As a result of Indonesia’s location on the Pacific Ring of Fire, it is susceptible to earthquakes, tsunamis, and explosive volcanic activity. Nearly the whole Indonesian island chain south of Java and Sumatra was shaken from 1987 to 2017. Because of the Eurasian plate, Kalimantan is relatively unaffected.
Malang was hit by a magnitude VIII-IX MMI earthquake in 1958 and a magnitude VIII-IX MMI earthquake in 1967. Meanwhile, an earthquake measuring 6.2 on the Richter Scale (SR) struck on February 19, 1967.
BMKG head Karangkates Malang, Ma’muri said in a webinar series on Earthquake and Tsunami Disaster Mitigation in Malang that the earthquake’s epicenter has not been found on a local fault. “The earthquake’s epicenter has not been found on a local fault,” he said.
Seismic activity has increased dramatically in the last five years, according to Ma’muri. The likelihood of an earthquake in Malang is rising. As a result, the BMKG feels empowered to provide recommendations to the local government about how to better prepare for earthquakes. A total of 453, 554, and 504 events were registered between 2017 and 2018, respectively, while 512 incidents were recorded for 2020.
From Pacitan to Banyuwangi, the shoreline is vulnerable to earthquake and tsunami disasters. The south coast of East Java is at risk of being impacted by a tsunami due to its proximity to a subduction zone. South of East Java, there is a seismic gap zone where earthquakes are rare but can last for long periods of time. This zone is quite tectonically active. There is therefore much energy saved that could be collected in the event that an earthquake occurs.
A fault runs across the seismic gap zone, increasing the risk of an earthquake. In 1994, Banyuwangi was hit by a tsunami that had a direct influence on Malang. Scientists in East Java have discovered that earthquakes originate from three distinct places. Megathrust segments, active ground faults, and volcanic earthquakes are all included.
Damage from the Tsunami
There are 127 districts/cities in Indonesia’s tsunami hazard zone on the map of tsunami-affected locations. With a population of 3.2 million and a forecast wave height of more than five meters. With a tsunami height of 1-3 meters and a population of 109 thousand, 46 districts/cities are in the high-risk zone with 758 thousand inhabitants and 26 districts/cities are in the medium-risk zone with a potential tsunami height of 1 to 3 meters.
In the meantime, practically everywhere in Java’s southern coast is at risk of being devastated by a tsunami. In 1840, 1843, and 1859, the tsunamis were caused by fault wave tsunamis. Meanwhile, a 13.9-meter-high tsunami struck Banyuwangi, Indonesia, in 1994, killing 259 people. Tsunamis and earthquakes are becoming more frequent. As a result, Ma’uri issued a warning to the residents on the southern coast.
An earthquake with a magnitude of 8.7 was simulated by Ma’muri. Tambak Rejo and Sempu, the nearest towns to the shore, should expect the waves to arrive in 18 to 20 minutes based on this prediction. So that a map can be drawn out in advance of an emergency. For the benefit of everyone.
To help with evacuation plans, representatives from BMKG and the Malang Regency Regional Disaster Management Agency (BPBD) will head out to the field. The height at which a person can safely self-evacuate is also determined. Between half and more than 14 meters high, the tsunami waves’ heights were estimated, he said.
To get the word out about the earthquake and tsunami, early warnings were sent out via social media and SMS. Tsunami earthquake data is also updated every three minutes via a Warning Receiver System (WRS). Malang Regency BPBD receives this information immediately.
As a result, he said, individuals are urged to leave their homes on their own if there is a major earthquake. While the waves take around 30 minutes to arrive, if you wait for orders, it will take much longer.” As he observed, “If you wait too long,”
Because of this, residents of Malang Regency’s southern coast should recognize their location. Please keep away from the beach if the earthquake is powerful and lasts a long period.
Disaster Preparation for Earthquakes and Tsunamis
Sadono Irawan, the Plt. Head of the BPBD Malang Regency’s Emergency and Logistics Division, outlined the region’s ten main catastrophe hazards. This includes floods, extreme waves and abrasion, earthquakes, fires in forests and on the land, drought, epidemic and disease outbreaks, volcanic eruptions and extreme weather.
As a result, the population’s vulnerability to earthquake and tsunami disasters is very acute. In Malang Regency, earthquake intensity is quite high. There were 151 events in 2020, and 122 incidents from March 2021 to March 2022. In Malang Regency, he asserted, “there is not one inch of land that is protected from earthquakes”.
