Karate class for beginners
All ages, Wednesday through Friday, 1:30-2:30 p.m. at the National Museum, Avenida 2, Central. Info: 2256-4139, 2256-8643.

Movement therapy workshop
By Sol Carballo, 8:30-10 a.m., Kapoli, Escazú. Info: 2203-4759, solcostarica@gmail.com. 

Liverpool in concert
Rock, 9 p.m., El Observatorio, Barrio La California, opposite Cine Magaly. Info: 2223-0725.

Five small earthquakes felt throughout the Central Valley on Monday night and early Tuesday did little to steady the nerves of residents still shaken from last Thursday's magnitude 6.2 earthquake.

But seismologists say such aftershocks are normal and to be expected in the wake of such a temblor.

The five mini-quakes, the majority of which qualified as aftershocks from Thursday's, occurred between 6:45 p.m. Monday and 1 a.m. Tuesday. Three of them registered magnitudes over 4.0, with the last at 4.3, and were centered around the Poás Volcano, the epicenter of Thursday's quake, and were felt throughout the Central Valley.

Costa Rica is situated over a “diffuse seismic zone,” said Javier Pacheco, a research scientist with the Volcanological and Seismological Observatory of Costa Rica (OVSICORI), based at Universidad Nacional (UNA) in Heredia, north of San José.

Unlike the San Andreas fault along the West Coast of the United States, which scientists have been able to clearly demarcate, Costa Rica is at the convergence of four plates – including one microplate – explained Tico seismologists. Mapping it – and therein identifying what specific tectonic movements are taking place, is an uncertain task – and debate persists among scientists as to what plates are in motion.

Pacheco described Thursday's earthquake as local lateral movement between the Panama microplate, on which the majority of Costa Rican territory sits, and the Caribbean plate, which runs under only the country's northern border area.

U.S. scientists, on the other hand, are sticking with the theory that the country is situated on just the three large plates. George Choy, a seismologist with the U.S. Geological Survey's regional office in Denver, said the recent activity is the result of a strike-slip mechanism that occurs as the Cocos plate, under the Pacific Ocean, slides over the Caribbean plate. This type of conversion, called subduction, occurs at a rate of 77 millimeters per year, forming a trench over the western edge of Costa Rican territory. But, he added, most seismologists believe in the microplates hypothesis, too.

Both scientists said it is normal for the plates to shift and readjust in the wake of an earthquake such as Thursday's. “With high seismic activity, there will be aftershocks,” said Pacheco. “After a fault breaks, all the other faults that are strengthened by it get set off.”

The aftershocks will likely last “a few months,” said Pacheco. “Of course, the intensity will go down over time until only seismological instruments register it.”

For now, scientists are taking as much information from the recent series of quakes as they can. “There's still a lot to learn,” said Pacheco. “It's such a complex system.”

See Friday's print or digital edition of The Tico Times for more earthquake coverage and analysis.

Costa Rica was hit with at least five smaller earthquakes Monday night ranging in magnitude from 2.8 to 4.3, and indirectly causing the death of a teenage girl.

Meanwhile, authorities Tuesday unearthed three more bodies from last week's 6.2 magnitude quake, bringing the death toll to at least 21, according to the Red Cross.

José Gregorio Soro, a close family friend of 17-year-old Arelys Rodríguez Miranda, said the girl died about 5 a.m. today after becoming stressed as a result the aftershocks.

According to the Volcanological and Seismological Observatory of Costa Rica (OVSICORI), a 2.8 magnitude quake hit 1 kilometer south of Vara Blanca at 6:45 p.m. Monday. It was followed at 7:25 p.m. by a 3.4 magnitude tremor 7 kilometers northeast of Bajos del Toro.

At 8:23 p.m., a quake measuring 4.1 struck 7 kilometers southwest of Cinchona, one of the hardest hit communities that is now abandoned. At 9:37 p.m., a 4.0 quake struck 10 kilometers north of Bajos del Toro, and at 1:09 a.m. a quake measuring 4.3 struck in Fraijanes, another region heavily damaged by Thursday's quake.

National Emergency Commission (CNE) spokesman Reinaldo Carballo said that his office has yet to receive any reports of serious damage following the succession of the overnight temblors, all of which were centered in the Poás Volcano region, the epicenter of Thursday's 6.2 magnitude quake.

Carballo said officials are inspecting the area. In the first hours following Thursday's quake, there were few reports of damage or deaths.

The scope of Thursday's disaster – an estimated 21 deaths, 17 missing and $100 million in damage – is still unfolding.

Javier Pacheco, of OVSICORI, said smaller aftershocks will continue for a few months as the plates readjust, but will become smaller.

MANAGUA – At least three people were injured and 160 were arrested when protesters armed with guns, clubs and stones battled police trying to clear them from a highway, Nicaraguan authorities said Tuesday.

In the brawl, which began at sundown Monday and went on until dawn Tuesday, two policemen and one civilian were injured, National Police spokeswoman Vilma Reyes said.

The fight took place in the northern municipality of Tipitapa after thousands of farmers, storekeepers, employees and small business-owners blocked the highway to demand approval by lawmakers of a moratorium on debt repayments to so-called micro-lenders.

Police used tear gas to disperse the demonstrators, who set fire to a number of tires to block traffic and resisted attempts to make them raise the blockade.

Paramedics treated hundreds of local residents including dozens of women and children who were hurt by the tear gas, although none suffered any serious harm.

The leader of the protesters, Omar Vílchez, said on La Primerisima radio that they would continue until the National Assembly approves a debt moratorium and the micro-lenders suspend for three years asset seizures from delinquent borrowers.

The Nicaraguan Association of Microfinance Institutions said in a communiqué that the demonstrators want to create more economic problems than those already facing the country.

"It's obvious that this movement has the express intention of destabilizing the economy and the country," said the note released by 22 micro-lending institutions that serve 559,267 clients in Nicaragua.