasio Colombia who reports on a strong earthquake in the Isthmus of Panamá: On May 6 of the current year around 1:30 a.m. an earthquake never felt before even by the oldest neighbors terrified the inhabitants of the town of San Francisco Xavier de Cañasas, jurisdiction of the Province of Veraguas, and surroundings villages. He mentioned that it even moved the boulders of the rivers near the house, the inhabitants could not stand on their feet, because the earth waves were like those of the sea, they stayed lying on the ground. The house was bended and cut by a crack which crossed the house and extended to the backyard, as when a strong summer cracks the ground with very deep fissures.

The church built in the year 20, next day resulted cracked in three parts and its tower lost its entire roof, which collapsed and the arch at entrance of the temple had considerable fissures.

Roberts, a British privateer who lived among the indians of the Caribbean coast of Panamá from 1817 to 1822 was near the epicenter area at the time of the event and reported the following: “On the night that this event took place, I was in an indian house at Monkey Point (Punta Chica today), and had an opportunity of witnessing its effect on that part of the coast. About the middle of the night in question, I found the frame of the wicker bedstead on which I slept, shaken with very great violence; supposing that it was either my companion (one of the traders), or some of my indian friends who wished to frighten, or awaken me suddenly, I rather angrily demanded, whether they meant to shake me to pieces? In a few seconds, however, the screams of the women, and the cries of the men, in the adjoining huts; together with the rolling motion of the earth, which was twisting the hut in all directions, put an end to my suspense. I instantly ran out of the place to the open air; and, although scarcely able to keep upon my feet from the rolling and trembling motions of the earth, I observed such a scene as will never to the last hour of my existence be erased from my memory. The ground under our feet seemed to heave convulsively, as if ready to open and swallow us, producing a low terrific sound; the trees, within a short distance of the huts, were so violently shaken from their upright position, that their branches were crashing and their trunks gridding against each other.

The shock gradually became less violent, and towards daybreak, has entirely subsided. No lives were lost here, or at the other Indian settlements in the neighborhood, but ground appeared rent in various places, the sand on the beach was either raised in ridges, or depressed in furrows; a place, in which several canoes were floating, was now become quite dry; most of the huts were violently cracked and twisted; and the effects of the earthquake, were everywhere visible.
    
The only persons in the neighborhood not frightened by this event, were a trader, and some of his indian friends, who were so intoxicated at the time it happened, that, until next morning, they were not aware that any extraordinary occurrence had taken place. They had a confused recollection that a puncheon of rum, which was in the hut, could not be kept from rolling on the floor; but whether some person was trying to steal it from them, or it was endeavoring to run away of its own accord, they could not, at the time, determine.
      
Monkey Point is located by Roberts as follows: From the Tiribí River to Monkey Point the last headland in the Province of Veragua the distance is not more than eight or ten miles. It is easily known by a remarkably bluff rocky islet, distant only few yards from the mainland.

We think it is worth of note to mention that Roberts also refers to a sandy bay between the Snake River and the Grape Cay, before 1822 earthquake. According to Valdez the Snake River is the one located between Cahuita Point and la Mona Point and marks the boundary between Colombia and Costa Rica. If we look an older map we observe that between this river and Mona Point there is not a Grape Cay at all, but there is a Grape Point. These indicate the possibility that in this coast occurred coseismic vertical deformation on May 1822.

An isoseismic map for this earthquake is on the figure. We estimated an epicentral intensity of IX (IMM), and from this value we calculated a surface magnitude of 7.6.
      
Macroseismic map of the May 7, 1822 earthquake. The epicenter is indicated by a black star.

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