Together with BMKG, BPBD has created an earthquake risk map. Donomulyo, Bantur, Gedangan, Sumbermanjing, Tirtoyudo and Ampelgading are shown on this map showing tsunami hazard hazard. Pre-disaster through post-disaster, BPBD has implemented disaster mitigation measures.
As one option, a disaster-resistant community can be established at the site where it’s most likely to occur. Installing evacuation signs on the south coast is also part of this effort. Installation of at least 100 new evacuation signs is carried out each year. “The number of small signs is not proportionate to the length of the beach,” he remarked.
Since the Southern Cross Line (JLS) was completed, many beaches have been made available for tourists to visit. Early warning systems, such as automatic wheater stations (AWS), have also been erected at a number of beaches. In Balekambang and Tambak Rejo a year ago, although the equipment didn’t live long, it was installed He said, “It’s been a year.”
According to him, the money should be used to educate the public about disaster early warning rather than spend it on expensive technologies. Included in this is the creation of a disaster-resistant village.
Andang Bachtiar, an independent geologist, urged people not to question when the earthquake and tsunami occurred. Since there is a high probability that the earthquake and tsunami in Indonesia will occur. “This tsunami and earthquake are like dead people, there’s no doubt about it. It’s hard to believe it’s been 200 years, or even 300 years. “There was a deep earthquake in Palangkaraya 4-5 years ago, and the home cracked,” he claimed.
So, the most critical consideration is how to minimize disaster damage in order to limit the likelihood of injury or death as well as material loss. It was noisy and tense the entire time. What should we do in advance? He inquired, “How is the early warning system?”
Liquidity risk from quake, tsunami, and earthquake
There are 15 areas in Indonesia where earthquakes, tsunamis, and liquefaction pose a threat, according to Andang. Among them are the Mentawai megathrust, the Sunda Strait megathrust, the Cimandiri fault, the Lembang fault, the Surabaya-Bojonegoro rising fault, the Madura Strait rising fault, and the South Segment Palu-Koro fault. Also included are the West Sulawesi offshore fault, the North Sulawesi subduction zone, the Tarakan earthquake and tsunami, the Sumatran fault, the fault Bar
An earthquake in Kendeng, the Surabaya-Bojonegoro rising fault, the Jember-Banyuwangi megathrust, and the Bali-Lombok megathrust could threaten Malang. At Sumbermanjing Wetan, there are normal faults, while at Dampit, there are horizontal faults. What is the status of this fault? Landslides will occur if it is not operational. Eruptions could be spawned if the fault is active, according to him.
He warned of the dangers of a movement from the megathrust infiltrating the continental plate and causing it to migrate away from its normal position. A massive earthquake can be triggered by moving layers as deep as 30 kilometers, as wide as 100 kilometers, and as long as 500 kilometers. According to him, the 2004 Aceh tsunami was the result of an earthquake with a depth of 30 kilometers and a length of 1000 kilometers.
Andang described the catastrophic potential as “exceptional, devastating.” Malang might be hit by a tsunami if the megathrust moves. Malang’s defects are expected to be mapped by the government, and which faults are most vulnerable. In order to gather data, BPBD and BMKG must carry out study and connect with nature enthusiasts.
From Pacitan to Banyuwangi, Andang Bachtiar of Adventurers & Mountain Climbers (AMC) Malang has been researching the area since 2006. Recording escape routes and previous calamities, they walked the streets. Nature-lovers can also use social media at this time. By uploading the coordinates of the location to social media, nature enthusiasts participate in study.
On social media, photos with GPS are shared.” Using hashtags, the data is gathered, he explained. This network concept makes it easier for the government to do its duties and can immediately mitigate disasters.
A number of sites that became natural strongholds for the tsunami, according to East Java Regional Council for the Forum for the Environment (Walhi), Purnawan D Negara, are in critical condition. Changes have occurred in the protected area’s role, transforming it into a restricted-production forest. Iron sand was mined in the once-protected area.
“The coastal area of South Malang is in a precarious ecological state. Also, he was threatened with the Southern Cross Line,” he claimed.
Land conversion has a negative impact on southern coast people, according to the chairman of Sahabat Alam, Andi Syaifudin. Because their homes are at risk in the case of an earthquake or tsunami. The parties must assist in catastrophe mitigation.
Volunteers and academics are needed to help us.” Disaster mitigation is a topic that is not well understood in the society,” stated the man. In the meantime, a growing number of fisherman are becoming tech-savvy. For example, in Kondangmerak, which employs apps to forecast wind and waves. To ensure their safety in the event of a tidal flood. As a result, there are less wasteful wastes of material.